Erosion Control Using Soil Amendments and Other Low Cost Methods Prior to Establishment of Vegetation

摘要

Disturbed areas especially as they occur on sloping land are highly erodible in humid environments until vegetation can be established. These critical areas produce considerable amounts of sediment and pollutants that can be carried either attached to the sediment or in soluble forms. The cost of many "engineering based" erosion control strategies is very high and often they fail in erosive events prior to stabilization of the area with vegetation. Methods such as hydromulching/hydroseeding on construction cut and fill slopes along highways in the USA are a frequent sight inspite of the expensive treatments since the underlying processes that lead to runoff and soil erosion still occur. We have been researching the use of various soil amendments that can positively affect erosion processes occurring at the soil/air/water interface that can be applied at low cost to serve as erosion control prior to establishment of vegetative cover. The objective of this work was to prevent runoff from occurring or reduce its magnitude or to slow the movement of water on slopes after it has occurred. Various materials studied included inorganic gypsum (CaSO_4 • 2H_2O), and anhydrite (CaSO_4), and organic polyacrylamide (PAM) and a biodegradable waste paper material. We applied these materials in field and laboratory studies at many different scales and slopes to determine what their effect was on various soil erosion processes with natural and simulated rainfall and with flowing water. The inorganic materials surface were applied normally at 5 MT/ha proved effective in lengthening the time to runoff and reducing the total runoff volume due to interrill erosion processes. These materials were effective by providing electrolytes to the low electrolyte rainwater thus promoting clay dispersion and prevention of surface sealing. These materials were also found to be beneficial by promoting the exchange of Ca ions over Mg and monovalent ions that tended to promote clay dispersion. However, once runoff did occur these materials behaved similarly to soil aggregates and were washed off the surface and had no effect on rill erosion processes. The organic materials studied included an anionic PAM with a medium molecular weight (45,000 gm/mol) and a medium hydrolysis (～35%) surface applied at a rate of 20kg/ha in liquid form and a product composed of waste newspaper and a C:N ratio of 20:1 balanced with dry poultry litter which was shallowly incorporated al 20 MT/ha. Both materials proved be beneficial on lengthening the time to runoff, reducing total runoff volume and at reducing soil erosion from both interrill and rill erosion processes. The use of PAM in combination with gypsum on 2:1 slopes proved the most effective treatment at controlling erosion and also in establishment of vegetation. The waste paper product significantly reduced soil erosion, decreased total runoff and reduced sediment concentrations and the soluble reactive phosphorus in runoff after runoff occurred. Additionally, the waste paper product because of the optimal C:N ratio and added nitrogen source from the poultry litter led to a more rapid establishment of vegetation following disturbance.