Size and density fractionation of carbon and nitrogen in long-term wheat management systems. (4048)
Authors:
F. Dou* - Texas A&M Univ.
A.L. Wright - Texas A&M Univ.
F.M. Hons - Texas A&M Univ.
Abstract:
Accumulation of soil organic carbon affects soil quality, greenhouse gas mitigation, and overall agricultural ecosystems. A conceptual model was utilized to explore the dynamics of soil C and N in continuous wheat (Triticum aestivum L.), continuous wheat/soybean [Glycine max (L.) Merr.], and wheat/soybean-sorghum [Sorghum bicolor (L.) Moench.] sequences under conventional tillage (CT) and no tillage (NT) with and without N fertilizer in a long-term (20-year) experiment. Only surface (0-5 cm) soil samples were studied. Soil organic C (SOC), total N (TN), particulate organic C, microaggregate C, silt- and clay-associated C and N, and biologically-resistant C (ROC) and N were determined. SOC and TN were 43% to 55% greater under NT than CT. However, a significant interaction between N fertilization and tillage treatments was observed. Nitrogen addition significantly increased SOC and TN only under NT. Soil C:N ratio was greater under CT than NT indicating a possibly greater accumulation of N under NT. Silt- and
clay-associated C, microaggregate C, ROC, and SOC were highly related. A greater portion of SOC in the smaller than 53 um fraction with CT contrasted with a greater portion of SOC in the microaggregate fraction with NT indicated that SOC under NT was more physically protected.
Speaker Information: Fugen Dou, Texas A&M Univ., Room 615 Heep Center Texas A&M University, College Station, TX 77843; Phone: (979)845-8738; E-mail:
Session Information: Monday, November 1, 2004, 1:00 PM-3:00 PM Presentation Start: 1:00 PM (Poster Board Number: 2726)
Keywords: Soil Organic C; Particulate organic C; Resistant Organic C; Silt and Clay associated C
