Document Type : Research Article
Author
Department of Soil Science, Agriculture Faculty, University of Mohaghegh Ardabili
Abstract
Abstract
One of the methods for improving soil physical quality of arid and semiarid regions is the application of cheap organic conditioners such as sewage sludge. This research was conducted in large pots (50 cm diameter, 25 cm height) to study the effects of Tabriz petrochemical biological sludge at 4 rates (25, 50, 75 and 100 tons/ha) on organic carbon (OC), mean weight diameter (MWD) of aggregates, water-dispersible clay (WDC), liquid limit (LL) and plastic limit (PL) moistures and plasticity index (PI = LL – PL) during time in a semiarid soil. There was also control treatment (without sludge) and all treatments included 3 replications. Incubation of treatments was done in a greenhouse with field capacity moisture content of 0.7 – 0.8 and temperature of
22 ± 4 ˚C for 6 months. All parameters were measured at 60, 120 and 180 days. The experiment was conducted as factorial (5 used rates of sludge (factor A) and 3 incubation times (factor B)) with randomized completely blocks design. Results showed that all used sludge rates significantly (P < 0.01) increased OC and decreased WDC as compared with the control. Negative correlation (r = - 0.84*) between OC and WDC was significant (P < 0.05). Moistures of LL and PL significantly (P < 0.01) increased with sludge application only at the rates of 75 and 100 tons/ha. Significant and positive correlation (r = 0.99***, P < 0.001) was found between OC with LL and PL. The effect of sludge used rates on MWD and PI was not significant. Significant and negative correlation (r = - 0.92***, P < 0.1) was found between MWD and WDC at 3 incubation times. This research indicated that petrochemical sludge as a cheap organic conditioner improved physical quality of the semiarid soil.
Keywords: Sewage sludge, Semiarid soil, Organic carbon, Aggregate stability, Consistency limit
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