Submitted to: International Conference on Diffuse Pollution
Publication Type: Abstract Only
Publication Acceptance Date: 9/23/2011
Publication Date: 9/23/2011
Citation: Tomer, M.D., Cruse, R.M. 2011. Agricultural intensification, hydrologic alteration, and increasing precipitation in the US Midwest: Implications for hydrology and water quality. International Conference on Diffuse Pollution. CD-ROM. Interpretive Summary:
Technical Abstract: Agriculture in the US Midwest is experiencing changes in climate impacting crop production systems. Climatic shifts show increases in precipitation, and particularly increased frequency of high intensity events. Meanwhile, agricultural production systems are responding to the demand for biofuel production, particularly corn-grain ethanol. This has shifted cropping systems towards increased maize (Zea mays L) production and is increasing amounts of land planted to maize in consecutive years. The result is loss of diversity in cropping patterns and increased use of fertilizer nitrogen. Studies comparing water quality effects of different crop rotations have shown continuous maize is associated with increased leaching losses of nitrate-N. Improved crop genetics, combined with climatic shifts that have lengthened the growing season in parts of the Midwest, have led to earlier planting and increased crop uptake of N. But the longer maturing varieties carries risks when conditions are too wet either to plant earlier in spring or harvest on time in the autumn. These risks are not ignored by farmers who recognize a greater need for sustained production and stable grain supplies. Farmers in the northern Midwest have responded to climate change by planting longer-maturing crop varieties. A shift in timing of N fertilization away from autumn to spring application may also be taking place, after wet spring conditions have meant traditional autumn applications had to be repeated the following spring for some farmers in several consecutive years. This shift helps increase the efficiency of fertilizer N uptake in the long term. The story is one of changing climate and agricultural markets, and how farmers are responding to improve their efficiency and profitability. This presentation will summarize a decade of hydrologic and water quality monitoring in a Midwestern (central Iowa) agricultural watershed experiencing these changes in climate and cropping systems. Shifts in discharge-concentration relationships for nutrients and increased challenges for managing the riparian corridor under more frequent flooding are two of the issues that will be highlighted.