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Polyacrylamide and Gypsiferous Material Effects on Runoff and Erosion under Simulated Rainfall

Peterson, J. R., Flanagan, D. C., Tishmack, J. K.
TRANSACTIONS OF THE ASAE ONLINE 2002 v.45 no.4 pp. 1011-1019
clay loam soils, control methods, electrolytes, erodibility, erosion control, fly ash, gypsum, polyacrylamide, rain, rain intensity, rainfall simulation, runoff, sediment yield, silty clay soils, solubility, vegetation
An indoor laboratory study was conducted to compare the dry versus sprayed application of polyacrylamide (PAM) and the use of different gypsiferous materials (gypsum and a class C ponded fly ash) on runoff and sediment yield. The six treatments incorporated in this study were: control, Nutra–Ash (NA), gypsum (G), sprayed PAM plus NA (PAMW+NA), sprayed PAM plus G (PAMW+G), and granular PAM plus G (PAMD+G). Simulated rainfall at an intensity of 70 mm hr–1 was applied for 2 hours to a silty clay loam soil packed into erosion pans. Only one of the two liquid PAM treatments (PAMW+G) significantly reduced runoff (35%), while both liquid PAM treatments (PAMW+G and PAMW+NA) significantly reduced sediment yield (74% and 77%) compared to the control. Sprayed PAM was more effective than granular application in terms of total runoff, but there was no statistical difference with regard to total sediment yield. Differences between the effects of sprayed and granular PAM are explained by the mechanisms by which they reduce erosion. Sprayed PAM, in combination with gypsum, increases infiltration during the first part of a rainfall event until sufficient rainfall has occurred to break down the PAM–treated aggregates, at which time runoff rate and sediment yield rate approach those of the control. Runoff and sediment yield rates from the granular PAM application were initially similar to those from the control. However, as time increased, sediment yield reached a maximum and then decreased without a corresponding decrease in runoff. This likely occurred because the PAM particles became activated during the rainfall and acted as a mortar to stabilize the soil matrix. Gypsum was a better source of electrolyte than a class C ponded fly ash, commercially known as Nutra–Ash (NA), likely due to its greater solubility. Addition of PAM decreased soil erodibility and may be a viable erosion control practice for soils susceptible to flow detachment. Choice of application method should be based on the expected amount and severity of precipitation before vegetation establishment. These results indicate that sprayed PAM, in combination with gypsum or Nutra–Ash, provides immediate erosion control, but its effectiveness decreases over time, as indicated by steadily increasing sediment yield rate. Dry PAM application was not as effective in the beginning of the experiment, but after sufficient rainfall it became “activated” and sediment yield continuously decreased over the remainder of the experiment.