北京“土壤-饲料-奶牛”系统氮磷流动及环境损失时空特征

Temporal and spatial characteristics of nitrogen and phosphorus cycling and environmental losses in the "soil-feed-dairy" production system in Beijing

  • 摘要: 分析大城市郊区“土壤-饲料-奶牛”养殖体系养分流动和环境排放特征是合理控制养殖规模、促进农牧结合、保护生态环境和保障畜禽产品供应等政策制定的基础。本研究选取北京市郊区28个规模化奶牛农场,调研包括饲料来源和投入、奶牛生产和粪尿管理以及产品输出情况。结合公开发表的文献数据和北京市统计数据,利用NUFER-animal模型对1980-2013年北京市规模化奶牛农场“土壤-饲料-奶牛”生产系统养分流动特征、利用效率和环境损失的时空变化进行了定量化分析。结果表明,1980-2013年,奶牛个体尺度(仅包括泌乳牛)氮利用效率从14.9%增加到21.2%,磷利用效率从13.8%增加到27.3%;群体尺度(包括犊牛、育成牛、青年牛、泌乳牛和干乳牛)氮利用效率从14.5%增加到18.2%,磷利用效率从15.8%增加到24.9%;系统尺度(土壤-饲料-奶牛)氮利用效率从11.3%增加到15.8%,磷利用效率从13.3%增加到22.3%。北京市奶牛养殖个体尺度、群体尺度和系统尺度氮利用效率在1985年前减少;而1985年后逐渐增加。个体尺度、群体尺度和系统尺度磷利用效率均不断增加。系统尺度氮总损失从1980年的1 516 t增加到2013年的16 973 t;磷总损失从114 t增加到1 763 t。生产1 kg氮磷产品造成的氮和磷损失均表现出不断减少的趋势。北京市“土壤-饲料-奶牛”生产系统氮磷流动特征发生了很大变化,养分利用效率和总环境损失不断增加。产生这一变化的原因是养殖数量的增加、养殖模式从传统向集约化转变和环保管理措施的完善。因此,调整奶牛养殖从数量型向质量型转变以及提高喂养技术和粪尿管理水平等是提高都市奶牛养殖可持续发展的必要措施。

     

    Abstract: With the increasing of urbanization rate and income, the food demand and food consumption structure has been changed greatly in China, especially for the dairy products. However, the environmental risk of livestock production is also growing quickly under the rapid increase of dairy population and intensification rate. Currently, dairy production is mainly concentrated around the peri-urban area in the big cities on the purpose of access to the market. However, there is little information about the nutrient flow and losses of peri-urban dairy production yet. Increasing understanding of this information is useful for policy makers to regulate the size and location of dairy production, and to achieve a crop-dairy integrated and environmental friendly dairy production system. Here, the performance of nitrogen (N) and phosphorus (P) flow, use efficiency and losses of peri-urban dairy farms in Beijing was assessed, using data of a comprehensive survey conducted on 28 dairy farms during 2012-2013 and calculations with the NUtrient flows in Food chains, Environment and Resources (NUFER) model. The feed formula and feed intake, feeding days and other parameters of the production system were derived from survey data for the year 2012 and 2013, and were derived from NUFER model for the period of 1980-2011. Our results showed that, nitrogen use efficiency (NUE) at the animal level (only lactating dairy cow) increased from 14.9% to 21.2% from 1980 to 2013, and phosphorus use efficiency (PUE) increased from 13.8% to 27.3% during the same period. At the herd level (including calves, breed cows, heifers and dry cows), NUE increased from 14.5% to 18.2%, and PUE increased from 15.8% to 24.9% for the past 33 years. Similarly, both the NUE and PUE increased at the system level (soil-feed-cow chain) during the period of 1980-2013, e.g., NUE increased from 11.3% to 15.8%, and PUE increased from 13.3% to 22.3%. NUE was decreased from 1980 to 1985 at all the three production level, however, steadily increased since 1985. Differed with that of NUE, PUE was steadily increased at all the three production level from 1980. The total nitrogen losses increased from 1 516 t N in 1980 to 16 973 t N in 2013, and the total phosphorus losses increased by 1 649 t P, from 114 t P to 1 763 t P during the same period. The average N or P losses to produce 1 kg N or P in products decreased greatly since 1980. In conclusion, the characteristics of N and P flow thorough the "soil-feed-dairy" production system have been greatly changed in Beijing. The nutrient use efficiency and total environmental losses are increasing. The reasons for these changes are the increasing of animal number, the transformation from the traditional to the intensive farming and the improvement of the environmental management measures. Therefore, it is necessary to improve the sustainable development of urban dairy farming by the adjustment of dairy production from quantity to quality, precision feeding technology, and waste management.

     

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