Nitrogen nutrient supply and greenhouse gas mitigation potentials from cover crops across Chinese croplands

Abstract

Cover crops can benefit agricultural systems greatly by improving soil fertility, increasing soil organic carbon (SOC) contents, and promoting grain yield. Recently cover crops have been recommended as a practice to ameliorate croplands and develop nature-based climate solutions. However, the information as to where is potentially suitable for developing cover crops is lacking. Here, we try to map the potential regions suitable for cover crops and to estimate nitrogen nutrient supply and greenhouse gas (GHG) mitigation potentials with the hypothesis that all the suitable fallow lands are used for cover crops. First, we generated a smoothed normalized difference vegetation index (NDVI) series by Savitzky-Golay method from 2019 to 2021. Then, we produced the phenology dates and tracked the regular crop fallow periods in the three years. Next, we extracted the potential regions for cover crops based on the effective accumulated temperature requirements and drainage limit. Finally, we estimated nitrogen supply and GHG mitigation potentials using the previous measurements. Results show that nearly 13.3% (∼26.7 Mha) of current croplands can be planted with cover crops, providing 1.21 ± 0.26 Tg N yr−1 of nitrogen fertilizer. The potential cover crops can mitigate 58.85 ± 9.95 Tg CO2-eq yr−1 of GHG emissions. SOC sequestration is the dominant process in the GHG mitigation with a rate of 48.15 ± 5.34 Tg CO2-eq yr−1, equal to 30.1% ± 3.4% of the current annual total SOC sequestration in Chinese croplands. The study demonstrates an advanced framework in mapping the potential croplands available for cover crops and providing evidence-based planning of extending cover crops across China. The framework can be widely applied to other regions, contributing to building climate smart agriculture and developing nature-based climate solutions.