College of Resources and Environment, Northwest A&F University, 712100 Yangling, China; Institute of Dryland Farming, Gansu Academy of Agricultural Sciences, Lanzhou 730000, China.
College of Resources and Environment, Northwest A&F University, 712100 Yangling, China.
Sci Total Environ. 2020 Sep 15;735:139370. doi: 10.1016/j.scitotenv.2020.139370. Epub 2020 May 14.
Returning sloping farmland (>25°) to forest/grassland (RFTF) is an effective ecological measure for soil and water conservation. However, changes in nutrient cycles and green development are still unclear. Ningxia, in Northwestern China, began to implement RFTF in 2000. Here, we used the NUFER model to calculate the input and loss of nitrogen and phosphorus, utilization efficiency, production and consumption at food-chain scale in Ningxia for the period 1985-2015. Five aspects comprised the evaluation of green development: society, economy, resources, environment, and productivity. Results showed that forest coverage rate increased from 7.74% to 33.2%, while cropping area decreased by 6.6%. NH loss increased from 53,000 to 83,000 tons (56%), NO increased from 1200 to 2300 tons (92%) and leaching loss from 18,000 to 62,000 tons (240%). Phosphorus leaching loss increased from 13,000 to 35,000 tons (130%). The environmental cost of food nitrogen per unit of production decreased from 8 to 6.7 kg/kg (19.4%). Nitrogen and phosphorus use efficiencies decreased by 4.8% and 58% in crops-animal systems, respectively, but increased by 652% and 430% in animal husbandry systems. The proportion of animal protein production increased from 18.3% to 39.0% (113%). The major source of organic waste was livestock and poultry manure and urine (70%). Indicators for achieving green development level increased from 14 to 18 (14.7%). Improving the level of scientific and technological management of aquaculture system, increasing the proportion of organic matter returned to farmlands, and paying attention to the combination of planting and breeding will effectively promote future cycling efficiency of nitrogen and phosphorus in the food chain, and the sustainability of agriculture towards green development.
退耕还林还草（RFTF）是水土保持的有效生态措施。然而，养分循环和绿色发展的变化仍不清楚。中国西北部的宁夏于 2000 年开始实施 RFTF。在这里，我们使用 NUFER 模型计算了 1985-2015 年宁夏氮磷的输入和损失、利用效率、食物链尺度上的生产和消费，以及绿色发展评价的五个方面：社会、经济、资源、环境和生产力。结果表明，森林覆盖率从 7.74%增加到 33.2%，而耕地面积减少了 6.6%。NH 损失从 53000 吨增加到 83000 吨（56%），NO 从 1200 吨增加到 2300 吨（92%），淋溶损失从 18000 吨增加到 62000 吨（240%）。磷的淋溶损失从 13000 吨增加到 35000 吨（130%）。单位粮食生产的环境代价氮从 8 公斤/公斤（19.4%）下降到 6.7 公斤/公斤。氮磷在作物-动物系统中的利用效率分别下降了 4.8%和 58%，而在畜牧业系统中分别增加了 652%和 430%。动物蛋白产量的比例从 18.3%增加到 39.0%（113%）。有机废弃物的主要来源是畜禽粪便（70%）。达到绿色发展水平的指标从 14 个增加到 18 个（14.7%）。提高水产养殖系统科学技术管理水平，增加有机物质返回农田的比例，注意种植与养殖相结合，将有效促进未来食物链氮磷循环效率，推动农业向绿色发展的可持续性。
