Comparative effects of cropping systems on yield, water productivity, and environmental sustainability

Crop yield, water productivity, and evapotranspiration are key ecological indicators for assessing sustainable intensification in cropland management. However, comprehensive studies assessing the combined effects of cropping systems on these variables remain limited, leaving the mechanisms by which cropping systems improve productivity through more efficient water use insufficiently understood. A two-year (2023–2025) lysimeter based field experiment was conducted to compare the yield potential, resource use efficiency, and environmental impacts of three cropping systems: winter wheat–soybean, winter wheat–millet, and conventional winter wheat–summer maize. These systems were evaluated under optimized irrigation and reduced fertilization (70% of conventional inputs). Actual crop evapotranspiration (ET c act ) was determined using a water balance method based on weight changes monitored by the weighing lysimeter. The highest water depletion occurred under wheat–millet, while the lowest occurred under wheat–soybean. Seasonal ET c act differed significantly, with wheat–maize reaching the highest value (around 871 mm), and both wheat–soybean and wheat–millet showed identical ET c act (approximately 754 mm). However, the wheat–soybean system achieved the highest protein water productivity (0.65 kg m⁻ 3 ), and a higher partial factor productivity of nitrogen (26.8 kg kg⁻ 1 ). Nitrate was the predominant form of nitrogen loss, reaching up to 61 mg L⁻ 1 , while ammonium losses were negligible. Average nitrogen losses were comparable between wheat–soybean and wheat–millet, while wheat–maize exhibited greater variability. In contrast, carbon, dissolved organic carbon and dissolved inorganic carbon losses were higher in the order wheat–maize˃ wheat–soybean˃ wheat–millet. Economic analysis revealed that the wheat–soybean system generated substantial net profits ($3816.0 ha⁻ 1 ), with an income to cost ratio of 2.4, and a production to investment (fertilizer and irrigation) ratio of 6.4, confirming its economic viability. These findings highlight the agronomic, environmental, and economic trade-offs among cereal and cereal–legume systems and provide insights for developing sustainable cropping strategies.