Soil Aggregation and Carbon and Nitrogen Storage under Soybean Cropping Sequences
2004
Wright, Alan L. | Hons, Frank M.
Management practices, such as no-tillage (NT) and high-intensity cropping sequences, have the potential to enhance C and N sequestration in agricultural soils. The objectives of this study were to investigate the impacts of conventional-tillage (CT), NT, and multiple cropping sequences on soil organic carbon (SOC) and nitrogen (SON) sequestration and on distribution within aggregate-size fractions in a southcentral Texas soil after 20 yr of treatment imposition. No-tillage management increased soil aggregation compared with CT, with the bulk of SOC and SON storage present in larger aggregate-size fractions (>2 mm, 250 μm to 2 mm) at both soil depths. Multiple cropping systems, such as a grain sorghum [Sorghum bicolor (L.) Moench]/wheat (Triticum aestivum L.)/soybean [Glycine max (L.) Merr] (SWS) rotation and a wheat/soybean (WS) doublecrop had the highest SOC and SON storage, while the continuous monoculture soybean treatment had the lowest storage. Soil organic C and SON storage were significantly greater under NT than CT for all cropping sequences at 0 to 5 cm and for SWS and WS at 5 to 15 cm. At the 0- to 5-cm depth, NT increased SOC storage by 64% and SON storage by 76% compared with CT. However, at 5 to 15 cm, NT only increased SOC storage by 28% and SON storage by 40%. The use of NT showed a greater impact for increasing SON storage than for SOC storage, suggesting that N cycling is an important factor related to soil C sequestration potential.
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