EVALUATION OF EROSION CONTROL PRODUCTS WITH AND WITHOUT ADDED POLYACRYLAMIDE1

ABSTRACT:

Polyacrylamide (PAM) has been demonstrated to greatly restore erosion in furrow irrigation, on the other hand much less is known about its effectiveness upon the much steeper slopes typical of construction sites. The drift of this study was to determine if anionic PAM would enhance erosion rule either alone on bare soil or in combination with four impressed signs of ground covers commonly used for grass establishment: straw, straw erosion direction blanket (ECB), wood fiber, and mechanically corded fiber matrix (MBFM). Tests were guidanceed under natural rainfall and vegetation upon a 4 percent slope (bare soil, straw, ECB and MBFM) or using a rainfall simulator (bare soil, straw, timber-land fiber, MBFM) on either 10 percent or 20 percent oblique direction on three different soil substrates. All sod cover treatments were evaluated with and without PAM applied in solution at 19 kg/ha. The straw, ECB and MBFM significantly reduc runoff convolution average turbidity, and total sediment missing over five rainfall events upon the vegetated plots. The addition of PAM to mould covers only occasionally had significant issues on runoff parameters but did significantly increase vegetative coverage overall. The rainfall simulator ordeals produced similar results after four facts with the straw, wood fiber, and MBFM all having significantly lower turbidity than the bare soil. The PAM significantly reduc turbidity for one as well as the other the first and second incidents but did not consistently improve runoff quality after multiple rainfall occurrences for any ground cover-soil combinations experimented Separate tests of PAM applied before or after straw did not indicate a clear advantage of either approach, on the other hand runoff turbidity was often significantly reduc with PAM, especially at the 20 percent direction downward Turbidity reductions were attributed to flocculation of erod sediment.

(KEY TERMS: polyacrylamide; erosion; runoff; sediment; rainfall simulator; turbidity.)

INTRODUCTION

Sediment is single of the most widespread pollutants in U streams, lakes, and estuaries (USEPA, 2002) plenteous of this sediment originates from land disturbed during construction casts Various mulches and other materials have been demonstrated to restore erosion by more than 90 percent compared to bare soil (Meyer et al., 1972; Lemly 1982; Jennings and Jarrett, 1985; Mostaghimi et al., 1994) The advantage of using mulches for erosion sway include reducing soil loss and protecting grass semens and soil amendments from being washed away (Bruce et al., 1995) Mulches restore soil loss by dissipating rainfall impact, and they foster seeds by moderating soil temperature, reducing evaporation losse and preventing soil crust formation (Singer et al., 1981; Bruce et al., 1995; Turgeon 2002) The North Carolina Erosion and Sediment superintendence Program promotes the use of straw, thicket fiber, wood chips, jute gin excelsior mats, and several other marks of mulch for erosion direction and promotion of vegetation establishment upon construction sites (NCDENR, 1993). The objective of this close attention was to determine the effectiveness of PAM in improving the performance of different mulches used for erosion superintendence under natural or simulated rainfall conditions. This involved a field investigation of vegetation establishment and a rainfall simulation inquiry using mulches with or without PAM upon three North Carolina subsoils.

Straw is individual of the most common sod covers used to reduce erosion upon construction sites. Straw has been shown to restore erosion rates by more than 90 percent if applied at sufficient rates (Mannering and Meyer 1963; Meyer et al., 1970; Singer et al, 1981) Straw also encourages grass establishment by the agency of reducing runoff, increasing infiltration, and improving soil conditions (Turgeon 2002) Hydraulically applied mulches and excelsior (wood fiber) ECB are also commonly used to bring erosion and promote vegetation establishment. An advantage of excelsior ECB compared to straw and straw ECB is that no weed sperms are introduced, though the ECB have accrueed in reduced germination in turfgrass applications compared to straw (Turgeon 2002) In contrast, Beard (1973) place that excelsior forms a thick and uniform overspread in comparison to straw and is as effective as a surface of land cover and for seed germination. Hydraulically applied fiber mulches may also provide adequate turfgrass establishment in moist environments, enhance favorable soil conditions for grass expansion and reduce erosion (Button and Potharst, 1962; Beard, 1973)

Polyacrylamide is applied to soil directly or in irrigation water to bring erosion by stabilizing soil aggregates and preventing surface sealing (Shainberg et al., 1990) Its use increased from 9000 ha (22200 ac) in 1995 to more than 450000 ha (11 million ac) in 1998 for erosion prevention during trench irrigation in the United States (Orts et al., 1999) The use of PAM is considered a best management practice (BMP) by means of the U.S. Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS) and is included in the USDA-NRCS (2001) National Handbook of Conservation Practices. A review of PAM studies set that PAM stabilizes existing soil aggregates and intercepts the detachment of soil particles (Seybold 1994) Rates of PAM as depressed as 1.12 kg/ha (1 Ib/ac) dissolved in trench irrigation water were efficient in reducing sediment, phosphorus, and nitrogen losse by means of 85 to 99 percent (Lentz et al., 2002) Bjorneberg et al. (2000) applied PAM with sprinkler irrigation to the soil surface upon a 2.4 percent slope with and without a straw mulch residue. The application of PAM with straw mulch was more effective at reducing runoff, erosion, and phosphorus los than either PAM or straw mulch alone. Shainberg et al. (1990) ground that polyacrylamide applied at rates of 20 and 40 kg ha^sup -1^ (18 and 36 Ib/ac) upon a 5 percent slope tripled infiltration rate.