The use of urea hydrogen peroxide as an alternative N-fertilizer to reduce accumulation of arsenic in rice grains

Abstract

A greenhouse experiment was conducted to examine the effects of urea hydrogen peroxide (UHP) on reducing the accumulation of As in rice grains. The results show that UHP effectively triggered Fenton-like reaction by reacting with Fe2+ in the paddy soils. This significantly inhibited the activities of As(V)-reducing microbes, causing impediment of As(V)–As(III) conversion following inundation of dryland crop soils for paddy rice cultivation. As-methylating microbes were also inhibited, adversely affecting As methylation in the soils. These processes led to the reduction in phyto-availability of As in the soil solutions for uptake by rice plant roots, and consequently reduced the accumulation of As in the rice grains. In this study, an UHP application rate of 0.0625% on three occasions (tillering, heading and filling) during the rice growth period was sufficient to lower the rice grain-borne As concentration to below 0.2 mg/kg, meeting the quality standard set by the Chinese government. No additive effect on reducing grain-borne As was observed for the joint application of UHP and biochar or biochar composite. The use of UHP for soil fertilization had no adverse impact on rice yield in comparison with the application of urea at an equal amount of nitrogen.