Short-term residual effect of municipal sewage sludge on the soil properties and potato yield

Sewage sludge (SS) is one of the significant wastes of modern city lifestyle with environmental consequences. This study was conducted to determine the effect of the municipal sewage sludge on the potato plant’s yield and nutrient elements and heavy metals content in a clay loam textured calcareous soil. The field treatment (corn-wheat-potato rotation) was implemented as fixed randomized blocks with 3 replications. The treatments were: control (without fertilizer), optimum fertilizer (OCF), 20, 40, 80, 100, and 120 ton ha-1 SS incorporation. The third-year results regarding the potato cultivation were presented. Results indicated that 4 ton ha-1 SS treatment resulted in a greater yield than the optimum fertilizer. The sewage sludge influenced the mineral nutrient composition of the leaves and the roots and the heavy metal concentrations in the plants were below the Turkish legal threshold values. Excessive application of SS had an inverse effect on the yield and reduced the essential nutrient concentrations of the leaves of the potato plants. This suggested that the residual effects of SS in the third year were considerable for either heavy metal concentrations or plant nutrients in the soil. Therefore, it can be concluded that a site-specific determination of the SS application rate is required to avoid potential deleterious effects of SS.