EFFECT OF DRAINAGE WATER MANAGEMENT ON SOLUBLE NUTRIENT CONCENTRATIONS IN CROPLAND DRAINAGE WATER
Wm. Bruce Clevenger
Associate Professor and Field Specialist, Farm Management
Ohio State University Extension
Concentrations of soluble nutrients in fresh water watersheds have an impact on water quality. The Western Lake Erie Basin (Northwest Ohio) is impacted by water soluble nitrogen and phosphorus. Concentrations of nitrate-nitrogen (N-NO3) above 10 ppm trigger human drinking water advisories and concentrations of dissolved reactive phosphorus (P-PO4) above 0.03 ppm contribute to growth of harmful algae. A research study began in 2005 to examine controlled drainage (CD) compared to conventional free drainage (FD) from cropland on concentrations of soluble nutrients in subsurface tile drainage water. A paired plot design was established using four subsurface drainage designs, then duplicated giving eight total plots. Two drainage designs used 4 inch inside diameter (i.d.), corrugated plastic tubing (CPT) tile; one at 20 foot and another at 40 foot lateral spacing. Two additional drainage designs used 2 inch i.d., CPT tile; one at 10 foot and another at 20 foot lateral spacing. During the research period 2007-2013, plots were planted to a corn-soybean rotation and managed to have treatments of CD or FD annually. Eight automated water samplers collected samples (n=5,632) for each rainfall event for nutrient analysis. Differences in annual N-NO3 and P-PO4 concentrations in drainage water from CD (16.96 ppm and 0.20 ppm, respectively) vs. FD (13.44 ppm and 0.19ppm, respectively) were not significant. While concentrations were not significantly affected by drainage water management, CD has potential to reduce total volume of water leaving cropland on an annual basis, thus reducing total nutrient release from subsurface drained cropland to the watershed.
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Authors: W.B. Clevenger, B.J. Allred, D.L. Gamble
Clevenger, W. Assistant Professor and Extension Educator, Ohio State University Extension, Ohio, 43512
Allred, B. Adjunct Assistant Professor/ Research Scientist, Ohio State University/USDA A.R.S., Ohio, 43210
Gamble, D. Hydrologic Technician, Ohio State University/USDA A.R.S., Ohio, 43210