流域尺度种养系统养分管理研究的意义与重点以长江流域为例
Research priority and main points of integrated nutrient management in the crop-livestock system at the basin scale: a case study of Yangtze River Basin
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摘要: “农牧分离”加剧了种养系统的养分资源浪费和环境污染风险, 而种养一体化是促进养分循环和减少养分损失的重要途径。开展流域尺度种养系统养分管理研究可以将田块尺度的农牧业生产技术上升到流域尺度, 提高种养系统养分利用效率; 在生产优化的基础上, 还可以以流域环境阈值为卡口, 进一步实现养分环境减排; 在流域实行养分管理研究是种养系统大面积协同实现养分高效和环境减排的关键, 也可为农业绿色发展提供支撑。本文以长江流域为例, 综述了流域尺度种养一体化养分管理研究对农业绿色发展的重要意义、种养一体化养分管理的技术和模式以及基于种养系统资源环境代价的空间优化, 并提出未来流域尺度种养一体化养分管理和研究的重点。研究表明: 长江流域已有一系列种养一体化养分管理技术, “自下而上”地大面积推广应用, 可以实现增产增效, 减少养分环境排放。但部分地区种养系统养分承载力与环境排放量过高, 仅通过技术改进仍无法将养分损失控制在环境阈值以内, 还需“自上而下”地对流域种养产业进行优化布局。未来, 流域尺度种养系统养分管理研究应包括: 1)流域尺度种养系统养分流动与环境排放特征及其影响因素; 2)流域尺度养分环境排放脆弱区划分; 3)基于脆弱区的流域种养系统养分分区调控策略与评价研究。Abstract: Separation of crop and livestock production increases the risk of environmental pollution and the wastage of nutrient resources derived from crop-livestock systems. Integration of crop and livestock production is an important pathway for promoting nutrient cycling and reducing nutrient losses. Research on nutrient management at the basin scale can upscale agricultural production technologies from the farm scale to the basin scale and improve nutrient-use efficiency. Based on production optimization, the environmental threshold of the basin can be used as a bayonet to further reduce environmental nutrient losses. In addition, it is important to achieve higher nutrient efficiency and greater environmental emission reduction of crop-livestock production systems in a large area via nutrient management at the basin scale, which may also support the green development of agriculture. Taking the Yangtze River Basin as an example, this study reviewed the significance of nutrient management based on the integration of crop and livestock production at the basin scale with green development, nutrient management technologies based on the integration of crop and livestock production, and spatial optimization based on the environmental cost of the crop-livestock production system. In addition, the present study focuses on the nutrient management of crop-livestock production systems at the basin scale. Based on the present review, we found that there are a series of nutrient management technologies for crop-livestock systems in the Yangtze River Basin, and the promotion and application of these technologies via a bottom-up approach could further reduce nutrient losses and improve agricultural production efficiency. However, the nutrient losses of the crop-livestock system in some areas are too high and cannot be controlled within the environmental threshold only through technical improvement; it is also necessary to conduct spatial planning for crop-livestock systems via a top-down approach. Future studies on nutrient management of crop-livestock systems at the basin scale should include (1) characteristics and driving factors of nutrient flow and environmental emissions at the basin scale, (2) classification of vulnerable areas of nutrient losses at the basin scale, and (3) evaluation and optimization of crop-livestock systems based on vulnerable areas.