NITROGEN-FERTILIZER AND NITRATE CONCENTRATIONS IN TRIBUTARIES OF UPPER SANGAMON RIVER IN ILLINOIS

Cross section multiple regressions were used to test the importance of nitrogen fertilizer use for variations in the nitrate nitrogen concentrations in 16 small tributaries of the Sangamon River. Data were collected and regressions were run for 2 years, 1974 and 1975. Nitrate nitrogen concentrations in the spring of each year were regressed on estimated nitrogen fertilizer use per hectare of watershed in the previous crop or calendar year and variables representing other aspects of agronomic practice and hydrologic features. The fertilizer data were collected by surveying approximately 300 farmers. Nitrate nitrogen concentrations were measured at 4-week intervals. The regression results are not clear-cut but lend support to nitrogen fertilizer use as an important explanatory variable for variations in nitrate nitrogen concentrations.