Is rice field a nitrogen source or sink for the environment?

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Rice fields are traditionally viewed as nitrogen (N) sources to the environment.
• A comprehensive assessment of the net N balance (source vs. sink) of rice fields is lacking.
• Surrounding water bodies and atmospheric exchange influence the N budget of rice fields.

Purpose of the Study:

• To comprehensively assess the nitrogen budget of rice fields.
• To identify opportunities for shifting rice fields from N sources to N sinks.
• To evaluate the effectiveness of improved agricultural management practices on N balance.

Main Methods:

• Conducted 3-year systematic observations of N budget at a site in Jingzhou, Central China.
• Utilized process-based simulations to model N dynamics.
• Evaluated the impact of "4R-nutrient stewardship" and improved irrigation/drainage.

Main Results:

• Rice fields acted as N sources to waterbodies (24.2-28.7 kg N ha⁻¹) but N sinks for the atmosphere (2.2-8.8 kg N ha⁻¹) under wet/normal conditions.
• "4R-nutrient stewardship" alone facilitated atmospheric N sink role in dry years.
• Combined management practices shifted fields to N sinks for both atmosphere and waterbodies, reducing N application and irrigation use.

Conclusions:

• Improved agricultural management can transform rice fields into nitrogen sinks.
• Integrated strategies including "4R-nutrient stewardship" and optimized water management are key.
• This approach offers a pathway to environmentally friendly rice cultivation without compromising yield or soil health.