The application of 32 t/hm² biochar and 1.6 t/hm² PAM significantly increased the rice grain yield. The combined application of 32 t/hm² biochar + 0.6 t/hm² PAM increased the net photosynthetic rate by 26.0% and the transpiration rate by 24.8% relative to the control. The application of either biochar or PAM increased the rice net photosynthetic rate, transpiration rate, and stomatal conductance. The soil property results showed that wheat straw biochar and PAM lowered soil total salt and bulk density, but increased the soil organic matter (SOM), mean weight diameter of water-stable aggregates (MWD), and macroaggregate (> 0.25 mm) content. The experiment described in this study was conducted over five consecutive growing seasons (from 2016 to 2020) with biochar (at 0, 32, and 79 t/hm²) and PAM (at 0, 0.6, and 1.6 t/hm²) applications to study the effects of amendments on soil properties, rice photosynthesis, and rice yield in coastal saline land. Biochar and polyacrylamide (PAM) have been widely applied as soil amendments to enhance soil structure, but the interactive effects of biochar and PAM on rice growth are unclear.

Hence, it is essential to choose suitable and efficient approaches to revitalize coastal saline soil quality and improve agricultural productivity. Poor soil quality is affected by salinity, which limits land productivity and sustainable agricultural development in coastal China.

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