Effect of soil NO3-nitrogen content and nitrogen fertilizer on yield of barley and canola grown on organic soils
Toews, Edward John.
Twenty field experiments were conducted in 1986 and 1987 to obtain information which would be useful for making N fertilizer recommendations for barley and canola crops grown on organic soils. Nitrogen fertilizer applied as NH4NO3 at rates of 10 to 250 kg ha-1, resulted in significant yield increases in eight of twelve barley experiments and five of eight canola experiments. Maximum grain yields for all sites averaged 2811 kg ha-1 for barley and 1122 kg ha-1 for canola. Fertilizer N required to reach 90% of maximum grain yield (90%MGY) and maximum economic grain yield (MEY) ranged between 30-130 kg ha-1 and varied inversely with spring soil NO3-N levels for most sites where economic response to N fertilizer occurred. Relationsips between % yield [yield of unfertilized treatment / maximum yield of fertilized treatment) * 100] and soil NO3-N content were evaluated for the 0-15, 0-30, 0-60, 0-90, and 0-120 cm sampling depths. The relationship of % yield to soil NO3-N to a depth of 30 or 60 cm was reasonably good and was best described by quadratic regression equations for both barley (r=0.86 for the 30 cm depth) and canola (r=0.86 for the 60 cm depth). The relationship between N uptake by the crop and soil NO3-N content was described equally well by linear or quadratic equations for all depths down to 90 cm for barley, with r values ranging from r=0.80 to 0.91, whereas quadratic models fit the relationship better at all depths for canola. The relationship between seed yield and N uptake of the crop was poor and low r values were obtained for quadratic or linear regression equations for both barley (r=0.55 and 0.53, respectively) and canola (r=0.39 and 0.36, respectively). Apparent amounts of N mineralized during the growing season ranged from 7 to 73 kg N ha-1 and averaged 33.2 kg N ha-1 for soils low in NO3_N at the time of seeding. Percent utilization of fertilizer N averaged 45% for barley and 28% for canola. Soil NO3-N levels remained relatively constant from fall to spring at sites with low initial NO3-N levels.