作物-奶牛生产体系氮磷养分流动与循环规律研究

Nitrogen (N) and phosphorus (P) are essential elements for plant and animal production, which are also important contributors to the environmental pollution. The flow and recycling of N and P among the cropping and livestock system are the fundemental factors for yields increases and human health, however, their over-loading in soils and water bodies have caused the largest environmental issue. Therefore, characterizing the flow and recycling of N and P within the cropping-livestock system has become a key reserach topic in the acchivement of agricultural sustainability. At present, macro-scale analysis on the nutrients flow and recycling of N and P within the cropping-livestock system in China has been performed, however, the analysis at micro- or mid-scale is still lacking. In this project, detailed analysis on the N and P flows and recycling among the cropping and dairy systems will be made through feeding and monitoring in situ experiments in combination with the model analysis at dairy cattle, dairy farms and regional scale, respectively. In subsequent, based on the previous acchivements, a model characterzing the flows and recycling of N and P within the cropping-dairy system will be developed in order to imporve the use efficiencies and recycling of N and P, identify major control sectors, dominant factors and evaluate the respective enviromental impacts of cropping-dairy system as well as the potential beneficial management practices (BMP). This is not only very helpful for the optimization of the N and P managements in the cropping-dairy system, it will also provide useful theories and techniques to maintain the sustainability of other animal productions in China.

氮磷是动植物必需的营养元素，也是重要的环境污染因子，其在农田-畜牧体系适量的流动和循环，是保证粮食增产和人类健康的基础，它们的过量则是当今世界面临的最大环境污染问题之一。因此，阐明农田-畜牧体系氮磷流动和循环规律已经成为农牧业可持续发展的重要科学命题。目前，我国已有一些研究对农田-畜牧体系的养分流动规律进行了宏观分析，但仍缺乏中微观的试验研究。为此，本研究以作物-奶牛生产体系为对象，从奶牛个体、奶牛场和区域三个尺度，通过饲喂试验、定点跟踪监测、模型分析等手段，深入剖析不同作物-奶牛生产模式氮磷流动规律、农田循环特征及其环境影响；在此基础上，构建适合我国作物-奶牛生产体系特点的氮磷养分流动和循环模型，探讨提高氮磷养分利用率和循环率、降低环境效应的主控环节、主导因素和有效途径。研究结果不但对于作物-奶牛体系氮磷优化管理具有重要理论和实践意义，也可为其他作物和动物生产体系提供方法和理论。

氮磷是动植物必需的营养元素，也是重要的环境污染因子，其在农田-畜牧体系适量的流动和循环，是保证粮食增产和人类健康的基础，它们的过量则是当今世界面临的最大环境污染问题之一。因此，农田-畜牧体系氮磷流动和循环规律已经成为农牧业可持续发展的重要科学命题。为此，本项目通过饲喂试验、定点跟踪监测、田间试验、模型分析等手段，经过4年深入研究，（1）明确了集约化养殖和小区养殖模式下奶牛氮磷养分流动特征与养分利用效率，发现集约化养殖牛奶产量、年氮素投入、年氮素利用效率和磷利用效率均高于养殖小区，但集约化养殖每生产1t牛奶投入的氮磷和环境排放氮磷却低于养殖小区。适当降低日粮的蛋白和磷水平可以提高奶牛的氮利用效率而不影响生产性能，同时可以起到减少环境排放的作用。（2）从奶牛场和区域尺度，阐明奶牛-作物体系粪尿 “畜舍-储藏/处理-农田施用”全链条养分流动和农田循环利用特征，发现“畜舍-储藏/处理”环节氨挥发是氮素损失的主要途径；明确奶牛场粪尿氮素排放日变化和季节变化规律，表明奶牛养殖场的氨气排放高峰主要出现在08：00h和18：00h，期间的氨气排放速率为全年日均值的6.1(4.4-9.1)、2.2(1.4-4.2)、3.0(1.4-3.1) 和1.7(1.0-2.1)倍；探明了不同作物体系（菜田、果园和大田作物）牛粪施用后氮磷养分去向及其环境影响。（3）构建农场尺度氮磷养分流动模型，探明了区域作物-奶牛生产体系氮磷养分循环特征及其主导因素，发现奶牛养殖氮磷以外部输入为主，内部循环所占比重较小；氮素损失占输出较大比重，而磷素则通过粪尿输出到外部农田。（4）阐明了作物-奶牛生产体系提高氮磷养分利用率、降低环境效应的调控机制，发现适当降低氮磷投入、优化养殖结构、改造畜舍和运动场以减少氨挥发、增加粪尿还田等是增效减排的主要途径。研究结果不但对于作物-奶牛体系氮磷优化管理具有重要理论和实践意义，也可为其他作物和动物生产体系提供方法和理论。