Managing Applied Nitrogen On Winter Canola in Oregon.

Adequate nitrogen is essential for high yield and good seed quality of winter canola. Nitrogen uptake by winter canola in Oregon is illustrated in the figure below.  Both amount and timing of available nitrogen are important.  The optimum amount must be present prior to the rapid growth in April. Using this uptake curve, we have been experimenting with timing and rates of applied.  The OSU fertilizer guide for canola (http://extension.oregonstate.edu/catalog/pdf/em/em8943-e.pdf ) has a customary recommendation of 7 lb N per 100 lbs of expected grain yield.  Following this general recommendation we have been investigating timing and rates of application in dryland conditions in semiarid eastern Oregon.  Rates applied are 0, .5x, 1x and 1.5x of the recommendation.  Splitting applications varies between 1) all a planting, 2) 2/3 at planting, 1/3 spring topdress, and 3) 1/3 at planting and 2/3 spring topdress.  In general yields are best at the recommended rate (7 lb N/100 lb expected grain yield) and when all N is applied at planting or split with 2/3 at planting and 1/3 topdress.  Precipitation below average for the crop year favors application at planting.  Spring topdress allows the opportunity for adjusting N amounts when more is known about the precipitation outlook.