Slope Position, Nitrogen Fertilizer, and Fungicide Effects on Diseases and Productivity of Wheat on a Hummocky Landscape

Precision agriculture technology allows growers to selectively apply inputs to different management units within a single field. A 4-yr study consisting of a split-split block experiment was conducted in the northern prairies to determine the effects of foliar fungicide (FU) and N fertilizer application to slope (SL) position based management units across a hummocky landscape on leaf spot and root diseases, biomass and seed yield, and seed quality of wheat (Triticum aestivum L.). Fertilizer rates (0, 40, 80, and 120 kg N ha^-1) were applied in strips across two SL positions (upper and lower) as main plots with FU application (treated and untreated) as subplots. Leaf spot diseases were consistently more severe on the upper than lower SL and reduced by FU treatment but varied inconsistently with changes in N rate. Biomass and seed yield in the two dry years were greater on the lower than upper SL. They were increased by FU treatment in 3 of 4 yr and N rate in 1 yr. Thousand-kernel weight (TKW) and grain test weight (TW) were usually greater on the upper than lower SL, and TKW was increased by FU application in 2 yr. Protein content usually increased with increasing N rate, but the effect of SL and FU varied among years. The paucity of interactions among treatment factors indicated that selective application of FU and N fertilizer to SL position based management units for improvement of yield and seed quality was not warranted.