Organic inputs to reduce nitrogen export via leaching and runoff: A global meta-analysis

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Chemical fertilizers can lead to nitrogen (N) losses through leaching and runoff.
• Organic inputs offer a potential mitigation strategy, but their effectiveness varies with application methods.

Purpose of the Study:

• To compare the effects of different organic input application approaches on N export via leaching and runoff.
• To determine the optimal substitution rates for reducing N losses without compromising crop yield.

Main Methods:

• A global meta-analysis of 129 studies was conducted.
• Compared three application approaches: substitution with equal total N, substitution with equal mineral N, and additional organic fertilizer N.
• Analyzed effects on N leaching, runoff, and crop yield.

Main Results:

• Organic inputs reduced overall N leaching by 15% and runoff by 29% without yield loss.
• Substitution with equal total N decreased leaching and runoff by over 30%.
• Substitution with equal mineral N increased leaching by 21% and yield by 6%; additional organic N had no effect.

Conclusions:

• Substituting chemical fertilizers with organic inputs at equal total N levels is the most effective strategy for reducing N leaching and runoff.
• Optimal substitution rates for leaching range from 40-60%, and for runoff from 60-100%.
• This approach minimizes environmental N losses while maintaining crop production.