Farmers’ Crop Choice and Soil Sustainability: A Simulation Analysis Based on Perceived Profitability and Soil Load in Shan State, Myanmar

Cash crop expansion has contributed to income growth among smallholder farmers in developing countries, but its long-term implications for soil fertility remain insufficiently understood. In particular, few studies have incorporated farmers’ perceptions of crop profitability and soil impacts into dynamic simulation models. This study examines the long-term effects of crop-choice behavior on soil fertility in Shan State, Myanmar, using a perception-based dynamic simulation model. Profit indices and soil-load indices for major cash crops were constructed from interviews with local farmers and applied to three crop-choice scenarios: profit maximization, continuous cropping restriction, and crop rotation. Soil fertility was simulated over a 50-year period under each scenario. Under the interview-derived parameter settings, the profit maximization scenario, corresponding to continuous cultivation of perilla, achieved both the highest cumulative profit and the highest level of soil fertility. In contrast, the continuous cropping restriction scenario resulted in the greatest decline in soil fertility because the replacement crop, peanut, was also perceived as imposing a relatively high soil load. Incorporating sweet potato into a four-year crop rotation substantially improved soil fertility compared with the continuous cropping restriction scenario, demonstrating that the effectiveness of crop rotation depends on the combination of crops included in the rotation. These findings suggest that farmers’ perceptions of crop profitability and soil impacts can strongly influence long-term land-use outcomes and highlight the importance of considering local farming knowledge when designing sustainable agricultural management strategies.