Effect of municipal waste leachate on soil properties and growth and yield of rice

Making use of any organic matter sources, including municipal waste leachate (MWL) produced in process of converting solid waste refuses into compost in and and semi-arid regions like central Iran, is very important. During 1998, a field experiment was conducted to investigate the effects of MWL on soil properties, growth, and yield of rice (Oriza sativa L.). The treatments consisted of 0, 150, 300, and 600 t of MWL ha(-1) and a control nitrogen-phosphorus-potassium-zinc (N-P-K-Zn) fertilizer treatment in a randomized complete block design with three replications. Rice seedlings were transferred to 4 X 4 m plots, which were flooded previously. Municipal waste leachate was applied at tillering and particle stages. At harvest, straw and grain yield as well as concentrations of several nutrients and heavy metals were determined in rice straw and grain. Application of 150 and 300 t of MWL ha(-1) increased the straw and grain yield, but 600 t ha(-1) treatment decreased the yield of grain compared to the control fertilizer treatment. Municipal waste leachate increased the amounts of available macro- (N, P, K) and micronutrients [iron (Fe), manganese (Mn), Zn, and copper (Cu)] in soil, which in turn enhanced soil productivity and crop yield. The straw and grain yields were increased from 7.0 and 4.2 t ha(-1) in NO MWL to 16.7 and 6.9 t ha(-1) in 300 t ha(-1) MWL treatment, respectively. The amounts of nutrient uptake were highest in 300 t of MWL ha(-1). Application of MWL significantly increased the levels of EDTA-extractable nickel (Ni), chromium (Cr), cobalt (Co), and lead (Pb) in the soil. Although MWL increased concentrations of some heavy metals in rice, particular in 600 t ha(-1) MWL treatment, the concentrations were below the reported critical levels for these metals. Municipal waste leachate is rich in plant nutrients and OM and is acidic; therefore, it may be used as a liquid fertilizer especially in calcareous soils.