Zinc oxide nanoparticles in combination with biochar alleviates arsenic accumulation in field grown rice (Oryza sativa L.) crop

Plants require zinc (Zn) as an essential micronutrient since Zn plays important roles in metabolism. Arsenic (As) is a toxic metalloid whose accumulation in plants hampers growth of plants. Rice crops are grown under flooded conditions that make them vulnerable to double jeopardy of Zn deficiency and As stress. The goal of this study was to observe the effect of ZnO nanoparticle (NP) and ZnO-NP + biochar on As and Zn accumulation in and growth of rice plants grown under flooded conditions. The study area was Chausa block in Buxar district, Bihar, India. Rice crops were treated with 80 mg L⁻¹ of ZnO-NP and biochar was added to soil at rate of 10 t ha⁻¹. ZnO-NP were sprayed at heading and jointing stage of crop development. The results showed a significant increase in rice growth and yield by 14–26% and 30–33% respectively along with total chlorophyll content in ZnO-NP and ZnO-NP + biochar as compared to control. The level of electrolytic leakage and malondialdihyde (MDA) content was observed to decrease by 48–62% and 14–55%, respectively in treated plants as compared to control. Further, As accumulation was reduced in rice grains by >90% while Zn accumulation was increased by >50% in ZnO-NP and ZnO-NP + biochar treatments than that in control. The enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and catalase (CAT) showed higher activity in treated crop plants than in control plants. The findings confirm that ZnO-NP and their combined use with biochar in flooded agricultural soil can help to improve growth, yield and reduce As accumulation in rice plants.