College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, Ministry of Education, China Agricultural University, 100193 Beijing, China.
College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, Ministry of Education, China Agricultural University, 100193 Beijing, China.
Sci Total Environ. 2020 Jul 10;725:138482. doi: 10.1016/j.scitotenv.2020.138482. Epub 2020 Apr 5.
China produces approximately half of the world's pork at a high environmental cost. Implementing mitigation measures requires a better understanding of pig farming systems that are often diverse in practice. Nutrient uses and losses can be largely altered due to these variations but have not, however, been fully evaluated; moreover, attention is rarely paid to pollution swapping. Our study evaluated carbon (C) and nitrogen (N) flows among pig farms on the North China Plain using the mass flow approach. The impacts of advanced mitigation measures on nitrogen use efficiency (NUE) and on C and N emissions were further analyzed via scenario analyses. The results showed that large variations among farms were observed by comparing the best-performing farms ("top 20%") with the "other" farms; the comparisons showed 31.3 vs. 21.3% for the system NUE, 3.0 vs. 5.7 kg N ·100 kg liveweight gain (LWG) for manure N losses, and 108.1 vs. 146.4 kg CO-eg·100 kg LWG for greenhouse gas (GHG) emissions, respectively. Lower system NUE was caused by lower NUEs of pigs, followed by high N emissions from manure and excessive manure application. Scenario analyses indicated that the total N loss of systems can be mitigated by 10-13% through dietary manipulation and by 26%, 27%, and 13% by low-emission storage, biogas production with improved storage, and balanced fertilization, respectively. Anaerobic digestion was solely effective for GHG mitigation (46% reduction), but no impacts were observed for all other low-NH measures. Combining mitigation measures simultaneously decreased total N and GHG losses by 56% and 54%, respectively, and increased the system NUEs by 89%. The wide variations among farms suggest largely attainable improvements in productivity and nutrient use by closing the management gaps related to these factors. Proper combinations of advanced measures are further needed to achieve more effective mitigation goals for multiple pollutants.
中国以高环境代价生产了全球约一半的猪肉。实施缓解措施需要更好地了解养猪系统，而这些系统在实践中往往存在多样性。由于这些变化，养分的利用和损失可能会发生很大变化，但尚未得到充分评估；此外，人们很少关注污染转移。本研究采用质量流方法评估了华北平原养猪场的碳（C）和氮（N）流动。通过情景分析进一步分析了先进缓解措施对氮利用效率（NUE）以及 C 和 N 排放的影响。结果表明，通过比较表现最好的农场（“前 20%”）与“其他”农场，可以观察到农场之间存在很大差异；比较结果显示，系统 NUE 分别为 31.3%和 21.3%，粪肥 N 损失的粪肥 N 分别为 3.0 千克和 5.7 千克/100 千克活体重增加（LWG），温室气体（GHG）排放的分别为 108.1 千克和 146.4 千克 CO2 当量/100 千克 LWG。较低的系统 NUE 是由于猪的 NUE 较低，其次是粪肥中 N 排放较高和粪肥施用量过多所致。情景分析表明，通过饮食调控可以减少 10-13%的系统总氮损失，通过低排放储存、沼气生产和改进储存、平衡施肥，分别减少 26%、27%和 13%。厌氧消化仅对 GHG 减排有效（减少 46%），但对所有其他低 NH 措施均无影响。同时结合缓解措施可分别减少总氮和 GHG 损失 56%和 54%，系统 NUE 提高 89%。农场之间的广泛差异表明，通过缩小与这些因素相关的管理差距，可以大大提高生产力和养分利用效率。还需要适当组合先进措施，以实现对多种污染物更有效的缓解目标。
