|Fortuna, Ann Marie|
|STEINER, JEAN - Kansas State University|
|Starks, Patrick - Pat|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2020
Publication Date: N/A
Interpretive Summary: Globally and regionally, retention and distribution of organic material and nutrients in agroecosystems vary due to landscape scale management and terrain attributes (elevation, slope, aspect, microclimate, water storage and movement) as well as anthropogenic management. Therefore, we carried out an experiment at three 1.6 ha Water Resources and Erosion paddocks established in 1978 in El Reno, OK to determine and quantify spatial variability to more accurately quantify effects of land management and conservation practices on soil properties. The current study, initiated in 2018, includes paddocks managed under conventional and reduced tillage systems, with and without forage cover crops, with one paddock of tallgrass prairie serving as a control. A suite of physical, chemical and biological indicators of soil quality were taken at the riser, side and toe slopes of three watersheds that included measures of soil carbon, plant nutrients, soil texture, bulk density and pH. The majority of variables associated with soil classification varied with landscape position and depth. Soil carbon and nitrogen varied with land use and or depth. Our initial efforts to parameterize the inherent spatial variability of these watersheds in order to determine the effects of land management on soil quality were successful. Collected measurements will be used to monitor soil health as well as parameterize and validate hydrologic models used to predict the effects of alternative land management on soil and water quality.
Technical Abstract: The establishment of replicate sampling stations that account for and limit the spatial variability of edaphic properties within defined landform complexes enables researchers to more accurately quantify the effects of conservation practices and land management. Our experiment was applied to a site established in 1978, consisting of eight 1.6 ha paddocks developed as self-contained watersheds that are representative of southern tallgrass prairie, or winter wheat (Triticum aestivum), and managed under a variety of systems from 1978 to 2018. The current study, initiated in 2018, includes paddocks managed under a combination of offset disking and chisel plowing and reduced tillage systems, with and without cover crops, with one paddock of tallgrass prairie serving as a control. A class I soil survey was conducted in 2018 by grid sampling the landscape of the site. The sampling indicated four distinct catena were present across all paddocks, which enabled use of a split block design to be applied. This design allowed testing of interactions among management practices to obtain means and standard errors for different soil attributes. One hundred and forty-four soil cores were collected using a hydraulic probe from three of the watersheds at tread, riser and toe slopes. Each watershed by slope contained four, 4.6 m x 3.8 m blocks from which four random soil cores 0-30-cm were taken. Baseline analyses included: Mehlich-3, soil sulfate and DTPA-sorbitol extractions, soil texture, bulk density, pH, soil organic carbon (C) and nitrogen (N), particulate organic matter (POM) and the resistant fraction of soil organic C. The majority of variables associated with soil classification varied with landscape position and depth. These included clay content, base saturation (Ca+2, Mg+2, K+) and pH as well as sulfur in the form of sulfate (SO4-S) and phosphorus (P). Carbon and N fractions varied with land use, conservation practices and or depth. Our initial efforts to parameterize the inherent spatial variability of these watersheds in order to determine the effects of land management on soil quality were successful. Measurements collected from replicated meter square sized spatial zones will be used to parameterize and validate hydrologic models, such as the Agricultural Policy/Environmental eXtender (APEX), which are to predict the effects of alternative land management on water quality.