Utilization of Biosolids as a Fertilizer for Canola

Abstract

A two-year study was conducted to determine the crop yield and nutrient uptake in canola and elemental levels in soils amended with biosolids applied at four rates for seven years. The biosolids application rates of 0, 1.9, 5.8, and 11.7 Mg ha−1 (dry basis) were based on providing the following amounts of total N (in kg N ha−1): 0 (control), 57 (low), 170 (medium), and 340 (high). After second year harvest, soil samples were collected from 0-15 and 15-45 cm depths and analyzed for total and water-extractable essential (N, Ca, Mg, K, P, S, B, Mn, Zn, and Cu) and nonessential elements (Cd, Cr, Co, and Ni), pH and electrical conductivity (EC). Generally, biosolids application significantly increased the concentrations of total and water extractable essential elements at the 0-15 cm depth, whereas concentrations of total and water extractable nonessential elements (Cd, Cr, Co, and Ni) were only detected at trace levels for both depths. There was a significant increase in soil EC and soil organic matter content with biosolids application at the 0-15 cm depth. Biosolids treatments significantly increased the total dry matter yields 1.5 to 3.8 times above that of the control and increased concentrations of most essential elements in canola leaves. The overall results suggest that amending sandy loam soils with biosolids of the tested quality can increase yield and forage quality of canola leaves with negligible increases in nonessential trace element concentrations in soil and/or in leaves.