NITROGEN, POTASSIUM, SULFUR, AND BORON FERTILIZATION OF CANOLA

Increased demand and developing infrastructure may result in canola (Brassica napus and campestris) acreage expanding in the midwestern USA. Fertility requirements and critical tissue levels of canola grown in the Midwest have not been reported. The objective of the experiment was to examine current N, K, S, and B fertilizer requirements for canola production in Illinois. These field experiments were conducted at Brownstown, IL (1989 and 1990), on a Cisne silt loam soil (fine, montmorillonitic, mesic Mollic Albaqualf) and at Urbana, IL (1990), on a Flanagan silt loam soil (fine, montmorillonitic, mesic Aquic Argiudoll). The fertilizer treatments were: N (60, 120, 180 lb N/acre in 1989 and 0, 60, 120, 180, and 240 lb N/acre in 1990), K (0 and 125 lb K/acre) at Brownstown only, S (0, 10, 20 lb S/acre), and B (0 and 1 lb B/acre). Application of all fertilizers increased concentration of each respective nutrient, but only N affected grain yield. Increasing N rate significantly increased vegetative dry weight at the start of flowering, delayed maturity, and increased grain yield. The calculated optimum economic N fertilizer rate was 225 lb N/acre at Urbana and 236 lb N/acre at Brownstown. At the onset of flowering, whole-plant N concentration less than 3.5 to 4.0% was associated with reduced yields. This may indicate the critical N concentration for canola. Because of the indeterminate growth habit, time of sampling will have to be standardized. Sufficiency levels for Illinois conditions are 2.0 to 3.5% K, 0.4 to 0.5% S, and 20 to 30 ppm B, respectively.