|Douglas Jr, Clyde|
Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/1998
Publication Date: N/A
Technical Abstract: Winter runoff from croplands results in less water available for low spring- and summer-flows, and potentially contributes to sediment and nutrient loading in streams. We hypothesize that winter infiltration and runoff properties are related to soil organic carbon and soil fertility, which is related to crop and residue management. We have begun to assess the hydrologic properties of a crop management study begun in 1931. The original study examined the influence of fertilizer and crop residue management in a winter wheat/summer fallow system. Plots are 11.6 m x 40.2 m on slopes from 0 to 4 percent. We instrumented four treatments to measur winter runoff and sediment loss. Treatments selected from this long-term residue management study consisted of fertilizer applications (nitrogen 0 and 90 kg/ha, manure = 146 kg/ha), and no burn or repeated spring-burn of cereal residue. The winter runoff season (Nov. to March) consisted of 19 rainfall events greater than 0.10 inch of rainfall. Twelve percent more runoff events were observed from the spring burn plots than from the no burn plots. Based on these preliminary findings, runoff and erosion appear inversely related to soil organic carbon content. Crop management practices that deplete soil organic carbon detrimentally effect the environment. Water loss from croplands due to winter runoff impacts crop productivity, dry-season low stream flows, and impacts water quality and instream habitat. Crop management practices that leave the soil resource bereft of soil organic carbon and deteriorated soil structure are indicative of unsustainable agricultural practices. These changes occur slowly, but will make future management more difficult.