Agronomic Evaluation of Novel Green Manures for Organic Grain Production in Eastern Canada
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Green manures (GrM) are used to meet organic crop-N needs. Productivity and N-accumulation of three spring-planted full-season GrM in Nova Scotia and two in Québec were compared. Hairy vetch-oats accumulated 123-292 kg biomass-N ha-1 and this was significantly correlated to growing degree days (GDD). In two site years out of four however, red clover was able to fix from the atmosphere a statistically equivalent amount of N as hairy vetch. Green manures were incorporated either in the fall or the spring the following year. Over the course of a 1225 GDD soil incubation, hairy vetch-oats and red clover or red clover-oats mineralized statistically similar rates and quantities of mineral-N (93.7-111.4 kg N ha-1 and 30.0-43.7 kg N ha-1 in soils from Nova Scotia and Québec, respectively). In Nova Scotia, spring incorporation of GrM resulted in greater spring wheat N-uptake (48.6 kg N ha-1) than fall incorporation (40.6 kg N ha-1).