湖北省秸秆和畜禽粪污还田化肥替减潜力与环境承载力分析

湖北省畜禽业规模化养殖水平显著提高，秸秆资源量逐年提升，农业废弃物还田不仅可以减少农业面源污染，还可以减少化肥施用。该文将湖北省分为5个种植区域（即鄂东南低山丘陵区、鄂北低山丘岗区、鄂西北山地区、鄂中平原区以及鄂西南山地区）。基于2019年－2020年统计数据，收集不同区域主要畜禽（猪、肉牛、奶牛、羊、肉鸡、蛋鸡）的存栏量、出栏量以及饲养周期，主要农作物种植面积和经济产量，计算湖北省畜禽粪污的养分供给量，评估不同区域的畜禽养殖现状是否超过土地承载畜禽粪污的最大容许数量。根据不同农作物的草谷比以及秸秆养分含量，计算出湖北省农作物秸秆的养分资源量以及养分还田量。湖北省不同区域畜禽养殖量均未超出当地最大承载容纳量，其中鄂北地区的土地承载力指数最高，达到了0.35～0.78，鄂中地区的土地承载力指数仅在0.17～0.54，有较大的空间来发展畜禽养殖业。2019年湖北省畜禽粪污养分资源量分别为36.89万t N、14.03万t P2O5、52.06万t K2O。按照畜禽粪污肥料化还田率65%计算，畜禽粪肥的养分还田总量分别为23.98万t N、9.12万t P2O5、33.70万t K2O，理论可替减化肥比例分别为17.3%、11.9%、56.2%。湖北省主要农作物秸秆资源总量以鄂中地区秸秆资源量最高，鄂西北地区最低。当前湖北省秸秆养分资源为31.07万t N、9.98万t P2O5、68.30万t K2O，理论可替减化肥比例分别为22.5%、13.1%、114.0%。湖北省主要农业废弃物还田理论可基本满足主要农作物的钾素需求，实现氮肥消费量减少39.8%、磷肥消费量减少25.0%。该文通过计算湖北省主要农业废弃物（畜禽粪污、秸秆）的养分资源量，评估农业废弃物还田的化肥可替减潜力以及畜禽粪污土地承载力，为湖北省农业绿色发展提供理论依据和数据支撑。

Reduction potential and environmental carrying capacity of straw and livestock manure returning to fields in Hubei Province of China

The large-scale breeding level of livestock and poultry industry in Hubei Province has been significantly improved, and the amount of straw resources has been increased year by year. Returning agricultural wastes to the field can not only reduce agricultural non-point source pollution, but also reduce the application of chemical fertilizers. Based on relevant statistical data and literature, this study collected the amount of livestock and poultry (i.e., pigs, beef cattle, dairy cows, sheep, broilers, layers) in stock, market and growth cycle, and the planting area and economic yield of various crops (i.e., the low hilly area in southeastern Hubei, the low hilly area in northern Hubei, the mountainous area in northwestern Hubei, the plain area in central Hubei, and the mountainous area in southwestern Hubei). Based on the statistical data from 2019 to 2020, We calculated the nutrient supply of livestock and poultry waste, and further evaluated whether the current situation of livestock and poultry breeding in Hubei Province exceeded the maximum allowable amount of soil carrying livestock and poultry waste. According to the ratio of straw to grain of different crops and nutrient content of straw, we analyzed the nutrient resources and the theoretical nutrient returning amount of crop straw. The land carrying capacity index of livestock was the highest in Northern Hubei, reaching to 0.35-0.78. The land carrying capacity index of Central Hubei was only 0.17-0.54, indicating that there would be a large space to develop livestock and poultry breeding. In 2019, the nutrient resources of livestock and poultry waste in Hubei Province were 368 900 t N, 140 300 t P2O5 and 520 600 t K2O, respectively. Based on 65% of livestock manure and fertilizer returning to the field, the total nutrient returning to the field of livestock and poultry manure would be 239 800 t N, 91 200 t P2O5 and 337 700 t K2O, respectively, with the ratio of fertilizer replacement of 17.3%, 11.9% and 56.2%, respectively. The total amount of straw resources of main crops in Hubei Province was the highest in Central Hubei and the lowest in Northwest Hubei. At present, the nutrient resources of straw in Hubei province were 310 700 t N, 99 800 t P2O5 and 683 000 t K2O, and the proportion of theoretical fertilizer replacement were 22.5%, 13.1% and 114.0%, respectively. The livestock and poultry production in different regions of Hubei province did not exceed the local maximum carrying capacity. The livestock and poultry breeding volume in different regions of Hubei Province did not exceed the local maximum carrying capacity. The theory of returning major agricultural wastes in Hubei Province can reduce nitrogen fertilizer consumption by 39.8% and phosphate fertilizer consumption by 25.0%. The total K amount from agricultural wastes return to the field could theoretically meet the demand for potassium of main crops. By calculating the nutrient resources of the main agricultural wastes (i.e., livestock and poultry waste, and straw) in Hubei Province, we evaluated the potential of fertilizer reduction of agricultural waste returning to the field and the carrying capacity of livestock and poultry waste soil, providing theoretical basis and data support for agricultural green development in Hubei Province.