TILLAGE INTENSITY EFFECTS ON CORN AND GRAIN-SORGHUM GROWTH AND PRODUCTIVITY ON A VERTISOL

Sustainable production systems and conservation tillage practices are needed to control water erosion on vertisols. Five levels of tillage i ntensity were tested for 3 yr for effects on growth and yield of corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench.] on a Ho uston Black clay soil (fine montmorillonitic, thermic Udic Pellusterts ). Tillage intensity treatments included: chisel plow with secondary t illage; disk only; no-till with residue rakes at planting; no-till wit h midseason cultivation; and no-till. Corn plant populations were grea ter in tilled treatments than in no-till treatments in 2 of the 3 yr. Corn above-ground biomass production was generally reduced in no-till treatments early in the growing season, but by silking differences amo ng treatments were not significantly different. Corn yielded 840 lb/ac re more on average with tillage than with no-till. Plant population di fferences accounted for much of the difference in corn grain yields, w ith low plant populations restricting yield in some years. Grain sorgh um populations were not consistently affected by tillage intensity, an d biomass production was less sensitive to tillage intensity than corn . Grain sorghum yields were as large or larger in no-till treatments t han in tilled treatments, except in one instance where population was reduced.