Transport and fate of nitrate within soil units of glacial origin |
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| Authors: | Suzanna L Moore Eric W Peterson |
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| Institution: | (1) Department of Geography-Geology, Illinois State University, Normal, IL 61704, USA;(2) Present address: Patrick Engineering, Inc., 300 W Edwards St # 200, Springfield, IL 62704, USA |
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| Abstract: | Questions concerning the influence of soil type and crop cover on the fate and transport of nitrate (NO3−) were examined. During a growing season, soils derived from glacial material underlying either corn or soybeans were sampled
for levels of NO3− within the pore water. Measured levels of NO3− ranged from below detection limit to 14.9 g NO3− per kilogram of soil (g/kg). In fields with the same crop cover, the silty-clayey soil exhibited a greater decrease in NO3− levels with depth than the sandier soil. Crop uptake of NO3− occurs within the root zone; however, the type of crop cover did not have a direct impact on the fate or transport during
the growing season. The soils underlying soybeans had an increase in NO3− levels following harvest, suggesting that the decomposition of the soybean roots contributed to the net gain of NO3− in the shallow soil. For all of the soil types, conditions below 100 cm are conducive for microbial denitrification, with
both a high water saturation level (>60%) and moderate organic carbon content (1–2%). At depths below 100 cm, temporal differences
in NO3− levels of over a magnitude, up to a 95% reduction, were recorded in the soil units as the growing season progressed. Physical
properties that control the transport of NO3− or denitrification have a larger influence on NO3− levels than crop type.
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| Keywords: | Nitrate transport Denitrification Vadose zone Illinois |
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