Effects of Buried Straw Strips with Different Internal Structures on Water and Salt Distribution and Leaching Efficiency in Coastal Saline Soil

Straw strip burial in saline soil is an effective method for tideland reclamation in China, but optimal forms of straw strips for regulating soil water and salinity remain unclear. An indoor soil column test investigated the water and salt distribution in soil treated with four different straw forms under freshwater irrigation. The treatments included no straw layer (CK), straw stalks arranged longitudinally (T₅), horizontally (T₂₅), longitudinally combined horizontally in layers (T_25+2.5), and randomly (T_2.5). The results showed that compared to CK, T₂₅, T₅, and T_25+2.5 significantly reduced the infiltration rate of irrigation water, leading to prolonged infiltration times. Wetting front curves under T₅, T_25+2.5, and T₂₅ exhibited similar inverted “V” shapes, while CK and T_2.5 showed fluctuating parallel lines. Water retention in the soil was higher under straw strip treatments (T₅, T₂₅, T_25+2.5) and straw layer treatment (T_2.5) compared to CK after 24 h of the first irrigation. T₅ demonstrated the most effective salt removal, surpassing other treatments, with a desalination rate of 97.71%. Additionally, T₅ had the highest salt leaching efficiency (SLE) in the 0–20 cm soil layer, recommending it as the optimal form for managing saline soils in crop production due to its simplicity and higher SLE. We found that buried straw strips reduced soil water infiltration rate and wetting front propulsion speed, increased soil water content and enhanced salt leaching efficiency in the saline soil. Our findings provide a basis for developing strategies that improve soil quality and irrigation efficiency, mitigate the effects of salinity on crop production, and ensure food security for a rapidly growing global population.