College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, Ministry of Education, China Agricultural University, Beijing 100193, China.
College of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
Proc Natl Acad Sci U S A. 2021 Sep 28;118(39). doi: 10.1073/pnas.2106576118.
Hundreds of millions of smallholders in emerging countries substantially overuse nitrogen (N) fertilizers, driving local environmental pollution and global climate change. Despite local demonstration-scale successes, widespread mobilization of smallholders to adopt precise N management practices remains a challenge, largely due to associated high costs and complicated sampling and calculations. Here, we propose a long-term steady-state N balance (SSNB) approach without these complications that is suitable for sustainable smallholder farming. The hypothesis underpinning the concept of SSNB is that an intensively cultivated soil-crop system with excessive N inputs and high N losses can be transformed into a steady-state system with minimal losses while maintaining high yields. Based on SSNB, we estimate the optimized N application range across 3,824 crop counties for the three staple crops in China. We evaluated SSNB first in ca. 18,000 researcher-managed on-farm trials followed by testing in on-farm trials with 13,760 smallholders who applied SSNB-optimized N rates under the guidance of local extension staff. Results showed that SSNB could significantly reduce N fertilizer use by 21 to 28% while maintaining or increasing yields by 6 to 7%, compared to current smallholder practices. The SSNB approach could become an effective tool contributing to the global N sustainability of smallholder agriculture.
数以亿计的新兴国家小农过度使用氮肥 (N)，导致当地环境污染和全球气候变化。尽管在当地示范规模上取得了成功，但要广泛动员小农采用精确的 N 管理实践仍然是一个挑战，主要是因为相关成本高，采样和计算复杂。在这里，我们提出了一种没有这些复杂问题的长期稳定氮平衡 (SSNB) 方法，适用于可持续的小农农业。SSNB 概念的基本假设是，一个集约化的土壤-作物系统，氮肥投入过多且氮损失率高，可以转变为一个稳定的系统，损失最小，同时保持高产量。基于 SSNB，我们估计了中国三种主要作物在 3824 个作物县的优化 N 施用量范围。我们首先在约 18000 个由研究人员管理的田间试验中评估了 SSNB，然后在由当地推广人员指导下应用 SSNB 优化 N 率的 13760 个小农田间试验中进行了测试。结果表明，与当前的小农实践相比，SSNB 可以将氮肥用量减少 21%至 28%，同时保持或提高产量 6%至 7%。SSNB 方法可以成为一种有效的工具，有助于实现小农农业的全球 N 可持续性。
