Abstract
ABSTRACTLand application of composted feedlot manure (CM) instead of stockpiled manure (SM) at increasing application rates to cropland, or use of wood-chip (WD) instead of straw (ST) bedding, may influence the nitrogen (N) balance and cause N surpluses. This could result in environmental losses of N to the atmosphere, surface, or ground waters. We determined the influence of manure type, bedding material, and application rate (13, 39, 77 Mg ha−1 dry wt.) on cumulative N inputs, outputs, and N balance (aboveground system) for a long-term (since 1998) field experiment where manure had been repeatedly applied for 2, 7, and 12 yr. The annual N inputs considered were N in organic amendments or inorganic fertilizer (IN), and N in irrigation water. The annual N outputs considered were N in crop uptake, NH3 volatilization, and N2O gaseous loss. After 12 applications, cumulative N deficits occurred for the unamended control (−1140 kg N ha−1) and IN treatment (−678 kg N ha−1), and cumulative N surpluses were found for the organic amendments (689 to 12,200 kg N ha−1). Manure type, bedding, and application rate influenced the N balance for the three timelines but their effects often involved two- or three-way interactions. The N balance after 7 and 12 applications was significantly lower for CM-WD treatment compared to CM-ST, SM-ST, and SM-WD at the 39 and 77 Mg ha−1 rates, suggesting that composted manure with wood chips might be used to reduce cumulative N surplus at these two higher rates in the longer term.
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