From Cotton to Wheat–Maize: Farmer Decision-Making and Cropping Structure Transformation in a Smallholder County of China

Adjusting cropping structure is a key way smallholder agriculture adapts to changing labor availability, production costs, mechanization, and agricultural services. Most studies explain such change through macro-level factors—prices, policies, and resource endowments—and pay less attention to how farmers perceive these changes and adjust their crop choices over time. Taking Xiajin County, Shandong Province, China, as a case, this study combines sown-area data for major crops from 1980 to 2023, provincial cost–benefit records for wheat, maize, and cotton, and retrospective semi-structured interviews with 57 respondents to examine how changing crop choice criteria shaped county-level cropping structure transformation. The county shifted from cotton dominance to wheat–maize dominance, with rising structural concentration. Farmers’ criteria also changed: early decisions reflected drought tolerance, subsistence grain, and cash income, whereas later ones emphasized labor saving, income stability, mechanization compatibility, and outsourcing feasibility. Under labor out-migration, rural aging, rising labor opportunity costs, and service expansion, wheat and maize became more attractive than cotton because their key stages were easier to mechanize and outsource. County-level transformation thus emerged from the accumulation of farmers’ repeated crop choice adjustments under changing constraints, rather than from external change alone. Grain-oriented concentration should be balanced with crop diversity and sustainable farming systems.