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ABSTRACT
Over the past century, a significant proportion of the native grasslands that once occupied much of the middle third of the United States have been converted to cultivated agriculture, causing short- and long-term variations in soil physical and hydraulic properties that influence runoff-infiltration partitioning and runoff water quality. Eastern Arkansas is highly agriculturally productive when irrigated. However, the long history of irrigated agriculture and more recent shifts in rainfall patterns during the growing season have resulted in regional groundwater aquifer depletion with minimal regional recharge. The objective of this study was to evaluate the effects of land use on soil physical properties, runoff-infiltration partitioning, and runoff water quality on a typical agricultural soil in the Mississippi River Delta region of eastern Arkansas. Small-plot rainfall simulations were conducted on an Immanuel silt loam, (fine-silty, mixed, active, thermic, Oxyaquic Glossudalf) in plots (1.5 × 2 m) under native tallgrass prairie (PR) and two cultivated agroecosystems, ridge-tillage (RT), and conventional-tillage (CN). Residue cover was greatest in the PR and lowest in the CN system and differed significantly (p < 0.05) among all three land uses. However, runoff from the two agroecosystems did not differ, averaging 87% of the total amount of water applied, but both were significantly greater (p < 0.05) than that from the PR system, which averaged 62% of the total amount of water applied. Runoff turbidity and suspended solid concentration and load were greater (p < 0.05) from the CN than from the RT or PR systems. The CN system also had the greatest (p < 0.05) total P concentration and load, but the RT system produced runoff with the greatest (p < 0.05) soluble reactive P concentration and load of the three systems. Results indicate that land use and the degree of soil disturbance significantly affects runoff-infiltration partitioning and runoff water quality on this typical eastern Arkansas agricultural soil. Should results prove consistent on other regional soils, further depletion of local aquifers and degradation of surface water quality will likely continue if more sustainable agricultural practices are not increased.