Runoff water quantity and quality data from native tallgrass prairie and crop-livestock systems in Oklahoma between 1977 and 1999

Authors: Nelson, Amanda; Moriasi, Daniel; Fortuna, Ann Marie; STEINER, JEAN - Retired ARS Employee; Starks, Patrick; Northup, Brian; Garbrecht, Jurgen

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2020
Publication Date: 4/2/2020
Citation: Nelson, A.M., Moriasi, D.N., Fortuna, A., Steiner, J.L., Starks, P.J., Northup, B.K., Garbrecht, J.D. 2020. Runoff water quantity and quality data from native tallgrass prairie and crop-livestock systems in Oklahoma between 1977 and 1999. Journal of Environmental Quality. https://doi.org/10.1002/jeq2.20075.
DOI: https://doi.org/10.1002/jeq2.20075

Interpretive Summary: Eight Water Resources and Erosion (WRE) watersheds were established in Oklahoma in 1976 to determine the effects of systems of agricultural management on water quality (nitrogen, phosphorus, and suspended sediments), and variation or change in water availability on soil erosion, crop productivity, resilience, and sustainability of managed agricultural lands. The watersheds were equipped to measure precipitation and surface runoff quantity and quality. Initially, all watersheds were in native tallgrass prairie, but later four of the them were cropped into winter wheat (two conventionally tilled (CT), one no-till (NT), and one no-till with a summer forage crop (SF)), while the other four watersheds remained in native tallgrass prairie. While there have been many previous peer reviewed experiments from the WRE watersheds, none included all the data sets collected during the period 1977-1999. In this study, we provided a discussion of all available archived historical data, including methods of collection and analyses. Such a long-term research database is essential for determining the impact of different agricultural management systems, understanding the processes related to hydrologic transport and water quality, and validation and development of models capable of defining hydrology responses and water quality. We compared trends and long-term averages for surface runoff, sediment, and nutrients across management systems. Conversion of the CT system to the NT and SF, reduced surface runoff by 5 and 18%, respectively; sediment by 7 and 54%, respectively; total phosphorus by 68 and 19%, respectively; and total nitrogen lost by 70 and 31%, respectively. These findings contribute to the Conservation Effects Assessment Project (CEAP) and Long-term Agricultural Research (LTAR) network, whose goal is to quantify the effects of land management on soil and water resources under variable climate.

Technical Abstract: In 1976, eight 1.6 ha watersheds were established and instrumented at the USDA-ARS Grazinglands Research Laboratory, approximately 30 miles west of Oklahoma City near El Reno, Oklahoma. The watersheds were constructed and instrumented to measure precipitation and surface runoff quantity and quality. The cropped watersheds are surrounded by manmade berms and the grassed watersheds by ridges and natural boundaries. Land use of the watersheds has remained constant since 1976. Prior to construction, all watersheds were in native grass. After construction, four of the eight watersheds were cropped into winter wheat (two conventionally tilled and two no-till), while the other four watersheds remained in native tallgrass prairie. Variations in land management have been dictated by research objectives (surface runoff and erosion, water quality, spatial variability of soil properties, soil moisture distribution, groundwater levels, impact of land management alternatives, effects of land use and so forth) and largely representative of native grass and wheat management in the Southern Great Plains. While there have been many previous peer reviewed experiments from the WRE watersheds, none included all the data sets collected during the period 1977-1999. The objectives of this study were to 1) present and discuss all archived historical data, including methods of collection and analysis, and 2) compare trends and long-term averages for select components and forms of nutrient across treatments. The tallgrass prairie watersheds had lower amounts surface runoff, sediment, total phosphorus, and total nitrogen lost (0.25 mm, 0.9 kg/ha, 288 'g/L, 2.5 mg/L, respectively) when compared to the maximally tilled watersheds (0.30 mm, 88.5 kg/ha, 2131 'g/L, 11.6 mg/L, respectively). However, for the two watersheds that were initially maximally disturbed and then converted to minimally disturbed systems, the results were not as clear cut due to an early lag of a few field seasons immediately after the changes in management. In general, minimally disturbed management systems led to lower soil erosion and nutrient losses.