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Positioning Strategy of Maize Hybrids Adjusting Plant Population by Management Zones
A. A. Anselmi, J. P. Molin, R. Trevisan, M. T. eitelwein, A. Colaço
University of São Paulo

Choice of hybrid and accurate amount of plants per area determines grain yield and consequently net incomes. Local field adjustment in plant population is a strategy to manage spatial variability and optimize environmental resources that are not under farmer control (like soil type and water availability). This study aims to evaluate the response of hybrids by levels of plant population across management zones (MZ). Six different hybrids and five rates of plant populations were analyzed starting with a local recommended seeding rate (55000 pl ha-1) and offsetting it in 40% and 20% below and above this reference. Three field experiments were conducted in commercial fields from 2012 to 2015 in Brazil tropical region (Maracaju – MS) where corn is grown as a secondary crop following soybean. MZ were establish by cluster analysis of soil electrical conductivity (ECa), yield maps (YM) and elevation. Long strip tests with fix rate of plants were carry out crossing different zones. High yielding MZ reached higher average yield compared to the low yielding MZ. The optimal plant population can vary by up to 5743 pl ha-1 across MZ within the same field, depending on hybrid. Responsive hybrids to plant population are key to achieving positive results using variable rate seeding (VRS). Grain yield achieved by farmers in the second crop is limited by use of low plant population density, about 25% away from the optimal plant density. Years with lower yield averages have a narrow optimal plant population interval. Although, further studies are required to understand the potential of VRS within fields also considering levels of fertilization and different planting dates. However, to increase the adoption of VRS it is necessary to facilitate the process of MZ setting and optimal plant population choice.

Keyword: Management zones (MZ); variable rate seeding (VRS); corn yield; spatial variability