Growing dryland grain sorghum in clumps to reduce vegetative growth and increase yield

Stored soil water and growing season precipitation generally support early season growth of grain sorghum (Sorghum bicolor L. Moench) in dryland areas but are insufficient to prevent water stress during critical latter growth stages. The objective of this study was to determine if growing plants in clumps affected early season growth and subsequent grain yield compared to uniformly spaced plants. We hypothesized that growing grain sorghum plants in clumps would result in fewer tillers and less vegetative growth so that more soil water would be available during the grain-filling period. Results from 3 yr at Bushland, TX, and I yr at Tribune, KS, showed that planting grain sorghum in clumps of three to six plants reduced tiller formation to about one per plant compared to about three for uniformly spaced plants. Grain yields were increased by clump planting by as much as 100% when yields were in the 1000 kg ha(-1) range and 25 to 50% in the 2000 to 3000 kg ha(-1) range, but there was no increase or even a small decrease at yields above 5000 kg ha(-1). Our results suggest that planting grain sorghum in clumps rather than spaced uniformly conserves soil water use until later in the season and may enhance grain yield in semiarid dryland environments.