Combining engineering drainage with crop rotation patterns: A suitable approach to enhancing crop yield in waterlogged farmlands

Drainage techniques exert pronounced regulatory effects on soil water content, crop growth, and grain yield in waterlogging-prone crop rotation systems. This study systematically evaluated the impacts of straw blind ditch (spacings of 2, 3, 4, and 5 m, denoted as S2, S3, S4, S5) and subsurface pipe drainage (spacings of 6, 9, and 12 m, denoted as G6, G9, G12) in rice-wheat and rice-oilseed rape rotations, with conventional surface drainage as the control (CK). The goal was to identify effective strategies for enhancing crop yields in rotation systems through the integration of agronomic and engineering approaches. Results showed that straw blind ditch drainage reduced soil water content more effectively than subsurface pipe drainage and CK, especially at smaller spacings. S2 decreased 0–60 cm soil water content by 6.4–8.6% relative to subsurface pipe drainage and 14.5–21.2% relative to CK, while increasing drainage volume by 10.1–35.8%. Crop growth indicators responded significantly to drainage treatments, with S3 outperforming G9 and CK in leaf area index (LAI), plant height, and dry matter accumulation. Although S2 achieved the strongest soil dewatering effect, the 3 m-spacing straw blind ditch balanced water retention and waterlogging elimination, increasing the annual total yields of rice-wheat and rice-oilseed rape rotations by 32.1% and 25.9% relative to CK, respectively. Structural equation modeling revealed that drainage treatments significantly enhanced aboveground biomass accumulation by increasing cumulative drainage volume, thereby leading to substantial yield increases in the rice-wheat/rice-oilseed rape rotation systems (0.583***, 0.674***). The findings suggest that a 3 m blind ditch spacing optimally addresses both waterlogging and yield enhancement in rotation systems. These findings provide guidance for the design, selection, and implementation of drainage systems in waterlogging-prone rotation farmlands of the middle-lower Yangtze River region.