Phosphorus-arsenic interaction mitigates toxicity and accumulation of arsenic in rice grown in contaminated fields

The study shows that strategic intensification of phosphorus serves as a dual-function mechanism for effectively reducing arsenic movement to grains in rice and boosting crop yield. However, phosphorus-use efficiency is a variety-specific phenomenon, and it defines the resilience of the variety to low-phosphorus doses. This positions the combined management of nutrients and variety as a robust strategy for achieving safer rice cultivation in environments tainted with arsenic. Arsenic (As) contamination in rice is a serious threat to food security worldwide. Phosphorus (P) plays a crucial role in modulating As uptake in rice plants. Elevated P content in the soil may hinder the uptake of As by competing with the transporter system and altering rhizosphere chemistry. This study aimed to investigate the effect of varied P fertilizer levels on rice (Oryza sativa L.) plants in terms of growth and As accumulation, grown in two different As-contaminated fields. The study was conducted during the rice-growing season from mid-July to November 2023. The experiment included the recommended (60 kg h^-1), half (30 kg h^-1), and double (120 kg h^-1) doses of diammonium phosphate (DAP). Two contrasting varieties of rice were used that differed in phosphorus use efficiency (PUE): P-efficient DNA Sribala (DS) and P-inefficient Sai Kasturi (SK). SK suffered significant reductions in shoot and panicle lengths under low P doses (up to 35 and 18%, respectively), whereas DS showed non-significant effects. Arsenic accumulation in grains increased by 20% under low P doses for SK but decreased by 9-11% with higher P doses. In contrast, DS demonstrated tolerance to low phosphorus concentrations and no significant change in As accumulation was observed. In addition, the yield of rice was also increased in high P doses, which was 14-23% at two sites for SK, while 17-20% for DS. These findings underscore the critical role of P management in mitigating As toxicity and optimizing rice productivity in contaminated environments.