Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 23, 1996
Publication Date: N/A
Interpretive Summary: We report the results of a long-term (10 year) study to evaluate combinations of tillage and dryland cropping systems that use precipitation efficiently to produce grain and at the same time, conserve and protect soil and water resources in the dry, wind-erosion prone, Southern Great Plains. We evaluated no-tillage (NT) management for which all crop residues are left on the surface and weeds are controlled with herbicides and stubblemulch management for which large sweeps are used to undercut the soil surface at a 3 to 5 inch depth to control weeds. Stubblemulch tillage buries 15-20% of surface residues with each operation. Cropping rotations were wheat-fallow (WF), wheat-sorghum-fallow (WSF), annual cropped sorghum (CS), and annual cropped wheat (CW). Results show that no-tillage reduced evaporation and conserved precipitation and soil resources but that it only increased grain yield about 10%. In contrast, cropping systems exerted a threefold effect on annual grain production. The most efficient cropping system was CS, which produced 92% more total grain than WSF, 240% more than CW, and 320% more than WF. Thus while tillage system selection is extremely important for reducing evaporation and reducing wind and water erosion, crop selection and sequencing (rotation) were much more important in determining annual grain production.
Technical Abstract: We compared no-tillage (NT) and stubblemulch (SM) residue management effects from 1984 to 1993 on leveled minibenches at Bushland, TX, using four dryland cropping systems: winter wheat (Triticum aestivum L.) - fallow (WF); continuous wheat (CW); wheat - sorghum (Sorghum bicolor [L.] Moench) - fallow (WSF); and continuous sorghum (CS) systems. Our objective ewas to quantify and compare soil water storage, water use, and grain production for differing intensity cropping systems with SM and NT residue management. No-tillage management of wheat residues after harvest increased average profile soil water contents at planting of the next crop by 22 mm on WSF; 15 mm on WF; and 29 mm on CW in comparison to SM. Mean grain yields were not affected significantly by residue management on any cropping system because the additional soil water stored with NT management during all years was small in relation to seasonal ET. Cropping systems had major impacts on grain yield and production. Systems with fallow (WSF WF) normally had higher yields than the same crop grown in annual cropping systems (CW, CS). However, when the effects of time required by fallow were included in grain production on an annual basis, the CS system was by far the most efficient system for using precipitation, producing 92% more grain than WSF, 240% more than CW, and 320% more than WF. Grain production was more than twice as great with sorghum as with wheat as a result of greater biomass production and a 33% greater harvest index. Although wheat is the major dryland crop, sorghum appears much better adapted to the predominately late spring-summer rainfall distribution pattern of the Southern High Plains.