Surface runoff losses of fertilizer elements from forage plots on Loring silt loam soil (5% slope) were monitored from three separate studies during an 11‐month period. Incorporating approximately equal amounts of N and P from commercial fertilizer (150‐66, kg N‐P/ha) and sewage sludge (177‐54, kg N‐P/ha) did not significantly affect differences in N and P losses. Surface application of sewage sludge resulted in higher N and P losses than those from incorporated sewage sludge. The surface‐applied sludge plots in the second experiment (14.8 metric tons/ha) had the highest N and P runoff losses of 3.24 and 0.39 kg/ha, respectively. These losses were due to a heavy rain that fell early in the test period. Increasing the rates of surface‐applied sewage sludge from 16.2 to 28.9 metric tons/ha did not increase runoff losses of N but did increase P losses by 28%. The N and P losses for all treatments were < 1% of that added. The highest K losses (1.24 kg K/ha) came from the fertilized plots. In all sewage‐treated plots, K losses were approximately equal to or lower than the control values. Precipitation was found to contain substantial quantities of NH 4 ‐N and NO 3 ‐N with respect to losses of these ions in the surface water. Work with 15 NH 4 ‐N indicated that the 15 NH 4 ‐N in the rain could contribute substantially to the total amount of N lost in the surface runoff waters. There was also exchange of rain‐NH 4 and soil‐NH 4 . Fecal coliform indicator bacteria (FC) counts in surface runoff waters from sewage‐treated plots were very high in the first 11 to 17 days of the second and third experiments; Counts of FC were as high as 55,000/ml. However, numbers decreased rapidly as the soil became drier.
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Dunigan et al. (1980) studied this question.