Soil physics and hydrology: Conditioners

The use of naturally occurring materials as soil-stabilizing conditioners has been part of agriculture and general land management for millennia. Some of the most familiar conditioners in use since ancient times include animal and green manures, peat, crop residues, organic composts, and lime. These early uses of conditioners resulted from knowledge gained from trial and error long before there was scientific understanding of how efficacy was derived. Other conditioners in use for centuries or decades include composted manures, various organic debris, including sawdust or other milling residues, food, textile, and paper-processing wastes and other organic industrial wastes, as well as mineral materials such as rock phosphates, gypsum, coal dust, rock flour, and san

Biopolymer additives for the reduction of soil erosion losses during irrigation

High molecular weight, synthetic polyacrylamides (PAM) are relatively large, water soluble polymers that are used increasingly by farmers to prevent erosion and increase infiltration during irrigation. A lab-scale erosion test was conducted to screen biopolymer solutions for a similar efficacy in reducing shear-induced erosion. In lab-scale mini-furrow tests, chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm respectively, reduced suspended solids in the runoff water from test soil. None of these biopolymers, however, exhibited the >90% runoff sediment reduction shown by PAM at concentrations as low as 5 ppm. Preliminary field tests results showed that chitosan solutions were only marginally effective in reducing runoff from a 137m long furrow. There were indications that results were dependent on the length of the furrow. Erosion of some clay-rich soils from Northern California was reduced up to 85% by increasing the concentration of exchangeable calcium to >2.5mMole, with or without the addition of polymer additives

Polyacrylamide in agriculture and environmental land management

Anionic polyacrylamide (PAM) has been sold since 1995 to reduce irrigation-induced erosion and enhance infiltration. Its soil stabilizing and flocculating properties improve runoff water quality by reducing sediments, N, dissolved reactive phosphorus (DRP) and total P, chemical oxygen demand (COD), pesticides, weed seeds, and microorganisms in runoff. PAM used for erosion control is a large (12-15 Mg mol -1) water-soluble (non-cross-linked) anionic molecule, containing <0.05% acrylamide monomer. In a series of field studies, PAM eliminated 80-99% (94% avg.) of sediment in runoff from furrow irrigation, with a 15-50% infiltration increase compared to controls on medium to fine-textured soils. Similar but less dramatic results occur with sprinkler irrigation. In sandy soils infiltration is often unchanged by PAM or can be slightly reduced. Typical seasonal application totals in furrow irrigation vary from 3 to 7 kg ha -1 . Research has shown little or no consistent adverse effect on soil microbial populations. Some evidence exists for PAM-related yield increases where infiltration was crop-limiting, especially in field portions having irregular slopes, where erosion prevention eliminated deep furrow cutting that deprives shallow roots of adequate water delivery. Modified water management with PAM shows great promise for water conservation. High effectiveness and low cost of PAM for erosion control and infiltration management, coupled with easier implementation than traditional conservation measures, has resulted in rapid adoption. About 800,000 ha of US irrigated land use PAM for erosion and/or infiltration management. In recent years, PAM has been deployed for uses beyond agricultural erosion control, including construction site erosion control, use in storm water runoff ponds to accelerate water clarification, soil stabilization and dust prevention in helicopter-landing zones, and various other high-traffic military situations. Among the newest topics being researched is the use of PAM to reduce ditch, canal, and pond seepage, using specific application protocols that take advantage of its increase of water viscosity at higher concentrations

Synthetic- and bio-polymer use for runoff water quality management in irrigation agriculture

Low concentrations of synthetic- or bio-polymers in irrigation water can nearly eliminate sediment, N, ortho- and total-P, DOM, pesticides, micro-organisms, and weed seed from runoff. These environmentally safe polymers are employed in various sensitive uses including food processing, animal feeds, and potable water purification. The most common synthetic polymer is anionic, high purity polyacrylamide (PAM), which typically provides 70-90% contaminant elimination. Excellent results are achieved adding only 10 ppm PAM to irrigation water, applying 1 -2 kg ha. -1 per irrigation, costing $4-$12 kg -1 . Biopolymers are less effective. Using twice or higher concentrations, existing biopolymers are ,r=60% effective as PAM, at 2 - 3 times the cost. A half million ha of US irrigated land use PAM for erosion control and runoff protection. The practice is spreading rapidly in the US and worldwide. Interest in development of biopolymer surrogates for PAM is high. If the supply of cheap natural gas (raw material for PAM synthesis) diminishes, industries may seek alternative polymers. Also "green" perceptions and preferences favor biopolymers for certain application

Synthetic- and Bio-polymer use for runoff water quality management in irrigated agriculture

Low concentrations of synthetic- or bio-polymers in irrigation water can nearly eliminate sediment, N, ortho- and total-P, DOM, pesticides, micro-organisms, and weed seed from runoff. These environmentally safe polymers are employed in various sensitive uses including food processing, animal feeds, and potable water purification. The most common synthetic polymer is anionic, high purity polyacrylamide (PAM), which typically provides 70-90% contaminant elimination. Excellent results are achieved adding only 10 ppm PAM to irrigation water, applying 1-2 kg ha-lper irrigation, costing $4-$12 kg-1. Biopolymers are less effective, but show promise; they include starch co-polymers, microfibril suspensions, chitin, polysaccharides and protein derivatives. Using twice or higher concentrations, existing biopolymers are ~60% effective as PAM, at 2-3 times the cost kg-1. A half million ha of US irrigated land use PAM for erosion control and runoff protection. The practice is spreading rapidly in the US and worldwide. Interest in development of biopolymer surrogates for PAM is high. If the supply of cheap natural gas (raw material for PAM synthesis) diminishes, industries may seek alternative polymers. Also "green" perceptions and preferences favor biopolymers for certain applications. More complete history, user/technical information and bibliography are found at

Use of synthetic polymers and biopolymers for soil stabilization in agricultural, construction, and military applications

Three relatively new applications for controlling wind and water erosion using polyacrylamide copolymers arc described that take advantage of their ability to stabilize and add structure to soil. In the first application, low concentrations of anionic, high purity polyacrylamide (PAM) eliminates sediment in runoff water by more than 90% when added to irrigation water at 10 ppm, or at a rate of 1 to 2 kg ha-1 per irrigation. Lab-furrow tests were utilized to characterize the role of molecular weight. charge, and ion concentrations in applying PAM during irrigation. In the second application, PAM is applied at construction sites and road cuts at rates of 22.5 kg ha -2 (tenfold higher rates than in irrigation control) resulting in reduction in sediment runoff by 60-85% during (simulated) heavy rains. Finally, a formulation of PAM mixed with aluminum chlorohydrate and cross-linked poly(acrylic acid) superabsorbent at a ratio of (6:1:1) has been applied to create helicopter landing pads that minimize dust clouds during helicopter operation. This formulation was specifically developed to minimize dust clouds during landing of helicopters in fine, arid soils such as those potentially encountered in the Middle East. A biodegradable alternative to PAM, acid-hydrolyzed cellulose microfibrils, was tested in lab-scale furrows and was less effective than PAM at similar concentrations, but show promises. Microfibrils reduce sediment run-off in lab-furrow tests by 88% when applied at eight- to tenfold the concentration of PAM

Irrigating with polyacrylamide (PAM) - Nine years and a million acres of experience

Polyacrylamide (PAM) has been available commercially since 1995 for reducing irrigation-induced erosion and enhancing infiltration. The first series of practical field tests was conducted in 1991. PAM used for erosion control is a large water soluble (non-crosslinked) anionic molecule (12-15 megagrams per mole) containing < 0.05% acrylamide monomer. In controlled field studies PAM eliminated, on average, 94% (80-99% range) of sediment loss in field runoff from furrow irrigation, with a typical 15-50% relative infiltration increase on medium to fine textured soils compared to untreated controls. Similar but less dramatic results have been seen with sprinkler irrigation. Under some conditions infiltration is unchanged or can even be slightly reduced, e.g. in sandy soils or where PAM application rates are very high. Results are achieved with per irrigation field application rates of about 1 kg per hectare, for furrow irrigation, and 2 to 4 kg per hectare for sprinkler irrigation. Cost of PAM is $7 to$13 per kg. Seasonal application totals vary from 3 to 7 kg per hectare. Farmer field sediment control has been around 80% of test plot results. Substantial runoff reductions have been documented for nutrients, pesticides, microorganisms, BOD, and weed seed. No adverse effects have been seen for soil microbial populations. Crop yields have not been widely documented, though evidence exists for yield increases related to infiltration improvement. High effectiveness, low cost, and ease of application, compared to traditional conservation measures, has resulted in rapid technology acceptance in the US and internationally. PAM-use for runoff water quality protection is one of the most potent new irrigation environmental technologies in the market place. New uses in construction and dryland erosion control are being developed rapidly. This paper discusses new insights and understanding of PAM-use and potential for future development

Soil physics and hydrology: Conditioners

The use of naturally occurring materials as soil-stabilizing conditioners has been part of agriculture and general land management for millennia. Some of the most familiar conditioners in use since ancient times include animal and green manures, peat, crop residues, organic composts, and lime. These early uses of conditioners resulted from knowledge gained from trial and error long before there was scientific understanding of how efficacy was derived. Other conditioners in use for centuries or decades include composted manures, various organic debris, including sawdust or other milling residues, food, textile, and paper-processing wastes and other organic industrial wastes, as well as mineral materials such as rock phosphates, gypsum, coal dust, rock flour, and san

Biopolymer additives for the reduction of soil erosion losses during irrigation

High molecular weight, synthetic polyacrylamides (PAM) are relatively large, water soluble polymers that are used increasingly by farmers to prevent erosion and increase infiltration during irrigation. A lab-scale erosion test was conducted to screen biopolymer solutions for a similar efficacy in reducing shear-induced erosion. In lab-scale mini-furrow tests, chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm respectively, reduced suspended solids in the runoff water from test soil. None of these biopolymers, however, exhibited the >90% runoff sediment reduction shown by PAM at concentrations as low as 5 ppm. Preliminary field tests results showed that chitosan solutions were only marginally effective in reducing runoff from a 137m long furrow. There were indications that results were dependent on the length of the furrow. Erosion of some clay-rich soils from Northern California was reduced up to 85% by increasing the concentration of exchangeable calcium to >2.5mMole, with or without the addition of polymer additives

Polyacrylamide in agriculture and environmental land management

Anionic polyacrylamide (PAM) has been sold since 1995 to reduce irrigation-induced erosion and enhance infiltration. Its soil stabilizing and flocculating properties improve runoff water quality by reducing sediments, N, dissolved reactive phosphorus (DRP) and total P, chemical oxygen demand (COD), pesticides, weed seeds, and microorganisms in runoff. PAM used for erosion control is a large (12-15 Mg mol -1) water-soluble (non-cross-linked) anionic molecule, containing <0.05% acrylamide monomer. In a series of field studies, PAM eliminated 80-99% (94% avg.) of sediment in runoff from furrow irrigation, with a 15-50% infiltration increase compared to controls on medium to fine-textured soils. Similar but less dramatic results occur with sprinkler irrigation. In sandy soils infiltration is often unchanged by PAM or can be slightly reduced. Typical seasonal application totals in furrow irrigation vary from 3 to 7 kg ha -1 . Research has shown little or no consistent adverse effect on soil microbial populations. Some evidence exists for PAM-related yield increases where infiltration was crop-limiting, especially in field portions having irregular slopes, where erosion prevention eliminated deep furrow cutting that deprives shallow roots of adequate water delivery. Modified water management with PAM shows great promise for water conservation. High effectiveness and low cost of PAM for erosion control and infiltration management, coupled with easier implementation than traditional conservation measures, has resulted in rapid adoption. About 800,000 ha of US irrigated land use PAM for erosion and/or infiltration management. In recent years, PAM has been deployed for uses beyond agricultural erosion control, including construction site erosion control, use in storm water runoff ponds to accelerate water clarification, soil stabilization and dust prevention in helicopter-landing zones, and various other high-traffic military situations. Among the newest topics being researched is the use of PAM to reduce ditch, canal, and pond seepage, using specific application protocols that take advantage of its increase of water viscosity at higher concentrations