Biochar Mitigates Combined Effects of Soil Salinity and Saltwater Intrusion on Rice (Oryza sativa L.) by Regulating Ion Uptake

Abstract

Salinity intrusion is a significant threat to crop productivity and food security worldwide. The aims of the current study were to evaluate the effects of rice husk biochar amendment on the growth and yield of rice grown in saline soil with saltwater intrusion at the seedling stage and to investigate the mechanism by which biochar mitigates the harmful effects of salinity intrusion on rice. Phitsanulok 2 rice was grown in pots containing saline soil amended with 0%, 10%, 20%, and 30% (w/w) rice husk biochar. Pots were put in a pond and 6 dS/m of NaCl was applied for 28 days. The results showed that biochar application significantly increased the survival, shoot height, shoot dry weight, yield, and yield components of rice. Biochar addition significantly decreased shoot Na+ contents and increased the shoot K+/Na+ ratio. By using a Fourier-transform infrared spectrometer and a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer, it was found that the negative surface charge of rice husk biochar was due to carboxyl and hydroxyl groups, and Na+ was detected on the surface of the biochar. We concluded that rice husk biochar amendment at a rate of 30% (w/w) could mitigate the negative effects of salt stress by absorbing Na+ in the saline soil, reducing Na+ uptake to the shoot, and increasing the shoot K+/Na+ ratio. Therefore, rice husk biochar amendment is a potential strategy for enhancing rice productivity in salt-affected soils with saltwater intrusion.