Organic Rice Production: Minimizing Exposure to Grain Arsenic.

The market demand for organically produced rice continues to increase in the USA. In 2011, some 23,000 acres of organic rice were produced with a $35 million value. Research is needed to optimize organic production practices to strengthen this developing market.  In addition, there has been concern in recent years regarding the presence of arsenic in rice.  Arsenic is a naturally occurring element found in soils throughout the USA. Rice is typically produced in flooded fields primarily as a weed control measure. This is particularly important in organic production where herbicides are not used. However, flooded soils result in anaerobic conditions that ultimately make soil arsenic more available for uptake by the rice plant. A multi-year study was conducted in Beaumont, TX to evaluate the impact of cultivars, organic fertilizer products and various green manure crops on yield potential and grain arsenic accumulation when rice is produced in an organic management system. Results were highly variable across years. Under environments where organic yields were relatively low, there was no correlation with yield and grain arsenic. However, under conditions where overall yield potential was high, there was a positive association with yield and grain arsenic. Production following green manure crops resulted in higher grain arsenic levels than following fallow fields.  Cultivars were significantly different for yield potential and grain arsenic levels under organic management. Choice of cultivar was a more effective method for maximizing yield and minimizing grain arsenic content under organic management than fertilizer amendments or green manure crops.