An original method of straw returning enhanced the improvement effect of saline-alkali soil, thereby promoting the growth of tomatoes

• The powdered straw interlayer & mixed returning significantly reduced upper soil salinity by 89.42 % and 95.30 % ( P < 0.05), respectively, while simultaneously increasing the soil salinity ratio by 12.79 times and 13.89 times, compared to the CK treatment. • The straw interlayer & mixed returning reduced the accumulation of Na + and promoted the absorption of K + and Ca 2+ in leaves and fruit. Concurrently, it enhanced the activities of antioxidant enzymes and reduced the concentration of MDA in leaves. • The powdered straw interlayer & mixed returning significantly increased fruit production and dry matter mass by 89.03 % and 63.44 % ( P < 0.05), respectively, while reducing the blossom-end rot incidence by 57.96 % and 58.50 % ( P < 0.05), relative to CK treatment. Soil salinization poses a significant threat to the safety of food production and necessitates the implementation of effective mitigation measures. Straw returning has been demonstrated as a viable method for improving saline-alkali soil. However, conventional straw returning methods exhibited certain limitations in their practical efficacy, necessitating targeted enhancements and optimization. This study developed an original straw returning method designed to enhance saline-alkali soil improvement and promote crop growth. A pot experiment was conducted using tomato plants ( Solanum lycopersicon L. ), incorporating different straw morphologies ( M l : long-strip, M s : short-strip, M p : powdered) and straw burial methods ( R i : interlayer, R m : mixed, R c : interlayer & mixed). The present study investigated the influence of straw returning methods on the salt distribution of saline-alkali soil through measuring the salinity of upper soil and lower soil. Furthermore, biochemical and growth indicators of tomatoes were determined in order to explore the response adjustment and growth feedback of tomatoes grown in saline-alkali soil under various straw returning methods. The results demonstrated that: (1) The straw interlayer & mixed returning ( R c treatment) effectively decreased the salinity of upper soil, and created a more significant vertical heterogeneous soil salinity. (2) The straw interlayer & mixed returning ( R c treatment) enhanced the response adjustment of tomato resistance to salt stress. The R c treatment reduced the accumulation of Na + in leaves and fruits, promoted the absorption and utilization of K + and Ca 2+ , and increased the K + /Na + ratio and Ca 2+ /Na + ratio in leaves and fruits. Concurrently, the R c treatment enhanced the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in leaves, and reduced the concentration of malondialdehyde (MDA) in leaves, thereby effectively alleviating the damage caused by salt stress in plants. (3) The straw interlayer & mixed returning ( R c treatment) significantly promoted the growth in tomatoes grown in saline-alkali soil. The R c treatment increased plant height, stem diameter, fruit yield, and dry matter mass. Additionally, the R c treatment effectively reduced the incidence of blossom-end rot. It was concluded that the straw interlayer & mixed returning ( R c treatment) led to a substantial reduction in the salinity of upper soil, concomitant with the manifestation of a more pronounced heterogeneous soil salinity. These effects enhanced the response adjustment of tomatoes and mitigated the deleterious effects of salt stress, ultimately promoting tomato growth and yield. In particular, the powdered straw interlayer & mixed returning ( M p R c treatment) exhibited a superior efficacy in improving saline-alkali soil properties and promoting plant growth. Compared to the CK treatment, the M p R c treatment reduced upper soil salinity by 89.42 % and 95.30 % ( P < 0.05), while simultaneously increasing the soil salinity ratio by 12.79 times and 13.89 times. Furthermore, it increased fruit production and dry matter mass by 89.03 % and 63.44 % ( P < 0.05), while reducing the incidence of blossom-end rot by 57.96 % and 58.50 % ( P < 0.05) in 2023 and 2024 tests. These findings suggested that this original straw returning method demonstrates considerable promise for scalable implementation and broader agricultural adoption.