Recycling rate of N, P and K in animal feed and bedding material and use efficiency of manure N, P and K in agro-ecosystems

摘要

The losses of N and P in farmlands are of major concern due to their effects on economic and environmental sustainability in agro-ecosystems. We conducted a 9-year study to assess the cycling of N, P and K in farm produces and the use efficiency of manure N, P and K. It was found that the feeding-composting cycle caused an average loss of N, P and K in the harvested produces by about 55%, 15% and 10%, respectively. Under high-yielding conditions, the amounts of recycled N, P and K from the harvestedproduce and the feeding-composting cycle were about 30-50 kg N/ha, 8-14 kg P/ha and 18-30 kg K/ha, respectively, equivalent to 25-33% N, 36-65% P and 30-50% K fertilizers applied to the farming systems. The use efficiency of N, P and K in organic manuresin the current season increased with the extended fertilization, indicating a contributing factor of soil residual effects. The use efficiencies of N, P and K in organic manures over the 9-year period were 58%, 38% and 44%, respectively. The results suggest that nutrient recycling in farming systems improves soil fertility and nutrient use efficiency, and also reduces the use of fertilizer.