Agronomic solutions to decrease arsenic concentrations in rice

Abstract

Rice plants accumulate arsenic (As), a toxic metalloid found both naturally and as a form of anthropogenic pollution in rice fields. Arsenic concentrations in rice grain may pose human health risks, particularly when consumed regularly or used in food products for infants and young children. The purpose of this review is to summarize evidence-based mitigation strategies for minimizing the As content of rice and establish recommendations for their implementation. Mitigation strategies include irrigation management practices that introduce aerobic periods, applying soil and foliar amendments that decrease As plant-uptake, selecting and developing cultivars with lower rates of As-uptake, and post-harvest processing. In addition to a literature review, we interviewed rice producers and stakeholders to identify barriers or knowledge gaps to implementing the mitigation strategies. Alternate wetting and drying irrigation showed high effectiveness in decreasing grain As concentrations and is also climate-smart and can be cost-neutral. Combining irrigation management with select amendments maximized the decrease of grain As concentrations. Combining treatments will allow a choice of options to accommodate different farm circumstances, though nearly all field-level treatments lack experimental evidence from trials at production-scale operations (i.e., > 1 ha, with commercial management). Thus, more research is needed to develop best management strategies at the field scale in collaboration with farmers.

Keywords: Alternate wetting and drying; Arsenic toxicity; Rice; Soil amendments.

Fig. 1

Overview of the mechanism of action for each amendment in the soil and in the plant