Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, The Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang 050021, Hebei, China; University of Chinese Academy of Sciences, 19 A Yuquan Road, Shijingshan District, Beijing 100049, China.
Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, The Chinese Academy of Sciences, 286 Huaizhong Road, Shijiazhuang 050021, Hebei, China.
Sci Total Environ. 2017 Nov 15;598:1095-1105. doi: 10.1016/j.scitotenv.2017.04.165. Epub 2017 May 2.
The dairy industry in China was rapidly expanded and intensified from 1980 to 2010, engendering potential long-term impacts on the environment and natural resources. However, impacts of dairy intensification on nitrogen (N) and phosphorus (P) losses and greenhouse gas (GHG) emissions were unknown. This study was undertaken to examine these relations using the NUtrient flows in Food chains, Environment and Resources use (NUFER)-dairy model. Results showed that milk yield increased by 64% from 1980 to 2010 on average, and the use of concentrate feeds increased by 57% associated with a shift of production from traditional and grassland systems to collective and industrialized systems. At herd level, the N use efficiency (NUE; conversion of N inputs to products) doubled from 7 to 15%, and the P use efficiency (PUE) increased from 10 to 17%, primarily resulting from increased milk yield per cow. In contrast, at the system level, NUE showed a small increase (from 10 to 15%, associated with reduced gaseous losses) while PUE decreased from 46 to 30% due to a large increase in manure discharges. This is attributed to decoupling of feed and dairy production, as the proportion of manure N and P recycled to cropland decreased by 52% and 54%, respectively. Despite this, the average total N loss decreased from 63 to 48gkg milk, and the average GHG emissions from 1.7 to 1.1kgCOequivalentkg milk associated with increased per-cow productivity. However, average P loss increased from 1.4 to 2.8gPkg milk due to higher discharge rate to wastewater and landfill in collective and industrialized systems. Anyhow, average N and P losses exceeded levels in developed countries. There were large regional variations in nutrient use efficiency, nutrient losses and GHG emissions in China, largely determined by the dairy production structure. Average N losses and GHG emissions per unit of milk showed a negative correlation with production intensification based on the proportion of farms in collective or industrialized systems, while average P losses per unit of milk in different regions showed a positive relationship with intensification. In conclusion, dairy intensification was associated with increased milk yield per cow and reduced average N losses and GHG emissions per unit of milk, but reduced system level PUE and manure recycling contributed to high levels of total N and P losses. Dairy production in China is likely to continue to be intensified as a result of rising milk demand, and significant improvements must be made in manure management to control N and P losses and GHG emissions.
中国的乳制品行业从 1980 年到 2010 年迅速扩张和集约化，这对环境和自然资源产生了潜在的长期影响。然而，乳制品集约化对氮（N）和磷（P）损失和温室气体（GHG）排放的影响尚不清楚。本研究使用 NUtrient flows in Food chains, Environment and Resources use (NUFER)-dairy 模型来研究这些关系。结果表明，1980 年至 2010 年间，牛奶产量平均增长了 64%，浓缩饲料的使用量增长了 57%，这与生产从传统和草原系统向集体和工业化系统的转变有关。在牛群水平上，N 利用效率（NUE；将 N 投入转化为产品）翻了一番，从 7%提高到 15%，而 P 利用效率（PUE）从 10%提高到 17%，主要是由于每头牛的牛奶产量增加。相比之下，在系统水平上，NUE 略有增加（从 10%增加到 15%，与气态损失减少有关），而 PUE 从 46%下降到 30%，这是由于粪便排放量大幅增加。这归因于饲料和乳制品生产的脱钩，因为粪肥中 N 和 P 分别有 52%和 54%被回收利用到农田。尽管如此，平均总 N 损失从 63gkg 牛奶下降到 48gkg 牛奶，平均 GHG 排放量从 1.7kgCOequivalentkg 牛奶下降到 1.1kgCOequivalentkg 牛奶，这与每头牛生产力的提高有关。然而，由于集体和工业化系统中废水和垃圾填埋场的排放率较高，平均 P 损失从 1.4gPkg 牛奶增加到 2.8gPkg 牛奶。无论如何，中国的平均 N 和 P 损失超过了发达国家的水平。中国的养分利用效率、养分损失和 GHG 排放存在较大的区域差异，这主要取决于乳制品生产结构。基于集体或工业化系统中农场的比例，单位牛奶的平均 N 损失和 GHG 排放量与生产集约化呈负相关，而不同地区单位牛奶的平均 P 损失与集约化呈正相关。总之，奶牛集约化与每头牛牛奶产量的增加以及单位牛奶的平均 N 损失和 GHG 排放量的减少有关，但系统水平的 PUE 降低和粪肥循环利用导致了总 N 和 P 损失的增加。由于牛奶需求的上升，中国的乳制品生产可能会继续集约化，必须在粪肥管理方面做出重大改进，以控制 N 和 P 的损失和 GHG 的排放。
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