ABSTRACT

Soil carbon, nitrogen and phosphorus concentrations were determined and the soil structure evaluated for four annual courses in a rotation (Year 1, fattening, non-nose-ringed pigs at a stocking density of one pig produced per 150–200 m² depending on seasonal conditions; Years 2 and 3, spring wheat; Year 4, reseeded grass-clover) for organically accredited pig production on a shallow calcareous soil in southwest England. Soil nitrogen and phosphorus concentrations and organic decomposition rates were highest when pigs were present, consistent with recent inputs of feed and nutrient redistributed in dung and urine. Soil nitrogen and phosphorus concentrations and organic decomposition rates declined over the subsequent courses. The overall production system was sustained by inputs of pig feed one year in four, with nutrients being carried over to subsequent years. The pigs caused significant physical damage leading to soil disaggregation, but the soil structure recovered over the following 2 years. The high concentrations of inorganic nitrogen, particularly nitrate at high concentration ‘hot-spots’ around feeders and housings, and the poor soil structure caused by the pigs represented a significant risk of loss of nutrients and soil. At this site, vertical movement of disaggregated soil and nutrients through cracks and fissures in the underlying limestone may have been an additional route of loss alongside denitrification, volatilisation, erosion and run-off.

摘要

测定土壤碳、氮和磷浓度，并对土壤结构进行四个年度轮作的评估（第 1 年，育肥、无鼻环猪，放养密度为每 150-200 m ^{2生产一头猪）}视季节条件而定；第 2 年和第 3 年，春小麦；第 4 年，重新播种的草三叶草）用于在英格兰西南部的浅钙质土壤上进行有机认证的生猪生产。当有猪存在时，土壤氮和磷浓度以及有机物分解率最高，这与最近在粪便和尿液中重新分配的饲料和养分输入一致。土壤氮和磷浓度以及有机分解率在随后的过程中下降。整个生产系统由四年中一年的猪饲料投入维持，营养物质被转移到随后的几年。猪造成了严重的物理损害，导致土壤解体，但土壤结构在接下来的 2 年内恢复。高浓度的无机氮，尤其是在喂食器和鸡舍周围的高浓度硝酸盐“热点”，以及由猪造成的土壤结构差，是养分和土壤流失的重大风险。在这个地点，分解的土壤和养分通过下层石灰岩的裂缝和裂缝的垂直运动可能是除硝化、挥发、侵蚀和径流之外的另一条损失途径。