Effect of three-year amendment measures on coastal saline-alkali soil conditions during the growing season

Seawater intrusion and fluctuations in the water table in coastal areas lead to seasonal variations in soil salinity and pH, which greatly limit the development of coastal protection forests. In a 3-year field study, the impact of five soil amendment measures were evaluated on soil conditions in coastal areas. Amendments included biochar, biochar with arbuscular mycorrhizal fungi (AMF), straw with AMF, straw alone, and AMF alone, compared to a control (CK) with no additive. Results indicated that combinations of straw, biochar, and AMF reduced soil pH across various layers and seasons, with electrical conductivity mainly decreasing in spring. During the summer, at the 0–20 cm soil depth, microbial biomass carbon notably increased due to these mixtures. Additionally, AMF alone and biochar with AMF significantly improved enzyme activities in the 0–40 cm layer in spring, while in fall, AMF alone notably increased nutrient availability in the same layer. Linear regression analysis revealed a negative correlation between electrical conductivity, microbial biomass carbon, enzyme activity, and nutrient availability with pH. The biochar–AMF mixture emerged as the most effective soil amendment, suggesting that using it in conjunction with seasonal management could optimize soil health and promote silviculture in coastal regions.