Soil aggregate size distribution and total organic carbon in intra-aggregate fractions as affected by addition of biochar and organic amendments
Authors: Odugbenro George O. , Liu Zhihua , Sun Yankun 
Published: June 2020

<p>A two-year field trial on maize (<em>Zea mays</em> L.) production was established to determine the influence of biochar, maize straw, and poultry manure on soil aggregate stability, aggregate size distribution, total organic carbon (TOC), and soil microbial biomass carbon (MBC). Seven treatments with four replications, namely CK, control; S, 12.5 Mg ha-1 straw; B1, 12.5 Mg ha-1 biochar; B2, 25 Mg ha-1 biochar; SB1, straw + 12.5 Mg ha-1 biochar; SB2, straw + 25 Mg ha-1 biochar; and M, 25 Mg ha-1 manure were tested at four soil depths (0–10, 10–20, 20–30, and 30–40 cm). Aggregates were grouped into large macro-aggregates (5–2 mm), small macro-aggregates (2–0.25 mm), micro-aggregates (0.25–0.053 mm) and silt + clay <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">(&lt;0.053 mm). Biochar, straw,<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> and manure applications all had significant effects (<span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"><em>p </em><span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">&lt; 0.05) on aggregate stability, with B<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">2 <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">at<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> 20 cm soil depth showing the greatest increase (62.1%). SB<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">1 <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">of small macro-aggregate fraction<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> showed the highest aggregate proportion (50.59% ± 10.48) at the 20–30 cm soil depth. The highest TOC was observed in SB<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">2 <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">(40.9 g kg<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">-1<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">) of large macro-aggregate at 10–20 cm soil depth. Treatment effects on soil MBC was high, with B<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">1 <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">showing the greatest value (600.0 µg g<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">-1<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">) at the 20–30<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> cm soil depth. Our results showed that application of biochar, straw, and manure to soil increased<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> aggregate stability, TOC as well as MBC.</span></span></span></span></span></span><br style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" /></span></span></span></span></span></span></span></span></span></span></span></span></span></span></p>