Impact of cover crop and season on nutrients and sediment in runoff water measured at the edge-of-fields in the Mississippi Delta of Arkansas

Authors: ARYAL, NIROJ - Orise Fellow; Reba, Michele; STRAITT, NADINE - Arkansas State University; TEAGUE, TINA - Arkansas State University; BOULDIN, JENNIFER - Arkansas State University; Dabney, Seth

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2017
Publication Date: 1/1/2018
Citation: Aryal, N., Reba, M.L., Straitt, N., Teague, T.G., Bouldin, J., Dabney, S.M. 2018. Impact of cover crop, irrigation and season on nutrient and sediment in the runoff water measured at the edge-of-fields in northeast Arkansas. Journal of Soil and Water Conservation. 73(1):24-34. https://doi.org/10.2489/jswc.73.1.24.
DOI: https://doi.org/10.2489/jswc.73.1.24

Interpretive Summary: The northeast region of Arkansas (Arkansas Delta) produces a major quantity of row crops annually. The losses of nutrients and sediment from the cotton fields in the region are unknown. Researchers measured nitrogen, phosphorus and sediment loss from fields with and without a cover crop in the non-growing season (Nov-Apr), and with cotton crops in the growing season (May-Oct) at four fields in two locations for 2-3 years. Cover crops reduced concentrations of pollutants leaving the fields in the winter. Loss of nutrients occurred higher during the non-growing season than during the growing season. Runoff water quality after irrigation was not different from that after rainfall. These findings support the implementation of practices including cover crops at the field in the winter. Producers can reduce the loss of nutrients and sediment from the fields by planting cover crops in the winter.

Technical Abstract: Improved understanding of water quality at the edge-of-field (EOF) from production-size fields is needed to better inform agriculture and resource managers regarding sustainable farming practices and environmental stewardship. We measured runoff water quality at EOF of paired commercial fields in Mississippi and Craighead counties (total of four fields) in the Mississippi Delta region of eastern Arkansas, an understudied agricultural region. The paired fields had similar size, soil properties, and crop (cotton [Gossypium hirsutum L.] or corn [Zea mays L.]). Runoff water quality (nitrate [NO3], nitrite [NO2], total nitrogen [TN], phosphate [PO4], total phosphorus [TP], and suspended sediment concentration) and quantity (discharge) were measured using sensors and automated water samplers installed in surface drainage pipes at the EOF and laboratory analysis. We monitored both precipitation and irrigation events for three years, with the first two years in cover crop and the third year in baseline study. We used the data to evaluate (1) the effectiveness of cover crops in reducing nutrients and sediment losses, (2) differences in growing season and nongrowing season losses, and (3) changes in runoff water quality from irrigation tailwater compared to rainfall event runoff during the growing seasons. We also compared variations in pollutant loadings in the paired fields under identical crop and management practices for baseline monitoring. Cover crops effectively reduced concentrations of NO3-N and PO4-P from one field pair at the Caraway location. Generally, concentrations of pollutants were lower in the growing period (May through October) than in the nongrowing period (November through April), suggesting the need for practices such as cover crops to reduce winter loads. Runoff water quality after irrigation was not different from that after rainfall. These findings support the need for baseline studies before actual evaluation of conservation practices, and practices including cover crops at the field in winter.