Effects of Ardabil Municipal Sewage Sludge on Some Physical and Hydraulic Properties of a Coarse-Textured Soil under Wheat Cultivation

Coarse-textured soils have generally low organic matter and unstable structure. Using cheap waste materials such as sewage sludge is one of the solutions for their associated problems. The purpose of this study was to investigate the effects of Ardabil municipal sewage sludge on some physical and hydraulic properties of a sandy loam soil selected from Ardabil plain under cultivation of spring wheat. A greenhouse experiment was done as randomized complete block design with 5 treatments and 4 replications. The treatments were zero (control), 11.5, 23, 46, 69 g of air dried sludge per kg of air dried soil equivalent to zero, 30, 60, 120 and 180 tons of sludge/ha, respectively. After mixing the sludge with the soil, the spring wheat seeds were sown in pots. Parameters were measured after wheat harvest, 4 months after mixing the sludge with the soil. The results showed that the all rates of sludge from 30 to 180 ton/ha significantly decreased soil bulk density, particle density macropores (> 75 µm) and saturated hydraulic conductivity, relative to the control, in the ranges of 3.34 to 9.88, 1.32 to 4.43, 9.12 to 145.8 and 12.93 to 44.05 percents, respectively. Also application of the sludge at rates 30 to 180 ton/ha, increased organic carbon, mean weight diameter of aggregates, total porosity, field capacity, permanent wilting point, available water capacity, micropores (< 30 µm), and mesopores (30-75 µm), as compared with the control, within the ranges of 1.24 to 6, 1.91 to 15.14, 1.3 to 15.85, 2.22 to 14.98, 1.56 to 24.19, 10.7 to 29 percents, respectively. According to the findings of the present research, Ardabil municipal sewage sludge can be used to improve the physical quality of coarse-textured soils especially under plant cultivation.