Nitrous oxide emissions in Chinese vegetable systems: A meta-analysis

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• China is the world's largest producer of vegetables, contributing over half of global production.
• Understanding nitrous oxide (N2O) emissions from Chinese vegetable systems is crucial for environmental management.
• Intensive agricultural practices, particularly high nitrogen fertilizer inputs, are associated with N2O emissions.

Purpose of the Study:

• To quantify N2O emissions and nitrogen (N) fertilizer-based emission factors (EFs) in Chinese vegetable systems.
• To analyze the impact of N fertilizer rates and types on N2O emissions in open-field and greenhouse settings.
• To compare N2O emissions and EFs between greenhouse and open-field vegetable production.

Main Methods:

• A meta-analysis was conducted using 153 field measurements from 21 distinct field studies in China.
• Data were analyzed to determine average N2O emission rates and fertilizer N-based EFs.
• Statistical methods were employed to assess the influence of fertilizer N rate and type, and cultivation system (greenhouse vs. open-field).

Main Results:

• Chinese vegetable systems exhibited an average N2O emission of 3.91 kg N2O-N ha⁻¹ with an EF of 0.69%.
• While the EF was below the IPCC default (1.0%), average N2O emissions were higher than in other cropping systems due to elevated N fertilizer inputs.
• Greenhouse systems showed approximately 1.4 times greater N2O emissions than open-field systems, though EFs were similar. N2O emissions increased with N fertilizer rate, but EFs were not significantly affected by N rate or fertilizer type (under equivalent N rates).

Conclusions:

• Intensive Chinese vegetable production contributes significantly to N2O emissions, driven by high synthetic N fertilizer application.
• Optimizing fertilizer management, specifically using a combination of synthetic N fertilizer and manure at economic rates, offers a viable strategy to reduce N2O emissions without compromising crop yields.
• Further research and refined management practices are needed to mitigate greenhouse gas emissions from this vital agricultural sector.