Biopolymer additives to reduce erosion-induced soil losses during irrigation

Abstract

A series of biopolymers added to irrigation water were tested for their efficacy in reducing shear-induced erosion in a laboratory-scale mini-furrow. Suspensions of chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm, respectively, reduced suspended solids by more than 80%. None of these biopolymers, however, exhibited the > 90% runoff sediment reduction shown by the present industry standard, synthetic polyacrylamide polymers, PAM. PAM is effective at concentrations as low as 5 ppm. In field tests, chitosan solutions were only marginally effective in reducing runoff from the end of a 137 m long furrow, with indications that results were dependent on the length of the furrow. Sediment runoff of some clay-rich Northern California soils was reduced by up to 85% by increasing the concentration of exchangeable calcium to > 2.5mM. Calcium improved the sedimentation of the polyelectrolytic polymers in this study.

Use of Synthetic Polymers and Biopolymers for Soil Stabilization in Agricultural, Construction, and Military Applications

“…For modeling agricultural use of PAM during erosion, control laboratory-scale furrows were created as outlined previously (Orts et al 2000), Soils were dried, sieved and remoisturized to 18% (w/w) water content, and then formed into miniature furrows roughly 1/100th the size of a full furrow. Furrows were created by cutting a v-shaped wedge-cut 2.5 cm wide and 2.5 cm deep into a 1-in-long polystyrene foam slab.…”

“…There is increasing incentive to develop biodegradable, renewable PAM alternatives that will reduce wind and water erosion and be suitable for organic farming operations. We have screened over 100 biopolymers for their sorptive behavior with soil and their ability to control water-induced erosion (Orts et al 2000). These include chitin, chitosan, substituted starches (ether and ester linked starches), substituted cellulosics (cellulose xanthate, cationic cellulose, hydroxymethycellulose, etc.…”

Polyacrylamide preparations for protection of water quality threatened by agricultural runoff contaminants

“…Coulombic and Van der Waals forces attract soil particles to PAM (Orts et al, 1999(Orts et al, , 2000. These surface attractions stabilize soil structure by enhancing particle cohesion, thus increasing resistance to shear-induced detachment and preventing transport in runoff.…”

Erosion Control in Furrow Irrigation Using Polyacrylamide

“…while the injected PAM and sprayed PAM lost 3.10 g l -1 , as compared with the reference furrow loses on average 30.8 g l -1 , for an efficiency of 90-99% in the control of erosion. Orts et al, (2000) obtained a 97% reduction in soil erosion by applying PAM; however, the flow rate used was 23 l h -1 . On the other hand, with flow of 250 l h -1 the control furrow lost about 45 g l -1 while the furrows treated with granular PAM saw loses 9 g l -1 , and sprayed PAM on the soil saw loses of less than 5 g l -1 .…”

“…Soil detachment increases with the degree of slope and hydraulic radius of the section of the channel. One of the main mechanisms that cause water erosion is the formation of surface sealing when the soil is exposed to the action of the impact of raindrops and concentrated flows in the rills (Orts et al, 2000). Seal formation is the result of two complementary mechanisms (Yu et al, 2003): a) physical disintegration of surface soil aggregates, and b) the physicochemical dispersion of clay, moving to deeper soil layers by infiltrating water.…”