EFFECTS OF AGRONOMIC BIOSOLIDS UTILIZATION ON SOIL QUALITY

Land application of biosolids as a fertilizer amendment to agricultural land is a controversial issue despite the long history of the practice. Public concerns surrounding biosolids application include potential pollution of soils, crop tissue and groundwater by excess nutrients and trace elements that are present in biosolids. This 3-year study was designed to assess the effects of long-term biosolids application on the quality of soils and crop tissue in Pennsylvania. This study is unique in that these effects were assessed at actual agricultural biosolids application sites, rather than at highly controlled research plots. Soil and crop tissue samples were collected in the fall of each year, from 18 farms throughout the state and tested for nutrients, trace elements and other soil quality parameters. Soil samples were collected from depth increments of 1-10, 10-20, and 20-40 cm, and crop tissue samples were collected from the same locations as the soil samples. Within each farm, soil and crop tissue parameters from a field that had received biosolids (treated) were compared with those from a field that never received biosolids (control). The paired fields within each farm (treated and control) had similar soil type and similarcropping histories, so that the primary difference between members of a pair was the application of biosolids. For each parameter measured, the average of all within farm differences wascompared to variability across all farms to determine statistical significance of that parameter. This was done for each year individually and for combined analysis of all 3 years of the study.Soil pH, cation exchange capacity, and organic C were similar in treated and control fields. The combined 3-year analysis showed that soil concentrations of Cu, Cr, Hg, Mo, Mn, Pb and Zn were higher in the treated fields than the control fields. These differences, while statistically significant, were small (