GRAIN YIELD COMPARISON OF PURE STANDS AND EQUAL PROPORTION MIXTURES FOR SEVEN HYBRIDS OF MAIZE

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Abstract
The objective of this study was to compare yielding ability and competitive effects in pure stands and equal-proportion mixtures of maize hybrids. Seven maize (Zea mays L.) hybrids were grown for 2 yr in pure stand and in all equal-proportion, two-component mixtures at plant densities of 61 500 and 136 000 plants per hectare. In 1978, a year of severe moisture stress, mixtures yielded 6% more grain on average than expected on the basis of pure stand yields. Half of the mixtures yielded more than the pure stand yield of the high-yielding component; however, one mixture yielded significantly less than predicted based on pure stand yields. In 1979, mixtures yielded as expected based on pure stand yields. The yield difference between 1978 and 1979 for mixtures was less than the difference between pure stands indicating that mixtures were, on average, more consistent in performance across environments than their components. The yield advantage of mixtures in 1978, however, was too low to recommend growing blends as a production practice. Relative yields of individual hybrids were different in pure stands compared to mixtures. Furthermore, the order of hybrids ranked according to their pure-stand yields differed from the order based on yielding ability in mixtures. In general, a direct relationship existed between yielding ability in mixtures and competititve influence. Hybrids with a high average yield across mixtures yielded more in mixtures with low-yielding hybrids than in mixtures with high-yielding hybrids. Conversely, low-yielding hybrids produced less grain when in mixtures with a high-yielding hybrid than in mixtures with a low-yielding hybrid. However, the one hybrid which was consistently the most competitive was not the highest yielding under stress conditions.Key words: Blends, corn, grain yield, hybrid mixtures, population stress, Zea mays

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