The influence of plant densities on yields and agronomic performance of a semi-dwarf and a conventional type corn hybrid in southern Manitoba

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Murphy, Keith
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Plant density (number of plants/unit area of land) is an important factor in both grain and silage corn production. Optimum plant densities result in the highest level of production per unit area of land, therefore it is important that they be determined for the specific area in which the corn hybrids are grown. The recent introduction of a semi-dwarf corn hybrid in Ontario has prompted optimum semi-dwarf corn plant density studies such as the one described in this thesis. Original studies with semi-dwarf corn in Ontario, pegged optimum plant densities at 172,000 plants/ha, which is approximately three times that of current recommendations for conventional hybrids. Grain yields from populations sown at this plant density were comparable with yields from conventional hybrids sown at the recommended plant density of approximately 50 - 60,000 plants per hectare. The present study was undertaken to determine the optimum plant density of the semi-dwarf hybrid (391134R) for both grain and silage production in southern Manitoba. It was also intended to compare the semi-dwarf's yield to those of a commonly grown corn hybrid in Manitoba. The two corn hybrids (391134R and the check hybrid - Pioneer 3995) were grown at 3 locations over the growing seasons of 1984 and 1985. The replicated tests included 5 plant densities for each hybrid for the over-all six station year testing program. Besides grain and silage yields, measurements on development and agronomic characteristics were recorded and analysed. The results indicated that the plant densities of 11.5 and 13.8 plants/m2 were optimum for 391134R for grain and silage yields, respectively. Although an optimum grain yield for the conventional hybrid, Pioneer 3995, was not clearly defined by this experiment, an optimum silage yield for this hybrid was determined to be 6.9 plants/m2. This result corresponds with the provincially recommended seeding rates for silage corn. The semi-dwarf hybrid (3991134R) significantly outyielded Pioneer 3995 (at the recommended 5.7 plants/m2) consistently in this experiment. Agronomic advantages for 391134R were also measured in comparison to Pioneer 3995, the greatest of which was the semi-dwarfs' relatively low values for stalk breakage and root lodging. Although 391134R matured a few days later than Pioneer 3995, it met all the criteria put forth in this study to be considered a viable hybrid in this province.