Comparative productivity of maize, sorghum and pearl millet in a semi-arid tropical environment II. Effect of water deficits

Abstract

The comparative productivity of maize, sorghum and pearl millet subjected to water shortage during different stages of growth was analysed in terms of differences in radiation interception, radiation-use efficiency and dry-matter partitioning to grain. Those environments in the semi-arid tropics to which these species are best suited were defined. Maize out-yielded sorghum and millet under water deficit where maize grain-yield was at least 6 t ha −1, whereas sorghum yielded more than millet and maize where maize yield ranged from 1 to 2 t ha −1. Only where maize produced no grain under water deficit did millet yield the same as sorghum. In millet, grain-yield was more stable than biomass in response to water shortage, but in maize and sorghum biomass was more stable. The decrease in biomass in response to water deficit was associated more with a reduction in radiation-use efficiency than with a decrease in radiation interception, except when the water deficit was imposed during early vegetative growth, when the opposite was the case. Mobilization of pre-anthesis assimilate to grain occurred in sorghum and millet but not in maize. Where water shortage occurred, harvest index was more conservative than biomass accumulation; harvest index was reduced only when water deficits severely decreased grain-yield.