Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 1996
Publication Date: N/A
Interpretive Summary: Soil organic carbon is an important soil property which is often used as an indicator of soil quality. Historically, tillage has resulted in a decrease in soil organic carbon which has resulted in lower soil quality. Recently, reduced tillage farming systems has resulted in an increase in soil organic carbon near the surface. This has been found most often in the Northern parts of the United States where it is colder and where reduced tillage farming systems have been more rapidly adopted. The effect of reduced tillage farming systems in Texas can only now be evaluated because research has been conducted long enough to make the effects of reduced tillage on soil organic carbon measurable. In this study, we determined soil organic carbon contents of soil with 3 crop rotations and 2 tillage systems at Bushland, Texas, which is in the drier Panhandle region of Texas. Soil organic carbon was increased with continuous cropping of either wheat or grain sorghum with no- till farming practices. Tillage resulted in lower amounts of soil organic carbon. Crop rotations which included fallow, the practice of not cropping the soil to store water, did not increase soil organic carbon amounts regardless of the farming practice used. This study helped define conditions which allow increases in organic carbon in soils in the Southern Great Plains.
Technical Abstract: Limited information is available regarding soil organic carbon (SOC) distribution and total amounts that occur in a dryland cropping situation in semiarid regions. We determined crop rotation, tillage, and fertilizer effects on SOC distribution and mass in the semiarid southern Great Plains. A cropping system study was conducted for 10-yr at Bushland, TX to compare no-till and stubblemulch management on four dryland cropping systems: continuous wheat (CW) (Triticum aestivum L.); continuous grain sorghum (CS) (Sorghum biocolor [L.] Moench.); wheat - sorghum-fallow (WSF); and wheat - fallow (WF). Fertilizer (45 kg N ha-1) was added at crop planting to main plots witch subplots in each tillage and croping treatment receiving no fertilizer. Ten yr after treatment initiation, soil cores were taken incrementally to a 65-cm depth and subdivided for bulk density and SOC determination. The no-till treatments resulted in significant differences in SOC distribution in the soil profile compared to stubblemulch tillage in all four crop rotations, although differences were largest in the continuous cropping systems. Organic carbon was concentrated in the surface seven cm of soil in the no-till system. Total SOC mass in the surface 20 cm was increased in the no-till system compared to the stubblemulch system in the CW and CS systems. No-till management with continuous crops sequestered carbon in comparison to stubblemulch management on the southern Great Plains. Fallow limits carbon accumulation.