Combining polyacrylamide amendment to mitigate negative effect of biochar on the soil conservation of saline-sodic soil

High sodium salt stress and low soil organic carbon (SOC) inhibit the saline-sodic soil improvement and vegetation restoration in tidal flat reclamation areas in China. Applying biochar (BC) improved soil properties and supplied SOC, but it increased the risk of soil erosion. Combining polyacrylamide (PAM) with BC was hypothesized to mitigate the negative effect of BC on soil conservation while retaining the positive effect of BC on soil improvement. Nine factorial treatments with three application rates of wheat straw BC-mixed soils (0, 20, and 50 g kg −1 ) and three PAM-mixed soils (0, 0.4, and 1.0 g kg −1 ) were exposed to two 60-min sequential simulated rainfall events at intensity of 60 mm h −1 . The results showed that the soil loss rate (Rs) significantly increased with BC increasing, which was mainly attributed to the significant decrease in cohesion by BC application. The synergistic decreasing effects of BC and PAM on the Rs were significant. By combining PAM with BC, no significant difference of cohesion and Rs was observed between different BC application rates under the same condition of PAM dosage. The Rs were significantly reduced by 47.9–78.0% with PAM application rates of 0.4 g kg −1 compared with 0 g kg −1 PAM. A PAM application rate of 0.4 g kg −1 combined with 20 g kg −1 BC was selected as optimum treatment not only for significantly decreasing the Rs and runoff, but also for taking advantage of BC on increasing the SOC, cation exchange capacity (CEC), and plant-available water capacity (PAWC).