Legume Crops to Improve Soil Fertility for Enhanced Canola Production.

Hybrid canola is a strong consumer of nitrogen fertilizer. Legume crops fix nitrogen from the atmosphere. The objective of this study was to investigate the effects of growing legumes in rotation on hybrid canola productivity. Experiments were established at 7 locations across western Canada in 2009. Crops seeded (treatments) were field pea, lentil, faba bean, canola and wheat grown for seed, and faba bean used as a green manure. The legumes received no fertilizer nitrogen while canola and wheat were fertilized according to the soil test recommendations. In 2010, hybrid canola was seeded across all treatments and nitrogen was applied at 0, 30, 60, 90 and 120 kg/ha. Growing faba bean as a green manure resulted in the highest canola yields. In most cases, there was also a canola yield advantage when the previous crop was pea or lentils grown for seed (compared to wheat or canola). This yield benefit was not evident when faba bean was grown for seed. Growing canola on canola almost always resulted in the poorest yields possibly due to excessive depletion of soil nitrogen during the first canola year.  The results suggest that growing some legume crops the year before canola can contribute to the nitrogen economy of canola and possibly reduce fertilizer nitrogen costs.