Over the past 15-years, swine-producing confined animal feeding operations (CAFOs) have proliferated throughout the Southeastern United States, particularly in North Carolina. Waste at these facilities is collected in open-air lagoons and the liquid phase is land-applied as fertilizer by sprinkler irrigation. Numerous investigations have focused on individual aspects of the fate of nitrogenous liquid waste, but none has attempted a comprehensive analysis of post-application transformations and losses. On three occasions, we experimentally applied liquid swine waste at typical industry doses of 1.2 and 2.5 cm-ha (40-130 kg N ha À1 ) to carefully defined plots in an active spray field on a representative North Carolina CAFO and constructed a nitrogen mass balance for the waste by assessing most N pools and transformations in post-application observation periods of 14-19 days. We consistently recovered more N than applied, by an average of 126%. This was likely due to mineralization of endogenous organic-N, a reservoir that was not measured. Plant assimilation clearly represented the most important N sink for this fertilizer type, accounting for 25-117% of the applied N. Offsite loss to leaching and volatilization and onsite accumulation in the inorganic phase and in microbial biomass all assumed secondary and roughly equal importance; each term represented about 5-20% of the applied N. Denitrification was inconsequential in N loss from a mass standpoint, accounting for 2% of the effluent. The post-application fate of N in liquid swine waste did not differ fundamentally from other organic and inorganic fertilizers, as the relative importance of all loss and storage terms fell within the ranges of values given for other fertilizers. However, liquid swine waste did differ from other N fertilizers in the rate of processing. Transformations occurred rapidly due to the immediate post-application contact of liquid swine waste-N with plant roots and microbes in a form (NH 4 + -N) immediately available for use.
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