Effects of straw application on coastal saline topsoil salinity and wheat yield trend

Owing to an irrigation water shortage and a shallow underground water table in coastal zones, soil salinization is becoming a serious and complicated problem. Different practices are being explored to reduce its negative effect on land productivity. In this work, the effect of combined straw and inorganic N applications at different rates on topsoil (0-20 cm) salinity and wheat growth was evaluated in a coastal field. Maize straw was applied at the rates of 5.0 × 103 kg ha−1(S) and 1.0 × 104 kg ha−1 (2S) and inorganic N was applied at the rates of 75 kg ha−1(N1/2), 150 kg ha−1(N), and 300 kg ha−1(N2). Treatment without addition of straw but with inorganic N application at the rate of 150 kg ha−1 was used as the control (CK). Thus, there were six treatments: SN1/2, SN, SN2, 2SN, 2SN2, and CK. During the early growth stages (seedling, jointing, and booting) of wheat, straw application significantly decreased topsoil salinity from 13.8% to 30.4% in comparison to the CK treatment (p < 0.05), and the decrease was enhanced with increase in the straw application rate. This positive influence decreased substantially during wheat growth. Soil dissolved organic carbon and microbial biomass carbon both increased significantly (p < 0.05) after straw addition; in contrast, there was a significant reduction in available N from March to April. The greatest wheat grain yield and aboveground biomass were produced in 2SN2, and yield increased by 15.1% in comparison to CK. In contrast, yield decreased by 5.1-9.6% in SN, 2SN, and SN1/2. Thus, straw application may be an effective practice for reducing topsoil salinity in the coastal zones, and an adequate N supply should be applied to maximize crop yield.