Effect of Addition of Secondary-Treated Domestic Sewage Sludge To Diammonium Phosphate Fertilizer on Element Content of Artificial Pasture Herbage and Their Availability in Soil

Abstract

Organic matter deficiency limits plant production in arid and semi-arid areas. Secondary treated sludge is an effective source of organic waste. The effect of sewage sludge in addition to diammonium phosphate (DAP) fertilizer on nutrient and metal concentrations of herbage and soil in an artificial pasture under arid and semi-arid condition was examined in this study. The pasture consisted of Onobrychis sativa (35%), Poterium sanguisorba (40%) and Agropyron elongatum (25%) mixture. A total of 150 kg ha-1 DAP was applied to all plots with sowing. Additionally, 30, 60 and 90 tonne ha-1 of sewage sludge was applied in a randomized block design. The addition of the sewage sludge increased P and K concentrations, however decreased B and Pb concentrations in the herbage significantly. Fe, Cu, Zn, Co, Se, Mo, Mn, Ni, Cr concentrations also decreased, but this change was not significant. The concentration of Cd in herbage increased with increasing sewage sludge doses. Sewage sludge improved pH, electrical conductivity and organic matter at two soil depths and increased N, P and K concentrations in both the topsoil and subsoil. The addition of domestic secondary treated sewage sludge could reduce the efficacy of some DAP-sourced metals.