Treated Municipal Wastes: Are they Contaminating or Enriching the Soil?

Treated municipal wastes could be a mixture of treated sewage biosolids and green wastes (Kala compost) that can be applied for agricultural production. It can improve soil fertility and plant growth. However, long-term application of treated sewage biosolids could result in heavy metal accumulation and some health problems. The objective of this study is to evaluate the effect of different fertilizers, especially Kala compost, on the soil fertility and plant productivity. An open field was divided into nine plots and received either treated municipal wastes (Kala compost) or inorganic fertilizer, or a mixture of both fertilizers. The field was irrigated by drip system, and commercial cucumber, tomato, cabbage, lettuce, carrot, and potato were grown in each plot. Soil and plant were monitored continuously and samples were taken at different stages of the study. No symptoms of physical or chemical problems were observed in the open field and measured soil samples. Moreover, the soil had sufficient amount of different nutrients for plant growth and all measured micronutrients (heavy metals) were within the safe limit and below the allowable safe limit of the international standards. Good growth was observed in all grown crops and no symptoms of element toxicity were observed. Chemical analysis for fruit samples did not show any accumulation of heavy metals and all measured elements were within the safe limit for human consumption. It can be concluded that treated municipal wastes (Kala compost) were good media for plant growth that can enrich the soil with different elements needed for higher yield. However, more monitoring is needed with treated biosolid application and good management could be the key to avoid any adverse effect of any contaminant.