Temporal Variations of Biochemical and Chemical Properties in a Calcareous Soil Amended with Tabriz Petrochemical Sludge

Recently, sewage sludge as a cheap organic fertilizer and rich in nutrients has received considerable attention in many countries. The aim of this study was to determine the effects of Tabriz petrochemical factory’s biological sludge on some soil biochemical and chemical indices such as the number of microorganisms, substrate-induced respiration, electrical conductivity, hot water-soluble carbohydrates and total nitrogen as well as their temporal variations in a calcareous soil selected from Mohaghegh Ardabili University’s Research Station. The greenhouse experiment was done as a factorial randomized complete block design with three replicates. The first factor was the rates of applied sludge as 0 (control), 25, 50, 75 and 100 ton/ha of air dry soil and the second factor was the incubation times as 30, 90 and 180 days. Incubation of the treatments was done at 22±4 ◦C and 0.75 field capacity moisture for 6 months. The results indicated that the all rates of applied sludge significantly increased the average of number of microorganisms, substrate-induced respiration, electrical conductivity, hot water-soluble carbohydrates and the percentage of soil total nitrogen 23, 53, 105, 58 and 138% as respectively compared to the control. Also, the effect of incubation time on all parameters except for the number of microorganisms was significant. The rates of carbohydrate and nitrogen in sludge treatments significantly increased at 180 days rather than the 30 days.