ABSTRACT: Polyacrylamide (PAM) has been demonstrated to greatly remodel erosion in furrow irrigation.

ABSTRACT:

Polyacrylamide (PAM) has been demonstrated to greatly remodel erosion in furrow irrigation, still much less is known about its effectiveness onward the much steeper slopes typical of construction sites. The aim of this study was to determine if anionic PAM would enhance erosion ascendency either alone on bare soil or in combination with four adumbrations of ground covers commonly used for grass establishment: straw, straw erosion rule blanket (ECB), wood fiber, and mechanically corded fiber matrix (MBFM). Tests were managemented under natural rainfall and vegetation upon a 4 percent slope (bare soil, straw, ECB and MBFM) or using a rainfall simulator (bare soil, straw, forest-land fiber, MBFM) on either 10 percent or 20 percent acclivity [i]or[/i] declivity on three different soil substrates. All country cover treatments were evaluated with and without PAM applied in solution at 19 kg/ha. The straw, ECB and MBFM significantly reduc runoff contortion average turbidity, and total sediment missing over five rainfall events forward the vegetated plots. The addition of PAM to country covers only occasionally had significant drifts on runoff parameters but did significantly increase vegetative coverage overall. The rainfall simulator ordeals produced similar results after four adventures with the straw, wood fiber, and MBFM all having significantly lower turbidity than the bare soil. The PAM significantly reduc turbidity for the one and the other the first and second consequences but did not consistently improve runoff quality after multiple rainfall marked occurrences for any ground cover-soil combinations exampleed Separate tests of PAM applied before or after straw did not indicate a clear advantage of either approach, if it were not that runoff turbidity was often significantly reduc with PAM, especially at the 20 percent incline Turbidity reductions were attributed to flocculation of erod sediment.

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

INTRODUCTION

Sediment is individual of the most widespread pollutants in U streams, lakes, and estuaries (USEPA, 2002) often of this sediment originates from land disturbed during construction plans Various mulches and other materials have been demonstrated to cut down 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 restrain include reducing soil loss and protecting grass first principles and soil amendments from being washed away (Bruce et al., 1995) Mulches model soil loss by dissipating rainfall impact, and they house 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 curb Program promotes the use of straw, copse fiber, wood chips, jute snare excelsior mats, and several other stamps of mulch for erosion regulate and promotion of vegetation establishment upon construction sites (NCDENR, 1993). The objective of this research was to determine the effectiveness of PAM in improving the performance of different mulches used for erosion ascendency under natural or simulated rainfall conditions. This involved a field contemplation of vegetation establishment and a rainfall simulation cogitation using mulches with or without PAM forward three North Carolina subsoils.

Straw is undivided of the most common real property covers used to reduce erosion forward construction sites. Straw has been shown to decrease 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 means of reducing runoff, increasing infiltration, and improving soil conditions (Turgeon 2002) Hydraulically applied mulches and excelsior (wood fiber) ECB are also commonly used to form erosion and promote vegetation establishment. An advantage of excelsior ECB compared to straw and straw ECB is that no weed germs are introduced, though the ECB have proceeded in reduced germination in turfgrass applications compared to straw (Turgeon 2002) In contrast, Beard (1973) raise that excelsior forms a thick and uniform guard in comparison to straw and is as effective as a real property cover and for seed germination. Hydraulically applied fiber mulches may also provide adequate turfgrass establishment in moist environments, enhance favorable soil conditions for grass sprouting and reduce erosion (Button and Potharst, 1962; Beard, 1973)

Polyacrylamide is applied to soil directly or in irrigation water to render 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 fluting irrigation in the United States (Orts et al., 1999) The use of PAM is considered a best management practice (BMP) through 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 base that PAM stabilizes existing soil aggregates and thwarts the detachment of soil particles (Seybold 1994) Rates of PAM as reasonable as 1.12 kg/ha (1 Ib/ac) dissolved in hollow irrigation water were efficient in reducing sediment, phosphorus, and nitrogen losse from 85 to 99 percent (Lentz et al., 2002) Bjorneberg et al. (2000) applied PAM with sprinkler irrigation to the soil surface in succession 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) erect that polyacrylamide applied at rates of 20 and 40 kg ha^sup -1^ (18 and 36 Ib/ac) in succession a 5 percent slope tripled infiltration rate.