Nitrogen budgets following land application of composted or stockpiled feedlot manure containing wood-chips or straw bedding to barley silage for 12 years.

摘要

Land 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.