世界银行-固定氮肥_农业生产力_环境脆弱性和补贴的作用（英）-2025.1_23页_750kb

Fixing Nitrogen: Agricultural Productivity, Environmental Fragility, and the Role of Subsidies

Summary

World Bank policy research paper 11050 analyzes the global impact of fertilizer subsidies, particularly nitrogen-based ones, on agricultural productivity and environmental outcomes. The study combines satellite data, subsidy records, nitrogen use, and water quality measurements to identify that subsidized nitrogen fertilizer leads to overapplication, diminishing returns in crop yields and causing significant nitrogen pollution in waterways.

Key Findings:

1. Diminishing Returns: Nitrogen fertilizer application increases agricultural yields up to a certain point but exhibits diminishing returns at high levels, varying by region.

   • Example: East Asia (medians at 95th percentile) already faces declining returns, while Sub-Saharan Africa operates at low yield levels but faces nutrient imbalances.

2. Environmental Damage: A 10% increase in nitrogen fertilizer use correlates with a 1.6–3.4% rise in nitrogen pollution in water, contributing to hypoxia, algal blooms, and blue baby syndrome.

3. Subsidy Effects:

   • Coupled Subsidies: Reduce input costs, encourage overuse, increasing pollution.
   • Decoupled Subsidies: Alleviate negative spillovers but require policy reforms to phase out harmful subsidies.

Policy Recommendations:

• Adopt precision agriculture, the 4Rs (right nutrient, rate, time, place), and soil-targeted fertilizers to improve nitrogen use efficiency.
• Utilize digital tools (satellite monitoring, mobile apps) for tailored fertilizer recommendations.
• Reform subsidy programs to phase out coupled inputs, promote decoupled payments, and invest in farmer education and training.

The study concludes that poorly designed subsidies exacerbate environmental costs, urging well-intentioned policies to address nitrogen management globally.