Peanut shell biochar increases rice yield in highly saline-alkali paddy fields by regulating of leaf ionic concentration and improving leaf photosynthesis rate

Abstract Aims Saline-alkali soil seriously restricts the crop growth and production. Biochar addition could alleviate the adverse impacts of saline-alkali stress in crops. However, little information is available on the ionic accumulation and photosynthesis rate of rice in highly saline-alkali paddy fields. This study aimed to evaluated the influence of the peanut shell biochar on leaf ionic concentration, stress physiology indices, photosynthesis related parameters and rice yield in highly saline-alkali paddy field condition. Methods Field experiment was conducted using two nitrogen applied rate treatments (0 and 225 kg N ha− 1) and four biochar applied rate treatments (0%, 1.5%, 3.0% and 4.5% w/w). The field experiment was arranged in a complete randomized design with three replications. Results The results show that peanut shell biochar significantly reduced the leaf Na+ concentration, Na+/K+ ratio, abscisic acid and malondialdehyde concentration of rice, while enhanced leaf K+ content, and improved leaf water status and relative electrical leakage in treatments both with or without N fertilization. Furthermore, peanut shell biochar could provide beneficial effects on chlorophyll content, leaf N content, leaf area index, photosynthetic potential, stomatal conductance, and transpiration rates, which is of great benefit to the enhancement of leaf photosynthesis rate and net assimilation rate of rice population. In addition, the biomass, grain yield and harvested index were remarkably increased. Conclusions These results indicated that peanut shell biochar could effectively ameliorate saline–alkali stress and increase rice yield by regulating of leaf ionic concentration and improving leaf photosynthesis rate.