bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐Term Tillage and Rotation Effects on Properties of a Central Ohio Soil
Authors: Lal R. , Mahboubi A. A. , Fausey N. R.
Published: July 2010

Sustainable use of soil resources can be assessed from management‐induced changes in soil properties from long‐term experiments. Such data are scanty, especially with regard to changes in soil physical properties. Therefore, soil physical and chemical analyses were performed 28 yr after initiating a crop rotation‐tillage experiment on a well‐drained Wooster silt loam soil (fine‐loamy, mixed, mesic Typic Fragiudalf) at Wooster, OH. All combinations of three rotations (continuous corn [CC; Zea mays L.]; corn and soybean [Glycine max (L.) Merr.] in a 2‐yr rotation [CS]; and corn, oat [Avena sativa L.], and meadow in a 3‐yr rotation [COM]) and of three tillage treatments (no‐tillage [NT]; chisel plow [CP]; and moldboard plow [MP]) were maintained on the same plots for the entire length of study. All crops were grown every year. Soil properties studied for the 0‐ to 15‐cm layer were: structural stability of aggregates, bulk density, total porosity, penetration resistance, organic C, pH, cation‐exchange capacity (CEC), and exchangeable K, Ca and Mg. Mean bulk densities measured prior to tillage treatments and planting were 1.18, 1.24, and 1.28 Mg m−3 for CC, CS, and COM rotations, respectively. The lowest bulk density was observed for the CC‐NT combination. Total aggregation in CS was 26.9% greater than CC and 111.2% greater than COM. With tillage treatments, aggregation was in the order of NT>CP>MP. Rotation treatments had no effect on aggregate size. In accord with bulk density, the relative magnitude of organic C content was 100, 85, and 63 for CC, CS, and COM rotations, respectively.
Long‐Term Effects of Residue Management in Wheat‐Fallow: I. Inputs, Yield, and Soil Organic Matter
Authors: Rasmussen P. E. , Parton W. J.
Published: July 2010

Soil organic matter (SOM) is valuable, because of both its beneficial effect on soil quality and crop productivity and its potential to sequester C. Long‐term experiments provide an opportunity to identify crop management practices that enhance or degrade soil quality. This study was initiated in 1931 to determine residue management effects on crop yield and SOM (organic C and N) in a winter wheat (Triticum aestivum L.)‐fallow system. The soil is a coarse‐silty, mixed, mesic Typic Haploxeroll. Treatments include (units ha−1 crop−1) 22.4 Mg manure, 2.24 Mg pea vine residue, 0, 45, and 90 kg N with and without spring burning of straw, and 0 kg N with fall burning of straw. Yearly C and N inputs and removals have been determined since 1976, and calculated for prior periods. Soil C and N have been determined at ≈ 11‐yr intervals. Manure, which supplies 111 kg N ha−1 crop−1, has consistently produced the highest yield and maintained the highest soil C and N contents. Other treatments initially yielded from 80 to 90% of the manure treatment, but have progressively declined in direct relation to decreasing soil N content. Low‐fertility treatments currently yield from 43 to 57% of the manure treatment. The change in soil C and N with time is nearly linear for all treatments, and highly correlated with residue input. Treatment effects on soil C and N have been confined to the top 30 cm of soil, but there has been a slow steady decline in C and N in the 30‐ to 60‐cm zone that is not related to residue management.
Preferential Transport of Nitrate through Soil Columns Containing Root Channels
Authors: Li Yimin , Ghodrati Masoud
Published: July 2010

Preferential flow has been increasingly recognized as an important mechanism for water and solute transport. The objectives of this study were to characterize transport of NO3 through root channels in uniformly packed soil columns and to compare three commonly used solute transport models in describing NO3 transport through the soil‐root channel columns. Root channels were created by growing corn (Zea mays L.) or alfalfa (Medicago sativa L.) in 0.6‐m‐long soil columns. Transport of NO3 was then systematically studied with each of these macropore systems at a range of fluxes (from 0.042Ksm to 0.47Ksm, where Ksm is the saturated hydraulic conductivity of the macroporous system). A nonlinear least‐squares program was used to fit the convection‐dispersion equation (CDE), the physical nonequilibrium model (MIM) and a stochastic model (SM) to the experimental data. The results show that significant preferential movement of NO3 occurred in the decayed root channels at fluxes as low as 0.042Ksm. The MIM model provided a better description of the breakthrough curves than the CDE and the SM, while none of them were adequate to predict the preferential movement of the solute.
Effects of Magnesium on Cation Selectivity and Structural Stability of Sodic Soils
Authors: Curtin D. , Steppuhn H. , Selles F.
Published: July 2010

This study was conducted to evaluate the effects of Mg on the cation‐exchange relationships and structural stability of sodic soils. Samples of prairie soils (Haploborolls) from Saskatchewan, Canada, were equilibrated with sodic solutions [sodium adsorption ratio (SAR = Na/(Ca + Mg)0.5, where concentrations are expressed in millimoles per liter) ranging from 5 to 40] with different Ca/Mg ratios. Exchangeable Na increased as the Mg/Ca ratio increased. Averaged from all SAR treatments, the Mg‐Na systems had between 17 and 37% more exchangeable Na than did the Ca‐Na systems. The Mg‐induced increase in exchangeable Na was directly related to a preference by the soils for Ca over Mg, which makes Na more competitive against Mg than against Ca. The influence of Mg on structural stability was examined by measuring saturated hydraulic conductivity (K) using Mg‐Ca‐Na solutions (Mg/Ca ratios ranging from 0:1–1:0) with SARs of 10 and 20. The Mg‐Na system developed considerably lower K than did the Ca‐Na system when leached with solutions with total electrolyte concentration ≤ 100 mmolc L−1. Systems with intermediate Mg/Ca ratios (i.e., Mg/Ca of 1:2 and 2:1) behaved more like the Ca‐Na than the Mg‐Na system. Clay concentration in leachate from the soil columns increased as Mg/Ca ratio increased, suggesting that a major effect of exchangeable Mg was that it increased the tendency for clay dispersion. Dispersion tests confirmed that the effect of Mg was greater than could be explained by the higher exchangeable Na level in the Mg system, i.e., Mg had a specific effect on clay dispersion. Our results suggest that exchangeable Mg is about 5% as dispersive as exchangeable Na.
Soil Organic Matter Testing and Labile Carbon Identification by Carbonaceous Resin Capsules
Authors: Johns Mitchell M. , Skogley Earl O.
Published: July 2010

An alternative test for soil organic matter that does not produce toxic dichromate waste, as does the Walkley‐Black test, and that also allows identification of labile soil C components is currently desired. The objectives of this study were to apply carbonaceous resin capsules for measurement of soil organic C (SOC) and for identification of soluble SOC constituents. Seven carbonaceous resins, selective for nonpolar organic adsorbates, were evaluated. The resins were tightly packed as spherical capsules and placed in saturated soil pastes of 19 Montana soils. Resin capsules were desorbed with NaOH, CH3OH, CHCl3, and C6H14. Capsules extracted with the organic solvents were used in identification by nuclear magnetic resonance and infrared spectroscopy. Ultrafiltration and atomic absorption spectrophotometry of trace metals were also used. All resin capsules sorbed measurable levels of soil labile C (LC). All the resin types provided statistically significant prediction of SOC. The Ambersorb 564 resin showed the highest prediction, with a linear relationship between capsule‐extracted LC (NaOH) and SOC of r2 = 0.09 (P < 0.0001). Prediction results from these soils suggested a linear relationship between soluble SOC and solid‐phase SOC, describable as constant partitioning. Labile C was composed of mostly aliphatics and some aromatics. Carbohydrates, OH, COOH groups, and metal‐organic complexes were present. Most of the LC was composed of low molecular weight humics (<1000 daltons). The ability of LC to be desorbed by the more nonpolar solvents indicated an amphipathic character for some LC constituents. The resin capsule methodology showed good testing potential for these SOC investigations.
Soil Microbial Dynamics: Short‐ and Long‐Term Effects of Inorganic and Organic Nitrogen
Authors: Fauci Mary F. , Dick R. P.
Published: July 2010

Soils with minimal long‐term organic inputs typically have reduced biological activity, which has implications for current interests in shifting from inorganic to organic inputs and promoting efficient nutrient cycling in agroecosystems. A greenhouse experiment was conducted to investigate the long‐ and short‐term effects of organic vs. inorganic N on microbial biomass, metabolic quotient, and key soil enzymes (protease, l‐histidine NH3‐lyase, and β‐glucosidase) involved in N and C cycles. Treatments applied factorially to four corn (Zea mays L.) crops grown for 306 d were: four soils from long‐term field plots (beef manure, pea vine [Pisum sativum L.], 0, or 90 kg N ha−1, each applied biennially for 59 yr); four greenhouse organic residues (pea vine, beef manure, poultry manure, or control); and four rates of inorganic N fertilizer (0–1600 mg NH4NO3‐N pot−1 with 2 kg soil pot−1). In the long‐term, soil microbial biomass and enzyme activity correlated with total C inputs. Recent organic inputs, regardless of long‐term management, had a large effect on soil biological response, which was controlled by residue composition (lignin content) and supported 80 to 400% greater microbial biomass C than the control. Long‐term inorganic N applications decreased organic matter and biological activity, whereas short‐term inorganic N applications had limited effects on soil enzyme activities and microbial biomass C, suggesting that inorganic N can maintain plant productivity during a transition to organic N sources without inhibiting the buildup of microbial biomass. The metabolic quotient gave mixed results as a soil biological indicator, being high with long‐term N or recent beef manure applications and low with recent N applications.
Soil Isotopically Exchangeable Phosphorus: A Comparison between E and L Values
Authors: Frossard E. , Morel J. L. , Fardeau J. C. , Brossard M.
Published: July 2010

This study was designed to explain the apparent discrepancies often reported in the literature between E and L values, two parameters obtained from isotopic exchange experiments and commonly used to quantify available soil phosphate. The E and L values of the surface horizons of 10 soils from tropical, mediterranean, and temperate regions were determined. The L value was measured from a 13‐wk pot experiment with common bentgrass (Agrostis capillaris L.) where the available soil P was labeled with 32PO4 ions in the presence of a carrier (25–50 mg 31P kg−1 soil). To determine the E value, the isotopic exchange kinetic experiment was carried out on each soil. Carrier‐free 32PO4 was added to the soil‐solution system at a steady state and the quantity of isotopically exchangeable soil phosphate at time t, E(t), was calculated from the kinetic equation describing the decrease of radioactivity in solution with time. Results showed that L values determined after 13 wk were not significantly different from E(t) values extrapolated to the same period (t = 131040 min). It was concluded that (i) the L value is a particular point of the kinetic equation and (ii) isotopically exchangeable phosphate is the available P for common bentgrass. A strict equality between E(13wk) and L values was not, however, reached for all samples. Possible causes for the differences were: (i) an overestimation of the water‐soluble phosphate due to the presence of silica and (ii) disturbance of the steady state following a too large uptake of phosphate by the crop or the application of too large quantities of carrier compared with the initial quantity of exchangeable soil phosphate.
Identification and Properties of Fragipan Soils in the Piemonte Region of Italy
Authors: Ajmone‐Marsan F. , Pagliai M. , Pini R.
Published: July 2010

The presence of a fragipan horizon in the soil profile restricts plant growth and limits nonagricultural uses. This is of special concern in the Piemonte region, in northwestern Italy, where the soil of numerous areas is reported to have a fragipan. Four sites were selected for this study with the aim of ascertaining the presence in the profile of a horizon that meets the criteria for a fragipan. In addition to standard morphological observations and physical analyses, Hg intrusion porosimetry and image analysis of thin sections were used to help in fragipan characterization. The pan of all four sites showed a suite of characteristics such as coarse prismatic primary structure, prominent vertical mottling, extremely hard dry consistence, brittleness, and absence of roots that indicated the presence of a fragipan. Other pedogenic features, e.g. clay films, mangans, ferrans, and concretions, were observed in the field. Although some of the Bx horizons had a clay content slightly higher than prescribed, in general textures were within the range prescribed for fragipans, as were bulk densities. Mercury intrusion showed a decrease in total porosity with depth, residual pores becoming dominant over storage and transmission pores in the fragipans. Image analysis of thin sections revealed a decrease of elongated pores and the presence of vesicles and compound packing voids. Also, oriented clay coatings within the pores and mangans and ferrans were observed in the fragipan. Pore‐size distribution and pore shape appeared to be useful in characterizing the fragipan.
Characterizing Changes in Aggregate Stability Subsequent to Introduction of Forages
Authors: Rasiah V. , Kay B. D.
Published: July 2010

Limited information exists on the methods used to compute the changes in wet aggregate stability, WAS, with time subsequent to changes in management practices. The objectives of this study were to: (i) develop a model to compute the net gain in WAS, WASnet, with time subsequent to the introduction of forages, (ii) assess the model using data from different soils, and (iii) determine the influence of soil properties on the regeneration of WAS. Stability measurements were made at monthly intervals during the 1989, 1990, and 1991 growing seasons from seven different soils under continuous conventional corn (Zea mays L.) and forage treatments established in 1989. The interaction of cropping treatment, time of sampling, and gravimetric soil water content, θ, at sampling was significant for six out of seven soils at P = 0.05. Using the relation between WAS and θ and the changes in WAS with time, a semiempirical model was developed to predict WASnet. The model parameters described (i) the duration of delay before any observable changes in WAS occurred, (ii) the rate at which WAS increased from an initial to a maximum value, and (iii) the maximum potential change in WAS. The R2 for the best fit of the model ranged from 0.31 to 0.72 for the seven soils. The projected half‐life for WASnet, computed using the 3‐yr data, ranged from 4.52 yr for a clay loam to 7.75 yr for a sandy loam. Pedotransfer function analysis indicated that WASnet increased with increasing clay and organic matter contents and pH of soil. The model parameters and the associated pedotransfer functions were useful in assessing the influence of soil properties on stability following changes in management practices.
Dynamics of Ammonia Volatilization from Turkey Manure and Urea Applied to Soil
Authors: Nathan Manjula V. , Malzer G. L.
Published: July 2010

Field measurements of NH3 volatilization from both surface‐applied and incorporated turkey (Meleagris gallopavo) manure (20 g of N m−2, which compares with 16 Mg of manure ha−1) and urea (20 g of N m−2) were made using the forced‐draft technique for a 6‐d period in early June 1991. The soil (temperature and water potential) and atmospheric parameters (relative humidity, wind speed, and air temperature) affecting NH3 volatilization rate were also measured. Ammonia losses for manure and urea followed a diurnal pattern; maxima occurred shortly after midday (between 1200 and 1800 h), when soil temperature was nearing maximum and wind speed was highest, and minima occurred during midnight to early morning hours (between 2400 and 0600 h), when the soil temperature was lowest and relative humidity was highest. Significant positive correlations between rates of NH3 volatilization and soil temperature, atmospheric temperature, and wind speed were observed. Relative humidity was generally negatively correlated with NH3 volatilization. Ammonia volatilization from the surface‐applied manure was highest immediately after application and gradually decreased with time, whereas ammonia volatilization from surface‐applied urea did not start until Day 2 and reached a maximum on Day 6. The total NH3 loss from incorporated manure was 23 times lower than that from surface‐applied manure (0.5 vs. 11.5 kg of N ha−1), whereas NH3 loss from urea was eight times lower when incorporated (0.2 vs. 1.5 kg N ha−1) during a 6‐d period. Total N loss (6 d) from surface‐applied urea was eight times lower than an equivalent amount of inorganic N in turkey manure (1.5 vs. 11.5 kg of N ha−1). Ammonia volatilization from turkey manure and urea was found to be influenced by a combination of environmental factors and the method of application.
Effects of Soil Surface Management on Water Flow Distribution and Solute Dispersion
Authors: Poletika N. N. , Jury W. A.
Published: July 2010

A known benefit of cultivation is increased infiltration rates during subsequent irrigation or precipitation events. This study was conducted to investigate the effects of cultivation and irrigation method on uniformity of water flow and dispersion of solutes leached through a Tujunga loamy sand (mixed, thermic, Typic Xeropsamment) at Etiwanda, CA. Outflow from undisturbed, unsaturated field soil contained in a 0.8 by 0.8 by 0.3 m lysimeter was sampled by a 64‐cell grid of fiberglass wick solution samplers. Daily 20‐mm water inputs were applied at a rate of 5 mm h−1 for 4 h by hydraulic spray nozzles (HSN) mounted on a motorized boom or by low‐volume sprinklers (LVS). Narrow pulse inputs of Cl−, NO−3, and Br− solutions were used to evaluate solute dispersion and travel paths. Four experiments were conducted sequentially in the same lysimeter: (i) light raking, broadcast Cl− and local NO−3, and HSN, (ii) light raking, local Cl−, HSN, (iii) shallow cultivation and releveling, no solute, and LVS, and (iv) broadcast Br− and HSN. Based on drainage positions observed with locally applied solutes, flow appeared to be one‐dimensional through most of the transport volume. Switching from HSN to LVS and then back to HSN apparently had much less effect on water‐flow variation than did shallow cultivation and releveling. The overall trend with time was decreasing variability in locally measured water flow, and only in the last experiment were the flow patterns time invariant. Areaveraged solute breakthrough curves for transport experiments conducted before and after cultivation showed less dispersion following cultivation. The decrease in solute spreading estimated from fitted convection‐dispersion model parameters and by travel time moment analysis was of similar magnitude to the reduced variation of the locally measured water flows. Shallow cultivation appeared to lower the hydrodynamic dispersion of the flow field at the scale measured in this study, thus decreasing the spreading of the leached solute pulse.
Hydraulic Flow and Water Quality Characteristics in Rill Erosion
Authors: Shainberg I. , Laflen J. M. , Bradford J. M. , Norton L. D.
Published: July 2010

The effects of interaction between water flow characteristics, soil sodicity, and water quality on the detachment of soil particles by flowing water was studied in the laboratory. Specific objectives of this study were to evaluate: (i) the use of flow shear stress and stream power for estimating soil detachment, (ii) the effect of low soil sodicity (exchangeable sodium percentage [ESP] <10) and water quality (deionized water [DW] and 0.005 M CaCl2 solution [TW]) on soil detachment, and (iii) the effect of negatively charged polyacrylamide (PAM) polymer on soil detachment. Detachment rates were measured in a small hydraulic fume. Several bed slopes and flow rates were studied. Detachment rate increased linearly with both shear stress and stream power of the flow. The rill erodibility of the Miami soil (fine‐loamy, mixed, mesic Typic Hapludalf) agreed well with field data. Water quality had no effect on rill erodibility for the soil tested when ESP < 3.0. Use of TW reduced the erodibility of soils with ESP 5 and 10 compared with DW. Surface treatment with PAM (0.05 g m−2) prevented soil detachment in flows with high shear stress. The formation of a surface soil layer with high cohesion and aggregate stability prevented soil detachment. Soil surface properties and not bulk soil properties determined soil detachment.
Organic and Conventional Management Effects on Biologically Active Soil Organic Matter Pools
Authors: Wander M. M. , Traina S. J. , Stinner B. R. , Peters S. E.
Published: July 2010

Specific impacts of organic management practices on soil organic matter characteristics have not been documented. This study tested how organic management practices influence soil fertility by investigating whether 10 yr of organic or conventional management generated differences in biologically active soil organic matter (SOM) pools at the Rodale Institute Research Center's long‐term Farming Systems Trial experiment (FST). The experiment included an organically managed rotation that was animal based, an organic treatment that was cash‐grain based, and a conventional cash‐grain‐based rotation. The biologically active SOM matter pools of the three FST treatment soils were compared through characterization of soil CO2 evolution, available inorganic N pools and N mineralization rates, water‐dispersible organic carbon (WDOC), and particulate organic matter (light fraction). Soils receiving the organic treatments accumulated biologically active C. Accumulated organic matter in the manureamended soil was the most labile whereas the cover‐cropped soil accumulated the most organic matter overall. In the cover‐cropped soil, higher total C and N, particulate SOM, and reduced WDOC contents indicated that its SOM was more stable than SOM in the other two treatment soils. The conventionally managed soil had the lowest biological activity (N supply and soil respiration rates) and did not accumulate SOM during the 10‐yr experiment. Assays that characterize particulate organic matter emerged as the best indices of biologically active SOM because they documented important quality (i.e., biological lability) and quantity aspects of SOM character in the Rodale FST soils.
Carbon Turnover in Soil Physical Fractions
Authors: Buyanovsky G. A. , Aslam M. , Wagner G. H.
Published: July 2010

Soil organic matter (SOM) as represented in mathematical simulation models involves several hypothetical pools of differing resistance to decay. These conceptual pools satisfy requirements of modeling, but usually have little in common with existing information on physical and chemical properties of SOM. Using our data on turnover times for soil C in fractions of natural aggregates and primary particles, we attempted to relate age of C in physical fractions with that in widely accepted theoretical pools. Soil from a field experiment with 14C‐labeled soybean residues was sampled periodically and separated into physical fractions. The amounts of 14C associated with these fractions at different times provided data for calculation of decay rates and turnover times. The most labile fraction of SOM was plant fragments with turnover time ranging from 1 to 3 yr, which was inversely related to fragment size. Soil aggregates were found to be enriched in C compared with whole soil. This was most pronounced for coarser aggregates whose construction apparently involved the relatively labile plant fragments in some progressive state of decay. The macroaggregates with partially processed C showing turnover from 1 to 3 yr contrasted with microaggregates that included more highly humified C having a longer residence time of ≈7 yr. Various soil fractions differing in residence time of associated C were assembled into several groups that demonstrated consistency with conceptual pools of two widely accepted simulation models. Data from 13C natural abundance studies of soil and of primary fractions were in harmony with models requiring at least two pools of stable SOM.
Sealing, Amendment, and Rain Intensity Effects on Erosion of High‐Clay Soils
Authors: Reichert José Miguel , Norton L. Darrell , Huang Chi‐hua
Published: July 2010

The physicochemical composition of and processes acting on the soil‐fluid interface determine detachment and transport of soil particles by erosive forces at the surface during rain. It is hypothesized that fluidized bed combustion (FBC) bottom ash and soil surface condition change the relationship between rain intensity and runoff and sediment yield. On small erosion pans, aggregates from five clayey soils (Alfisol, Oxisol, Ultisol, and Vertisols) with distinct swelling and flocculation characteristics were subjected to simulated rainfalls of 74, 39, and 107 mm h−1 for 90, 30, and 30 min, respectively. This rain sequence was applied on freshly tilled (FT), dried‐crust (DC) and wet‐crust (WC) soil. Fluidized bed combustion bottom ash was spread on FT soil at a rate of 5 Mg ha−1. Power functions described well sediment yield as a function of rain intensity, with exponents of 1.97 for FT, 1.74 for DC, and 1.72 for WC; thus as the soil sealed and consolidated, rain intensity influenced the erosion rates less. Dried‐crust was the most erodible surface for half of the soils. Clay shrinkage disrupted aggregates and preformed crusts, whereas rewetting caused differential swelling and raindrops pitted the soil surface. Runoff decreased from FT to DC, but no increase was observed from DC to WC. Smectitic and illitic soils had a longer‐lasting positive effect of FBC bottom ash on reducing soil and water losses. For the highly smectitic Vertisols, FBC bottom ash was effective on reducing erosion even after 552 mm of rain. Kaolinitic soils were more stable, generating lower runoff and soil loss rates.
Soil Drainage Class Effects on Early Response of Balsam Fir to Precommercial Thinning
Authors: Briggs Russell D. , Lemin, R. C.
Published: July 2010

Precommercial thinning (PCT), a silvicultural treatment commonly used to increase individual tree growth rate and reduce the time required to attain merchantability for young fir (Abies spp.)‐spruce (Picea spp.) stands, is both biologically effective and expensive ($300–500/ha in 1993). Forest managers desire to allocate silvicultural capital to maximize return on investment. This study was initiated to identify criteria that could be utilized to rank sites according to response of balsam fir [Abies balsamea (L.) Mill.] to PCT. Sixty‐two plots were established in young fir‐spruce stands in Maine that had been precommercially thinned between 1977 and 1987. Volume increments 3 yr prior to (VI3PRE) and 3 yr after (VI3POST) PCT were reconstructed from detailed stem analyses of 427 balsam fir trees. Increased radial increment following PCT was visually apparent and significant for each sample tree. The magnitude of the response was strongly affected by soil drainage class. Regression with dummy variables showed that VI3POST, expressed as a function of VI3PRE, increased as soil drainage class improved from poorly (mottling within 10 cm of mineral soil surface) to well (mottling >60 cm below mineral soil surface) and somewhat‐excessively drained (loam textured cap overlying deep sand), then decreased for trees growing on excessively drained (sandy‐textured) soils. Soil drainage class can be used effectively to rank sites according to expected response to PCT on large land bases.
Fertilizer Nitrogen Requirements for Cotton Production as Affected by Tillage and Traffic
Authors: Torbert H. A. , Reeves D. W.
Published: July 2010

Soil compaction and its associated problems have led to interest in investigating the interactive effects of traffic and tillage systems on fertilizer N requirement for cotton (Gossypium hirsutum L.). In 1987, a study was initiated on a thermic Typic Hapludult soil complex with a cropping system of wheat (Triticum aestivum L.)‐cotton double cropped. The experimental design was a split‐split plot with four replications. Main plots were two traffic treatments (conventional and no‐traffic), subplots were four tillage systems for cotton (surface tillage without subsoiling [surface‐only], surface tillage and annual in‐row subsoiling [subsoiling], surface tillage with one‐time‐only complete disruption of the tillage pan [complete], or no surface tillage and in‐row subsoiling [strip‐till]), and sub‐subplots were four N rates (0, 45, 90, and 135 kg N ha−1). In addition, application of 15N‐labeled NH4NO3 was made to microplots inside each tillage‐traffic‐90 kg N ha−1 plot. In 1990 and 1991, increasing N application increased cotton biomass and decreased lint percentage. In the dry year of 1990, no‐traffic decreased seed cotton yield from 1500 to 1360 kg ha−1, while tillage had no significant effects on cotton yield components. Above‐normal rainfall in 1991 resulted in the strip‐till with no‐traffic treatment having the highest seed cotton yield (2749 kg ha−1) and the greatest fertilizer N uptake efficiency (35%). Results indicate that the detrimental effects of traffic on N uptake efficiency may be reduced with conservation tillage systems and that higher fertilizer N application rates may not be needed for conservation tillage practices such as strip‐till in Coastal Plain soils.
Root‐Zone Mineral Nitrogen Changes as Affected by Crop Sequence and Tillage
Authors: Meek B. D. , Carter D. L. , Westermann D. T. , Peckenpaugh R. E.
Published: July 2010

Crop sequence and tillage affect soil mineral N (NH4 plus NO3) and NO3 leaching below the root zone following alfalfa (Medicago sativa L.). A 2‐yr field experiment was conducted in south‐central Idaho to determine the effect on soil NO3 levels of a corn (Zea mays L.)‐wheat (Triticum aestivum L.) rotation compared with a bean (Phaseolus vulgaris L.)‐bean rotation and to demonstrate improved N utilization with a corn‐wheat rotation. Alfalfa, growing on an irrigated Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid), was killed in October 1989 with herbicide. Treatments were: (i) BT‐BT: conventional tilled bean grown in 1990 and 1991; (ii) CNT‐WNT: no‐till silage corn grown in 1990, and no‐till winter wheat grown in 1990–1991; and (iii) CT‐WT: same as CNT‐WNT but under conventional tillage. Similar amounts of soil N were mineralized the first (275 kg N ha−1) and second (213 kg N ha−1) year after killing the alfalfa in all treatments. The BT‐BT treatment had the highest growing‐season soil mineral N (up to 251 kg ha−1, 0–0.45‐m depth) because the N uptake by bean was lower (187 kg N ha−1) than corn (252 kg N ha−1, average of CT‐WT and CNT‐WNT treatments) in 1990 and later than winter wheat uptake in 1991. Most wheat N uptake had occurred by late June when bean uptake was just starting. A rotation that follows alfalfa with corn or a crop with a similar N uptake pattern, instead of bean, will save N fertilizer, lower soil NO3 levels, and reduce NO3 leaching potential.
Fluidized Bed Bottom‐Ash Effects on Infiltration and Erosion of Swelling Soils
Authors: Reichert José Miguel , Norton L. Darrell
Published: July 2010

Fluidized bed combustion (FBC) bottom ash, rather than being used as fill at dumping sites, can be utilized to amend certain soils for erosion control. Because FBC bottom ash is a source of both electrolytes and alkalinity, its effectiveness in controlling runoff and erosion should be greater on soils with a predominance of permanent charges. Five soils, with and without addition of 5 Mg ha−1 surface‐applied FBC bottom ash, were prewetted and subjected to 110 mm h−1 rain for 90 min. The critical flocculation concentration (CFC) varied from 0.5 mmolc L−1 for the smectitic‐kaolinitic soil to 3.5 mmolc L−1 for the illitic soil. Steady‐state infiltration rates (Is) for the control were very low, ranging from 1.8 to 5.8 mm h−1. These rates were increased 3.6‐ to 5.0‐fold with the application of FBC bottom ash, with a lesser increase for the highly smectitic and illitic soils. For the control, total soil loss ranged from 220 to 1998 g m−2, and total water loss from 78 to 112 mm, with the greatest losses for soils with a large cation‐exchange capacity/clay ratio. The FBC bottom ash reduced total water loss by 1.1‐ to 2.0‐fold and total soil loss by 1.5‐ to 3.9‐fold. The CFC of the soil was correlated with Is, while aggregate stability was correlated with erosion and total runoff. The FBC bottom ash effectiveness in increasing infiltration and controlling erosion on these soils is attributed to an increase in electrolytes in the runoff, thus decreasing soil swelling and the dispersion of clay platelets and preventing surface sealing.
Temporal Variability of Selected Properties of Loessial Soil as Affected by Cropping
Authors: Scott H. D. , Mauromoustakos A. , Handayani I. P. , Miller D. M.
Published: July 2010

Quantification of the relationships between short‐ and long‐term variability of soil properties is needed to understand the effects of cropping on soils. These relationships were studied in four adjacent fields of a Typic Albaqualf or a Typic Glossaqualf which included a prairie and three fields that had been cropped for 3, 14, or 32 yr. The fields were sampled monthly from March 1989 to March 1990. Soil samples were collected at depth intervals of 0 to 5 cm and 5 to 10 cm at each sampling time. The statistical model assumed that the fields studied represented a random sample of fields from a large population. One of the ways in which these fields differ is in cropping duration. Field and sampling time variabilities were treated as random effects in a mixed model including soil depth. We defined the variability among fields as long‐term and the variability among sampling times within a field as short‐term. Statistical analyses indicated that the soil properties vary with cropping, depth interval, and sampling time within a year. The highest ratio of long‐ to short‐term variability (r) was found to be 26 with total C, and the lowest ratio was 0.52 with saturated hydraulic conductivity (Ksat). Values of r for most of the soil properties examined ranged between 1.7 and 2.8 and tended to be higher in the first depth interval. The large estimated standard errors for these ratios indicated that even though r was greater than 1.0, the long‐term variability was not statistically significantly greater than the short‐term variability at α = 0.05.
Seasonal Preferential Flow in Two Sierra Nevada Soils under Forested and Meadow Cover
Authors: Burcar S. , Miller W. W. , Tyler S. W. , Johnson D. W.
Published: July 2010

The preferential movement of surface‐applied solutes is a potential source of groundwater contamination and could subsequently provide a major source of nutrients to Lake Tahoe. This study investigated seasonal infiltration, water repellency, and preferential water flow in two Sierra Nevada soil types (a granitic and a volcanic soil) in forest and meadow areas using a rainfall simulator. Infiltration and runoff were measured at the plot surface. Plots were subsequently excavated to measure preferential water flow. Water repellency was found to affect infiltration and nonuniform preferential flow was observed. The volcanic soil demonstrated continuous preferential flow with depth, whereas in the granitic soil, preferential flow rapidly dissipated. Wetting patterns showed greater preferential flow in the forested areas for both soils compared with the meadow areas. Higher initial water content and reduced water repellency in the early spring generally produced more typical matrix water flow in the coarser textured granitic soil. Since preferencial flow was most evident in all forested conditions, nutrient bypass potential is considered greatest on soils in forested areas near tributaries and the lake.
Cobalt, Cadmium, and Lead Sorption to Hydrous Iron Oxide: Residence Time Effect
Authors: Ainsworth Calvin C. , Pilon James L. , Gassman Paul L. , Van Der Sluys William G.
Published: July 2010

The adsorption‐desorption of the divalent metal cations (Me2+) Co2+, Cd2+, and Pb2+ to hydrous ferric oxide (HFO) was investigated as a function of oxide aging and Me2+‐oxide residence time. The HFO was produced and stored for up to 86 wk. Periodically, Me2+ sorption was determined across the pH range of 2.5 to 12. In addition, the Me2+ ions were contacted with freshly produced HFO and stored at a pH that dictated that 80 to 100% of the Me2+ would be in the sorbed state; desorbability of the Me2+ was determined as a function of Me2+‐oxide residence time. The change in the crystallinity of the HFO as a function of time was also monitored. The HFO aged without the Me2+ ions displayed no hysteresis between the adsorption‐desorption curves and no substantial shifts in fractional Me2+ adsorption were observed with pH throughout 21 wk of aging. The HFO aged with the Me2+ ions displayed increasing desorption hysteresis with time for Co2+ and Cd2+, but not Pb2+. The magnitude of hysteresis followed the order Co > Cd > Pb, which is the inverse of the ionic radii of the metal sorbates. While oxalate‐extractable Fe decreased with time during a 20‐wk period, powder x‐ray diffraction was unchanged during the same period. The data presented here suggest that Co and Cd are being incorporated into the metal oxide structure via recrystallization, but Pb remains associated with the surface and excluded from incorporation.
Solute Partitioning in a Calcium Carbonate‐Phosphoric Acid‐Water System
Authors: Salingar Yigal , Kochva Malik
Published: July 2010

A range of Ca phosphates form in a time‐dependent process, when calcite interacts with a dilute orthophosphate solution. This study was conducted to ascertain the possible formation of a stable CaCO3‐PO4 compound on calcite surfaces and to characterize its precursors. The solution's ionic speciation provided evidence of the formation of a CaHCO3‐PO4 compound (CBP) with a stoichiometric Ca/P ratio of 3 and a solubility product, Ksp, of (Ca2+)3(HCO−3)3(PO3−4) = 10−28.36. This hypothesis was also supported by electron spectroscopy analyses of the surface layers of the final solid product and scanning electron microscopy (SEM). Prior to the CBP formation, either a compound with the same Ca/P ratio as dicalcium phosphate (DCP, CaHPO4) formed, or CBP was in quasi‐equilibrium at a Ca/P ratio of 1.5 to 2.3. Another possibility is that a poorly crystalline or amorphous Ca phosphate solid phase was formed. Finally, the newly formed CBP converted to hydroxyapatite (HAP, Ca5 (PO4)3OH).
Measurement of Microbial Biomass by Fumigation‐Extraction in Soil Stored Frozen
Authors: Winter Julien P. , Zhang Zhiyuan , Tenuta Mario , Voroney R. Paul
Published: July 2010

This research examined the effect of freezing on soil microbial C and N measured by CHCl3 fumigation‐extraction (CFE). A soil was stored frozen (−15°C) and sampled after 1, 7, and 170 d. Compared with a nonfrozen soil, freezing had no effect on microbial C or N, except after 7 d when C increased by 24% and N increased by 34%. The soil was also subjected to freeze‐thaw cycles (18/6 h). Microbial C and N were unaffected by one cycle, increased with two, and decreased with three cycles. In a second experiment, soil was amended with 14C‐glucose and incubated for 1, 7, or 35 d (25°C), then stored frozen for either 1, 7, 21, or 35 d. Soil incubated for 1 d showed a decline in microbial 14C (measured by CFE) after freezing for 7 to 35 d. Soil incubated for 7 and 35 d contained a 14C microbial population that was unaffected by freezing. At first glance, these observations indicated that the CFE assay was not greatly affected by freezing soils; however, closer examination indicated that microbial mortality had been masked by a freezing‐induced improvement in CFE efficiency. Increased efficiency may have resulted from improved aggregate dispersal following freezing. Homogenization of soil samples improved extraction of microbial C by 40%. In conclusion, we don't recommend that soils be frozen prior to CFE. Also, the physical disruption of soil during CFE must be severe to remove any interference of aggregate stability on the results of this assay.
Parameters Affecting Residue Nitrogen Mineralization in Flooded Soils
Authors: Becker M. , Ladha J. K. , Simpson I. C. , Ottow J. C. G.
Published: July 2010

If N mineralization from organic residues could be matched to plant uptake, N loss will be reduced. However, it is important to understand the transformations of residues and their controlling factors. Six‐week phytotron and two‐season field experiments were conducted to determine the influence of soil properties, residue composition, and soil fauna on N mineralization in flooded soils. Seven legume species, three legume‐rice (Oryza sativa L.) straw combinations, rice straw alone, and an Azolla sp. were incorporated into two soils (an Andaqueptic Haplaquoll and a Tropofluvent) at 100 mg N kg−1 dry soil and incubated for 6 wk. Residue N release in clay was about twice that of sandy soil, but was not correlated with the residues' N, C/N, water, or polyphenol contents. Net N mineralization was correlated to lignin/N (L/N). In the field, Sesbania rostrata Brem. & Oberm. and S. emerus Taub were incorporated at 60 kg N ha−1 1 d before rice transplanting. Additionally, rice straw was applied at 30 kg N ha−1 alone or with S. rostrata. Soil exchangeable NH+4‐N in unplanted light and dark subplots was measured biweekly. As in the phytotron study, initial soil NH+4‐N accumulation rates were higher from residues with relatively low L/N (S. rostrata) than from materials with higher L/N (S. emerus and S. rostrata‐rice straw mixture). Soil invertebrates were absent from dark subplots, where residue N mineralization during the first 6 wk was 30% lower than in plots exposed to light. The L/N of an applied residue may be a suitable indicator for predicting its N mineralization rate in flooded soils. Soil invertebrates may play a role in N mineralization.
Regression Models for Estimating Soil Properties by Landscape Position
Authors: Brubaker S. C. , Jones A. J. , Frank K. , Lewis D. T.
Published: July 2010

Slope geometry and the associated variation in soil properties influence runoff, drainage, soil temperature, the extent of soil erosion and deposition, and crop yields. With the current emphasis on prescription farming, approaches are needed to more effectively match inputs to production system needs while accounting for variation in soil and water resources within a field. The objective of the study was to develop simplified regression models to predict soil properties on different landscape positions from observed values on the nearly level upper interfluve. Soil samples were taken from the upper and lower interfluve, shoulder, upper and lower linear, and footslope at each of four sites in eastern Nebraska. Predictive equations were developed for 20 soil properties using multiple linear regression. Independent variables included were observed values of the property being modeled from the upper interfluve, sampling depth, and an irrigation code. Of the 100 models developed, only eight included significant contributions from all three independent variables. Models for pH, organic matter, electrical conductivity, exchangeable K, base saturation percentage, and available P and K consistently had R2 values greater than 0.50. The upper interfluve contributed significantly to the prediction of each of these properties except electrical conductivity. A comparison between average observed and predicted values for each soil property at each sampling depth revealed that the observed values generally fell within a 95% confidence interval about the predicted values. The confidence interval half‐width was generally <10% of the mean for the observed values. Further evaluation with independent data sets could be used to help strengthen and refine such generalized or geographically based models.
Characterization of the Least Limiting Water Range of Soils
Authors: da Silva A. P. , Kay B. D. , Perfect E.
Published: July 2010

The supplies of O2 and water and the mechanical impedance of soil are determined by soil structural form and soil water content. The range in soil water content in which limitations for plant growth associated with matric pressure, aeration, and mechanical resistance are minimal was defined as the least limiting water range (LLWR). This study was carried out to evaluate the LLWR as an index of the structural quality of soils. Undisturbed soil cores were taken from the 5‐ to 10‐cm depth of a silt loam and a loamy sand, cropped to corn (Zea mays L.) and red clover (Trifolium pratense L.). Soil water retention, soil resistance, air‐filled porosity, and bulk density (Db) were measured. Water contents at critical limits associated with field capacity (−0.01 MPa), wilting point (−1.5 MPa), air‐filled porosity (10%), and soil resistance (2.0 MPa) were predicted and the LLWR calculated for each measured Db. The natural variation in Db on both soils gave rise to a wide variation in LLWR. Values of LLWR varied from 0 to 0.14 cm3 cm−3 for the silt loam soil and from 0.05 to 0.13 cm3 cm−3 for the loamy sand soil. At Db above 1.36 g cm−3 for the silt loam and 1.43 g cm−3 for the loamy sand, the LLWR declined sharply with increasing bulk density. Further research relating LLWR to crop response is required before LLWR can be recommended as a soil structural quality index for crop production.
Heterogeneous Flow and Solute Transport in an Unsaturated Stony Soil Monolith
Authors: Buchter B. , Hinz C. , Flury M. , Flühler H.
Published: July 2010

Field studies of solute transport have shown that water flow velocity may vary tremendously across a field. To assess the effects of flow heterogeneity on solute transport in a stony subsoil, miscible displacement experiments were conducted in a large undisturbed gravel monolith (75‐cm length, 30‐cm diam.). The soil sample contained about 0.8 kg kg−1 of gravel. Two consecutive pulses (runs) of a Cl− solution were leached through the monolith, each at matric pressures ranging from −2.0 to −2.2 kPa. The cumulated outflows, collected with 19 separate porous plates located at the bottom, ranged from 0 to 3000 mL. The outflow rates of the individual plates were constant and highly correlated between the two runs (r = 0.95). The Cl− breakthrough curves (BTCs) of the total and individual BTCs could be well described by the classical convective‐dispersive equation. Pore water velocities, dispersion coefficients, and dispersivities of the two runs indicated a high correlation of the breakthrough behavior of the individual outlets (r = 0.995, 0.88, and 0.97, respectively). In addition, the iodine starch method revealed a heterogeneous flow pattern. Even though the column was resaturated and drained between the two runs, the results between the two consecutive runs were consistent. This suggests that the flow paths of water remained invariant and might be an intrinsic feature of a soil medium for a given water content.