<table><caption>**Table 13.** Total plant- (AX) and microbe-derived (GMRF) carbohydrates and GMFR/AX ratio in whole soil (WS) and clay- and fine silt-sized fractions in 0–5, 20–30 and 75–100 cm layers of an Acrisol submitted to conventional tillage (CT) and no tillage (NT), with oat/maize (O/M) or oat+vetch/maize+cowpea (OV/MC) succession, and with (180 kg of urea ha⁻¹ [180N]) or without (0N) fertilization.</caption><thead><tr><th rowspan="2">Tillage</th><th rowspan="2">Crop</th><th rowspan="2">Fertilization</th><th colspan="3">AX‡</th><th colspan="3">GMFR‡</th><th colspan="3">GMRF/AX ratio</th></tr><tr><th>WS</th><th>Clay</th><th>FS</th><th>WS</th><th>Clay</th><th>FS</th><th>WS</th><th>Clay</th><th>FS</th></tr></thead><tbody><tr><td colspan="11" style="text-align:center; font-weight:bold;">0-5 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>657.6</td><td>988.8</td><td>709.6</td><td>880.1</td><td>1813.2</td><td>981.0</td><td>1.39</td><td>1.83</td><td>1.38</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>1015.4</td><td>1283.3</td><td>1628.1</td><td>1156.5</td><td>2443.2</td><td>244.0</td><td>1.13</td><td>1.90</td><td>1.50</td></tr><tr><td>OV/MC</td><td>0</td><td>1541.2</td><td>1744.1</td><td>1833.8</td><td>1506.5</td><td>3100.4</td><td>265.0</td><td>0.98</td><td>1.78</td><td>1.45</td></tr><tr><td>OV/MC</td><td>180</td><td>2096.0</td><td>1875.7</td><td>2059.0</td><td>1880.5</td><td>3398.2</td><td>294.0</td><td>0.90</td><td>1.81</td><td>1.43</td></tr><tr><td rowspan="3">Contrast†</td><td>No-tillage</td><td></td><td>-357.8#</td><td>-294.5**</td><td>-918.5***</td><td>-276.4#</td><td>-629.9**</td><td>-1463.7***</td><td>0.25</td><td>-0.07</td><td>0.13</td></tr><tr><td>Legumes</td><td></td><td>-1074.1**</td><td>-1612.3**</td><td>-714.3**</td><td>-1606.5**</td><td>-1053.2***</td><td>-636.6**</td><td>0.38*</td><td>0.22*</td><td>0.13</td></tr><tr><td>Fertilization</td><td></td><td>-554.8*</td><td>-131.6*</td><td>-225.3**</td><td>-374.0*</td><td>-297.8*</td><td>-294.9*</td><td>0.08</td><td>-0.04</td><td>-0.01</td></tr><tr><td colspan="11" style="text-align:center; font-weight:bold;">20-30 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>421.0</td><td>690.9</td><td>416.4</td><td>1051.6</td><td>1317.6</td><td>647.0</td><td>2.44</td><td>1.92</td><td>1.52</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>473.2</td><td>891.7</td><td>413.1</td><td>909.6</td><td>1686.7</td><td>667.0</td><td>1.93</td><td>1.89</td><td>1.60</td></tr><tr><td>OV/MC</td><td>0</td><td>506.0</td><td>917.2</td><td>438.0</td><td>1184.9</td><td>1845.4</td><td>683.0</td><td>2.33</td><td>2.05</td><td>1.55</td></tr><tr><td>OV/MC</td><td>180</td><td>491.2</td><td>805.9</td><td>347.1</td><td>972.4</td><td>1551.7</td><td>553.0</td><td>1.98</td><td>2.02</td><td>1.54</td></tr><tr><td rowspan="3">Contrast</td><td>No-tillage</td><td></td><td>-52.2</td><td>-200.8</td><td>6.3</td><td>141.7</td><td>-369.1*</td><td>-</td><td>0.51</td><td>0.03</td><td>-</td></tr><tr><td>Legumes</td><td></td><td>-</td><td>-23.7</td><td>98.9</td><td>-51.1</td><td>60.4</td><td>41.4</td><td>-0.46</td><td>-</td><td>0.12</td></tr><tr><td>Fertilization</td><td></td><td>15.2</td><td>111.3</td><td>90.9</td><td>212.6</td><td>293.6*</td><td>129.0</td><td>0.34</td><td>0.02</td><td>0.04</td></tr><tr><td colspan="11" style="text-align:center; font-weight:bold;">75-100 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>282.6</td><td>393.4</td><td>125.2</td><td>704.7</td><td>823.9</td><td>149.0</td><td>2.65</td><td>2.17</td><td>1.11</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>262.3</td><td>351.6</td><td>112.7</td><td>575.0</td><td>666.5</td><td>130.0</td><td>2.28</td><td>2.01</td><td>1.16</td></tr><tr><td>OV/MC</td><td>0</td><td>303.4</td><td>484.1</td><td>159.7</td><td>767.4</td><td>1034.3</td><td>180.0</td><td>2.85</td><td>2.17</td><td>1.12</td></tr><tr><td>OV/MC</td><td>180</td><td>369.5</td><td>476.9</td><td>138.6</td><td>853.9</td><td>1008.6</td><td>150.0</td><td>2.49</td><td>2.12</td><td>1.09</td></tr><tr><td rowspan="3">Contrast</td><td>No-tillage</td><td></td><td>20.4</td><td>41.8**</td><td>12.5</td><td>130.2*</td><td>157.3**</td><td>18.7</td><td>0.37</td><td>0.17</td><td>-0.14</td></tr><tr><td>Legumes</td><td></td><td>-471.8</td><td>-709.9***</td><td>-69.6</td><td>-148.3**</td><td>-257.9*</td><td>-</td><td>-0.79</td><td>-0.27#</td><td>0.11</td></tr><tr><td>Fertilization</td><td></td><td>-66.1</td><td>7.2</td><td>21.3</td><td>-86.5*</td><td>25.8</td><td>30.1</td><td>0.36</td><td>0.06</td><td>-0.04</td></tr></tbody></table>

†Contrast analysis was used to test the effects of no-tillage (CT O/M 0 vs. NT O/M 0), legume cover cropping (CT O/M 0 vs. NT OV/MC 0 + NT OV/MC 180) and nitrogen fertilization (NT OV/MC 0 vs. NT OV/MC 180). Significant differences between treatments at 10%, 5%, 1% and <1 % probability of error by F test are designed with (#), (*), (**) and (***) respectively.

‡ AX, sum of arabinose and xylose concentrations; GMFR, sum of galactose, mannose, fucose and rhamnose concentrations.
Microbe-derived carbohydrates (GMFR values in Table 13) ranged from 880 to 3398 mg kg⁻¹ in whole soil and fraction in the surface soil layer and declined more gradually than plant-derived carbohydrates down the soil profile, with values ranging from 554 to 1845 mg kg⁻¹ at 20–30 cm depth, and from 131 to 1034 mg kg⁻¹ at 75–100 cm depth. In surface soil layer, microbe-derived carbohydrates were more abundant under NT than CT in the fine silt and clay fractions; a similar trend was found for whole soil. Microbe-derived carbohydrates were also more abundant in the presence of legumes and with N fertilization in whole soil and fractions of the surface soil layer, and treatment effects were more obvious in fractions than in whole soil. A positive effect of NT and a negative effect of fertilization were found in the 20–30 cm soil layer in the clay fraction only. A negative effect of NT was found in whole soil and clay fraction at the 75–100 cm depth, whereas a positive effect of legumes was found in whole soil and both fractions. As compared to whole soil, the clay fraction was enriched in microbe-derived carbohydrates in all soil layers. In contrast, the fine silt fraction was enriched in microbial carbohydrates in the surface soil layer compared to whole soil but was impoverished at greater depths.

The microbe-to-plant-derived carbohydrate ratio (GMFR/AX values in Table 13) ranged from 0.90 to 2.85 and was generally narrower in surface than in deeper soil layers. In the whole soil and clay fraction of surface soil layer, the ratio was narrower with than without legumes. In contrast, the ratio was significantly wider with than without legume cover crops in clay fraction of 20–30 cm soil layer, and in whole soil and clay fraction of the 75–100 cm soil layer. Tillage and N fertilization had no effect on the microbe-to-plant-derived carbohydrate ratio.

### 6.4.5 Free Lipids

The ratio of short ($C_{16}-C_{25}$) to long chain ($C_{26}-C_{35}$) n-alkanes ($R_{S/L}$) ranged from 0.34 to 1.59 (Table 14). Wider values were found in the clay fraction and indicated the predominance of small chain *n*-alkanes ($R_{S/L} > 1$) compared to whole soil in the surface soil layer; predominance of small chain *n*-alkanes was also generally found in the clay fraction at greater depths. The $R_{S/L}$ values were
generally similar between CT and NT. In clay fraction of, the R<sub>S/L</sub> ratio was wider with than without legume cover crops in the 0–5 and 20–30 cm soil layers. Management practices did not influence R<sub>S/L</sub> in the 75–100 cm soil layer.

<table><caption>**Table 14.** Ratios of short chain-to-long chain *n*-alkanes in whole soil and the clay fraction of an Acrisol under conventional (CT) or no-tillage (NT), with oat/maize (O/M) or oat+vetch/maize+cowpea (OV/MC) succession, and with (180 kg urea-N ha<sup>-1</sup>) or without fertilization.</caption><thead><tr><th>Tillage</th><th>Crop succession</th><th>Fertilization</th><th>Whole soil Rs/l</th><th>Clay Rs/l</th></tr></thead><tbody><tr><td colspan="5" style="text-align: center; font-weight: bold;">0 – 5 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>1.01</td><td>2.61</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>0.73</td><td>2.99</td></tr><tr><td>OV/MC</td><td>0</td><td>0.89</td><td>6.76</td></tr><tr><td>OV/MC</td><td>180</td><td>0.34</td><td>4.19</td></tr><tr><td colspan="5" style="text-align: center; font-weight: bold;">20 – 30 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>nd</td><td>3.43</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>nd</td><td>0.73</td></tr><tr><td>OV/MC</td><td>0</td><td>nd</td><td>159.43</td></tr><tr><td>OV/MC</td><td>180</td><td>nd</td><td>50.43</td></tr><tr><td colspan="5" style="text-align: center; font-weight: bold;">75 – 100</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>nd</td><td>-</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>nd</td><td>2.90</td></tr><tr><td>OV/MC</td><td>0</td><td>nd</td><td>1.56</td></tr><tr><td>OV/MC</td><td>180</td><td>nd</td><td>2.98</td></tr></tbody></table>

## 6.5 Discussion

The greater SOC concentration under NT than CT in the surface soil layer was explained mainly by increases in LF-C and fine silt-C fractions. It is suggested that, compared to CT, reduced soil disruption under NT favoured the accumulation of plant residues at the soil surface (greater LF-C concentration) and its occlusion within aggregates (Conceição et al., 2013; Veloso et al., Submittted-a) where it became integrated in silt-sized MOAs. Soil aggregates under NT were proposed

<footnote n="1">¹Rs/l, ratio between short and long chain *n*-alkanes (ΣC<sub>16-25</sub>/ΣC<sub>26-35</sub>); nd = not determined.</footnote>
as microsites where decomposing organic residues SOC formation and stabilization occur through the formation of MOAs (Conceição et al., 2013). This is supported by the much greater amount of fine-silt C found under NT compared to CT in the surface soil layer. The positive effect of NT on SOC accumulation was more visible in the clay fraction in the 20–30 and 75–100 cm soil layers. That SOC accumulation was more directly associated with the clay fraction in deeper soil layers might be explained by the presence of biopores that possibly favoured the percolation of soluble C compounds down the soil profile, which were adsorbed by fine mineral particles (Hobley et al., 2016).

The generally greater SOC concentration with than without legume cover crops was mainly explained by greater C concentrations in LF and clay fractions in the surface soil layer. Consequently, both NT and the presence of legume cover crops favoured the concentration of plant residues (more LF-C). In contrast, C concentrated in different types of MOAs depending on management practice: while tillage influenced C concentration in the fine silt fraction only, legume cover cropping increased C concentration in fine silt and clay fractions. This may be related to the fact that tillage affects the distribution of crop residues within the soil and stimulates their initial decomposition and formation of coarse MOAs by increasing contact with mineral particles (Reis et al., 2014); in contrast, the presence of legumes may have a more direct impact on the formation of clay-size MOAs by stimulating microbial growth through low C/N substrates (Cotrufo et al., 2015). The C in the clay fraction favoured by two legume cropping system compared to with no legumes cropping system under NT led to SOC accumulation in whole soil profile which resulted in C sequestration rates higher than 0.9 Mg ha⁻¹ year⁻¹ (Table 11).

As compared to whole soil, the clay fraction was generally enriched in plant- and microbe-derived carbohydrates, and is generally attributed to combined microbial colonization, decomposition, and encrustation of plant residues leading to the formation of stable organic matter in clay-sized MOAs. The exception noticed for plant carbohydrates in the surface soil layer is likely the result of the large abundance of LF-C in the surface soil layer that led to an overwhelming
contribution of plant-derived carbohydrates. This is supported by the fact that plant-
derived carbohydrate concentrations were the closest between whole soil and
fractions in systems with legume cover cropping and N fertilization where LF-C
concentrations were the highest. Abundant LF-C in surface soil also explains the
relatively narrow microbe-to-plant-derived carbohydrate ratio found in whole-soil,
especially with legumes and N fertilization.

The widening of microbe-to-plant carbohydrate ratio between whole soil, fine silt, and clay fractions in the surface soil layer suggests that plant residues in whole soil (mainly LF-C) were gradually converted to smaller plant residues partly colonized by microbes and partly encrusted with minerals (fine silt-sized MOAs), and then to more thoroughly processed materials enriched in microbial metabolites (clay-sized MOAs). The enrichment in microbial carbohydrates and differences between whole soil and the clay fraction were markedly amplified by legume cover cropping (NT O/M 0N vs. NT OV/MC 0N). This is in good agreement with the marked widening of short-to-long *n*-alkanes chains under legume cover cropping in the clay fraction, indicating strong predominance of microbial residues in the presence of legume crops. These findings provide field-based evidence that high-quality legume residues favour the accumulation of carbon in fine MOAs, as compared to lower quality residues from maize and cereals, by favouring microbial processing and accumulation of microbial metabolites. These field-based results thus support the Microbial Efficiency-Mineral Stabilization theory (Cotrufo et al. 2013).

The positive effect of legume cover cropping on enrichment in microbe
carbohydrates was also observed in clay fraction of the 20–30 cm and 75–100 cm
soil layers. This suggests that legumes also stimulated accumulation of microbial
metabolites at depth and formation of fine MOAs, but that this effect was mainly
mediated by the rooting systems through root decay and/or exudation.

The positive effect of high-quality legume residues on accumulation of
microbial residues and formation of MOAs was further confirmed by the lack of
effect of nitrogen fertilization on carbohydrate and *n*-alkanes ratios in the clay
fraction. Compared to no fertilization, carbon return to soil with maize residues was
increased by N fertilization (Fig. 22). This resulted in greater LF-C concentration, but did not change C concentration in the fine silt and clay fractions, compared with no fertilization. In addition, the relative abundance of microbial-derived short chain n-alkanes was greater with than without N in the 0–5 and 20–30 cm soil layers. This is likely due to lower concentrations of N and soluble organic compounds in maize residues than in legume residues (Pimentel et al., 2015). In addition, the greater lignin concentration in maize than legume residues likely favoured the physical transfer of residues to soil as LF-C but not the stabilization in MOAs (Spielvogel et al., 2008; Cotrufo et al., 2015). Our results also agree with Yu et al. (2016) that found lower microbial biomass with than without N fertilization.

Whole soil was enriched in microbial carbohydrates in sub-surface layers whereas LF-C concentrations were one to two orders of magnitude lower than in the surface soil layer. Further to earlier discussion, changes in soil C and carbohydrate profile at depth were likely meditated by stimulation of soil microbes through root decay and exudation and accumulation. However, in contrast with surface soil, the microbe-to-plant carbohydrate ratio was generally wider in whole soil than in the fine silt and clay fractions. This indicates that preferential accumulation of microbial metabolites at depth did not necessarily lead to accumulation in MOAs in the bulk soil but may have been limited to rhizosphere, root channels and other macropores with little interaction with the bulk soil mineral matrix as previously proposed for accumulation of C in forest soil profiles (e.g., Guggenberger & Kaiser (2003)).

## 6.6 Conclusions

Using a long-term field experiment, we found that tillage influenced C concentration in the fine silt fraction only, while legume cover cropping increased C concentration in fine silt and clay fractions. Our results suggest that fine silt MOAs is an intermediate between young organic matter (LF) and stabilized OM in clay MOAs. Our results confirmed the hypothesis that carbon present in mineral-organic associations is dominated by microbial-derived residues. The legume cover crops under NT further favour the dominance of microbial over plant-derived
residues in fine fractions. The addition of residues enriched in nitrogen and soluble
fraction through legume cover crops are the main driver to C accumulation in
mineral-organic association. These results were verified in whole soil profile (100
cm soil depth) and support the high carbon accumulation obtained in subtropical
region with the adoption of no-tillage and legume cover crops.
# 7. SOIL AGGREGATION AND CARBON ACCUMULATION ARE MEDIATED BY FUNGI IN A SUBTROPICAL SOIL UNDER CONSERVATION AGRICULTURE

## 7.1 Abstract

No-tillage (NT) and legume cove crops have been found to improve the quality of tropical and subtropical soils. Microbial cell-wall constituents have been evidenced as important contributors to soil aggregation and soil organic carbon (SOC) formation. We performed a study to investigate the influence of NT and legume cover crops on the microbial cell-wall constituents [glucosamine (GlcN), taken as indicator of fungal cell-wall constituents; muramic acid (MurN), taken as indicator of bacterial cell-wall constituents] and their potential influence on soil aggregation and SOC accumulation in a subtropical Acrisol in Southern Brazil. The GlcN content ranged from 450.5 mg kg⁻¹ in the 0–5 cm soil layer to 20.5 in the 75–100 cm soil layer, approximately 10 times the range of MurN contents, from 53.1 to 2.7 mg kg⁻¹ for the same soil layers. NT and legume cover crops favoured the accumulation of fungal and bacterial cell-wall constituents in whole soil, especially in the top 5 cm of soil with a preferential enrichment of soil organic C in GlcN. In that soil layer, the GlucN/MurN ratio was strongly and positively correlated with the content of light-fraction organic matter (LF) and mean-weight diameter of soil aggregates. Fungal-derived glucosamine also preferentially accumulated down to 100 cm depth, and more specifically in the clay-sized fraction of soil, suggesting a specific role in SOC accumulation at depth. In the surface soil, the greater LF content under NT and legume cover crops favoured the fungal community which, in turn, mediated the improvement in soil aggregation. Overall, our study provides field-based evidence that the accrual of fungal cell-wall constituents is a key process leading to SOC accumulation and soil aggregation under NT and legume cover crops in subtropical soils.
## 7.2 Introduction

Adoption of conservation practices is essential to maintain or improve crop production and the sustainability of agricultural systems, especially in tropical and subtropical environments where SOC has a central role in soil functioning (Lal, 2009; Powlson et al., 2016), and where its decline has been observed following intensive cultivation (Zanatta et al., 2007).

No-tillage (NT) agriculture is practiced on about half of the agricultural land of Brazil (FEBRAPDP, 2012) and generally favours SOC accumulation compared to conventional tillage systems (Bayer et al., 2006a). The effect of NT on SOC is closely linked to soil macroaggregation through occlusion mechanisms (Veloso et al., Submitted-a). When coupled with NT, cover cropping with legumes has also been shown to favour SOC accumulation and soil aggregation under tropical/subtropical conditions (Conceição et al., 2013).

Changes in soil microbial communities, including increases in bacterial and fungal biomass, have been observed after conversion from CT to NT in temperate environments (Minoshima et al., 2007). Soil microbes, especially fungi, have long been recognized as playing a significant role in the formation and stabilization of soil aggregates (Chantigny et al., 1997). Moreover, fungi contribute more to the formation of aggregates in NT than CT soils (Beare et al., 1992; Helgason et al., 2010). Fungal hyphae increase the resistance of aggregates to mechanical breakdown and resistance to the action of water (Abiven et al., 2007).

Recent models of SOC formation now consider microbial residues as the main source for stable soil organic matter (Kogel-Knabner, 2002). Moreover, SOC stabilization by the soil matrix and consequent soil aggregation would be favoured by more labile C inputs (Cotrufo et al., 2015). More field-based observations are needed to support these concepts. Cell-wall constituents of fungi and bacteria in soil can provide the “fingerprint” for SOC formation (Ding et al., 2011). Contents of muramic acid (MurN) and glucosamine (GlcN) have been used to distinguish respectively bacterial and fungal cell wall residues, mainly in temperate environments (Chantigny et al., 1997; Amelung et al., 2008). Only recently few
studies have been performed in subtropical/tropical soils where a favorable effect
of NT in total amino-sugar with preferential glucosamine enrichment in comparison
to conventionally-tilled soil (Ding et al., 2011) and a co-accumulation in similar
proportion of both MurN and GlcN by the use of legume cover crops has been
noticed (Martins et al., 2012b).

Thus, the literature available on the influence of conservation practices on
soil bacterial and fungal constituents, in relation to soil aggregation and SOC
dynamics, is scant for subtropical and tropical conditions. We performed a study
to investigate the influence of NT and legume cover crops on microbial cell wall
constituents in a subtropical Acrisol in Southern Brazil, and examined the
relationships with soil aggregation and accumulation of organic C in whole soil and
SOC fractions.

**7.3 Materials and Methods**

**7.3.1 Description of the experiment**

The study was conducted in a 30-years old experiment located at the
Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in
Eldorado do Sul, Brazil (30º06'S, 51º40'W; altitude 96 m asl). The climate is
subtropical (Cfa according to the Köppen classification), with mean annual
temperature and annual rainfall of 19.4 °C and 1440 mm, respectively. The soil of
the experiment was classified as sandy clay loam, granite-derived Acrisol (FAO,
2015). However, the clay content increases from 217 g kg⁻¹ at 0–5 cm to 511 g
kg⁻¹ at 75–100 cm depth. The main clay minerals are kaolinite (720 g kg⁻¹ clay)
and iron oxides (109 g kg⁻¹ clay) (Bayer et al., 2001).

Until 1969, the area was under native grassland (mainly *Paspalum* and *Andropogon*). In the following 16 years, the soil was seriously degraded by intensive plowing and disking operations for annual cropping, until the establishment of the experiment in 1985.

The experimental treatments comprised two tillage systems, CT, reduced tillage and NT applied in main plots of 15 × 20 m, and combined with three cropping systems applied in subplots of 5 × 20 m in size. The cropping systems were: black
oats (Avena strigosa Schreb) / maize (Zea mays L.) (O/M), vetch (Vicia sativa L.) / maize (V/M), and oats + vetch / maize + cowpea (Vigna unguiculata (L.) Walp) (OV/MC). Each of the nine tillage-cropping combinations was submitted to two fertilization levels: 0 and 180 kg urea-N ha⁻¹ (0N and 180N), banded in the maize crop, in sub-subplots of 5 × 10 m. The experimental treatments were arranged in a split-split plot design with three replicates. More details are provided in Bayer et al. (2000) and Zanatta et al. (2007).

Trenches were opened with a backhoe and eight soil layers (0–5, 5–10, 10–15, 15–20, 20–30, 30–50, 50–75 and 75–100 cm) were sampled in September 2014, prior to soil tillage and maize planting. Four treatments were selected (CT O/M 0N, NT O/M 0N, NT OV/MC 0N and NT OV/MC 180N) for the present study. Soil samples were air dried and ground to ≤2 mm; and a subsample of ~2 g was further ground to ≤250 µm for determination of accumulation of organic C via dry combustion (FlashEA 1112, Thermo Electron Corporation, Milan, Italy) and amino-sugars in whole soil and SOC fractions.

Annual carbon inputs in the cropping systems were calculated using a database compiling information since inception of the experiment in 1985 (Zanatta et al., 2007), and updated until year 2014 (root C input was estimated to be 30% of C input from aboveground parts) (Table 15).
<table><caption>**Table 15.** Soil characteristics of the long-term field experiment (30 years) used in this study, comparing conventional tillage (CT) and no-tillage (NT) combined with three cropping systems: (i) black oat (Avena strigosa Schreb) as winter cover crop followed by maize (Zea mays L.) as summer grain crop (O/M) and (ii) oat plus vetch (Vicia sativa) followed by maize in summer intercropped with cowpea cover crop (Vigna unguiculata (L.) Walp) (OV/MC).</caption><thead><tr><th rowspan="3">Characteristic</th><th>CT</th><th colspan="3">NT</th></tr><tr><th>---</th><th colspan="3">--------------------------------</th></tr><tr><th>O/M 0N</th><th>O/M 0N</th><th>OV/MC 0N</th><th>OV/MC 180N</th></tr></thead><tbody><tr><td>C addition (Mg ha<sup>-1</sup> yr<sup>-1</sup>)<sup>2</sup></td><td>4.8</td><td>5.2</td><td>9.2</td><td>10.2</td></tr><tr><td>Soil carbon (g kg<sup>-1</sup>)<sup>2</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>0–5 cm</td><td>10.6</td><td>15.0</td><td>20.9</td><td>25.9</td></tr><tr><td>20–30 cm</td><td>9.1</td><td>10.0</td><td>10.6</td><td>10.0</td></tr><tr><td>75–100 cm</td><td>5.4</td><td>6.5</td><td>6.7</td><td>6.7</td></tr><tr><td>Light fraction-C (g kg<sup>-1</sup>)<sup>3</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>0–5 cm</td><td>1.5</td><td>3.2</td><td>6.0</td><td>9.2</td></tr><tr><td>20–30 cm</td><td>0.2</td><td>0.3</td><td>0.3</td><td>0.3</td></tr><tr><td>75–100 cm</td><td>0.1</td><td>0.1</td><td>0.1</td><td>0.1</td></tr><tr><td>Clay-C (g kg<sup>-1</sup>)<sup>3</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>0–5 cm</td><td>6.5</td><td>7.1</td><td>9.2</td><td>10.0</td></tr><tr><td>20–30 cm</td><td>7.4</td><td>8.3</td><td>8.8</td><td>8.4</td></tr><tr><td>75–100 cm</td><td>4.7</td><td>5.7</td><td>5.8</td><td>5.9</td></tr><tr><td>Aggregate distribution (%)<sup>2</sup></td><td></td><td></td><td></td><td></td></tr><tr><td>0–5 cm</td><td></td><td></td><td></td><td></td></tr><tr><td>&nbsp;&nbsp;&nbsp;&nbsp;&gt; 2 mm</td><td>12.5</td><td>29.2</td><td>37.3</td><td>-</td></tr><tr><td>&nbsp;&nbsp;&nbsp;&nbsp;2–0.25 mm</td><td>52.6</td><td>45.1</td><td>42.3</td><td>-</td></tr><tr><td>&nbsp;&nbsp;&nbsp;&nbsp;&lt; 0.25 mm</td><td>34.9</td><td>23.7</td><td>20.4</td><td>-</td></tr></tbody></table>

### 7.3.2 Amino-sugar determination

Amino-sugars were measured in whole soil, and in fine-silt and clay sized fractions. The soil fractions were obtained through a fractionation scheme detailed in Chapter 5 of this thesis. Briefly, the light fraction (LF) was separated using a sodium polytungstate (NaW) suspension after dispersion of soil by sonication. The

<footnote n="2">² original data presented by Veloso et al. (Submitted a); ³ Original data presented in Chapter 5.</footnote>
floating LF was removed using vacuum and washed with water and calcium chloride 0.01 mol L⁻¹ to remove NaW. The material was dried (50°C, 48 h) and weighed to determine dry matter content, and analyzed for C content by dry combustion. The suspension was then passed through a sieve of 53 µm in order to separate the sand fraction. The portion passed through the sieve was transferred to a graduated cylinder (1L) where 55 samples of the clay fraction (<0.002 mm) were made, based on Stokes' Law, until its complete removal. The material remaining in the graduated cylinder, corresponding to the silt fraction, was also separated according to Stokes' Law in coarse-silt (0.05-0.02 mm) and fine-silt (0.02-0.002 mm). The corse silt, fine silt and clay fractions were flocculated with CaCl₂ 2 mol L⁻¹, and then oven dried at 50 °C, weighed and grounded in agate mortar.

Amino-sugar content was determined by the method of Angers & Chantigny (2008), as modified from (Zelles, 1988). Briefly, 1 g of air-dried and finely ground (<0.15 mm) soil was transferred to 30-mL glass test tubes, and 20 mL of 6 mol L⁻¹ HCl was added to the tubes and mixed thoroughly on a vortex. The mixture was carefully bubbled with N₂ to remove O₂ and minimize amino-sugar oxidation. Tubes were sealed with screw caps, incubated for 6 h in an oven set at 105 °C, then cooled on ice and centrifuged at 1500×g for 10 min. A 1-mL aliquot of the supernatant was transferred to a 25-mL boiling flask and evaporated to dryness with a rotary vacuum evaporator. The precipitate was dissolved in 980 µL of O-phthaldehyde (5 g OPA L⁻¹ dissolved in 0.5 mol L⁻¹ potassium tetraborate solution), and 20 µL of 2-mercaptoethanol was added to the flask, starting the derivatization. The mixture was vortexed, transferred to a 1.5 mL Eppendorf tube, and centrifuged at 20,000×g for 3 min. Five minutes (±15 s) after 2-mercaptoethanol addition, a 25-µL aliquot of the supernatant was injected in a high-performance liquid chromatograph (Waters, Milford, MA, USA) was equipped with a pump (model 515, Waters) and an analytical column (4 mm, 8×100 mm, Nova-Pak C18, Waters) maintained at 40 °C. The eluents used were: solution A (0.05 mol L⁻¹ sodium citrate; 0.05 mol L⁻¹ sodium acetate; methanol : tetrahydrofuran, in proportion 18 : 1.7 : 1) and solution B (65% methanol) at a flow
rate of 1.5 mL min⁻¹. The proportion of solution A (gradual change) was: 85%, 0 to 2.5 min; 70%, 2.5 to 17.5 min; 85% 17.5 to 30 min. Detection was performed by fluorescence (scanning fluorescence detector, model 474, Waters) with an emission wavelength of 425 nm and an excitation wavelength of 338 nm using a Xenon lamp. Amino-sugars from soil samples were identified and quantified by comparison to chromatograms of standard solutions containing mixed MurN and GlcN. Amounts of C in amino-sugars were calculated considering that MurN contains 43% C and GlcN contains 40% C.

Total MurN-C in the soil was taken as a proxy for total bacterial cell-wall mass as bacterial cells are considered the exclusive source of MurN in soil (Zelles, 1988; Angers & Chantigny, 2008). Bacteria cell walls also contain GlcN in a ratio of 2:3 with MurN, on a C basis. We therefore subtracted 0.67 times MurN-C from soil total GlcN-C to estimate fungal-derived GlcN content (Chantigny et al., 1997). Potential error in this estimation is considered to be insignificant as soil GlcN content in the present study was 6 to 11 times greater than the soil MurN content in whole soil and fractions.

### 7.3.3 Statistical analyses

The data distribution was tested for normality by the Kolmogorov-Smirnov test and for homogeneity of variance by the Levene test. The effects of tillage and cropping systems were submitted to an analysis of variance (ANOVA; SAS® v.9.4, Statistical Analysis System Institute, Cary, North Carolina). The statistical model in the analysis of variance to analyze amino-sugar concentration was: $Y_{ij} = \mu + B_i + T_j + \text{Error}_{(ij)}$ where $\mu$ is the general average of the experiment, $B_i$ is block i (1, 2, 3), $T_j$ represents treatment j (1, 2, 3, 4), and $\text{Error}_{(ij)}$ represents the experimental error. Treatment effects were tested using Tukey's test and declared significant at $P < 0.05$. When effects were significant, treatments means were compared by contrast analysis to determine the effect of:

i) Tillage effect: CT O/M 0N vs. NT O/M 0N;

ii) Legumes effect: NT O/M 0N vs. NT OV/MC 0N and NT OV/MC 180N;

iii) Fertilization effect: NT OV/MC 0N vs. NT OV/MC 180N.
Regression analyses were performed (SigmaPlot for Windows v. 13.0, Systat Software, Inc., San Jose, CA) to explore the relationships between GlcN or MurN concentrations taken individually or the GlcN/MurN ratio and previously published soil parameters such as aggregate mean weight diameter (MWD) and light-fraction C (Chapter 5 of this thesis). In addition, relationships between GlcN/MurN ratio and fine-silt and clay-C content, (Chapter 5 of this thesis), were also performed.

## 7.4 Results

The MurN concentration ranged from 3 to 20 mg kg⁻¹ in the whole soil, and from 7 to 53 and 3 to 40 mg kg⁻¹ in the clay and fine-silt fractions, respectively (Table 16). The greatest differences were recorded in the 0–5 cm soil layer. In whole soil, MurN concentration was 1.74 times greater in NT than in CT soils, 1.46 times greater with than without legume cover crops, and 1.14 times greater with than without N fertilization. The greatest effect of tillage was observed in the fine-silt fraction, where MurN concentration was more than two times greater under NT than CT. The MurN concentration was also 1.15 times greater with than without legume cover crops in the clay fraction. The positive effect of NT and legume cover crops was also observed in the whole soil in the 20–30 cm layer, whereas N fertilization decreased significantly MurN concentration in the fine-silt fraction. Treatments did not influence MurN concentration in the 75-100 cm soil layer.

Fungal-derived GlcN concentration ranged from 37 to 287 mg kg⁻¹ in the whole soil, and from 63 to 451 and 21 to 597 mg kg⁻¹ in the clay and fine-silt fractions, respectively (Table 16). Fungal-derived GlcN concentration generally showed trends similar to MurN, with the greatest treatment effects found in the whole soil of the 0–5 cm layer. In the whole soil, fungal GlcN was 2.11 times greater under NT than CT, 1.58 times greater with than without legume cover crops, and 1.23 times greater with than without N fertilization. In fine-silt fraction of the top soil layer, GlcN concentration was more than two times greater under NT than CT; in the clay fraction, GlcN concentration was 1.64 times greater under NT than CT, and 1.30 times greater with than without legumes cover crops. The positive effect
of NT and legume cover crops was also observed in the whole soil in the 20–30 cm layer. Nitrogen fertilization had no significant effect on GlcN at the 20–30 cm soil layer. Positive effects of tillage, legumes and N fertilization were found in the clay fraction of the 75–100 cm soil layer.

.
<table><caption>**Table 16.** Muramic acid (MurN) fungal glusamine (GlucN) and GlucN/MurN ratio in whole soil and fine silt and clay fraction in 0–5, 20–30 e 75–100 cm layers from Acrisol submitted to conventional tillage (CT) and no tillage (NT) with oat/maize (O/M) and oat+vetch/maize+cowpea (OV/MC); and two nitrogen fertilization rates, 0 e 180 kg of urea ha⁻¹ (ON e 180N).</caption><thead><tr><th rowspan="3">Tillage</th><th rowspan="3">Cropping systems</th><th rowspan="3">N fertilization</th><th colspan="3">Muramic acid</th><th colspan="3">GlcN</th><th colspan="3">GlucN/ MurN</th></tr><tr><th>Whole soil</th><th>Clay</th><th>Fine silt</th><th>Whole soil</th><th>Clay</th><th>Fine silt</th><th>WS</th><th>Clay</th><th>FS</th></tr><tr><th colspan="9" style="text-align:center;">mg kg<sup>-1</sup></th></tr></thead><tbody><tr><td colspan="11" style="text-align:center; font-weight:bold;">0-5 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>7.04</td><td>30.85</td><td>11.77</td><td>78.45</td><td>208.12</td><td>142.58</td><td>11.15</td><td>6.79</td><td>12.39</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>12.24</td><td>45.33</td><td>26.54</td><td>164.46</td><td>341.92</td><td>367.39</td><td>13.43</td><td>7.47</td><td>14.24</td></tr><tr><td>OV/MC</td><td>0</td><td>16.65</td><td>50.69</td><td>37.85</td><td>232.43</td><td>439.03</td><td>525.69</td><td>13.95</td><td>8.72</td><td>13.99</td></tr><tr><td>OV/MC</td><td>180</td><td>19.05</td><td>53.08</td><td>39.79</td><td>286.77</td><td>450.49</td><td>597.33</td><td>15.20</td><td>8.49</td><td>15.00</td></tr><tr><td rowspan="3">Contrast</td><td>CT vs NT</td><td></td><td>-5.21*</td><td>-14.48**</td><td>-14.77**</td><td>-86.02**</td><td>-133.80*</td><td>-224.81**</td><td>-2.27*</td><td>-0.68</td><td>-1.84*</td></tr><tr><td>OM vs OVMC</td><td></td><td>-11.20***</td><td>-13.12*</td><td>-24.57**</td><td>-190.27**</td><td>-205.69*</td><td>-388.24**</td><td>-2.30*</td><td>-2.26*</td><td>-0.51</td></tr><tr><td>0 vs 180</td><td></td><td>-2.39*</td><td>-2.39</td><td>-1.94</td><td>-54.351**</td><td>-11.45</td><td>-71.63</td><td>-1.26</td><td>0.24</td><td>-1.02</td></tr><tr><td colspan="11" style="text-align:center; font-weight:bold;">20-30 cm</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>4.83</td><td>16.89</td><td>8.21</td><td>53.01</td><td>120.95</td><td>73.90</td><td>11.11</td><td>7.33</td><td>9.14</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>5.59</td><td>17.60</td><td>8.18</td><td>62.39</td><td>134.03</td><td>77.91</td><td>11.23</td><td>7.64</td><td>9.49</td></tr><tr><td>OV/MC</td><td>0</td><td>6.28</td><td>18.60</td><td>10.88</td><td>72.02</td><td>139.16</td><td>98.17</td><td>11.50</td><td>7.63</td><td>9.01</td></tr><tr><td>OV/MC</td><td>180</td><td>6.78</td><td>20.65</td><td>8.44</td><td>76.33</td><td>149.53</td><td>80.04</td><td>11.25</td><td>7.28</td><td>9.47</td></tr><tr><td rowspan="3">Contrast</td><td>CT vs NT</td><td></td><td>-0.77*</td><td>-0.71</td><td>0.03</td><td>-9.38*</td><td>-13.07*</td><td>-4.00</td><td>-0.13</td><td>-0.30</td><td>-0.35</td></tr><tr><td>OM vs OVMC</td><td></td><td>-1.88*</td><td>-4.03</td><td>-2.96</td><td>-23.57**</td><td>-20.64*</td><td>-22.40</td><td>-0.27</td><td>0.36</td><td>0.50</td></tr><tr><td>0 vs 180</td><td></td><td>-0.50</td><td>-2.05</td><td>2.44*</td><td>-4.31</td><td>-10.37</td><td>18.13</td><td>0.25</td><td>0.34</td><td>0.46</td></tr><tr><td colspan="11" style="text-align:center; font-weight:bold;">75-100</td></tr><tr><td>CT</td><td>O/M</td><td>0</td><td>2.71</td><td>6.46</td><td>3.74</td><td>36.46</td><td>63.44</td><td>27.24</td><td>13.56</td><td>10.11</td><td>7.26</td></tr><tr><td rowspan="3">NT</td><td>O/M</td><td>0</td><td>2.98</td><td>7.39</td><td>3.14</td><td>41.12</td><td>73.42</td><td>25.47</td><td>13.87</td><td>9.94</td><td>8.11</td></tr><tr><td>OV/MC</td><td>0</td><td>3.14</td><td>7.06</td><td>3.51</td><td>44.17</td><td>76.98</td><td>28.67</td><td>14.04</td><td>10.96</td><td>8.22</td></tr><tr><td>OV/MC</td><td>180</td><td>2.75</td><td>7.65</td><td>2.66</td><td>37.56</td><td>88.27</td><td>20.52</td><td>13.47</td><td>11.77</td><td>7.65</td></tr><tr><td rowspan="3">Contrast</td><td>CT vs NT</td><td></td><td>-0.27</td><td>-0.94</td><td>0.61</td><td>-4.69</td><td>-9.97*</td><td>1.76</td><td>-0.31</td><td>0.17</td><td>-0.85</td></tr><tr><td>OM vs OVMC</td><td></td><td>0.08</td><td>0.07</td><td>-0.01</td><td>-0.50</td><td>-18.42*</td><td>1.75</td><td>0.25</td><td>-2.86</td><td>-0.36</td></tr><tr><td>0 vs 180</td><td></td><td>0.38</td><td>-0.59</td><td>0.84</td><td>6.61</td><td>-11.28*</td><td>8.15</td><td>0.57</td><td>-0.81</td><td>0.58</td></tr></tbody></table>

Contrast analysis was used to test the effects of tillage (CT O/M 0 vs. NT O/M 0), legume cover cropping (CT O/M 0 vs. NT OV/MC 0 + NT OV/MC 180) and nitrogen fertilization (NT OV/MC 0 vs. NT OV/MC 180). Significant differences between treatments at 5%, 1% and <1% probability of error by F test are designed with (*), (**) and (***) respectively.
The GlcN/MurN ratio ranged from 11.1 to 15.2 in whole soil, and generally showed narrower values in the clay and fine-silt fractions, except for the fine-silt fraction in the 0-5 cm soil layer (Table 16). The GlcN/MurN ratio was affected by management system in the whole soil of the 0–5 cm soil layer, where it was greater under NT than CT, and greater with than without legumes. In that same soil layer, the GlcN/MurN ratio was greater under NT than CT in the fine-silt fraction, and greater with than without legumes in the clay fraction. Nitrogen fertilization had no effect on the GlcN/MurN ratio, and there were no treatment effects at the other soil depths. In the clay fraction, the GlcN/MurN ratio was greater at the 75–100 cm depth (10.7) than at 0-5 (7.9) and 20-30 (7.5) cm depths. By contrast, the GlcN/MurN ratio gradually declined with depth, from 13.9 to 7.8, in the fine-silt fraction.

Significant relationships were found between soil properties and amino-sugars in the 0–5 cm soil layer only and in the whole soil and clay- and fine-silt-sized fractions. Significant relationships between GlcN or MurN concentrations taken individually and LF-C (Fig. 23 a,b) and mean-weight diameter of water-stable soil aggregates (Fig 23 a,b) was observed. Besides, strong and positive relationships were found between the GlcN/MurN ratio and LF-C (Fig. 22c), and between the GlcN/MurN ratio and the mean-weight diameter of water-stable soil aggregates (Fig. 22c). In addition, positive relationships were observed between the GlcN/MurN ratio and C content in fine silt and clay fractions (Fig. 24) in the 0-5 cm soil layer only.
<figure><img src="image_30.png" /><figcaption>**Figure 23.** Regression of muramic acid concentration (a), glucosamine concentration (b) and glucosamine/muramic acid ratio (GlucN/MurN ratio) (c) as function of carbon content in light fraction (LF-C) of organic matter in the 0–5 cm soil deep layer from Acrisol submitted to conventional tillage (CT) and no tillage (NT) with oat/maize (O/M) and oat+vetch/maize+cowpea (OV/MC); and two nitrogen fertilization rates, 0 e 180 kg of urea ha⁻¹ (0N e 180N).</figcaption></figure>
<figure><img src="image_31.png" /><figcaption>**Figure 24.** Regression of mean weighted diameter (MWD) of soil aggregates as a function of muramic acid concentration (a), glucosamine concentration (b) and glucosamine/muramic acid ratio (GlucN/MurN ratio) c) in the 0–5 cm soil deep layer from Acrisol submitted to conventional tillage (CT) and no tillage (NT) under oat/maize (O/M) and oat+vetch/maize+cowpea (OV/MC) cropping systems.</figcaption></figure>
<figure><img src="image_32.png" /><figcaption>**Figure 25.** Regression of C content in fine-silt and caly fraction as a function of glucosamine/muramic acid ratio (GlucN/MurN ratio) in the 0–5 cm soil deep layer from Acrisol submitted to conventional tillage (CT) and no tillage (NT) under oat/maize (O/M) and oat+vetch/maize+cowpea (OV/MC) cropping systems and two nitrogen fertilization rates, 0 e 180 kg of urea ha⁻¹ (0N e 180N).</figcaption></figure>

**7.5 Discussion**

The long-term adoption of NT and legume cover crops increased soil macroaggregation and SOC content, specially the content of LF-C and clay-C at the 0–5 cm depth (Table 15). The MurN and GlcN concentrations measured in this experiment were similar to those reported by Martins et al. (2012b) under similar climate conditions. No-tillage, legume cover crops and N fertilization all favoured the co-accumulation of bacterial and fungal cell wall constituents in the whole soil, but the effects were mainly found in the top 5 cm of soil, and also to a
lower extent in the 20–30 cm layer for tillage and legume cover crops. This co-accumulation likely occurred because more substrates (e.g., greater C inputs through crop residues, and greater LF-C concentration; Table 15) were available for microorganisms in surface soil under NT, with legume cover crops, and with N fertilization. This is supported by the fact that microbial growth is generally mainly limited by the availability of labile C (Reinertsen et al., 1984; Bremer & van Kessel, 1992).

The mean GlcN/MurN ratio ranged from 6.8 to 15.2, consistent with values measured in top layers of a Brazilian Oxisol (Martins et al., 2012b). Besides the co-accumulation of bacterial and fungal cell wall constituents, tillage and legume cover cropping also significantly influenced the GlcN/MurN ratio. The greater GlcN/MurN ratio found under NT than CT indicates a preferential enrichment in fungal cell wall constituents under NT, in agreement with Frey et al. (1999). This preferential enrichment in fungal cell walls was likely due to greater C inputs from crop residues in the top 5 cm of soil (Table 15), which resulted in a marked accumulation of LF-C (Table 15). Accumulation of crop residues at or near the soil surface represents a good food source for microorganisms, and a favourable environment for extensive hyphal network development (Holland & Coleman, 1987), at the expense of bacteria which at less efficient than fungi at decomposing plant tissues (Griffiths et al., 1998; Boer et al., 2005).

The GlcN/MurN ratio was also significantly increased by the inclusion of legumes in the cropping system most likely because C inputs and LF-C accumulation were greater in cropping systems with than without legume cover crops (Table 15). In addition, living roots of legumes show greater root colonization by fungi than grasses (Scheublin et al., 2004). The influences of rooting patterns and densities should also be considered in GlcN enrichment since perennial legume showed significantly less amino sugars than perennial grasses, but annual legume (faba bean) showed more GlcN than annual grass species (wheat) (Chantigny et al., 1997).

Although N fertilization increased LF-C content compared to non-fertilized systems (Table 15), and GlcN and MurN concentrations in the top 5 cm of soil (whole soil only), there was no effect of N fertilization on either the GlcN/MurN ratio, indicating no preferential stimulation between either fungi or bacteria. Le
Guillou et al. (2012) also reported that N fertilization increased MurN and GlcN to similar extent in agricultural soils.

The strong and positive relationships found between the GlucN/MurN ratio and the mean-weight diameter of soil aggregates and LF-C concentration in the top 5 cm of soil suggest that the absence of physical soil disturbance under NT favoured the physical protection of LF in water-stable aggregates (Martins et al., 2012b; Conceição et al., 2013). Furthermore, soil aggregation around legume residues likely created an environment favourable to the colonization of LF by soil microbes (Six et al., 2002), and our results indicate that this environment was more favourable to the accumulation of fungal than bacterial cell wall constituents, as previously hypothesized by Martins et al. (2012b). That the relationship between GlcN/MurN ratio and soil aggregation was mostly limited to the top 5 cm of soil suggests that preferential accumulation of fungal components may be related to variations in soil moisture conditions, which are greater at the soil surface; it is recognized that fungi are more able than bacteria to cope with soil drying by crossing air-filled zones with their hyphae to access water and nutrients (Gordon et al., 2008; de Vries et al., 2012; Barnard et al., 2013). Increase in soil fungi populations under NT compared to CT have been documented previously, and were associated with increases in soil aggregation (Beare et al., 1997; Chantigny et al., 1997; Al-Maliki & Scullion, 2013), and more specifically in soil macroaggregates (Helgason et al., 2010). In turn, fungal hyphae improve aggregate resistance to mechanical breakdown and slaking (Abiven et al., 2009), and likely improved aggregate persistence in time.

For both amino-sugars, the highest concentration was found in the clay fraction which agrees with Simpson et al. (2004). In addition, we observed a significant positive effect of NT and legume cover crops on the accumulation of fungal glucosamine in the clay fraction down in the entire soil profile. This is consistent with findings in Chapter 5 of this thesis, who showed that C sequestration was likely related to microbial products accumulating at depth. Here we show that this is particularly true with fungal residues. This explains why the greater GlucN/MurN ratio in the clay fraction of deeper compared to superficial soil layers, suggesting an increase in the relative contribution of fungi over bacteria in deeper soil layers. It is possible that the low pH in deeper soil layers (the pH increases from 6.0 at 0–5 cm to 4.2 g kg⁻¹ at 75–100 cm depth),
which is more favourable to fungal than bacterial growth (Rousk et al., 2009). Whether accumulation of GlcN at depth is caused by the migration of fungal cell-wall components or to the growth of fungi (e.g., colonization of roots by mycorrhizae) at depth remains to be ascertained. Compared to bacteria, fungi have a lower energy requirement and higher efficiency in transforming C substrates into microbial components, two factors likely to favour C accumulation in soil (Alvarez et al., 1995; Cotrufo et al., 2013; Kallenbach et al., 2016). Thus, differences in composition between bacterial and fungal communities are likely to influence soil C accumulation and stabilization (Fig. 25) over time. That the preferential accumulation of fungal-derived amino-sugars at depth was specifically found in the clay fraction suggests that these components are likely included in stable mineral-organic complexes.

## 7.6 Conclusions

Our results indicate that tillage and cropping systems are key factors driving physicochemical and microbiological properties of an Acrisol under subtropical climate. We emphasize that no tillage and legume cover cropping, favoured the co-accumulation of bacteria- and fungi-derived cell wall constituents in whole soil and in clay- and fine-silt-sized fractions. This co-accumulation was however limited to the top 5 cm of soil with a preferential enrichment of soil organic C in fungal-derived glucosamine, whereas fungal-derived glucosamine also accumulated down to 100 cm depth, and more specifically in the clay-sized fraction of soil. Our data suggest that (i) fungal growth is favoured by no tillage and legume cover crops which helps in stabilizing structural stability of surface soil and (ii) the accrual of fungal cell-wall residues is an important process in C accumulation and stabilization throughout the soil profile under subtropical climate.
## 8. SYNTHESIS RESULTS

Considering the results obtained in the research project for obtaining of doctorate degree, we formulated theoretical models that encompass the impact of no-tillage and legume cover crops on mechanisms of stabilization and accumulation of carbon in soil. The mineral-organic association was the main mechanism of carbon stabilization in this subtropical Acrisol. Greater contribution of mineral-organic association to soil organic carbon compared to other mechanisms was observed. In addition, the mineral-organic association was responsible for the long-term stabilization (hundred years). According to our results, there are two main paths favouring the mineral-organic association in agricultural systems: the labile residue input and favouring the soil aggregation. Residue type control residue-derived C and N partitioning among soil organic matter fractions. We hypothesize that the non-labile residue input is physically transferred to the soil and recovered as a light fraction. The light fraction can be stabilized promoting soil aggregation and be protected by spatial inaccessibility (Cotrufo et al., 2015; Martins & Angers, 2015). The soil aggregation is impacted mainly in superficial soil layers, because of residues are inputted on surface soil. The greater light fraction under no-tillage compared to conventional tillage is available for microrganisms in surface and favour the fungal community (fungal hyphae) which in turn mediated improvement of structural stability, specially the macroaggregates. In large macroaggregates, the C occlusion appears to be the main mechanism of C stabilization, representing more than 70% of the MRT under NT and legume cover crops. In addition, the slower turnover of the macroaggregates under NT favour the C enrichment in microaggregates. Our study suggests that this especially the case when associated with legume cover crop, due to the importance of labile compounds in the formation of stable mineral-organic association.
The positive effect of high-quality residue such as legume cover crops in mineral-organic association was explained by favouring microbial processing. The greater contribution of microbial source to clay-C was observed more with than without legume cover crops, in surface and sub-surface soil layers, highlighting the role of soil microorganisms controlling the flow of C and N-residue to mineral-organic association. Some studies have shown that the low C/N ratio of substrate, such as legume, have favoured the carbon use efficiency by microorganisms (Manzoni et al., 2008). In addition, the legume cover crops favoured greater fungal community. Compared to bacteria, fungi have a lower energy requirement and higher efficiency in transforming C substrates into microbial components, two factors likely to favour C accumulation in soil (Alvarez et al., 1995; Cotrufo et al., 2013; Kallenbach et al., 2016). Thus, differences in composition between bacterial and fungal communities are likely to influence soil C accumulation and stabilization (Fig. 26) over time.

<figure><img src="image_33.png" /><figcaption>**Figure 26.** Theoretical model about stabilization and accumulation of carbon in soil profile.</figcaption></figure>

In the sub-surface soil layer, the contribution of min-OM to SOC was greater compared to superficial soil layer (Fig 25). In that soil layers, NT and legume cover crops also favoured the C enrichment. The preferential
accumulation of fungal-derived amino-sugars at depth is linked to carbon isotope
signature of cover crop residues at depth. The more negative values under
legume cover crops compared to without legume cover crops in the surface and
sub-surface layers are due to the greater contribution of residues of C3 plants
(oats, vetch and cowpea). We believe that mean annual precipitation is an
important factor to favour the leaching of soluble compounds to deeper soil
layers. The high mean annual precipitation in subtropical site (1440 mm year⁻¹),
taken together with the high residue input allied to the presence of biopores
formed under NT possibly, favour the leaching of soluble compounds in soil
profile that is adsorbed by mineral of sub-surface layers (Fig. 25). More than half
of the C sequestration was attributable to the increase in C stocks in the sub-
surface soil layer (30–100 cm), which add to the gains in C accumulation
observed in 0–30 cm after 30 years adopting no-tillage and legume cover crops.

<figure><img src="image_34.png" /></figure>

**Figure 27.** Conceptual model of carbon stabilization in mineral-organic associations from labile residue input considering the greater carbon use efficiency of soil fungal community.
9.REFERÊNCIAS BIBLIOGRÁFICAS

ABIVEN, S.; MENASSERI, S.; CHENU, C. The effects of organic inputs over time on soil aggregate stability – A literature analysis. **Soil Biology & Biochemistry**, Elmsford, v. 41, n. 1, p. 1-12, 2009.

ABIVEN, S. et al. Dynamics of aggregate stability and biological binding agents during decomposition of organic materials. **European Journal of Soil Science**, Oxford, v. 58, n. 1, p. 239-247, 2007.

AL-MALIKI, S.; SCULLION, J. Interactions between earthworms and residues of differing quality affecting aggregate stability and microbial dynamics. **Applied Soil Ecology**, Amsterdam, v. 64, p. 56-62, 2013.

ALBURQUERQUE, M.A. et al. Carbon and nitrogen in a Ferralsol under zero-tillage rotations based on cover, cash or hay crops. **Soil Use and Management**, Oxford, v. 31, n. 1, p. 1-9, 2015.

ALHAMEID, A. et al. Soil Organic Carbon Changes Impacted by Crop Rotational Diversity under No-Till Farming in South Dakota, USA. **Soil Science Society of America Journal**, Madison, v. 81, n. 4, p. 868-877, 2017.

ALVAREZ, R. et al. Soil organic carbon, microbial biomass and CO2-C production from three tillage systems. **Soil & Tillage Research**, Amsterdam, v. 33, n. 1, p. 17-28, 1995.

ALVARO-FUENTES, J. et al. Soil Aggregation and Soil Organic Carbon Stabilization: Effects of Management in Semiarid Mediterranean Agroecosystems. **Soil Science Society of America Journal**, Madison, v. 73, n. 5, p. 1519-1529, 2009.

AMADO, T.J.C. et al. Potential of carbon accumulation in no-till soils with intensive use and cover crops in southern Brazil. **Journal of Environmental Quality**, Madison, v. 35, n. 4, p. 1599-1607, 2006.

AMELUNG, W. et al. Combining biomarker with stable isotope analyses for assessing the transformation and turnover of soil organic matter. In: SPARKS,
D. L. (Ed.). **Advances in Agronomy**. San Diego: Elsevier Academic Press Inc., 2008. p.155-250. v. 100.

ANDRUSCHKEWITSCH, R.; KOCH, H.J.; LUDWIG, B. Effect of long-term tillage treatments on the temporal dynamics of water-stable aggregates and on macro-aggregate turnover at three German sites. **Geoderma**, Amsterdam, v. 217-218, p. 57-64, 2014.

ANDRUSCHKEWITSCH, R. et al. Effects of tillage on contents of organic carbon, nitrogen, water-stable aggregates and light fraction for four different long-term trials. **Geoderma**, Amsterdam, v. 192, p. 368-377, 2013.

ANGERS, D.; CHANTIGNY, M. Carbohydrates. **Soil Sampling and Methods of Analysis**. 2nd ed. Boca Raton: CRC Press, 2008. 1264 p.

ANGERS, D.A.; GIROUX, M. Recently deposited organic matter in soil water-stable aggregates. **Soil Science Society of America Journal**, Madison, v. 60, n. 5, p. 1547-1551, 1996.

ANGERS, D.A.; ERIKSEN-HAMEL, N.S. Full-Inversion Tillage and Organic Carbon Distribution in Soil Profiles: A Meta-Analysis All rights reserved. **Soil Science Society of America Journal**, Madison, v. 72, n. 5, p. 1370-1374, 2008.

ANGERS, D.A.; VORONEY, R.P.; CÔTÉ, D. Dynamics of Soil Organic Matter and Corn Residues Affected by Tillage Practices. **Soil Science Society of America Journal**, Madison, v. 59, n. 5, p. 1311-1315, 1995.

ANGERS, D.A.; RECOUS, S.; AITA, C. Fate of carbon and nitrogen in water-stable aggregates during decomposition of (CN)-C-13-N-15-labelled wheat straw in situ. **European Journal of Soil Science**, Oxford, v. 48, n. 2, p. 295-300, 1997.

BAI, Y. et al. Primary production and rain use efficiency across precipitation gradient on the Mongolia Plateau. **Ecology**, Washington, v. 89, n. 8, p. 2140-2153, 2008.

BAKER, J.M. et al. Tillage and soil carbon sequestration - What do we really know? **Agriculture Ecosystems & Environment**, Amsterdam, v. 118, n. 1-4, p. 1-5, 2007.

BALESDENT, J.; MARIOTTI, A.; BOISGONTIER, D. Effect of tillage on soil organic carbon mineralization estimated from 13C abundance in maize fields. **Journal of Soil Science**, Oxford, v. 41, n. 4, p. 587-596, 1990.

BARNARD, R.L.; OSBORNE, C.A.; FIRESTONE, M.K. Responses of soil bacterial and fungal communities to extreme desiccation and rewetting. **Isme Journal**, London, v. 7, n. 11, p. 2229-2241, 2013.
BAYER, C.; MIELNICZUK, J. Caracteristicas químicas do solo afetadas por métodos de preparo e sistemas de cultura. **Revista Brasileira de Ciência do Solo**, Viçosa, v. 21, n. 1, p. 105-112, 1997.

BAYER, C. et al. Organic matter storage in a sandy clay loam Acrisol affected by tillage and cropping systems in southern Brazil. **Soil & Tillage Research**, Amsterdam, v. 54, n. 1-2, p. 101-109, 2000.

BAYER, C. et al. Changes in soil organic matter fractions under subtropical no-till cropping systems. **Soil Science Society of America Journal**, Madison, v. 65, n. 5, p. 1473-1478, 2001.

BAYER, C. et al. Carbon sequestration in two Brazilian Cerrado soils under no-till. **Soil & Tillage Research**, Amsterdam, v. 86, n. 2, p. 237-245, 2006a.

BAYER, C. et al. A method for estimating coefficients of soil organic matter dynamics based on long-term experiments. **Soil & Tillage Research**, Amsterdam, v. 91, n. 1-2, p. 217-226, 2006b.

BAYER, C. et al. Cover Crop Effects Increasing Carbon Storage in a Subtropical No-Till Sandy Acrisol. **Communications in Soil Science and Plant Analysis**, New York, v. 40, n. 9-10, p. 1499-1511, 2009.

BEARE, M.H. et al. Influences of mycelial fungi on soil aggregation and organic matter storage in conventional and no-tillage soils. **Applied Soil Ecology**, Amsterdam, v. 5, n. 3, p. 211-219, 1997.

BEARE, M.H. et al. Microbial and Faunal Interactions and Effects on Litter Nitrogen and Decomposition in Agroecosystems. **Ecological Monographs**, Lawrence, v. 62, n. 4, p. 569-591, 1992.

BLAKE, G.R.; HARTGE, K.H. Bulk density. In: KLUTE, A. (Ed.). **Methods of Soil Analysis, Part 1. Physical and Mineralogical Methods**. Madison: ASA/SSSA. 1986. p. 363-382. v. 5.1.

BLANCO-CANQUI, H.; SCHLEGEL, A.J.; HEER, W.F. Soil-profile distribution of carbon and associated properties in no-till along a precipitation gradient in the central Great Plains. **Agriculture Ecosystems & Environment**, Amsterdam, v. 144, n. 1, p. 107-116, 2011.

BLANCO-MOURE, N. et al. Long-term no-tillage effects on particulate and mineral-associated soil organic matter under rainfed Mediterranean conditions. **Soil Use and Management**, Oxford, v. 29, n. 2, p. 250-259, 2013.

BODDEY, R.M. et al. Carbon accumulation at depth in Ferralsols under zero-till subtropical agriculture. **Global Change Biology**, Oxford, v. 16, n. 2, p. 784-795, 2010.

BOER, W.D. et al. Living in a fungal world: impact of fungi on soil bacterial niche development*. **FEMS Microbiology Reviews**, Oxford, v. 29, n. 4, p. 795-811, 2005.
BRASIL MINISTÉRIO DO MEIO-AMBIENTE. **Intended Nationally Determined Contributions**, iNDC BRASIL. Disponível em: <http://www.mma.gov.br/images/arquivo/80108/BRAZIL%20iNDC%20english%20FINAL.pdf>. Acesso em: 1 set. 2017.

BRASIL MINISTÉRIO DA AGRICULTURA, PECUÁRIA E ABASTECIMENTO (MAPA). **Plano Setorial de Mitigação e de Adaptação às Mudanças Climáticas para a Consolidação de uma Economia de Baixa Emissão de Carbono na Agricultura**: Plano ABC (Agricultura de Baixa Emissão de Carbono). Brasília: MAPA/ACS, 2012. 173 p.

BREMER, E.; VAN KESSEL, C. Seasonal Microbial Biomass Dynamics after Addition of Lentil and Wheat Residues. **Soil Science Society of America Journal**, Madison, v. 56, n. 4, p. 1141-1146, 1992.

BREVILIERI, R.C. **Carbono, nitrogênio e fluxos de N₂O e CH₄ em Latossolo subtropical sob sistemas de preparo e níveis de adubação.** 2016. 100 f.
Tese (Doutorado em Ciência do Solo) - Departamento de Solo, Universidade Federal do Paraná, Curitiba-PR. 2016.

BÜCHI, L. et al. Long and short term changes in crop yield and soil properties induced by the reduction of soil tillage in a long term experiment in Switzerland. **Soil & Tillage Research**, Amsterdam, v. 174, p. 120-129, 2017.

CAMBARDELLA, C.A.; ELLIOTT, E.T. Carbon and Nitrogen Distribution in Aggregates from Cultivated and Native Grassland Soils. **Soil Science Society of America Journal**, Madison, v. 57, n. 4, p. 1071-1076, 1993.

CAMPBELL, C.A. et al. Carbon Storage in Soils of the North American Great Plains. **Agronomy Journal**, Madison, v. 97, n. 2, p. 349-363, 2005.

CARPENEDO, V.; MIELNICZUK, J. Aggregate stability and quality of Dusky Red latosol submitted to different management practices. **Revista Brasileira de Ciência do Solo**, Viçosa, v. 14, n. 1, p. 99-105, 1990.

CATES, A.M. et al. Long-term tillage, rotation and perennialization effects on particulate and aggregate soil organic matter. **Soil & Tillage Research**, Amsterdam, v. 155, p. 371-380, 2016.

CHANTIGNY, M.H. et al. Soil aggregation and fungal and bacterial biomass under annual and perennial cropping systems. **Soil Science Society of America Journal**, Madison, v. 61, n. 1, p. 262-267, 1997.

CHEN, H. et al. Effects of 11 years of conservation tillage on soil organic matter fractions in wheat monoculture in Loess Plateau of China. **Soil & Tillage Research**, Amsterdam, v. 106, n. 1, p. 85-94, 2009.

CHESHIRE, M. **Nature and Origin of Carbohydrates in Soils**. [S.l.]: Academic Press, 1979.
CLAPP, C.E. et al. Soil organic carbon and 13C abundance as related to tillage, crop residue, and nitrogen fertilization under continuous corn management in Minnesota. **Soil & Tillage Research**, Amsterdam, v. 55, n. 3, p. 127-142, 2000.

CONAB. Companhia Nacional de Abastecimento. Disponível em: <http://www.conab.gov.br/conteudos.php>. Acesso em: 25 ago. 2016.

CONCEIÇÃO, P.C.; DIECKOW, J.; BAYER, C. Combined role of no-tillage and cropping systems in soil carbon stocks and stabilization. **Soil & Tillage Research**, Amsterdam, v. 129, p. 40-47, 2013.

CONCEIÇÃO, P.C. et al. Densimetric fractionation with sodium polytungstate to investigate physical protection of soil organic matter. **Revista Brasileira de Ciência do Solo**, Viçosa, v. 32, n. 2, p. 541-549, 2008.

COPPENS, F. et al. Soil moisture, carbon and nitrogen dynamics following incorporation and surface application of labelled crop residues in soil columns. **European Journal of Soil Science**, Oxford, v. 57, n. 6, p. 894-905, 2006.

COTRUFO, M.F. et al. The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter? **Global Change Biology**, Oxford, v. 19, n. 4, p. 988-995, 2013.

COTRUFO, M.F. et al. Formation of soil organic matter via biochemical and physical pathways of litter mass loss. **Nature Geoscience**, London, v. 8, n. 10, p. 776-779, 2015.

COURTIER-MURIAS, D. et al. Unraveling the long-term stabilization mechanisms of organic materials in soils by physical fractionation and NMR spectroscopy. **Agriculture Ecosystems & Environment**, Amsterdam, v. 171, p. 9-18, 2013.

DA SILVA, I.; MIELNICZUK, J. Avaliação do estado de agregação do solo afetado pelo uso agrícola. **Revista Brasileira de Ciência do Solo**, Viçosa, v. 21, n. 2, p. 313-319, 1997.

DE VRIES, F.T. et al. Land use alters the resistance and resilience of soil food webs to drought. **Nature Climate Change**, London, v. 2, p. 276, 2012.

DEEN, W.; KATAKI, P.K. Carbon sequestration in a long-term conventional versus conservation tillage experiment. **Soil & Tillage Research**, Amsterdam, v. 74, n. 2, p. 143-150, 2003.

DENEF, K. et al. Carbon sequestration in microaggregates of no-tillage soils with different clay mineralogy. **Soil Science Society of America Journal**, Madison, v. 68, n. 6, p. 1935-1944, 2004.
DENEF, K. et al. Microaggregate-associated carbon as a diagnostic fraction for management-induced changes in soil organic carbon in two Oxisols. **Soil Biology & Biochemistry**, Amsterdam, v. 39, n. 5, p. 1165-1172, 2007.

DIECKOW, J. et al. Land use, tillage, texture and organic matter stock and composition in tropical and subtropical Brazilian soils. **European Journal of Soil Science**, v. 60, n. 2, p. 240-249, 2009a.

DIECKOW, J. et al. Land use, tillage, texture and organic matter stock and composition in tropical and subtropical Brazilian soils. **European Journal of Soil Science**, Oxford, v. 60, n. 2, p. 240-249, 2009b.

DIEKOW, J. et al. Carbon and nitrogen stocks in physical fractions of a subtropical Acrisol as influenced by long-term no-till cropping systems and N fertilisation. **Plant and Soil**, The Hague, v. 268, n. 1-2, p. 319-328, 2005a.

DIEKOW, J. et al. Soil C and N stocks as affected by cropping systems and nitrogen fertilisation in a southern Brazil Acrisol managed under no-tillage for 17 years. **Soil & Tillage Research**, Amsterdam, v. 81, n. 1, p. 87-95, 2005b.

DIMASSI, B. et al. Long-term effect of contrasted tillage and crop management on soil carbon dynamics during 41 years. **Agriculture, Ecosystems & Environment**, Amsterdam, v. 188, n. 1, p. 134-146, 2014.

DING, X.L. et al. Effects of tillage and crop rotation on soil microbial residues in a rainfed agroecosystem of northeast China. **Soil & Tillage Research**, Amsterdam, v. 114, n. 1, p. 43-49, 2011.

DONG, W. et al. Tillage and residue management effects on soil carbon and CO2 emission in a wheat-corn double-cropping system. **Nutrient Cycling in Agroecosystems**, Dordrecht, v. 83, n. 1, p. 27, 2008.

DORAN, J.W.; ELLIOTT, E.T.; PAUSTIAN, K. Soil microbial activity, nitrogen cycling, and long-term changes in organic carbon pools as related to fallow tillage management. **Soil & Tillage Research**, Amsterdam, v. 49, n. 1, p. 3-18, 1998.

DU, Z.L. et al. Transition from intensive tillage to no-till enhances carbon sequestration in microaggregates of surface soil in the North China Plain. **Soil & Tillage Research**, Amsterdam, v. 146, n. 1, p. 26-31, 2015.

ELLERT, B.H.; BETTANY, J.R. Calculation of organic matter and nutrients stored in soils under contrasting management regimes. **Canadian Journal of Soil Science**, Ottawa, v. 75, n. 4, p. 529-538, 1995.

FABRIZZI, K.P. et al. Protection of soil organic C and N in temperate and tropical soils: effect of native and agroecosystems. **Biogeochemistry**, The Hague, v. 92, n. 1-2, p. 129-143, 2009.

FAO. **World reference base for soil resources 2014**. Rome: FAO, 2015. p. 203
FEBRAPDP. Área do Sistema Plantio Direto. Disponível em: < http://www.febrapdp.org.br>. Acesso em: 26 fev. 2015.

FIDALGO, E.C.C. et al. **Estoque de carbono nos solos do Brasil**. Rio de Janeiro: Embrapa Solos. 2007. 26 p.

FRANCHINI, J.C. et al. Evolution of crop yields in different tillage and cropping systems over two decades in southern Brazil. **Field Crops Research**, Amsterdam, v. 137, n. 1, p. 178-185, 2012.

FREY, S.D.; ELLIOTT, E.T.; PAUSTIAN, K. Bacterial and fungal abundance and biomass in conventional and no-tillage agroecosystems along two climatic gradients. **Soil Biology & Biochemistry**, Amsterdam, v. 31, n. 4, p. 573-585, 1999.

GARCIA-FRANCO, N. et al. Beneficial effects of reduced tillage and green manure on soil aggregation and stabilization of organic carbon in a Mediterranean agroecosystem. **Soil & Tillage Research**, Amsterdam, v. 153, n. 1, p. 66-75, 2015.

GOLCHIN, A. et al. Study of free and occluded particulate organic-matter in soils by solid-state C-13 CP/MAS NMR-Spectroscopy and Scanning Electron-Microscopy. **Australian Journal of Soil Research**, Melbourne, v. 32, n. 2, p. 285-309, 1994.

GORDON, H.; HAYGARTH, P.M.; BARDGETT, R.D. Drying and rewetting effects on soil microbial community composition and nutrient leaching. **Soil Biology & Biochemistry**, Amsterdam, v. 40, n. 2, p. 302-311, 2008.

GRANDY, A.S.; ROBERTSON, G.P. Land-use intensity effects on soil organic carbon accumulation rates and mechanisms. **Ecosystems**, New York, v. 10, n. 1, p. 58-73, 2007.

GRIFFITHS, B.S. et al. Soil microbial community structure: Effects of substrate loading rates. **Soil Biology & Biochemistry**, Amsterdam, v. 31, n. 1, p. 145-153, 1998.

GUGGENBERGER, G.; KAISER, K. Dissolved organic matter in soil: challenging the paradigm of sorptive preservation. **Geoderma**, Amsterdam, v. 113, n. 3, p. 293-310, 2003.

GWENZI, W. et al. Effects of tillage systems on soil organic carbon dynamics, structural stability and crop yields in irrigated wheat (Triticum aestivum L.)- cotton (Gossypium hirsutum L.) rotation in semi-arid Zimbabwe. **Nutrient Cycling in Agroecosystems**, Dordrecht, v. 83, n. 3, p. 211-221, 2008.

HADDAWAY, N.R. et al. How does tillage intensity affect soil organic carbon? A systematic review protocol. **Environmental Evidence**, New York, v. 5, n. 1, p. 1-8, 2016.
HELGASON, B.L.; WALLEY, F.L.; GERMIDA, J.J. No-till soil management increases microbial biomass and alters community profiles in soil aggregates. *Applied Soil Ecology*, Amsterdam, v. 46, n. 3, p. 390-397, 2010.

HELGASON, B.L. et al. Long-term microbial retention of residue C is site-specific and depends on residue placement. *Soil Biology & Biochemistry*, Oxford, v. 68, n. 1, p. 231-240, 2014.

HERMLE, S. et al. The effect of the tillage system on soil organic carbon content under moist, cold-temperate conditions. *Soil & Tillage Research*, Amsterdam, v. 98, n. 1, p. 94-105, 2008.

HOBLEY, E.U.; BALDOCK, J.; WILSON, B. Environmental and human influences on organic carbon fractions down the soil profile. *Agriculture Ecosystems & Environment*, Amsterdam, v. 223, n. 1, p. 152-166, 2016.

HOLLAND, E.A.; COLEMAN, D.C. Litter Placement Effects on Microbial and Organic Matter Dynamics in an Agroecosystem. *Ecology*, v. 68, n. 2, p. 425-433, 1987.

HUGGINS, D.R. et al. Corn-Soybean Sequence and Tillage Effects on Soil Carbon Dynamics and Storage. *Soil Science Society of America Journal*, Madison, v. 71, n. 1, p. 145-154, 2007.

IBGE. INSTITUTO BRASILEIRO DE GEOGRAFIA E ESTATÍSTICA. *Levantamento sistemático da produção agrícola*. Rio de Janeiro-RJ: [IBGE], 2016.

INDA JUNIOR, A.V. et al. Variáveis relacionadas à estabilidade de complexos organo-minerais em solos tropicais e subtropicais brasileiros. *Ciência Rural*, Santa Maria, v. 37, n. 1, p. 1301-1307, 2007.

JACOBS, A. et al. Effect of conventional and minimum tillage on physical and biochemical stabilization of soil organic matter. *Biology and Fertility of Soils*, Berlin, v. 46, n. 7, p. 671-680, 2010.

JANDL, G.; LEINWEBER, P.; SCHULTEN, H.R. Origin and fate of soil lipids in a Phaeozem under rye and maize monoculture in Central Germany. *Biology and Fertility of Soils*, Berlin, v. 43, n. 3, p. 321-332, 2007.

JENSEN, E.S. Barley uptake of N deposited in the rhizosphere of associated field pea. *Soil Biology & Biochemistry*, Amsterdam, v. 28, n. 2, p. 159-168, 1996.

JOHN, B. et al. Storage of organic carbon in aggregate and density fractions of silty soils under different types of land use. *Geoderma*, Amsterdam, v. 128, n. 1-2, p. 63-79, 2005.

KALLENBACH, C.M.; FREY, S.D.; GRANDY, A.S. Direct evidence for microbial-derived soil organic matter formation and its ecophysiological controls. *Nature Communications*, London, v. 7, n. 1, p. 13630, 2016.
KETTLER, T.A. et al. Soil quality assessment after weed-control tillage in a no-till wheat-fallow cropping system. **Soil Science Society of America Journal**, Madison, v. 64, n. 1, p. 339-346, 2000.

KHAN, S.A. et al. The Myth of Nitrogen Fertilization for Soil Carbon Sequestration **Journal of Environmental Quality**, Madison, v. 36, n. 6, p. 1821-1832, 2007.

KIBET, L.C.; BLANCO-CANQUI, H.; JASA, P. Long-term tillage impacts on soil organic matter components and related properties on a Typic Argiudoll. **Soil & Tillage Research**, Amsterdam, v. 155, n. 1, p. 78-84, 2016.

KIRCHMANN, H. et al. Properties of soils in the Swedish long-term fertility experiments: VII. Changes in topsoil and upper subsoil at orja and Fors after 50 years of nitrogen fertilization and manure application. **Acta Agriculturae Scandinavica Section B-Soil and Plant Science**, Copenhagen, v. 63, n. 1, p. 25-36, 2013.

KLEBER, M.; SOLLINS, P.; SUTTON, R. A conceptual model of organo-mineral interactions in soils: self-assembly of organic molecular fragments into zonal structures on mineral surfaces. **Biogeochemistry**, The Hague, v. 85, n. 1, p. 9-24, 2007.

KNICKER, H.; GONZALEZ-VILA, F.J.; GONZALEZ-VAZQUEZ, R. Biodegradability of organic matter in fire-affected mineral soils of Southern Spain. **Soil Biology & Biochemistry**, Amsterdam, v. 56, n. 1, p. 31-39, 2013.

KOGEL-KNABNER, I. The macromolecular organic composition of plant and microbial residues as inputs to soil organic matter. **Soil Biology & Biochemistry**, Amsterdam, v. 34, n. 2, p. 139-162, 2002.

KOGEL-KNABNER, I. et al. Organo-mineral associations in temperate soils: Integrating biology, mineralogy, and organic matter chemistry. **Journal of Plant Nutrition and Soil Science-Zeitschrift Fur Pflanzenernahrung Und Bodenkunde**, Weinheim, v. 171, n. 1, p. 61-82, 2008.

KOPITTKE, P.M. et al. Nitrogen-rich microbial products provide new organo-mineral associations for the stabilization of soil organic matter. **Global Change Biology**, Amsterdam, v. 24, n. 4, p. 1762-1770, 2017.

LAL, R. Soil Carbon Sequestration Impacts on Global Climate Change and Food Security. **Science**, New York, v. 304, n. 5677, p. 1623-1627, 2004a.

LAL, R. Soil carbon sequestration to mitigate climate change. **Geoderma**, v. 123, n. 1-2, p. 1-22, 2004b.

LAL, R. The Plow and Agricultural Sustainability. **Journal of Sustainable Agriculture**, Boca Raton, v. 33, n. 1, p. 66-84, 2009.
LAL, R. Soil carbon sequestration and aggregation by cover cropping. **Journal of Soil and Water Conservation**, Ankeny, v. 70, n. 6, p. 329-339, 2015.

LAL, R.; REICOSKY, D.L.; HANSON, J.D. Evolution of the plow over 10,000 years and the rationale for no-till farming. **Soil & Tillage Research**, Amsterdam, v. 93, n. 1, p. 1-12, 2007.

LAUENROTH, W.K.; BURKE, I.C.; PARUELO, J.M. Patterns of Production and Precipitation-Use Efficiency of Winter Wheat and Native Grasslands in the Central Great Plains of the United States. **Ecosystems**, New York, v. 3, n. 4, p. 344-351, 2000.

LAWRENCE, C.R. et al. Long-term controls on soil organic carbon with depth and time: A case study from the Cowlitz River Chronosequence, WA USA. **Geoderma**, Amsterdam, v. 247-248, p. 73-87, 2015.

LE GUILLOU, C. et al. Linking microbial community to soil water-stable aggregation during crop residue decomposition. **Soil Biology & Biochemistry**, Madison, v. 50, p. 126-133, 2012.

LOVATO, T. et al. Carbon and nitrogen addition related to stocks of these elements in soil and corn yield under management systems. **Revista Brasileira de Ciência do Solo**, Viçosa, v. 28, n. 1, p. 175-187, 2004.

LOWE, L.E. Total and labile polysaccharide analysis of soil. In: CARTER, M. R. (Ed.). **Soil sampling and methods of analysis**. Boca Raton: Lewis Publishers, 1993. p. 373-376.

LUO, Z.; WANG, E.; SUN, O.J. Soil carbon change and its responses to agricultural practices in Australian agro-ecosystems: A review and synthesis. **Geoderma**, Amsterdam, v. 155, n. 3, p. 211-223, 2010.

MACHADO, S.; RHINHART, K.; PETRIE, S. Long-term cropping system effects on carbon sequestration in eastern Oregon. **Journal of Environmental Quality**, Madison, v. 35, n. 4, p. 1548-53, 2006.

MACK, M.C. et al. Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization. **Nature**, London, v. 431, n. 7007, p. 440-443, 2004.

MANNA, M.C. et al. Carbon fractions and productivity under changed climate scenario in soybean-wheat system. **Field Crops Research**, Amsterdam, v. 145, p. 10-20, 2013.

MARSCHNER, B. et al. How relevant is recalcitrance for the stabilization of organic matter in soils? **Journal of Plant Nutrition and Soil Science**, v. 171, n. 1, p. 91-110, 2008.

MARTENS, D.A.; LOEFFELMANN, K.L. Improved accounting of carbohydrate carbon from plants and soils. **Soil Biology & Biochemistry**, Amsterdam, v. 34, n. 10, p. 1393-1399, 2002.
MARTINS, M.D.; ANGERS, D.A. Different plant types for different soil ecosystem services. **Geoderma**, Amsterdam, v. 237, p. 266-269, 2015.

MARTINS, M.D.; ANGERS, D.A.; CORA, J.E. Carbohydrate Composition and Water-Stable Aggregation of an Oxisol as Affected by Crop Sequence under No-Till. **Soil Science Society of America Journal**, Madison, v. 76, n. 2, p. 475-484, 2012a.

MARTINS, M.R.; ANGERS, D.A.; CORA, J.E. Co-accumulation of microbial residues and particulate organic matter in the surface layer of a no-till Oxisol under different crops. **Soil Biology & Biochemistry**, Amsterdam, v. 50, n., p. 208-213, 2012b.

MCCONKEY, B.G. et al. Crop rotation and tillage impact on carbon sequestration in Canadian prairie soils. **Soil & Tillage Research**, Amsterdam, v. 74, n. 1, p. 81-90, 2003.

MEDEIROS, J.C. **Sistemas de culturas adaptados a produtividade, recuperação e conservação do solo.** 1988. 99 f. Dissertação (Mestrado em Agronomia) - Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Porto Alegre, 1988.

MINASNY, B. et al. Soil carbon 4 per mille. **Geoderma**, Amsterdam, v. 292, p. 59-86, 2017.

MINOSHIMA, H. et al. Soil Food Webs and Carbon Dynamics in Response to Conservation Tillage in California. **Soil Science Society of America Journal**, Madison, v. 71, n. 3, p. 952-963, 2007.

MIRANDA, E. et al. Long-Term Changes in Soil Carbon Stocks in the Brazilian Cerrado Under Commercial Soybean. **Land Degradation & Development**, Chichester, v. 27, n. 6, p. 1586-1594, 2016.

MONREAL, C.M.; SCHULTEN, H.R.; KODAMA, H. Age, turnover and molecular diversity of soil organic matter in aggregates of a Gleysol. **Canadian Journal of Soil Science**, Ottawa, v. 77, n. 3, p. 379-388, 1997.

NELSON, P.W.; SOMMERS, C.E. Total C, organic C and organic matter. In: PAGE, A. L. (Ed.). **Methods of Soil Analysis (chemical)**, Madison, WI: Soil Science Society of America, 1996. p. 539-579.

OADES, J.M.; WAGNER, G.H. Biosynthesis of sugars in soils incubated with C-14 Glucose and C-14 Dextran. **Soil Science Society of America Proceedings**, Madison, v. 35, n. 6, p. 914-917, 1971.

OBOUR, A.K. et al. Changes in soil surface chemistry after fifty years of tillage and nitrogen fertilization. **Geoderma**, Amsterdam, v. 308, p. 46-53, 2017.

ONO, K., et al. Environmental Controls on Fallow Carbon Dioxide Flux in a Single-Crop Rice Paddy, Japan. **Land Degradation & Development**, Chichester, v. 26, n. 4, p. 331-339, 2015.
OTA, M.; NAGAI, H.; KOARASHI, J. Root and dissolved organic carbon controls on subsurface soil carbon dynamics: A model approach. **Journal of Geophysical Research-Biogeosciences**, Washington, D.C., v. 118, n. 4, p. 1646-1659, 2013.

PAUSTIAN, K. et al. Agricultural soils as a sink to mitigate CO2 emissions. **Soil Use and Management**, Oxford, v. 13, n. 4, p. 230-244, 1997.

PITTELKOW, C.M. et al. When does no-till yield more? A global meta-analysis. **Field Crops Research**, Amsterdam, v. 183, n. 1, p. 156-168, 2015.

PIVA, J.T. et al. No-till reduces global warming potential in a subtropical Ferralsol. **Plant and Soil**, The Hague, v. 361, n. 1-2, p. 359-373, 2012.

PLAZA-BONILLA, D.; CANTERO-MARTINEZ, C.; ALVARO-FUENTES, J. Tillage effects on soil aggregation and soil organic carbon profile distribution under Mediterranean semi-arid conditions. **Soil Use and Management**, Chichester, v. 26, n. 4, p. 465-474, 2010.

PLAZA-BONILLA, D. et al. Soil aggregation and organic carbon protection in a no-tillage chronosequence under Mediterranean conditions. **Geoderma**, Amsterdam, v. 193-194, n. 1, p. 76-82, 2013.

PLAZA, C. et al. Physical, chemical, and biochemical mechanisms of soil organic matter stabilization under conservation tillage systems: A central role for microbes and microbial by-products in C sequestration. **Soil Biology & Biochemistry**, Oxford, v. 57, n. 1, p. 124-134, 2013.

POIRIER, V. et al. Interactive Effects of Tillage and Mineral Fertilization on Soil Carbon Profiles. **Soil Science Society of America Journal**, Madison, v. 73, n. 1, p. 255-261, 2009.

POTTER, K.N. et al. Residue removal and climatic effects on soil carbon content of no-till soils. **Journal of Soil and Water Conservation**, Ankeny, v. 62, n. 2, p. 110-114, 2007.

POWLSON, D.S. et al. Does conservation agriculture deliver climate change mitigation through soil carbon sequestration in tropical agro-ecosystems? **Agriculture, Ecosystems & Environment**, Amsterdam, v. 220, n.1, p. 164-174, 2016.

PUGET, P.; ANGERS, D.A.; CHENU, C. Nature of carbohydrates associated with water-stable aggregates of two cultivated soils. **Soil Biology & Biochemistry**, Amsterdam, v. 31, n. 1, p. 55-63, 1998.

PUGET, P.; CHENU, C.; BALESDENT, J. Dynamics of soil organic matter associated with particle-size fractions of water-stable aggregates. **European Journal of Soil Science**, Oxford, v. 51, n. 4, p. 595-605, 2000.
QUÉNÉA, K. et al. Molecular and isotopic study of lipids in particle size fractions of a sandy cultivated soil (Cestas cultivation sequence, southwest France): Sources, degradation, and comparison with Cestas forest soil. **Organic Geochemistry**, Oxford, v. 37, n. 1, p. 20-44, 2006.

RABBI, S.M.F. et al. Aggregate hierarchy and carbon mineralization in two Oxisols of New South Wales, Australia. **Soil & Tillage Research**, Amsterdam, v. 146, p. 193-203, 2015.

RAPHAEL, J.P.A. et al. Soil organic matter in crop rotations under no-till. **Soil & Tillage Research**, Amsterdam, v. 155, p. 45-53, 2016.

RAZAFIMBELO, T.M. et al. Aggregate associated-C and physical protection in a tropical clayey soil under Malagasy conventional and no-tillage systems. **Soil & Tillage Research**, Amsterdam, v. 98, n. 2, p. 140-149, 2008.

REINERTSEN, S.A. et al. Role of available carbon and nitrogen in determining the rate of wheat straw decomposition. **Soil Biology & Biochemistry**, Amsterdam, v. 16, n. 5, p. 459-464, 1984.

REIS, C.E.S.D. et al. Carbon sequestration in clay and silt fractions of Brazilian soils under conventional and no-tillage systems. **Scientia Agricola**, Piracicaba, v. 71, p. 292-301, 2014.

ROGELJ, J. et al. Paris Agreement climate proposals need a boost to keep warming well below 2 °C. **Nature**, London, v. 534, n. 7609, p. 631-639, 2016.

ROUSK, J.; BROOKES, P.C.; BAATH, E. Contrasting soil pH effects on fungal and bacterial growth suggest functional redundancy in carbon mineralization. **Applied Environmental Microbiology**, Washington, v. 75, n. 6, p. 1589-96, 2009.

RUMPEL, C.; KOGEL-KNABNER, I. Deep soil organic matter-a key but poorly understood component of terrestrial C cycle. **Plant and Soil**, The Hague, v. 338, n. 1-2, p. 143-158, 2011.

RUMPEL, C.; EUSTERHUES, K.; KOGEL-KNABNER, I. Non-cellulosic neutral sugar contribution to mineral associated organic matter in top- and subsoil horizons of two acid forest soils. **Soil Biology & Biochemistry**, Amsterdam, v. 42, n. 2, p. 379-382, 2010.

SCHEUBLIN, T.R. et al. Nonlegumes, legumes, and root nodules harbor different arbuscular mycorrhizal fungal communities. **Applied Environmental Microbiology**, Washington, v. 70, n. 10, p. 6240-6246, 2004.

SIMPSON, R.T. et al. Preferential Accumulation of Microbial Carbon in Aggregate Structures of No-Tillage Soils. **Soil Science Society of America Journal**, Madison, v. 68, n. 4, p. 1249-1255, 2004.
SISTI, C.P.J. et al. Change in carbon and nitrogen stocks in soil under 13 years of conventional or zero tillage in southern Brazil. **Soil & Tillage Research**, Amsterdam, v. 76, n. 1, p. 39-58, 2004.

SIX, J.; ELLIOTT, E.T.; PAUSTIAN, K. Aggregate and soil organic matter dynamics under conventional and no-tillage systems. **Soil Science Society of America Journal**, Madison, v. 63, n. 5, p. 1350-1358, 1999.

SIX, J.; ELLIOTT, E.T.; PAUSTIAN, K. Soil macroaggregate turnover and microaggregate formation: a mechanism for C sequestration under no-tillage agriculture. **Soil Biology & Biochemistry**, Amsterdam, v. 32, n. 14, p. 2099-2103, 2000.

SIX, J. et al. Soil organic matter, biota and aggregation in temperate and tropical soils - Effects of no-tillage. **Agronomie**, Reims, v. 22, n. 7-8, p. 755-775, 2002.

SPIELVOGEL, S.; PRIETZEL, J.; KÖGEL-KNABNER, I. Soil organic matter stabilization in acidic forest soils is preferential and soil type-specific. **European Journal of Soil Science**, Oxford, v. 59, n. 4, p. 674-692, 2008.

STEINBACH, H.S.; ALVAREZ, R. Changes in soil organic carbon contents and nitrous oxide emissions after introduction of no-till in Pampean agroecosystems. **Journal of Environmental Quality**, Madison, v. 35, n. 1, p. 3-13, 2006.

TOMAZI, M.; BAYER, C.; CONCEIÇÃO, P.C. O uso de amostras peneiradas a dois milímetros subestima a proteção física da matéria orgânica no solo. **Revista Brasileira de Ciência do Solo**, Viçosa, v. 35, s.n., p. 1323-1329, 2011.

TORRES-SALLAN, G. et al. Clay illuviation provides a long-term sink for C sequestration in subsoils. **Scientific Reports**, London, v. 7, p. 45635, 2017.

VAN BERGEN, P.F. et al. Organic geochemical studies of soils from the Rothamsted Classical Experiments—IV. Preliminary results from a study of the effect of soil pH on organic matter decay. **Organic Geochemistry**, Oxford, v. 29, n. 5, p. 1779-1795, 1998.

VARVEL, G.E.; WILHELM, W.W. Long-Term Soil Organic Carbon as Affected by Tillage and Cropping Systems. **Soil Science Society of America Journal**, Madison, v. 74, n. 3, p. 915-921, 2010.

VELOSO, M.G. et al. Legume cover crops under no-tillage favor organomineral association in microaggregates and soil C accumulation. **Soil & Tillage Research**, Amsterdam, s.v., s.n., s.p., Submitted-a.

VELOSO, M.G. et al. High carbon sequestration in subtropical soil profiles under no-tillage with legume cover crop. **Agriculture Ecosystems & Environment**, Amsterdam, s.v., s.n., s.p., Submitted-b.
VENTEREA, R.T. et al. Carbon and Nitrogen Storage are Greater under Biennial Tillage in a Minnesota Corn-Soybean Rotation. **Soil Science Society of America Journal**, Madison, v. 70, n. 5, p. 1752-1762, 2006.

VIEIRA, F.C.B. et al. Building Up Organic Matter in a Subtropical Paleudult under Legume Cover-Crop-Based Rotations. **Soil Science Society of America Journal**, Madison, v. 73, n. 5, p. 1699-1706, 2009.

VIRTO, I. et al. Carbon input differences as the main factor explaining the variability in soil organic C storage in no-tilled compared to inversion tillied agrosystems. **Biogeochemistry**, Amsterdam, v. 108, n. 1, p. 17-26, 2012.

VON LUTZOW, M. et al. Stabilization of organic matter in temperate soils: mechanisms and their relevance under different soil conditions - a review. **European Journal of Soil Science**, Oxford, v. 57, n. 4, p. 426-445, 2006.

WALIA, M.K. et al. Deep soil carbon after 44 years of tillage and fertilizer management in southern Illinois compared to forest and restored prairie soils. **Journal of Soil and Water Conservation**, Washington, v. 72, n. 4, p. 405-415, 2017.

WANG, Q. et al. Soil chemical properties and microbial biomass after 16 years of no-tillage farming on the Loess Plateau, China. **Geoderma**, Amsterdam, v. 144, n. 3, p. 502-508, 2008.

WANG, Y. et al. Soil organic carbon in deep profiles under Chinese continental monsoon climate and its relations with land uses. **Ecological Engineering**, Amsterdam, v. 82, n., p. 361-367, 2015.

WEST, T.O.; POST, W.M. Soil organic carbon sequestration rates by tillage and crop rotation: A global data analysis. **Soil Science Society of America Journal**, Madison, v. 66, n. 6, p. 1930-1946, 2002.

WIESENBERG, G.L.B. et al. Source and turnover of organic matter in agricultural soils derived from n-alkane/n-carboxylic acid compositions and C-isotope signatures. **Organic Geochemistry**, Oxford, v. 35, n. 11-12, p. 1371-1393, 2004.

XU, S. et al. Effect of tillage practices on structural properties and content of organic carbon in tilth soil. **Zhongguo Shengtai Nongye Xuebao / Chinese Journal of Eco-Agriculture**, Beijing, v. 17, n. 2, p. 203-208, 2009.

XU, Y.; CHEN, W.; SHEN, Q. Soil Organic Carbon and Nitrogen Pools Impacted by Long-Term Tillage and Fertilization Practices. **Communications in Soil Science and Plant Analysis**, New York, v. 38, n. 3-4, p. 347-357, 2007.

YAMASHITA, T. et al. Organic matter in density fractions of water-stable aggregates in silty soils: Effect of land use. **Soil Biology & Biochemistry**, Amsterdam, v. 38, n. 11, p. 3222-3234, 2006.
YANG, X.-M.; WANDER, M.M. Tillage effects on soil organic carbon distribution and storage in a silt loam soil in Illinois. **Soil & Tillage Research**, Amsterdam, v. 52, n. 1, p. 1-9, 1999.

YANG, X.M.; KAY, B.D. Rotation and tillage effects on soil organic carbon sequestration in a typic Haplustalf in Southern Ontario. **Soil & Tillage Research**, Amsterdam, v. 59, n. 3, p. 107-114, 2001.

YU, H. et al. Decreasing Nitrogen Fertilizer Input Had Little Effect on Microbial Communities in Three Types of Soils. **Plos One**, San Francisco, v. 11, n. 3, p. e0151622, 2016.

ZANATTA, J.A. et al. Soil organic carbon accumulation and carbon costs related to tillage, cropping systems and nitrogen fertilization in a subtropical Acrisol. **Soil & Tillage Research**, Amsterdam, v. 94, n. 2, p. 510-519, 2007.

ZELLES, L. The simultaneous deterioration of muramic acid and glucosamine in soil by High-Performance Liquid Chromatography with precolumn fluorescence derivatization. **Biology and Fertility of Soils**, Berlin, v. 6, n. 2, p. 125-130, 1988.

ZINN, Y.L.; LAL, R.; RESCK, D.V.S. Texture and organic carbon relations described by a profile pedotransfer function for Brazilian Cerrado soils. **Geoderma**, Amsterdam, v. 127, n. 1, p. 168-173, 2005.

ZOTARELLI, L. et al. Impact of tillage and crop rotation on aggregate-associated carbon in two oxisols. **Soil Science Society of America Journal**, Madison, v. 69, n. 2, p. 482-491, 2007.
# 10. APENDICES

**Apêndice 1.** Densidade (g dm⁻³) de um Argissolo Vermelho, em dois métodos de preparo e três sistemas de cultura, trinta anos após o início do experimento.

<table><thead><tr><th rowspan="3">Tratamentos</th><th colspan="4">Dose N</th><th colspan="4">0 kg N ha⁻¹ no milho</th></tr><tr><th rowspan="2">Camadas</th><th colspan="3">Repetição</th><th rowspan="2">Média</th><th colspan="3">Repetição</th><th rowspan="2">Média</th></tr><tr><th>I</th><th>II</th><th>III</th><th>I</th><th>II</th><th>III</th></tr></thead><tbody><tr><td rowspan="7">PC A/M</td><td>0 - 5</td><td>1.52</td><td>1.51</td><td>1.43</td><td>1.49</td><td rowspan="7">PD A/M</td><td>1.43</td><td>1.44</td><td>1.40</td><td>1.42</td></tr><tr><td>5 - 10</td><td>1.69</td><td>1.62</td><td>1.69</td><td>1.67</td><td>1.58</td><td>1.70</td><td>1.60</td><td>1.63</td></tr><tr><td>10 - 15</td><td>1.72</td><td>1.73</td><td>1.69</td><td>1.71</td><td>1.62</td><td>1.75</td><td>1.61</td><td>1.66</td></tr><tr><td>15 - 20</td><td>1.75</td><td>1.75</td><td>1.75</td><td>1.75</td><td>1.68</td><td>1.73</td><td>1.70</td><td>1.70</td></tr><tr><td>20 - 30</td><td>1.70</td><td>1.72</td><td>1.71</td><td>1.71</td><td>1.57</td><td>1.69</td><td>1.56</td><td>1.61</td></tr><tr><td>30 - 50</td><td>1.57</td><td>1.57</td><td>1.57</td><td>1.57</td><td>1.55</td><td>1.66</td><td>1.49</td><td>1.57</td></tr><tr><td>50 - 75</td><td>1.50</td><td>1.53</td><td>1.53</td><td>1.52</td><td>1.49</td><td>1.58</td><td>1.43</td><td>1.50</td></tr><tr><td rowspan="7">PC V/M</td><td>0 - 5</td><td>1.49</td><td>1.47</td><td>1.42</td><td>1.46</td><td rowspan="7">PD V/M</td><td>1.32</td><td>1.32</td><td>1.23</td><td>1.29</td></tr><tr><td>5 - 10</td><td>1.68</td><td>1.70</td><td>1.61</td><td>1.67</td><td>1.52</td><td>1.59</td><td>1.55</td><td>1.55</td></tr><tr><td>10 - 15</td><td>1.72</td><td>1.75</td><td>1.63</td><td>1.70</td><td>1.54</td><td>1.66</td><td>1.64</td><td>1.61</td></tr><tr><td>15 - 20</td><td>1.73</td><td>1.74</td><td>1.68</td><td>1.72</td><td>1.57</td><td>1.68</td><td>1.68</td><td>1.64</td></tr><tr><td>20 - 30</td><td>1.67</td><td>1.64</td><td>1.61</td><td>1.64</td><td>1.55</td><td>1.57</td><td>1.59</td><td>1.57</td></tr><tr><td>30 - 50</td><td>1.59</td><td>1.52</td><td>1.61</td><td>1.57</td><td>1.52</td><td>1.54</td><td>1.49</td><td>1.52</td></tr><tr><td>50 - 75</td><td>1.53</td><td>1.47</td><td>1.59</td><td>1.53</td><td>1.50</td><td>1.51</td><td>1.49</td><td>1.50</td></tr><tr><td rowspan="7">PC A+V/M+C</td><td>0 - 5</td><td>1.53</td><td>1.44</td><td>1.54</td><td>1.50</td><td rowspan="7">PD A+V/M+C</td><td>1.27</td><td>1.15</td><td>1.20</td><td>1.21</td></tr><tr><td>5 - 10</td><td>1.55</td><td>1.65</td><td>1.67</td><td>1.62</td><td>1.59</td><td>1.48</td><td>1.53</td><td>1.53</td></tr><tr><td>10 - 15</td><td>1.62</td><td>1.68</td><td>1.68</td><td>1.66</td><td>1.63</td><td>1.61</td><td>1.62</td><td>1.62</td></tr><tr><td>15 - 20</td><td>1.63</td><td>1.70</td><td>1.76</td><td>1.70</td><td>1.67</td><td>1.68</td><td>1.65</td><td>1.67</td></tr><tr><td>20 - 30</td><td>1.53</td><td>1.62</td><td>1.69</td><td>1.61</td><td>1.60</td><td>1.60</td><td>1.61</td><td>1.60</td></tr><tr><td>30 - 50</td><td>1.56</td><td>1.58</td><td>1.62</td><td>1.58</td><td>1.49</td><td>1.50</td><td>1.44</td><td>1.48</td></tr><tr><td>50 - 75</td><td>1.51</td><td>1.54</td><td>1.50</td><td>1.52</td><td>1.45</td><td>1.49</td><td>1.47</td><td>1.47</td></tr><tr><td></td><td>75 - 100</td><td>1.44</td><td>1.51</td><td>1.42</td><td>1.46</td><td>1.42</td><td>1.46</td><td>1.42</td><td>1.43</td></tr></tbody></table>
<table><caption>**Apêndice 2.** Teores de carbono orgânico total¹ ((g dm⁻³) e densidade (DS) de um Argissolo Vermelho, em dois métodos de preparo e três sistemas de cultura, cinco anos após o início do experimento. (Bayer & Mielniczuk, 1997).</caption><thead><tr><th rowspan="3">Tratamentos</th><th colspan="5">Dose N</th><th colspan="5">0 kg N ha<sup>-1</sup> no milho</th><th colspan="5">120 kg N ha<sup>-1</sup> no milho</th></tr><tr><th rowspan="2">Camadas</th><th colspan="3">Repetição</th><th rowspan="2">Média</th><th rowspan="2">DS</th><th colspan="3">Repetição</th><th colspan="3">Média</th><th rowspan="2">DS</th></tr><tr><th>I</th><th>II</th><th>III</th><th>I</th><th>II</th><th>III</th></tr></thead><tbody><tr><td rowspan="3">PC A/M</td><td>0 - 2,5</td><td>1.09</td><td>1.12</td><td>1.05</td><td>1.09</td><td>1.52</td><td>1.31</td><td>1.17</td><td>1.04</td><td>1.17</td><td>1.52</td></tr><tr><td>2,5 - 7</td><td>1.12</td><td>1.07</td><td>0.98</td><td>1.06</td><td>1.69</td><td>1.15</td><td>1.17</td><td>1.10</td><td>1.14</td><td>1.69</td></tr><tr><td>7,5 - 17,5</td><td>1.20</td><td>1.17</td><td>0.99</td><td>1.12</td><td>1.72</td><td>1.21</td><td>1.11</td><td>1.06</td><td>1.13</td><td>1.72</td></tr><tr><td rowspan="3">PC A+T/M</td><td>0 - 2,5</td><td>1.21</td><td>1.13</td><td>1.10</td><td>1.15</td><td>1.52</td><td>1.19</td><td>1.17</td><td>1.29</td><td>1.22</td><td>1.52</td></tr><tr><td>2,5 - 7</td><td>1.22</td><td>1.09</td><td>1.14</td><td>1.15</td><td>1.69</td><td>1.23</td><td>1.58</td><td>1.28</td><td>1.36</td><td>1.69</td></tr><tr><td>7,5 - 17,5</td><td>1.05</td><td>0.90</td><td>1.16</td><td>1.04</td><td>1.72</td><td>0.95</td><td>0.90</td><td>1.06</td><td>0.97</td><td>1.72</td></tr><tr><td rowspan="3">PC A+T/M+C</td><td>0 - 2,5</td><td>1.22</td><td>1.23</td><td>1.13</td><td>1.19</td><td>1.52</td><td>1.27</td><td>1.26</td><td>1.10</td><td>1.21</td><td>1.52</td></tr><tr><td>2,5 - 7</td><td>1.21</td><td>1.16</td><td>1.12</td><td>1.16</td><td>1.69</td><td>1.25</td><td>1.18</td><td>1.08</td><td>1.17</td><td>1.69</td></tr><tr><td>7,5 - 17,5</td><td>0.95</td><td>0.92</td><td>0.86</td><td>0.91</td><td>1.72</td><td>1.04</td><td>0.98</td><td>0.94</td><td>0.99</td><td>1.72</td></tr><tr><td rowspan="3">PD A/M</td><td>0 - 2,5</td><td>1.39</td><td>1.78</td><td>1.39</td><td>1.52</td><td>1.52</td><td>1.57</td><td>1.64</td><td>1.62</td><td>1.61</td><td>1.52</td></tr><tr><td>2,5 - 7</td><td>1.07</td><td>1.19</td><td>1.16</td><td>1.14</td><td>1.69</td><td>1.11</td><td>1.29</td><td>1.26</td><td>1.22</td><td>1.69</td></tr><tr><td>7,5 - 17,5</td><td>0.82</td><td>1.02</td><td>0.88</td><td>0.91</td><td>1.72</td><td>0.08</td><td>0.09</td><td>1.05</td><td>0.41</td><td>1.72</td></tr><tr><td rowspan="3">PD A+T/M</td><td>0 - 2,5</td><td>1.63</td><td>2.00</td><td>1.62</td><td>1.75</td><td>1.52</td><td>2.04</td><td>2.16</td><td>2.21</td><td>2.14</td><td>1.52</td></tr><tr><td>2,5 - 7</td><td>1.31</td><td>1.24</td><td>1.25</td><td>1.27</td><td>1.69</td><td>1.28</td><td>1.53</td><td>1.29</td><td>1.37</td><td>1.69</td></tr><tr><td>7,5 - 17,5</td><td>0.09</td><td>0.10</td><td>0.09</td><td>0.09</td><td>1.72</td><td>0.94</td><td>0.99</td><td>0.94</td><td>0.96</td><td>1.72</td></tr><tr><td rowspan="3">PC A+T/M+C</td><td>0 - 2,5</td><td>1.82</td><td>2.24</td><td>1.92</td><td>1.99</td><td>1.52</td><td>1.97</td><td>1.99</td><td>1.95</td><td>1.97</td><td>1.52</td></tr><tr><td>2,5 - 7</td><td>1.17</td><td>1.36</td><td>1.33</td><td>1.29</td><td>1.69</td><td>1.27</td><td>1.36</td><td>1.35</td><td>1.33</td><td>1.69</td></tr><tr><td>7,5 - 17,5</td><td>0.84</td><td>0.91</td><td>0.95</td><td>0.90</td><td>1.72</td><td>0.92</td><td>1.02</td><td>0.87</td><td>0.94</td><td>1.72</td></tr></tbody></table>
<table><caption>**Apêndice 3.** Teores de carbono orgânico total<fnref n="1" /> (g kg⁻<fnref n="1" />) e densidade (DS) de um Argissolo Vermelho, em dois métodos de preparo e três sistemas de cultura, nove anos após o início do experimento.</caption><thead><tr><th rowspan="3">Tratamentos</th><th colspan="1">Dose N</th><th colspan="3">0 kg N ha<sup>-1</sup> no milho</th><th rowspan="3">Média</th><th rowspan="3">DS</th></tr><tr><th rowspan="2">Camadas</th><th colspan="3">Repetição</th></tr><tr><th>I</th><th>II</th><th>III</th></tr></thead><tbody><tr><td rowspan="5">PC A/M</td><td>0 - 2,5</td><td>16.70</td><td>16.90</td><td>15.60</td><td>16.40</td><td>1.44</td></tr><tr><td>2,5 - 5</td><td>15.90</td><td>15.60</td><td>14.80</td><td>15.43</td><td>1.54</td></tr><tr><td>5 - 7,5</td><td>15.70</td><td>16.90</td><td>14.20</td><td>15.60</td><td>1.54</td></tr><tr><td>7,5 - 12,5</td><td>14.60</td><td>15.40</td><td>13.50</td><td>14.50</td><td>1.52</td></tr><tr><td>12,5 - 17,5</td><td>15.10</td><td>15.40</td><td>14.60</td><td>15.03</td><td>1.52</td></tr><tr><td rowspan="5">PC A+T/M</td><td>0 - 2,5</td><td>17.70</td><td>16.40</td><td>17.00</td><td>17.03</td><td></td></tr><tr><td>2,5 - 5</td><td>15.60</td><td>14.80</td><td>16.70</td><td>15.70</td><td></td></tr><tr><td>5 - 7,5</td><td>15.90</td><td>15.10</td><td>16.20</td><td>15.73</td><td></td></tr><tr><td>7,5 - 12,5</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>12,5 - 17,5</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="5">PC A+T/M+C</td><td>0 - 2,5</td><td>17.50</td><td>20.70</td><td>16.60</td><td>18.27</td><td>1.44</td></tr><tr><td>2,5 - 5</td><td>20.20</td><td>18.00</td><td>17.80</td><td>18.67</td><td>1.54</td></tr><tr><td>5 - 7,5</td><td>18.30</td><td>17.20</td><td>16.10</td><td>17.20</td><td>1.54</td></tr><tr><td>7,5 - 12,5</td><td>18.20</td><td>19.10</td><td>14.90</td><td>17.40</td><td>1.52</td></tr><tr><td>12,5 - 17,5</td><td>17.40</td><td>16.20</td><td>15.40</td><td>16.33</td><td>1.52</td></tr><tr><td rowspan="5">PD A/M</td><td>0 - 2,5</td><td>22.50</td><td>22.00</td><td>25.00</td><td>23.17</td><td>1.55</td></tr><tr><td>2,5 - 5</td><td>19.00</td><td>1705.00</td><td>20.20</td><td>581.40</td><td>1.58</td></tr><tr><td>5 - 7,5</td><td>15.70</td><td>15.40</td><td>17.30</td><td>16.13</td><td>1.58</td></tr><tr><td>7,5 - 12,5</td><td>14.90</td><td>15.80</td><td>15.80</td><td>15.50</td><td>1.68</td></tr><tr><td>12,5 - 17,5</td><td>14.30</td><td>14.30</td><td>15.10</td><td>14.57</td><td>1.68</td></tr><tr><td rowspan="5">PD A+T/M</td><td>0 - 2,5</td><td>29.50</td><td>31.30</td><td>31.00</td><td>30.60</td><td></td></tr><tr><td>2,5 - 5</td><td>20.70</td><td>21.60</td><td>19.30</td><td>20.53</td><td></td></tr><tr><td>5 - 7,5</td><td>15.50</td><td>17.60</td><td>17.00</td><td>16.70</td><td></td></tr><tr><td>7,5 - 12,5</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>12,5 - 17,5</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="5">PC A+T/M+C</td><td>0 - 2,5</td><td>36.40</td><td>34.80</td><td>35.90</td><td>35.70</td><td>1.55</td></tr><tr><td>2,5 - 5</td><td>26.00</td><td>28.80</td><td>24.10</td><td>26.30</td><td>1.58</td></tr><tr><td>5 - 7,5</td><td>19.30</td><td>21.80</td><td>19.60</td><td>20.23</td><td>1.58</td></tr><tr><td>7,5 - 12,5</td><td>17.90</td><td>19.20</td><td>18.50</td><td>18.53</td><td>1.68</td></tr><tr><td>12,5 - 17,5</td><td>15.80</td><td>16.70</td><td>16.30</td><td>16.27</td><td>1.68</td></tr><tr><td></td><td>17,5 - 30</td><td>14.40</td><td>15.10</td><td>14.80</td><td>14.77</td><td>1.62</td></tr></tbody></table>

<footnote n="1">¹ Fonte: Bayer et al. (2000).</footnote>
<table><caption>**Apêndice 4.** Teores de carbono orgânico total (g dm⁻³) de um Argissolo Vermelho, em dois métodos de preparo e três sistemas de cultura, treze anos após o início do experimento. (Lovato et al., 2004)</caption><thead><tr><th rowspan="3">Tratamentos</th><th colspan="5">0 kg N ha<sup>-1</sup> no milho</th><th colspan="5">180 kg N ha<sup>-1</sup> no milho</th></tr><tr><th rowspan="2">Camadas</th><th colspan="3">Repetição</th><th rowspan="2">Média</th><th rowspan="2">DS</th><th colspan="3">Repetição</th><th rowspan="2">DS</th></tr><tr><th>I</th><th>II</th><th>III</th><th>I</th><th>II</th><th>III</th></tr></thead><tbody><tr><td rowspan="5">PC A/M</td><td>0 - 2.5</td><td>1.20</td><td>1.12</td><td>1.26</td><td>1.19</td><td>1.44</td><td>1.45</td><td>1.40</td><td>1.44</td><td>1.43</td></tr><tr><td>2.5 - 5</td><td>0.98</td><td>1.01</td><td>0.82</td><td>0.94</td><td>1.54</td><td>1.22</td><td>1.26</td><td>1.17</td><td>1.22</td></tr><tr><td>5 - 7.5</td><td>1.05</td><td>1.05</td><td>0.81</td><td>0.97</td><td>1.54</td><td>1.04</td><td>1.08</td><td>0.97</td><td>1.03</td></tr><tr><td>7.5 - 12.5</td><td>0.96</td><td>0.86</td><td>0.99</td><td>0.94</td><td>1.52</td><td>1.07</td><td>1.12</td><td>1.03</td><td>1.07</td></tr><tr><td>12.5 - 17.5</td><td>0.94</td><td>1.03</td><td>0.84</td><td>0.94</td><td>1.52</td><td>1.12</td><td>1.08</td><td>0.93</td><td>1.04</td></tr><tr><td></td><td>17.5 - 30</td><td>1.00</td><td>0.94</td><td>0.89</td><td>0.94</td><td>1.62</td><td>0.96</td><td>1.16</td><td>1.10</td><td>1.07</td></tr><tr><td rowspan="5">PC V/M</td><td>0 - 2.5</td><td>1.51</td><td>1.49</td><td>1.50</td><td>1.50</td><td>1.44</td><td>1.32</td><td>1.48</td><td>1.53</td><td>1.44</td></tr><tr><td>2.5 - 5</td><td>1.02</td><td>1.08</td><td>1.03</td><td>1.04</td><td>1.54</td><td>1.17</td><td>1.35</td><td>1.23</td><td>1.25</td></tr><tr><td>5 - 7.5</td><td>1.03</td><td>1.05</td><td>1.05</td><td>1.04</td><td>1.54</td><td>1.12</td><td>1.22</td><td>1.22</td><td>1.19</td></tr><tr><td>7.5 - 12.5</td><td>0.92</td><td>1.01</td><td>0.96</td><td>0.96</td><td>1.52</td><td>1.12</td><td>1.12</td><td>1.21</td><td>1.15</td></tr><tr><td>12.5 - 17.5</td><td>1.00</td><td>0.93</td><td>0.89</td><td>0.94</td><td>1.52</td><td>0.93</td><td>1.19</td><td>1.14</td><td>1.09</td></tr><tr><td></td><td>17.5 - 30</td><td>0.95</td><td>0.99</td><td>0.95</td><td>0.96</td><td>1.62</td><td>0.90</td><td>1.08</td><td>1.10</td><td>1.03</td></tr><tr><td rowspan="5">PC A+V/M+C</td><td>0 - 2.5</td><td>1.47</td><td>1.68</td><td>1.37</td><td>1.51</td><td>1.44</td><td>1.76</td><td>1.58</td><td>1.34</td><td>1.56</td></tr><tr><td>2.5 - 5</td><td>1.37</td><td>1.15</td><td>1.20</td><td>1.24</td><td>1.54</td><td>1.28</td><td>1.30</td><td>1.14</td><td>1.24</td></tr><tr><td>5 - 7.5</td><td>1.26</td><td>0.98</td><td>1.13</td><td>1.12</td><td>1.54</td><td>1.17</td><td>1.12</td><td>1.08</td><td>1.12</td></tr><tr><td>7.5 - 12.5</td><td>1.15</td><td>0.92</td><td>1.13</td><td>1.07</td><td>1.52</td><td>0.99</td><td>0.99</td><td>0.91</td><td>0.96</td></tr><tr><td>12.5 - 17.5</td><td>0.99</td><td>0.90</td><td>1.12</td><td>1.00</td><td>1.52</td><td>1.70</td><td>1.52</td><td>1.56</td><td>1.59</td></tr><tr><td></td><td>17.5 - 30</td><td>0.97</td><td>0.96</td><td>0.94</td><td>0.96</td><td>1.62</td><td>1.41</td><td>1.30</td><td>1.37</td><td>1.36</td></tr><tr><td rowspan="5">PD A/M</td><td>0 - 2.5</td><td>1.73</td><td>1.95</td><td>1.55</td><td>1.74</td><td>1.55</td><td>1.99</td><td>1.92</td><td>2.05</td><td>1.99</td></tr><tr><td>2.5 - 5</td><td>1.38</td><td>1.26</td><td>1.12</td><td>1.25</td><td>1.58</td><td>1.32</td><td>1.43</td><td>2.04</td><td>1.60</td></tr><tr><td>5 - 7.5</td><td>1.08</td><td>1.16</td><td>0.98</td><td>1.07</td><td>1.58</td><td>1.10</td><td>1.01</td><td>1.17</td><td>1.09</td></tr><tr><td>7.5 - 12.5</td><td>1.05</td><td>1.10</td><td>0.95</td><td>1.03</td><td>1.68</td><td>0.93</td><td>1.04</td><td>0.98</td><td>0.98</td></tr><tr><td>12.5 - 17.5</td><td>1.00</td><td>0.98</td><td>0.88</td><td>0.95</td><td>1.68</td><td>0.82</td><td>1.08</td><td>1.05</td><td>0.98</td></tr><tr><td></td><td>17.5 - 30</td><td>0.90</td><td>0.95</td><td>0.98</td><td>0.94</td><td>1.62</td><td>0.82</td><td>1.13</td><td>1.01</td><td>0.99</td></tr><tr><td rowspan="5">PD V/M</td><td>0 - 2.5</td><td>1.93</td><td>2.21</td><td>2.19</td><td>2.11</td><td>1.55</td><td>1.98</td><td>2.40</td><td>2.42</td><td>2.27</td></tr><tr><td>2.5 - 5</td><td>1.18</td><td>1.67</td><td>1.50</td><td>1.45</td><td>1.58</td><td>1.77</td><td>1.79</td><td>1.46</td><td>1.67</td></tr><tr><td>5 - 7.5</td><td>1.08</td><td>1.21</td><td>1.10</td><td>1.13</td><td>1.58</td><td>1.37</td><td>1.37</td><td>1.14</td><td>1.29</td></tr><tr><td>7.5 - 12.5</td><td>0.98</td><td>1.03</td><td>1.05</td><td>1.02</td><td>1.68</td><td>1.01</td><td>1.10</td><td>0.92</td><td>1.01</td></tr><tr><td>12.5 - 17.5</td><td>0.97</td><td>1.04</td><td>0.90</td><td>0.97</td><td>1.68</td><td>0.98</td><td>0.98</td><td>1.02</td><td>0.99</td></tr><tr><td></td><td>17.5 - 30</td><td>0.79</td><td>1.06</td><td>0.91</td><td>0.92</td><td>1.62</td><td>1.01</td><td>0.97</td><td>1.11</td><td>1.03</td></tr><tr><td rowspan="5">PD A+V/M+C</td><td>0 - 2.5</td><td>2.25</td><td>2.48</td><td>1.96</td><td>2.23</td><td>1.55</td><td>2.31</td><td>2.71</td><td>2.70</td><td>2.57</td></tr><tr><td>2.5 - 5</td><td>1.68</td><td>1.68</td><td>1.58</td><td>1.65</td><td>1.58</td><td>1.76</td><td>1.78</td><td>1.86</td><td>1.80</td></tr><tr><td>5 - 7.5</td><td>1.37</td><td>1.19</td><td>1.26</td><td>1.27</td><td>1.58</td><td>1.35</td><td>1.32</td><td>1.47</td><td>1.38</td></tr><tr><td>7.5 - 12.5</td><td>1.13</td><td>1.03</td><td>1.05</td><td>1.07</td><td>1.68</td><td>1.14</td><td>1.04</td><td>1.00</td><td>1.06</td></tr><tr><td>12.5 - 17.5</td><td>1.02</td><td>1.00</td><td>1.05</td><td>1.02</td><td>1.68</td><td>0.98</td><td>0.99</td><td>0.96</td><td>0.98</td></tr><tr><td></td><td>17.5 - 30</td><td>0.94</td><td>0.94</td><td>0.95</td><td>0.94</td><td>1.62</td><td>0.94</td><td>1.02</td><td>0.92</td><td>0.96</td></tr></tbody></table>
<table><caption>**Apêndice 5.** Teores de carbono orgânico total (g kg⁻¹) de um Argissolo Vermelho, em dois métodos de preparo e três sistemas de cultura, dezoito anos após o início do experimento. (Zanatta et al., 2007).</caption><thead><tr><th rowspan="3">Tratamentos</th><th colspan="2">Dose N</th><th colspan="6">0 kg N ha<sup>-1</sup> no milho</th><th colspan="6">180 kg N ha<sup>-1</sup> no milho</th></tr><tr><th rowspan="2">Camadas</th><th colspan="3">Repetição</th><th rowspan="2">Média</th><th rowspan="2">DS</th><th colspan="3">Repetição</th><th rowspan="2">Média</th><th rowspan="2">DS</th><th rowspan="2">Média</th></tr><tr><th>I</th><th>II</th><th>III</th><th>I</th><th>II</th><th>III</th></tr></thead><tbody><tr><td rowspan="5">PC A/M</td><td>0 -2.5</td><td>9.72</td><td>10.02</td><td>9.10</td><td>9.61</td><td>1.44</td><td>9.38</td><td>10.53</td><td>10.75</td><td>10.22</td><td></td><td></td><td></td></tr><tr><td>2.5-5.0</td><td>9.09</td><td>8.30</td><td>8.32</td><td>8.57</td><td>1.54</td><td>9.25</td><td>10.31</td><td>9.58</td><td>9.71</td><td></td><td></td><td></td></tr><tr><td>5-10</td><td>9.01</td><td>8.55</td><td>8.89</td><td>8.82</td><td>1.54</td><td>8.95</td><td>9.69</td><td>8.94</td><td>9.19</td><td></td><td></td><td></td></tr><tr><td>10-20</td><td>8.68</td><td>9.00</td><td>8.16</td><td>8.61</td><td>1.52</td><td>8.98</td><td>9.35</td><td>9.71</td><td>9.35</td><td></td><td></td><td></td></tr><tr><td>20-30</td><td>9.11</td><td>8.57</td><td>8.19</td><td>8.62</td><td>1.62</td><td>9.59</td><td>9.43</td><td>9.33</td><td>9.45</td><td></td><td></td><td></td></tr><tr><td rowspan="5">PC V/M</td><td>0 -2.5</td><td>10.56</td><td>11.11</td><td>10.65</td><td>10.77</td><td>1.44</td><td>10.16</td><td>10.38</td><td>11.89</td><td>10.81</td><td></td><td></td><td></td></tr><tr><td>2.5-5.0</td><td>9.43</td><td>9.44</td><td>11.04</td><td>9.97</td><td>1.54</td><td>10.46</td><td>9.24</td><td>11.22</td><td>10.31</td><td></td><td></td><td></td></tr><tr><td>5-10</td><td>9.87</td><td>10.04</td><td>10.17</td><td>10.03</td><td>1.54</td><td>10.58</td><td>9.21</td><td>9.81</td><td>9.87</td><td></td><td></td><td></td></tr><tr><td>10-20</td><td>9.39</td><td>9.96</td><td>10.01</td><td>9.79</td><td>1.52</td><td>9.95</td><td>9.41</td><td>10.74</td><td>10.03</td><td></td><td></td><td></td></tr><tr><td>20-30</td><td>9.69</td><td>9.17</td><td>9.93</td><td>9.60</td><td>1.62</td><td>9.80</td><td>9.40</td><td>10.49</td><td>9.90</td><td></td><td></td><td></td></tr><tr><td rowspan="5">PC A+V/M+C</td><td>0 -2.5</td><td>12.83</td><td>13.11</td><td>9.76</td><td>11.90</td><td>1.44</td><td>13.02</td><td>12.48</td><td>12.91</td><td>12.80</td><td></td><td></td><td></td></tr><tr><td>2.5-5.0</td><td>10.86</td><td>11.22</td><td>9.94</td><td>10.67</td><td>1.54</td><td>11.63</td><td>11.53</td><td>10.82</td><td>11.33</td><td></td><td></td><td></td></tr><tr><td>5-10</td><td>11.47</td><td>10.54</td><td>9.61</td><td>10.54</td><td>1.54</td><td>10.50</td><td>10.77</td><td>10.13</td><td>10.47</td><td></td><td></td><td></td></tr><tr><td>10-20</td><td>10.94</td><td>9.55</td><td>9.09</td><td>9.86</td><td>1.52</td><td>9.85</td><td>10.78</td><td>9.88</td><td>10.17</td><td></td><td></td><td></td></tr><tr><td>20-30</td><td>9.90</td><td>9.59</td><td>8.99</td><td>9.49</td><td>1.62</td><td>9.40</td><td>9.86</td><td>8.93</td><td>9.40</td><td></td><td></td><td></td></tr><tr><td rowspan="5">PD A/M</td><td>0 -2.5</td><td>14.94</td><td>16.23</td><td>18.17</td><td>16.45</td><td>1.55</td><td>19.44</td><td>19.75</td><td>20.48</td><td>19.89</td><td></td><td></td><td></td></tr><tr><td>2.5-5.0</td><td>10.17</td><td>12.14</td><td>12.42</td><td>11.58</td><td>1.58</td><td>15.85</td><td>13.30</td><td>13.69</td><td>14.28</td><td></td><td></td><td></td></tr><tr><td>5-10</td><td>8.72</td><td>9.14</td><td>8.61</td><td>8.82</td><td>1.58</td><td>9.41</td><td>9.42</td><td>9.95</td><td>9.59</td><td></td><td></td><td></td></tr><tr><td>10-20</td><td>8.50</td><td>9.30</td><td>8.50</td><td>8.77</td><td>1.68</td><td>7.88</td><td>8.46</td><td>8.10</td><td>8.15</td><td></td><td></td><td></td></tr><tr><td>20-30</td><td>9.21</td><td>9.10</td><td>10.07</td><td>9.46</td><td>1.62</td><td>8.47</td><td>8.40</td><td>10.10</td><td>8.99</td><td></td><td></td><td></td></tr><tr><td rowspan="5">PD V/M</td><td>0 -2.5</td><td>21.86</td><td>21.55</td><td>20.23</td><td>21.21</td><td>1.55</td><td>22.90</td><td>20.81</td><td>16.38</td><td>20.03</td><td></td><td></td><td></td></tr><tr><td>2.5-5.0</td><td>13.10</td><td>18.04</td><td>14.43</td><td>15.19</td><td>1.58</td><td>17.02</td><td>14.08</td><td>11.29</td><td>14.13</td><td></td><td></td><td></td></tr><tr><td>5-10</td><td>9.69</td><td>11.73</td><td>10.25</td><td>10.56</td><td>1.58</td><td>11.02</td><td>10.57</td><td>10.16</td><td>10.58</td><td></td><td></td><td></td></tr><tr><td>10-20</td><td>8.27</td><td>9.14</td><td>8.77</td><td>8.73</td><td>1.68</td><td>8.41</td><td>8.37</td><td>8.63</td><td>8.47</td><td></td><td></td><td></td></tr><tr><td>20-30</td><td>8.45</td><td>9.25</td><td>8.87</td><td>8.86</td><td>1.62</td><td>8.84</td><td>9.13</td><td>8.87</td><td>8.95</td><td></td><td></td><td></td></tr><tr><td rowspan="5">PD A+V/M+C</td><td>0 -2.5</td><td>21.30</td><td>22.41</td><td>22.79</td><td>22.17</td><td>1.55</td><td>19.70</td><td>28.50</td><td>24.70</td><td>24.30</td><td></td><td></td><td></td></tr><tr><td>2.5-5.0</td><td>14.33</td><td>15.74</td><td>17.59</td><td>15.89</td><td>1.58</td><td>14.28</td><td>18.45</td><td>17.46</td><td>16.73</td><td></td><td></td><td></td></tr><tr><td>5-10</td><td>9.58</td><td>10.65</td><td>11.79</td><td>10.67</td><td>1.58</td><td>10.25</td><td>12.30</td><td>12.51</td><td>11.69</td><td></td><td></td><td></td></tr><tr><td>10-20</td><td>8.27</td><td>8.71</td><td>10.17</td><td>9.05</td><td>1.68</td><td>9.19</td><td>8.81</td><td>9.48</td><td>9.16</td><td></td><td></td><td></td></tr><tr><td>20-30</td><td>8.79</td><td>9.04</td><td>10.36</td><td>9.40</td><td>1.62</td><td>8.76</td><td>9.89</td><td>9.99</td><td>9.55</td><td></td><td></td><td></td></tr></tbody></table>
<table><caption>**Apêndice 6.** Teores de carbono orgânico total (g kg⁻¹) de um Argissolo Vermelho, em dois métodos de preparo e três sistemas de cultura, trinta anos após o início do experimento, usados neste estudo.</caption><thead><tr><th rowspan="3">Tratamentos</th><th colspan="2">Dose N</th><th colspan="3">0 kg N ha⁻¹ no milho</th><th colspan="3">180 kg N ha⁻¹ no milho</th></tr><tr><th rowspan="2">Camadas</th><th colspan="3">Repetição</th><th rowspan="2">Média</th><th rowspan="2">DS</th><th colspan="3">Repetição</th><th rowspan="2">Média</th></tr><tr><th>I</th><th>II</th><th>III</th><th>I</th><th>II</th><th>III</th></tr></thead><tbody><tr><td rowspan="5">PC A/M</td><td>0-5</td><td>9.98</td><td>12.29</td><td>9.41</td><td>10.56</td><td>1.49</td><td>12.20</td><td>11.09</td><td>10.58</td><td>11.29</td></tr><tr><td>5-10</td><td>9.21</td><td>9.98</td><td>9.17</td><td>9.45</td><td>1.67</td><td>10.79</td><td>10.09</td><td>9.19</td><td>10.02</td></tr><tr><td>10-15</td><td>10.57</td><td>8.82</td><td>8.93</td><td>9.44</td><td>1.71</td><td>12.45</td><td>10.53</td><td>8.80</td><td>10.59</td></tr><tr><td>15-20</td><td>10.01</td><td>9.35</td><td>9.89</td><td>9.75</td><td>1.75</td><td>9.48</td><td>9.87</td><td>8.90</td><td>9.42</td></tr><tr><td>20-30</td><td>9.22</td><td>9.03</td><td>9.07</td><td>9.11</td><td>1.71</td><td>11.25</td><td>9.97</td><td>9.89</td><td>10.37</td></tr><tr><td rowspan="5">PC V/M</td><td>0-5</td><td>13.20</td><td>10.46</td><td>12.95</td><td>12.20</td><td>1.49</td><td>13.42</td><td>14.98</td><td>14.02</td><td>14.14</td></tr><tr><td>5-10</td><td>12.26</td><td>11.58</td><td>12.02</td><td>11.95</td><td>1.67</td><td>12.96</td><td>10.72</td><td>12.54</td><td>12.07</td></tr><tr><td>10-15</td><td>10.42</td><td>11.16</td><td>10.89</td><td>10.82</td><td>1.71</td><td>10.89</td><td>9.68</td><td>10.67</td><td>10.41</td></tr><tr><td>15-20</td><td>9.61</td><td>10.37</td><td>9.95</td><td>9.98</td><td>1.75</td><td>9.83</td><td>8.92</td><td>8.97</td><td>9.24</td></tr><tr><td>20-30</td><td>9.42</td><td>9.78</td><td>10.37</td><td>9.86</td><td>1.71</td><td>9.86</td><td>9.59</td><td>10.19</td><td>9.88</td></tr><tr><td rowspan="5">PC A+V/M+C</td><td>0-5</td><td>13.49</td><td>15.00</td><td>11.64</td><td>13.38</td><td>1.49</td><td>10.50</td><td>15.16</td><td>13.05</td><td>12.91</td></tr><tr><td>5-10</td><td>11.47</td><td>12.01</td><td>11.74</td><td>11.74</td><td>1.67</td><td>11.13</td><td>12.23</td><td>10.11</td><td>11.16</td></tr><tr><td>10-15</td><td>12.95</td><td>13.65</td><td>11.14</td><td>12.58</td><td>1.71</td><td>11.59</td><td>12.27</td><td>11.53</td><td>11.80</td></tr><tr><td>15-20</td><td>11.51</td><td>10.75</td><td>9.41</td><td>10.56</td><td>1.75</td><td>10.25</td><td>10.59</td><td>10.05</td><td>10.30</td></tr><tr><td>20-30</td><td>10.75</td><td>9.62</td><td>9.60</td><td>9.99</td><td>1.71</td><td>10.88</td><td>10.11</td><td>10.33</td><td>10.44</td></tr><tr><td rowspan="5">PD A/M</td><td>0-5</td><td>15.12</td><td>14.17</td><td>15.61</td><td>14.97</td><td>1.49</td><td>17.00</td><td>17.60</td><td>17.11</td><td>17.24</td></tr><tr><td>5-10</td><td>8.53</td><td>8.63</td><td>9.67</td><td>8.94</td><td>1.67</td><td>9.93</td><td>9.68</td><td>9.75</td><td>9.79</td></tr><tr><td>10-15</td><td>8.33</td><td>8.24</td><td>9.79</td><td>8.79</td><td>1.71</td><td>8.76</td><td>10.40</td><td>8.32</td><td>9.16</td></tr><tr><td>15-20</td><td>8.75</td><td>7.82</td><td>9.67</td><td>8.75</td><td>1.75</td><td>8.72</td><td>8.38</td><td>8.95</td><td>8.68</td></tr><tr><td>20-30</td><td>9.05</td><td>9.20</td><td>10.01</td><td>9.42</td><td>1.71</td><td>10.32</td><td>9.84</td><td>10.12</td><td>10.10</td></tr><tr><td rowspan="5">PD V/M</td><td>0-5</td><td>18.43</td><td>20.43</td><td>19.43</td><td>19.43</td><td>1.49</td><td>21.71</td><td>22.80</td><td>24.09</td><td>22.87</td></tr><tr><td>5-10</td><td>10.74</td><td>10.97</td><td>9.81</td><td>10.50</td><td>1.67</td><td>10.49</td><td>13.38</td><td>12.05</td><td>11.97</td></tr><tr><td>10-15</td><td>8.73</td><td>9.35</td><td>8.39</td><td>8.82</td><td>1.71</td><td>8.73</td><td>9.81</td><td>8.79</td><td>9.11</td></tr><tr><td>15-20</td><td>7.81</td><td>8.63</td><td>8.72</td><td>8.39</td><td>1.75</td><td>8.58</td><td>7.14</td><td>9.00</td><td>8.24</td></tr><tr><td>20-30</td><td>9.79</td><td>9.22</td><td>10.30</td><td>9.77</td><td>1.71</td><td>9.71</td><td>10.67</td><td>10.49</td><td>10.29</td></tr><tr><td rowspan="5">PD A+V/M+C</td><td>0-5</td><td>18.78</td><td>20.35</td><td>23.45</td><td>20.86</td><td>1.49</td><td>24.69</td><td>29.30</td><td>23.68</td><td>25.89</td></tr><tr><td>5-10</td><td>10.96</td><td>12.12</td><td>11.97</td><td>11.68</td><td>1.67</td><td>12.66</td><td>12.81</td><td>14.34</td><td>13.27</td></tr><tr><td>10-15</td><td>8.79</td><td>10.02</td><td>10.49</td><td>9.76</td><td>1.71</td><td>9.55</td><td>9.99</td><td>9.78</td><td>9.78</td></tr><tr><td>15-20</td><td>8.64</td><td>9.52</td><td>9.90</td><td>9.35</td><td>1.75</td><td>9.16</td><td>9.00</td><td>8.32</td><td>8.83</td></tr><tr><td>20-30</td><td>10.30</td><td>10.59</td><td>10.86</td><td>10.58</td><td>1.71</td><td>10.15</td><td>9.82</td><td>10.07</td><td>10.02</td></tr></tbody></table>