The effect of municipal sewage sludge on the quality of soil and crops

Purpose To examine the effects of the application ofcomposted sewage sludge fertilizer (commercially sold asKala compost) and inorganic (NPK) fertilizers on soilquality and on two crops (radish and beans) irrigated usinggroundwater and sewage treated wastewater (TWW) forirrigation by measuring heavy metals in the soil and plantsand other parameters such as crops yield, TOC in soil,chlorophyll index and total nitrogen.Methods The field experiments were conducted in an openarea in Agricultural Experimental Study at Sultan QaboosUniversity campus, Oman. In this research, ‘‘green beansand white radish’’ were examined under the application ofKala and NPK fertilizers. The experimental design was arandomized complete block with four replicates.Results The results showed that the yield, TOC andchlorophyll contents of green beans and white radishincreased when soil was amended with Kala compostcompared to NPK. Chemical analysis of soil and the twocrops did not show any risk of heavy metal accumulation.Conclusions Considering that the experiment was a shortduration one, there is a need for more continuous long-termexperiments (at least 5 years) that will improve theunderstanding on the effects of composted sewage sludgeon soil fertility and crop yield to contribute to the developmentof sustainable agricultural practices in an aridenvironment of Oman.