The effect of nitrogen rate and weed density on spring wheat yield at two landscape positions
Van Acker, R.C.
Site-specific fertilizer applications may have implications for weed population dynamics that have been largely ignored. The purpose of this study was to determine the effect of landscape specific nitrogen application on wild oat (Avena fatua L.) and wild buckwheat (Polygonum convolvulus L.) competitiveness in spring wheat. This experiment was a split-split plot design wherein the main plot was landscape position, the subplot was nitrogen rate, and the sub-subplot was target weed density. The main plots were planted with either wild oats or wild buckwheat. The experiment was conducted at two sites near Birtle and Carman, Manitoba. Measurements of weed competitiveness included wheat grain yield per plot (as percentage of weed-free treatment), and plant dry biomass (g/m2). Other measurements included soil fertility, gravimetric moisture, soil profile characterization, and site topographical characterization to provide a detailed description of the landscape encountered at each site. Results from three site years indicate that under high nitrogen rates relative wild oat competitiveness may increase with increasing density. Results from three site years suggest that increasing wild buckwheat density caused no consistent decline in wheat yield. Landscape position has no apparent effect on either wild oat or wild buckwheat competitiveness, though analysis is ongoing. Birtle 1999 plots and biomass data from all site-years have yet to be analyzed. Independent soil characteristics will be tested for correlation to yield, biomass, density and landscape position.
site-specific farming Introduction
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