Yield Gain and Risk Minimization in Maize (Zea Mays) through Cultivar Mixtures in Semi-arid Zones of the Rift Valley in Ethiopia

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Abstract
SUMMARY: The effect of mixtures of cultivars on yield and risk distribution in four maize cultivars grown at four different population levels was studied in semi-arid environments in Ethiopia. Mixtures yielded between 2 and 29% more than the pure stands, but late maturing pure stands produced more biomass than mixtures. Mixtures of cultivars with similar flowering periods yielded 60% more than the pure stands in dry growing seasons, but only 30% more when there was more rain. Yield gain was associated mainly with varietal synchrony of anthesis and silking. Mixtures composed of cultivars with different flowering times were less at risk from yield loss in the case of end-of-season drought and yielded 100% more than their late flowering component in pure stand. But in long growing seasons, with an early dry spell, pure stands of the late cultivar outyielded the mixtures whereas pure stands of the early flowering cultivars yielded less than the mixtures, except in years with a serious end-of-season drought. The results indicate that it would be profitable to grow mixtures in semi-arid regions if cultivars with similar height and synchronized flowering time were grown at populations of between 65 000 and 90 000 plants ha−1.