Effect of Nitrogen-Based Biosolid Application on Tree Growth, Water Quality, and Soil Phosphorus in Hybrid Poplar Plantations

A three-year study applied four N-based biosolid treatments to hybrid poplar trees over a two year period with spring and fall applications. All biosolid treatments had a faster rate of diameter and biomass growth (but not height) than the control, but the High and Medium application rates had the fastest rate of growth, and were not significantly different. There was no difference in foliar nitrogen and phosphorus levels between any of the treatments. Water quality data from suction lysimeters generated nitrate values below 20 ppm for the low treatment, which is similar to levels found in a cornfield. Four wells surrounding the site reported nitrate levels within the range of values found associated with other eastern shore cropland. P levels in soil samples escalated immediately after broadcast application to levels above the threshold in the state nutrient management regulation. The use of nitrogen based biosolid application in Maryland or other states with similar phosphorus-based nutrient management regulations is not feasible on the soil types tested.