10 research outputs found
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
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 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
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
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