鸡桑药共生模式库区土壤养分变化及流失风险

密云水库是北京市主要地表水源地,为了有效防控水源保护区坡耕地以氮磷流失为主的农业面源污染,开展污染防控植物篱种植区散养和单独喂养油鸡试验研究;采集两种模式区土壤和散养模式区饲用桑植物样品,测定氮磷钾养分含量,分析土壤养分变化规律及其流失风险,建立经济有效种养生态防控模式。结果表明,与对照相比,两种油鸡养殖模式区土壤有机质、全氮、速效氮磷钾及硝态氮含量都呈显著或极显著性地升高,促进了散养共生模式区饲用桑和药用植物的生长,增加了对土壤养分的吸收;受养殖密度的影响,60只/666.7m2高密度油鸡喂养模式区或散养集中活动区有机质、全氮、全磷含量显著高于散养活动较少低密度区;受地表径流的影响,散养共生模式区坡下部油鸡少活动区域土壤速效氮磷钾含量与上部活动较多区域相比分别升高20.3%、71.9%和21.9%。喂养模式区承载粪便氮磷环境负荷分别为189 kg/hm2和84.8 kg/hm2,超过欧盟农田氮限量标准170 kg/hm2和粪便年施磷限量80 kg/hm2,具有较大的流失污染风险;20只/666.7m2低密度散养模式区承载粪便氮磷负荷分别为75.6 kg/hm2和33.9 kg/hm2,远小于环境限量标准,具有较小的流失污染风险。饲用桑与药用植物间作植物篱种植区散养油鸡排泄粪便矿化分解提供了植物养分资源,促进它们的生长,形成发达根系系统又可有效阻截模式产生有机物和氮磷流失,同时该模式提供了散养油鸡饲料资源。以上结果说明,桑树/药用植物/低密度散养油鸡是一种有效的农业面源污染生态防控共生模式,资源循环利用效率高,生态环境和经济效益好。

Soil nutrient dynamics and loss risks in a chicken-forage mulberry-medicinal plant intercropping system

Miyun Reservoir is the main source of drinking water for Beijing. However, it is increasingly threatened by losses of nitrogen and phosphorus from slope farmland in the drinking water source protection catchment. A contour hedgerow intercropping system of forage mulberry (Morus multicaulis Perr.) and medicinal plant was planted to control and mitigate the non-point source contaminants in the catchment, and free-range chickens were raised in the intercropping areas (free-range mode) and feeding on mulberry additives were set up in the adjacent areas (feeding mode). Topsoil samples from the two modes were collected for determination of organic matter, nitrogen, phosphorus and potassium contents, and mulberry samples from the free-range mode and its control were collected for determination of nitrogen, phosphorus and potassium contents in the plant. The results showed that compared with the controls, the soil organic matter content(OM), total nitrogen(TN), available N, P and K, and nitrate of the two modes areas increased significantly, which promoted the growth of the mulberry and medicinal plant and the nutrient uptake; the soil organic matter, TN and total phosphorus(TP) were greater in the feeding and free-range mode with high density of 60 and low density of 20 chickens per mu, respectively, than those in the free-range mode with fewer activity. However, compared with the upper parts of the slope farmland in the free-range chickens with high density, the soil available N, P and K at the lower parts of the slope farmland were increased by 20.3%, 71.9% and 21.9%, respectively. It suggests that the soil nutrient accumulation could relate to the feeding density and runoff. The nitrogen and phosphorus load from chicken manure in the feeding mode were 189kg/hm2 and 84.8kg/hm2, respectively, which exceed the EU limits of 170kg N/hm2 and 80kg P2O5/ hm2, respectively; it could lead to high risk of the loss of N and P to the Reservoir. The N and P load in the free-range mode were 75.6kg/hm2 and 33.9kg/hm2, respectively, much less than the environmental limits, thus resulting in less risk of nutrient losses. Therefore, the decomposition and mineralization of chicken manure in the contour hedgerow intercropping system of forage mulberry and medicinal plant can supply nutrients to the intercropping plants, on the other hand, it can effectively prevent the loss of organic matter and nitrogen and phosphorus, and provide feed to free-range chickens. These results suggest that the intercropping system of forage mulberry/medicinal plant/ low-density free-range chicken is an effective ecological mode for controlling and mitigating water contamination by agricultural non-point source pollution in the catchment.