Maize response to plant population and soil water supply: I. Yield of grain and total above-ground biomass

Abstract

The effect of the level of water deficit on the yield of grain and total above-ground biomass of maize planted at greatly differing densities was investigated in a strictly controlled field experiment, repeated for four seasons. Differences in water supply were obtained by the seasonal variation in rainfall and by supplementing the rainfall with irrigation in some of the treatments. In each season the highest level of water represented conditions of adequate soil water supply. An abundant supply of inorganic nutrients enabled the study to be confined to an investigation of the interaction between level of soil water supply and planting density on the yields of maize. At adequate levels of soil water supply yields of grain and total above-ground biomass increased over the whole range of planting densities. The highest density employed (111 111 plants ha−1) gave rise to a LAI in excess of 8. Reduction in the supply of soil water caused a reduction in the critical planting density for maximum biomass production, but did not affect the asymptotic nature of the relationship between biomass yield and planting density. The relationship between the grain yield and planting density was influenced by a deficient level of soil water in two ways: firstly, by changing the nature of the yield response from nearly asymptotic to distinctly parabolic, and secondly, by reducing optimum density to lower levels as water stress became more severe. © 1992 Taylor & Francis Group, LLC.