Planting Geometry Effects On Sorghum Productivity in Water Limiting Conditions.

Prior studies indicate clumped planting can increase grain sorghum yield up to 45% under water deficit conditions possibly by reducing tiller number, increasing radiation use efficiency, and preserving soil water for grain fill. The objective of this study was to evaluate effects of planting geometry on sorghum grain yield formation. The field study was conducted in a split-plot design at three locations with two sorghum lines, four populations, and two planting geometries. Crop responses included leaf area index, light transmittance, radiation use efficiency, biomass harvest, and components of yield. Delayed planting decreased yield 39%, a later maturing hybrid increased yield, relative to an early hybrid by 11% under water sufficiency. Clumped planting increased the fraction of fertile culms (culms which formed panicles) from 5-14%. It reduced the number of culms m^-2 by 12% under water limiting conditions (at one of two locations) but increased culms m^-2 16% under water sufficiency. Seeds per panicle and seed weight generally compensated for differences in panicles m^-2 which resulted from planting population. Planting geometry altered components of yield for growing environments differing in planting date and available water.