Using soil binders to control runoff and soil loss in steep slopes under simulated rainfall
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Department of Soil Science, College of Agriculture and Natural Resources, University of Tehran, Karaj, P.O. Box 31587-77871, Iran
Research Institute of Forests and Rangelands, Tehran, P.O. Box 13185-116, Iran
Int. Agrophys. 2009, 23(2): 99-109
Runoff and soil erosion are serious and widespread land degradation problems throughout the world. Steep slopes are highly vulnerable to water erosion. Transport of eroded material from steep slopes has received significant attention, as sediment is both a pollutant and an effective vector for contaminant transport. Soil loss on hill slopes can be prevented by stabilizing aggregates at the soil surface with soil conditioners. In this study the effects of soil binders were investigated using the rainfall simulator and small flume facilities of IRFRI erosion laboratory. Series of experiments were conducted on soil of clay texture. Experimental treatments included different slopes (15, 20, 25 and 30 %), soil amendments and rain intensities (25, 50 and 75 mm h-1). The treatments consisted of: soil without cover (control), spraying the soil surface with three polyacrylamide solution concentrations of 25, 50 and 75 kg ha-1, mixing 10, 20 and 30 Mg ha-1 gypsum with upper 5 mm of the soil surface, and applying polyacrylamide and gypsum simultaneously at the rates of 25 kg ha-1 PAM + 10 Mg ha-1 gypsum, 50 kg ha-1 PAM + 20 Mg ha-1 gypsum and 75 kg ha-1 PAM + 30 Mg ha-1 gypsum. Amending the soil surface with soil binders in steep slopes did not reduce runoff significantly compared with the control. Application of soil binders alone had low efficiency as well. Application of 75 kg ha-1 PAM along with 30 Mg ha-1 gypsum reduced soil loss to non-detectable levels as compared with control (~ 99 %). Therefore, with the role of soil binders in flocculation of clay particles and improvement of soil physical properties, reduction in sediment concentration to a small level is not impossible. Because of the economic advantages of gypsum, application of polyacrylamide along with gypsum can be recommended for increasing their efficiency.
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