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In this report we present results from a research project that was set up to test the hypothesis that the use of shallow drainage systems on poorly drained soils in Illinois will reduce the concentration of nitrate in tile effluent without having an adverse effect on crop yield. It involves the continuous monitoring of tile effluent from drainage tiles installed at different depths in a 40-acre (16- ha) field. The use of a single field reduces the confounding influence of soil, crop, size, and climate, major sources of external variability, thereby reducing the length of time required to draw conclusions from a study such as this that involves complex systems.

Over the range of depths studied, 2ft (0.61m) to 4ft (1.22m), there appears to be a direct correlation between decreased tile flow and decreased tile depth. The same pattern holds true for nitrate mass loads. However, nitrate concentrations were not correlated with tile depth. These results are from but one year of study; more data are required to validate the conclusions.