Cropping and Tillage Systems for Dryland Grain Production in the Southern High Plains

Low precipitation and high evaporative potential limit yields of dryland crops in the semiarid Southern High Plains. Improved residue management can reduce evaporation and improve water conservation. We compared no-tillage (NT) and stubble mulch (SM) residue management effects from 1984 to 1993 on leveled minibenches at Bushland, TX, using winter wheat (Triticum aestivum L.)-fallow (WF), continuous wheat (CW), wheat-sorghum [Sorghum bicolor (L.) Moench]-fallow (WSF), and continuous sorghum (CS) systems. The soil was Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Our objective was to quantify and compare soil water storage, crop water use, and grain production in order to identify the most water-efficient production system. Relative to SM management, NT management of wheat residues increased average soil water contents at planting of the next crop by 22 mm with WSF, 15 mm with WF, and 29 mm with CW; it was not as effective with sorghum residues. Mean grain yields were not affected by residue management on any cropping system, because the additional water stored with NT management was slight in relation to seasonal evapotranspiration. Cropping systems had major effects on grain yield and production. Fallow systems (WSF, WF) normally resulted in higher yields than the corresponding annual cropping system (CW, CS). However, when grain production was adjusted to an annual basis including fallow time, the CS system was most efficient at 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 than with wheat, due to greater biomass production and a 33% greater harvest index. Although wheat is the major dryland crop in the Southern High Plains, sorghum seems much better adapted to the region's predominant pattern of late spring-summer rainfall.