Water Requirements and Comprehensive Benefit Evaluation of Diversified Crop Rotations in the Huang-Huai Plain

Abstract

An intensified farming system can significantly increase crop productivity but can also cause major groundwater overdraft for irrigation and the loss of crop diversity. It is imperative to develop alternative crop rotations beyond the simplified conventional winter wheat–summer maize (W–M) rotation for alleviating the groundwater over-extraction in China’s Huang-Huai Plain. This study systematically quantified crop water requirement (ETc) and irrigation water requirement (ETaw) of eight crops from 2013 to 2018 based on the SIMETAW model applied to the Shangqiu area in the Huang-Huai Plain. Fourteen crop rotations (CI (i.e., crop harvests per rotation cycle year) 1.5 or 2) were constructed based on the ROTAT model. Results showed that compared to W–M rotation, the alternative rotations (CI = 1.5) significantly reduced the annual ETc in wet, normal, and dry years by 9–21%. Replacing winter wheat in the double cropping system did not significantly decrease annual ETc. Wheat–soybean rotation had similar annual ETc and ETaw accompanied by higher economic output and equivalent yield about 1.2 times, with 9% more protein output than the W–M rotation. There were eight crop rotations having greater comprehensive evaluation index (CEI) than W–M rotation by Entropy-TOPSIS when considering 10 indicators including water requirements, yield, economic benefits, water use efficiency, energy, and nutritional values. Spring potato–summer soybean had the highest CEI of 0.627. Sweet potato and potato showed advantages when included in rotations by increasing yield. “Wheat–soybean”-based rotations (CI = 1.5) also performed well in profitability and protein output. Replacing summer maize with soybean is promising for profitability and nutrition output without increasing irrigation requirements. Therefore, decreasing the cropping index, or involving soybean or sweet potato in rotations can be a useful way to improve sustainable land use, save water, and ensure food products in this water stressed region.