Variation among sorghum hybrids in the plant density required to maximise grain yield over environments

Abstract

In circumstances of limited water supply, the stability of grain yield in sorghum may be improved by manipulating the interaction between plant spacing and crop maturity. The plant density which maximises grain yield over environments may also be influenced by differences in compensatory capacity among hybrids of the same maturity category. Consequently, variation among 8 sorghum hybrids in the response of grain yield to plant density was examined at 5 locations. When number was used as a covariate, the interaction between hybrid, density, and site was significant (P<0.05) for grain yield. Hybrids differed in the plant density which maximised grain yield, even among hybrids of similar maturity. For the medium maturity hybrids, Hylan 4x8 required a higher plant density than Goldmine to maximise its grain yield at each of the 5 sites, while for the quick hybrids, Pride required a higher density than Nugget II at 4 sites. Among the slow and very slow hybrids, the plant density which maximised grain yield did not differ consistently. Because discrimination among hybrids in the plant density required to maximise grain yield was much greater in low yielding environments, some advantage may be obtained by reducing the target plant density for hybrids of greater compensatory capacity, when drier than normal conditions are expected.