Effect of Diammonium Phosphate as In-Furrow Starter Fertilizer on Winter Canola Grain Yield and Quality

Winter canola is a valuable rotational crop in Oklahoma. Starter fertilizer application is viewed as a way to improve canola yields. Field experiments were conducted in Dacoma, El Reno, Fairview, Fort Cobb, Kingfisher, Lahoma, Lamont, Miami, and Perkins, OK to evaluate the effect of applying diammonium phosphate (DAP, 18-46-0: N-P2O5-K2O) in-furrow on winter canola grain yield and quality. Diammonium phosphate was applied with the seed at planting at 22 and 30 lb/ac in no-till (NT) and minimum/conventional till (CT) systems, respectively. Canola variety 'DKW 46-15' was seeded from September 10 to October 10, 2016 at 3.75 lbs/ac spaced at 7.5 (CT) and 15 in (NT). Four of the 10 locations responded to in-furrow application of DAP. Yield response ranged from 1 to 6 bu/ac. Locations that had low soil test phosphorus and low soil pH generally had higher yield response (3-6 bu/ac) than all other locations. Effect of in-furrow DAP on the oil and protein content of winter canola was not significant. Results indicated the importance of accounting for both soil test phosphorus and soil pH completely when providing nutrient recommendations in winter canola.