Simulation of the irrigation requirements for improving carbon sequestration in a rainfed cropping system under long-term fertilization on the Loess Plateau of China
2018
Qiu, Linjing | Wu, Yiping | Hao, Mingde | Shen, Jian | Lei, Xiaohui | Liao, Weihong | Li, Yinke
The nutrients and water supplied to rainfed agroecosystems need to be properly managed to meet food security and global warming challenges in the coming decades. A revised CENTURY model was adopted to evaluate the effects of long-term fertilization and supplemental irrigation (SI) on carbon (C) sequestration in a conventional 3-year rotation on the Loess Plateau of China (CWWM): spring corn in the first year, followed by 2 years of winter wheat, and fallow millet was sown in June of the third year. The simulation showed that grain C and soil organic C (SOC) benefited from long-term synthetic nitrogen (N) application. The contribution of this treatment to SOC accumulation was less than that of manure, but the concomitant increase in grain C was greater than that under manure treatment. Fertilization coupled with SI exerted a positive effect on grain C and SOC accumulation for both corn and wheat. The supply of 142 mm of irrigation water when the soil moisture status fell below 80% of the soil available water content (SAWC) in April for spring corn improved grain C accumulation by 33.7% compared with the control (CK); similarly, supplying 83 mm of irrigation water to winter wheat in October increased its grain C by 16.8%. Simulated SOC at the end of a 30-year period in which SI was applied once per month was higher than that obtained under SI in a single month. The highest SOC of 2256.5 g m−2, 4% higher than in CK, was obtained when SI was applied during corn growing season when the soil moisture fell below 50% of the SAWC. These findings implied that irrigation should be seriously considered for improving C sequestration in rainfed agroecosystems.
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