Growth, Mineral Nutrition and Selected Soil Properties of Lowland Rice, as Affected by Soil Application of Organic Wastes and Phosphorus

Lack of adequate organic matter (OM) in the agricultural soils of Iran is responsible for the poor physical condition of these soils. Thus, increasing soil OM is very important. On the other hand, the eutrophication of surface water caused by continuous use of phosphorus (P) fertilizer has created an interest in the combined use of organic wastes and P fertilizer. Hence, the present study was undertaken to study the effects of several levels of municipal waste compost (MWC), poultry manure (PM) and P on the growth and elemental composition of lowland rice (Oryza sativa L.) and on selected soil chemical characteristics. There was a consistent increase in the shoot dry weight as the levels of MWC, PM or P increased. However, rice shoot growth was stimulated more by MWC than by PM and the enhancing effect of P on shoot growth was greater in MWC-treated plants than that of PM. Shoot P concentration ncreased with increasing levels of MWC, PM and P, whereas nitrogen (N) concentration was only affected significantly by the two organic wastes. Iron (Fe) and zinc (Zn) concentration was suppressed by P supply in PM-amended soil and was not affected by MWC treatment. Rice seedlings treated with either of the biosolids accumulated more Fe, Zn, chloride (Cl) and sodium (Na) but less manganese (Mn) than the control plants. Furthermore, rice plants grown on MWC-amended soil contained higher Fe and Mn and lower Cl and Na than those grown on PM-treated soil. In the present study, lead (Pb) and cadmium (Cd) concentrations did not follow a definite pattern with either of the organic wastes, whereas they increased with P application. Post-harvest soil sample analysis indicated that soil addition of MWC and PM increased concentrations of soluble salt, OM, N, NaHCO3- soluble P and DTPA-extractable Fe, Mn, Cu, and Pb