基于土壤养分平衡的畜禽养殖承载力研究

Livestock and Poultry Carrying Capacity of Land Based on Soil Nutrient Balance

为了合理控制畜禽养殖规模、有效降低畜禽养殖污染,采集江门市新会区水田、菜地、园地和林地共35个土壤样品,监测N、P养分以及Cu、Zn、As等重金属含量。基于土壤养分平衡模型,对适宜的畜禽养殖量进行了研究。结果显示,新会区土壤肥力水平较高,在35个监测点中,有29个点位土壤的全氮含量超过1.2g·kg^(-1),占比82.9%;11个镇街中,除了大泽,其余10个镇街的部分土壤存在N肥或P肥过剩,部分农用地土壤还同时出现N肥和P肥过剩;部分果园土壤出现As超标,沙堆、古井、罗坑三个镇果园土壤As超标倍数分别为1.76、0.66、0.21,古井林地、双水、司前的水田As超标倍数分别为0.31、0.15、0.082;全区现状畜禽养殖总量为125.7万头猪当量,而基于土壤养分平衡的畜禽养殖总量为27.10万头猪当量。因此,在新会区畜禽养殖污染防治工作中,除了需要大幅削减各镇的养殖规模、提高有机肥施用比例外,同时需关注畜禽粪便施用可能导致的农用地As污染风险。

【Objective】As livestock and poultry droppings are rich in nutrients, such as nitrogen, phosphorus, potassium, etc., they are often used as organic manure in farmland fertilization. However, excessive application of the organic manure may lead to accumulation of nitrogen and phosphorus in the soil and consequently leaching of N and P from the soil with rainfall into water bodies, causing serious pollution of surface water and groundwater. In order to rationalize the scale of livestock feeding, effectively reduce pollution from the livestock and poultry feeding industry in Xinhui District, Jiangmen City and ensure healthy and sustainable development of the industryc, it is necessary to study current status of soil N and P in the farmlands and figure out how much livestock and poultry manure the farmlands demand 【Method】 A total of 35 soil samples were collected from paddy fields, vegetable plots, orchards and forest lands, separately, for analysis of N, P, Cu, Zn and As contents with the standard methods. By referring to the “Standard for Grading of Soil Fertility” and “Standard of Soil Environment Quality for Farmlands”, evaluation was done of soil nutrients and heavy metals in the soil relative to soil type in Xinhui Region, Based on the data cited from the “Statistic Yearbook of Xinhui” concerning types, yields and planting areas of the major crops in the region, crop nutrient demand was calculated. Based on the soil test for N and P contents in combination with crop planting areas, soil nutrient supplying capacity was worked out. In the end, Study was performed of rational livestock and poultry feeding scales, using a nutrient balance model. 【Result】All the findings in this study indicate that the soils in Xinhui are quite high in fertility. Among the 35 sampling points, 29 or 82.9% exceeded 1.2 g·kg^-1 in TN. The paddy soils were the highest in TN, reaching up to 2.92 g·kg^-1, and the orchard soils were in TP, reaching up to 3.51 g·kg^-1 in Gujing Town, where all towns, except for Daze Town, had soil N or P surplus, and some farmlands even did both. In addition, As pollution was found in some orchards, which might be attributed to the use of organic-arsenic pesticides in the past. Based on the nutrient balance model, livestock and poultry carrying capacity of Xinhui District was worked out to be 270 985 heads of pig equivalent. However, the current load of livestock and poultry has already reached as high as 1 257 295 heads of pig equivalent. Shuangshui and Siqian are the top two towns in, livestock and poultry carrying capacity, reaching 80 145 and 70 843 heads, respectively, the sum of which accounts for 55.7% of the total of the whole district. On the other hand, the following towns, Huicheng, Sanjiang and Daao, do not have any livestock and poultry carrying capacity. 【Conclusion】 Xinhui District is quite high in soil fertility. For the sake of environmental protection, it is essential to have the whole district adopt the practice of soil-test-based fertilization. Besides, to prevent and control of pollution from the livestock and poultry feeding industry in Xinhui, it is of paramount importance to limit the scale of livestock and poultry breeding and moreover to pay special attention to the risk of potential As pollution of the farmlands, while enlarging the proportion of organic manure in fertilization.