Abstract

Straw blind ditch is an ecological subsurface drainage technology with potential application value for the improvement of saline–alkali land. However, straw blind ditch burial depth is a key design parameter that directly affects drainage, salt leaching, and nutrient regulation. In this study, field experiments were conducted in 2024 and 2025 to evaluate the effects of different straw blind ditch burial depths on soil water content and temperature, soil salinity, nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), and available phosphorus (Olsen-P) in coastal saline–alkali soil. The experiment was arranged in a randomized complete block design (RCBD) with three replicates and included three straw blind ditch burial depths, 60 cm (SD60), 45 cm (SD45), and 30 cm (SD30), with no blind ditch as the control (CK). Across the 0–60 cm soil profile and the two growing seasons, SD60 reduced mean soil electrical conductivity (EC) by 48.9% compared with CK, while SD45 and SD30 reduced mean soil EC by 30.0% and 30.5%, respectively. In the 0–10 cm surface soil layer, the EC reduction under SD60 reached 50.4%. Straw blind ditch burial depth also markedly enhanced soil nitrogen and phosphorus availability. Across the 0–60 cm soil profile, soil NO3−-N under SD60, SD45, and SD30 increased by 26.0%, 18.0%, and 24.6%, respectively, compared with CK. The SD60 treatment exhibited the highest profile-averaged soil NH4+-N, with an increase of approximately 46.6% compared with CK. In addition, SD60 and SD45 increased profile-averaged soil Olsen-P by 60.4% and 64.3%, respectively, relative to CK. Overall, SD60 provided the most balanced improvement in soil salinity reduction and nitrogen availability, whereas SD45 showed the greatest enhancement of Olsen-P. These findings suggest that optimizing straw blind ditch burial depth can improve soil salinity and nutrient status in coastal saline–alkali soil.

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