The Effects of Sewage Sludge and Chemical Fertilizers on Concentration of Some Microelements in Soil and Lettuce <(Lactuca Sativa L.)>

The aim of the present study was to investigate the effects of sewage sludge (SS) application individually and with chemical fertilizer and application time on the micronutrient concentration in soil and lettuce (Lactuca sativa L.) in the field. The experiment was arranged in split plots based on complete randomized block design with two factors and three replications. The main plot included 6 fertilizer treatments consisting of control, chemical fertilizer (pottasium solfate, triple phosphate super of 75 and urea 200 kg/ ha) 20 and 40 ton.ha-1 of sewage sludge individually and with 50% chemical fertilizer. The sub-plots were considered as one year, two-year and three-year application of fertilizer. Experimental results showed that the treatment significantly affected the available Zn and Cu of soil and concentration of Fe, Zn, Cu and Mn in lettuce root and Zn and Cu in shoots. The results also showed that concentration of the microelement in soil and root and shoot of lettuce were affected significantly by annual application of fertilizers. Interaction of the two factors showed significant effect on available Zn content of soil, Zn and Mn concentration of root and Fe and Cu of shoot. The highest increase in content of soil and lettuce micronutrient belonged to the application of 40 ton. ha-1 sewage sludge individually and enriched with 50% chemical fertilizer.