Soils from several areas in Kentucky were placed in columns and leached with Ca(NO3)2. Subsoils high in iron oxide were found to retard the leaching of nitrate very significantly. In other soils, the nitrate moved through as fast as or slightly faster than the water.
Field application of nitrogen to corn was most efficient when done in the spring or summer near the time that the corn takes it up. The one exception to this was a red soil, where fall application of nitrogen resulted in little loss due to the retarding effect mentioned in the first paragraph.
Soils on which a sod or cover crop is killed and in which corn is planted have little loss of water by evaporation. Because of this, much more water movement occurs and nitrate moves out of the soil during the summer. In contrast, the soil without a killed sod mulch suffers no loss of nitrate during the growing season.
Stream samples taken in 1971 and 1972 during the months of January through May showed a poor relation between nitrate in the water and land use, The highest nitrate was found in a stream draining a grassland watershed where little fertilizer is used.
The tile drain effluent and total water reaching a drainage ditch were determined. The nitrate in the tile effluent was much higher than that in the non-tile drainage. This leads to the conclusion that the nitrate concentrations of tile effluents are not reliable indicators of nitrate leaving a tiled field.
Digital Object Identifier (DOI)
The work on which this report is based was supported in part by funds provided by the Office of Water Resources Research, United States Department of the Interior, as authorized under the Water Resources Research Act of 1964.
Thomas, Grant W. and McMahon, Matthew, "The Relation Between Soil Characteristics, Water Movement and Nitrate Contamination of Ground Water" (1972). KWRRI Research Reports. 143.