Plant Population, Rainfall and Sorghum Production in Botswana. I. Results of Experiment Station Trials

SUMMARY General mathematical relations between yield parameters, plant populations and rainfall were developed for an indigenous sorghum from the results of 28 population/row spacing trials conducted at four sites over five seasons. Populations maximizing yield increased from 25 000 to 69 000 plants ha−1 over the rainfall range 200–700 mm (pre-planting to harvest total). Tillering partly compensated for low populations but yields from 10000 plants ha−1 at 300 and 600 mm rainfall were only 80 and 61% of potential maximum, respectively. Row spacing at constant population affected tiller numbers and eventual panicle weights but not panicle numbers, and any yield differences were unrelated to rainfall.