A decision-making framework based on rain-fed crop suitability, water scarcity, and economic benefits for determination multiple-crop rotation strategy

Water scarcity under global climate change has impacted decreased agricultural productivity. Determining the suitable crop rotation strategy under water scarcity applicable to a specific region requires an evaluation of crop suitability, water scarcity, and economic benefits to farmers. This paper aims to improve agricultural productivity and economic benefits through crop rotation strategies under climate change. We developed seven crop rotation strategies, including rice, soybean, maize, and sweet potatoes, that were determined based on preliminary results of the crop suitability index using the EcoCrop model. The water scarcity index (WSI) in historical and future under climate change conditions is estimated using the CropWAT model. In addition, the economic benefit of each crop rotation strategy is evaluated. Finally, multi-criteria decision analysis (MCDA) using the Analytical Hierarchy Process (AHP) was employed to select the most suitable crop rotation strategy applicable to Taoyuan City, Taiwan, based on crop suitability assessment, water scarcity, and economic benefit analysis. Our result shows that WSI values are 0.37, 0.50, and 2.28 in the dry years of 2004, 2015, and 2020, respectively, due to decreasing rainfall and increasing temperatures. The 10-year and 20-year averages were 0.4 and 0.35, respectively, indicating that the issue of agricultural water scarcity is intensifying year by year. Cultivating sweet potatoes has less vulnerability to water scarcity by up to 90 % under climate change than rice. Sweet potatoes also generate farmers' income, which increases by 338 %, considering both rain-fed and irrigation efficiency conditions. Finally, the MCDA-AHP revealed that sweet potatoes and soybean-maize rotation in Taoyuan City were the most suitable and profitable crops for cultivating in Taoyuan City, especially under high and severe agriculture water stress events. Implementing a crop rotation strategy involving sweet potatoes and soybean-maize can effectively mitigate the impact of climate change and extreme drought on crop yield and ensure a stable income for farmers. Integrated irrigation and crop rotation strategies are crucial for providing farmers and other stakeholders with more informed decision-making in agriculture sectors while enhancing water use efficiency.