The nitrogen cycle, with its many forms of nitrogen, is a complicated process that is influenced by many factors includingweather, soil and physical, chemical and biological processes. Use the optimum amount of nitrogen, keeping in perspective that any nitrogen not used has the potential to leach below the root zone, volatilize into the atmosphere or denitrify (potentially to nitrous oxide - a greenhouse gas).Nitrate that could potentially leach out of the rooting zone includes nitrogen that is applied in excess of crop removal and nitrogen from manure or biosolids applied during the non-growing season (late summer or fall). In Ontario, most of the drainage to groundwater occurs during the late fall to early spring period, when precipitation exceeds evaporation. On sandy, well-drained soils, much of the nitrate present in the fall could be leached into groundwater if drainage occurs. On heavier soils, more of the loss will be through denitrification. Minimizing the amount of soil nitrate present in the fall will reduce both types of loss.Management practices to reduce the risk of nitrate losses include: growing cover crops whenever manure is applied in late summer or early fall timing nitrogen applications close to crop nitrogen uptake matching total nitrogen applications to crop requirements
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