Water quality of seasonally flooded agricultural fields in Mississippi, USA

Abstract

Planned flooding of agricultural fields is performed to prevent erosion (e.g. sheet, gully, and rill) and provide habitat for waterfowl. As a post-harvest field treatment, flooding is becoming more common in the agriculturally dominated landscape of the Mississippi Alluvial Valley (MAV) in the southeastern United States. Despite this trend, information pertaining to water quality characteristics of water remaining on fields during the winter and subsequent relationships with environmental and biological processes is sparse. Because the water retained on fields is eventually released into adjacent waterways prior to planting, it is critical to monitor water quality parameters of these flooded fields. Water quality parameters of flooded agricultural fields were assessed from January to March and compared to those observed in impounded wetlands. Temporal variation of parameters among sampling dates was also examined. Mean (±S.E.) suspended solids concentration was greater ( p<0.05) in flooded agricultural fields (283.3±98.7 mg l −1) than impounded wetlands (79.5±25.3 mg l −1) and an interaction of habitat and sampling date was detected on dissolved solids concentration ( p<0.05). Water temperature, pH, dissolved oxygen, ammonia, nitrate, total phosphorus, enterococci bacteria, and fecal coliform bacterial concentrations exhibited temporal variation among sampling dates ( p<0.05). For both flooded fields and wetlands, fecal coliform and enterococci concentrations peaked at 2887.5 and 675.0 colony forming units (CFU) 100 ml −1, respectively, during the first sampling date (January) and declined to 133.2 and 33.3 CFU 100 ml −1, respectively, in March. Results of this study indicated that: (1) flooded agricultural fields had greater variability of water quality parameters than wetlands; (2) 53% of measured water quality parameters exhibited temporal variation and (3) impounding water may facilitate decreases in bacterial concentrations. Holding water on agricultural fields and knowledge of temporal water quality trends may provide a means to decrease contaminant concentrations, thus improving quality of potential runoff that may enter adjacent bodies of water.