Rice (Oryza sativa) as a Remediation Tool for Nutrient Runoff

ABSTRACT

Hypereutrophication of U.S. surface waters is one of the leading causes of impairment for water quality. With nutrient criteria development and total maximum daily load (TMDL) issues looming for regulators, agricultural research is focusing on practices aimed at decreasing nutrient contributions to receiving aquatic ecosystems. This study examined the use of rice (Oryza sativa) for luxury uptake of nitrogen and phosphorus components associated with agricultural storm runoff. Mesocosms (379 L) planted with rice were exposed to two concentrations (5 and 10 mg/L) of nitrate, ammonia, and orthophosphorus. Results from these mesocosms were compared to unvegetated controls (also amended with 5 or 10 mg/L nitrate, ammonia, and orthophosphorus) to determine efficiency of rice in remediating nutrient runoff. Statistically significant differences in ammonia and nitrate retention of vegetated mesocosms amended with 5 mg/L versus vegetated mesocosms amended with 10 mg/L were noted after the first exposure. Although rice is a nutrient-dependent aquatic plant, this study suggests that more efficient mitigation is possible at lower inflow concentrations as opposed to higher inflow concentrations.

KEYWORDS:

• mitigation
• non-point source pollution
• water quality
• agriculture
• wetland

ACKNOWLEDGMENTS

Authors thank A. Delmastro, T. Flemons, L. Lee, and L. Williams for sample collection and analyses. Thanks also to T&J Farms, Inc., of Corning, Arkansas, for donation of rice seed.

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Notes

∗Data for second experiment were limited to the first 9 h of the 12-h exposure for comparative purposes.