Clump Planting to Reduce the Tiller Production and Increase the Yield in Dryland Corn.

Under dryland conditions of the Texas High Plains, grain production is limited by sparse and erratic precipitation that results in severe water stress during grain formation. When plant populations are reduced to conserve soil water for use during grain filling, tillers often form during the vegetative period and negate the expected benefit. We hypothesized that growing corn in clumps spaced 1 m apart to reduce tillers, increase mutual shading, and conserve soil water for grain filling would increase grain yield. Studies were conducted during 2006 and 2007 at Bushland, Tex. with two planting geometries (clump vs. equidistant), two irrigation methods (LEPA vs. LESA) at three irrigation rates (dryland, 75 mm and 125 mm in 2006; and dryland, 50 mm and 100 mm in 2007) with 4 plants m². For dryland plots in 2007, clump plants had only 0.17 tillers  compared with 1.56 tillers per plant for equidistant spacing. Tillers accounted for 13% of the stover for the equidistant plants, but less than 1% of the grain. Clump planting produced significantly greater dry weight grain yields (2761 vs 1935 kg ha^-1 and 3902 vs. 2512 kg ha^-1during 2006 and 2007, respectively) and harvest indexes (0.54 vs 0.49 and 0.52 vs 0.39 during 2006 and 2007, respectively) compared with equidistant plants in dryland conditions. Each additional mm of irrigation increased dry weight grain yield by 18.1 and 20.3 kg ha^-1 for clump and equidistant treatments, respectively. There was no yield difference for method of irrigation on water use efficiency. Our results suggest that growing plants in clumps compared with equidistant spacing reduced the number of tillers, early vegetative growth, and LAI so that more water was available during the grain filling stage. This may be a useful strategy for growing corn with low plant populations in dryland areas.