Nutrient and Coliform Losses in Runoff from Fertilized and Sewage Sludge‐Treated Soil

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Abstract
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 NH4‐N and NO3‐N with respect to losses of these ions in the surface water. Work with 15NH4‐N indicated that the 15NH4‐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‐NH4 and soil‐NH4.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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