Abstract
Maize was grown at different population densities and row spacings in 14 trials under rain-fed semi-arid conditions in Botswana. Yields ranged widely with density and rainfall, but row-spacing effects were not significant. Yield maxima and population optima given by fitted yield/population curves increased linearly and significantly with growth-period rainfall. Highly significant linear regressions of yield at specific plant densities on growth-period rainfall were used to generate annual yield estimates for periods of up to 50 years from the long-term rainfall records of five key meteorological stations; and these estimates have been used to calculate long-term yield means and frequencies of crop failure for four plant population densities. From these values maize population recommendations are made for commercial and subsistence farmers.
