ANALYSIS OF PRECIPITATION, STORM RUNOFF, AND SOIL LOSS IN DRYLAND FIELDS WITH CONSERVATION TILLAGE
Dockal, Justin Ryan
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Conservation of storm precipitation and mitigation of storm runoff and soil loss are important for successful dryland production in the semi-arid Southern High Plains. Precipitation, runoff, and soil loss data was evaluated from six paired No-Till (NT) and Stubble-Mulch (SM) tillage fields maintaining a Wheat-Sorghum-Fallow (W-S-F) rotation at the USDA-ARS Conservation and Production Research Laboratory in Bushland, Texas. Our purpose was to evaluate data collected from 1984-2010 to explain why similar storms and field conditions produce variable runoff and soil loss amounts. Storm and field management factors of precipitation, tillage, and crop phase were analyzed to understand runoff and soil loss variation. Data was categorized by year, precipitation depth, field, and crop rotation phase to determine trends of precipitation, runoff and soil loss events. Parametric and non-parametric comparisons of means and medians were used to identify differences in datasets with comparable field conditions. Simple linear regression was used to correlate precipitation with runoff amounts. Multiple linear regression methods were used to correlate precipitation and runoff with soil loss amounts. Storms with depths in the 76.3-101.6 mm range caused the greatest variations in runoff and soil loss measurements. Twenty-seven year means and totals followed trends of increased precipitation in the summer months, increased runoff with No-Till management and increased soil loss with Stubble-Mulch. Fallow periods were shown to have increased runoff and soil loss with wheat residues providing better protection from storm precipitation than sorghum residues.