Estimating the impact of manure nitrogen losses on total nitrogen application on agricultural land in Canada

Abstract

About 1 million tonnes (1 Tg=1012 g) of livestock manure N are applied to farmland in Canada each year. Comprehensive information on manure N production and losses from manure during on-farm storage, handling and field application is scarce, especially at a regional scale. However, manure N losses during storage and land application are of considerable concern with respect to nitrogen use efficiency and environmental pollution of air, soil and water. In this paper, manure N production, manure N losses during storage and land application and manure N mineralization from organic manure and the resultant manure N available for annual crops were estimated using the Census of Agriculture database, Farm Environmental Management Survey data and manure N loss factors obtained from the literature. A database of fertilizer N application rates for field crops was developed at the regional scale based on recommendations provided in agronomic extension bulletins and fertilizer N sales. Fertilizer N and available manure N (i.e., total manure N produced minus N losses plus N mineralized from manure applied in previous years) were allocated to each of 24 crops at the regional scale from 1981 to 2006. The amount of manure N produced in Canada increased by 18.7% from 0.928 Tg in 1981 to 1.102 Tg in 2006. We estimated that 35.6% of the manure N produced was immediately available to crops, 25.6% was lost during storage and land application and 38.8% was carried over to the next year as organic N. The amount of fertilizer N applied to crops increased dramatically from 0.928 Tg in 1981 to a peak level of 1.68 Tg in 2000. There were significant changes in manure N production and application to farmland both on a regional and a temporal basis.