381 research outputs found
Polyacrylamide as a tool for controlling sediment runoff and improving infiltration under furrow irrigation
Water-soluble anionic polyacrylamide (PAM) has been shown to be effective in controlling topsoil erosion,
preventing sedimentation of waterways, and simultaneously improving infiltration rates for furrow irrigation in the
western USA (Lentz et al. 1992; Lentz and Sojka 1994). PAM injected as a pulse into the irrigation stream as the
water advances has a stabilizing effect on the surface soil in the furrow. Controlling sediment runoff under intensive
irrigation has the dual advantage of conserving fertile topsoil and reducing downstream pollution from sediments in
waterways, particularly suspended sediments. Topsoil losses of 5 - 50 tonnes ha' yr 4 have been reported from
irrigated fields on erodible soils in the US Pacific Northwest. Polymers provide farmers with a practical and
economic management tool for conserving soil and preventing sedimentation of waterways from irrigated fields.
Increased net infiltration, which translates to more efficient water use, is a secondary benefit, especially for semiarid
and arid environments where water supplies are limited.
Results from field experiments on a highly erodible Portneuf silt loam (Durixerollic Calciorthid) in southern
Idaho are presented comparing the efficacy of three different molecular weights of PAM for controlling sediment
runoff and infiltration rates. Some potential environmental impacts of PAM applications under furrow irrigation are
briefly discussed
Polymer charge and molecular weight effects on treated irrigation furrow processes
Application of 5-10 mg L-1 water soluble anionic polyacrylamide (PAM) to furrow irrigation water
during flow advance substantially reduces sediment loss and increases net infiltration. We hypothesized
that PAM_s solvated molecular conformation influences its irrigation-management efficacy. The study
was conducted in Kimberly, Idaho, on Portneuf silt loam (Durinodic Xeric Haplocalcids); under furrow-
irrigated beans (Phaseolus vulgaris ) at a 1.5% slope. Polyacrylamides with contrasting molecular
weight (anionic: 4-7, 12-15 and 14-17 MDa, i.e. Mg mol -1 ), charge type (neutral, anionic, cationic), and
charge density (8, 19, 35 mol %) were tested in two studies. Inflow rate was 23 L min d during furrow
advance, and 15 L min-1 for the remaining set. Anionic and neutral PAMs were twice as effective as
cationic PAMs for controlling sediment loss in new furrows. The order of effectiveness for overall soilloss
control was: anionic > neutral > cationic PAM, and efficacy increased with increasing charge density
and/or molecular weight. Net furrow infiltration increased by 14 to 19% when PAM treatment molecular
weight was reduced from 17 to 4 MDa. General trends suggested that medium and high charge density
anionic and neutral PAM produced the greatest increase in infiltration compared with controls.
Compared with untreated furrows, neutral PAM gave the greatest season-long net infiltration gains (5%);
while charged PAMs tended to increase net infiltration early in the season on new furrows but decreased
infiltration on repeat-irrigated furrows later in the season
Scanning electron micrographs of polyacrylamide-treated soil in irrigation furrows
Polyacrylamide (PAM) is used at rates of i to 2 kg ha per irrigation on a half million
hectares of United States irrigated farmland to prevent 94% of irrigation-induced erosion and to
enhance infiltration by 15% to 50% on medium to fine-textured soils. The polyacrylamides used
for this application are large (12 to 15 megagrams per mole), water-soluble anion molecules
applied in the irrigation stream. Erosion prevention has been shown to result from stabilized soil
structure in the i to 5 mm veneer of surface soil that regulates infiltration, runoff, and sediment
loss on water application. We hypothesized that this could be confirmed from scanning electron
micrographs (SEMs) of PAM-treated soil. Both untreated and PAM-treated soils form surface
seals in irrigation furrows, but the stable surface structure of PAM-treated furrows is more
pervious. This is thought to result from a greater number of continuous unblocked pores at the
soil-water interface. SEMs of PAM-treated and untreated soil microstructures are presented
from thin surface samples of Portneuf silt loam, collected from furrows immediately following an
irrigation, and freeze-dried. SEMs of PAM-treated soil showed net or web-like microstructural
surface coatings about 1um thick on soil mineral particles, giving a glue-like porous appearance.
Individual strands of PAM were about 0.2 in diameter. Strands of PAM aggregated the soil by
ensnaring and bridging mineral particles while untreated soil had poorly aggregated,
unconnected particles. Thus, microstructural differences between PAM-treated and untreated
soil from irrigation furrows were consistent with erosion and infiltration results
Net and Tension infiltration effects of PAM in furrow irrigation
The history and fundamental aspects
of polyacrylamide (PAM)-use
in furrow irrigation water has been
covered in depth in several publications
(Barvenik, 1994; Lentz et al.,
1992; Lentz and Sojka, 1994a; Lentz,
1995; Lentz and Sojka, 1996; Sojka
and Lentz, 1996; Sojka and Lentz,
1997). In agriculture, the two greatest
benefits associated with this practice
are the near elimination of furrow
erosion and substantial increases
in infiltration compared to untreated
water. The large erosion reduction
has both on-site and downstream economic
and environmental benefits
(Agassi et al., 1995 ; Bahr et al., 1996;
Bahr and Steiber, 1996; Lentz et al.,
1992; Lentz, 1995; Lentz and Sojka,
1996; McCutchan eta!., 1993; Singh
et al., 1996; Sojka and Lentz, 1993;
Sojka and Lentz, 19946; Sojka et al.,
1995; Sojka and Lentz, 1997). Infiltration
effects are a substantial aspect
of these benefits, but have been less
thoroughly considered in data reported
to date
Subsoiling and surface tillage effects on soil physical properties and forage oat stand and yield
Much of New Zealand's agriculture integrates animal and crop production on poorly drained,
easily compacted soils. We hypothesized that soil properties affecting forage oat (Avena sativa,
cv Awapuni) establishment on land compacted by 15 years of conventional cropping might be
influenced by various subsoiling and surface tillage combinations. Plots on a Moutoa silty clay
(Typic Haplaquoil) were paraplowed (P), deep subsoiled (V), shallow subsoiled (5), or were left
as non-subsoiled controls (C). Subsequently, the surface 15 cm was surface-tilled (T) using a
power rotary-tiller and firmed with a Cambridge roller or were not tilled (N). Oats were then sown
with a cross-slot drill. Subsoiling greatly reduced soil strength. Cone indices showed disruption to
40cm with P, 36 cm for V, and 30 cm for S. Approximately 60% of profile cone indices to a depth
of 0.5 m from subsoiled treatments were less than 1.5 MPa, compared to approximately 30% for C.
T slightly improved strength distribution in non-subsoiled controls but had little effect in subsoiled
treatments. Subsoiling without T continued to show improved profile cone index cumulative
frequency 233 days after subsoiling, Subsoiling after T in this high rainfall climate eliminated
most of the separation in cumulative frequency of soil profile cone index values by two weeks
after T. T reduced emergence from 142 to 113 plants per square meter and reduced yield from
5318 to 3679 kg ha-1. Forage yield increased from 3974 to 4674 kg ha-1 with subsoiling. Soil
porosity, saturated and slightly unsaturated hydraulic conductivities (KSAT and K_40 ) and air
permeability were highly variable but generally increased with subsoiling. Oxygen diffusion rate
(ODR) (using Pt microelectrodes) was also variable, but N and C treatments had consistently
lower ODRs than T or subsoiled treatments. Generally, subsoiling without T produced better soil
conditions and oat crop performance than the prevailing New Zealand practice of T without subsoiling
Quantum Kinetic Theory III: Quantum kinetic master equation for strongly condensed trapped systems
We extend quantum kinetic theory to deal with a strongly Bose-condensed
atomic vapor in a trap. The method assumes that the majority of the vapor is
not condensed, and acts as a bath of heat and atoms for the condensate. The
condensate is described by the particle number conserving Bogoliubov method
developed by one of the authors. We derive equations which describe the
fluctuations of particle number and phase, and the growth of the Bose-Einstein
condensate. The equilibrium state of the condensate is a mixture of states with
different numbers of particles and quasiparticles. It is not a quantum
superposition of states with different numbers of particles---nevertheless, the
stationary state exhibits the property of off-diagonal long range order, to the
extent that this concept makes sense in a tightly trapped condensate.Comment: 3 figures submitted to Physical Review
Twin Paradox and the logical foundation of relativity theory
We study the foundation of space-time theory in the framework of first-order
logic (FOL). Since the foundation of mathematics has been successfully carried
through (via set theory) in FOL, it is not entirely impossible to do the same
for space-time theory (or relativity). First we recall a simple and streamlined
FOL-axiomatization SpecRel of special relativity from the literature. SpecRel
is complete with respect to questions about inertial motion. Then we ask
ourselves whether we can prove usual relativistic properties of accelerated
motion (e.g., clocks in acceleration) in SpecRel. As it turns out, this is
practically equivalent to asking whether SpecRel is strong enough to "handle"
(or treat) accelerated observers. We show that there is a mathematical
principle called induction (IND) coming from real analysis which needs to be
added to SpecRel in order to handle situations involving relativistic
acceleration. We present an extended version AccRel of SpecRel which is strong
enough to handle accelerated motion, in particular, accelerated observers.
Among others, we show that the Twin Paradox becomes provable in AccRel, but it
is not provable without IND.Comment: 24 pages, 6 figure
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
Polyacrylamide effects on infiltration in irrigated agriculture
Using polyacrylamide (PAM) following the NRCS conservation practice standard
increases infiltration in furrow irrigation. PAM at 10 g in-' (10 ppm) during water advance
nearly precludes detachment and transport of soil in furrows. If any sediment is entrained in the
flow, it is readily flocculated in the presence of PAM and settles to the furrow-bottom in loose pervious
structures. It was hypothesized that depositional surface seals that block pores are reduced or
made more permeable with PAM. On Portneuf silt beams (coarse-silty, mixed, superactive,
Durinodic Xeric Haplocalcid) furrow irrigation net infiltration increased 15%. Net increases on
finer textured soils were generally higher. Furrow streams containing more than 5 g L (5,000
ppm) sediment reduced infiltration and infiltration rate more than fivefold compared to streams
of clean water. Tension infiltrometry confirmed that PAM's maintenance of open pores to the furrow
surface provides the infiltration increase mechanism. Infiltration rates at 40 and 100 min
(1.6 and 3.9 inches) tension in PAM-treated furrows were double the rates of control furrows.
Recirculating infiltrometer data showed a 30% infiltration increase with PAM use and infiltration
was inversely related to maximum sediment concentration in the flow. Furrow inflow of
45 L min-1 (12 gal min-1 ) with PAM treatment decreased stream advance time 13% while reducing
sediment loss 76% compared to untreated 23 L min-1 (6 gal min-1) inflows. Use of
PAM in sprinkler irrigation streams reduced runoff 70% and sediment loss 75%, but tension infiltration
measurements were inconsistent, suggesting changes in surface-sealing effects with sprinkler
application of PAM are transient
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
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