1816 research outputs found
Sort by
Catering to bossy's sweet tooth
Get PDFDr. Doolittle, a cow and a sheep discuss animal forage preference
Scanning electron micrographs of polyacrylamide-treated soil in irrigation furrows
Get PDFPolyacrylamide (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
Using polyacrylamide with sprinkler irrigation to improve infiltration
Get PDFCenter-pivot irrigation systems often apply water at rates greater than the soil
infiltration rate. Applying high molecular weight, water-soluble, anionic polyacrylamide (PAM) to
the soil can improve infiltration and reduce soil erosion The objective of this study was to
determine whether single and multiple PAM applications with sprinkler irrigation improved
infiltration under field conditions. A two-year study conducted near Kimberly, Idaho, used a
solid-set sprinkler system, and a one-year study conducted in Monte dos Alhos near Alvalade do
Sado, Portugal, used a center pivot. At Kimberly, applying PAM with four irrigations (total
applied PAM was 2.1 kg ha-1 in 2000 and 3.0 kg ha-1 in 2001) significantly reduced total measured
runoff, from 5.9 mm (2000) and 9.2 mm (2001) for the control to 2.0 and 2.1 mm. Total measured
soil erosion was also reduced from 52 and 34 kg ha 1 for the control to 21 and 5 kg ha 1 for the
multiple PAM treatment. Applying similar or greater amounts of PAM with a single irrigation
reduced erosion, but not runoff, compared with the control. In the Monte dos Alhos study, runoff
was reduced by applying a total of 0.3 kg PAM ha 1 with a single irrigation (43 mm runoff) or
three irrigations (65 mm runoff) compared with the control (111 mm runoff). Measured soil
erosion was not significantly different among treatments. Applying PAM with multiple irrigations
extended its effectiveness as long as the application rate was great enough to adequately
stabilize the soil surface during the first irrigation
Phosphorus cycle
Get PDFPhosphorus is indispensable to life on Earth, as it
is involved in the passage of genetic information,
energy transfer, and the construction of plant cells.
Despite this, the amount of phosphorus available for
biological uptake is relatively small, so productivity
in many terrestrial and aquatic ecosystems is often
limited by phosphorus availability. As a result, human
interference in the phosphorus cycle can have severe
environmental consequences. For example, phosphorus
pollution of water bodies by sewage effluents
and drainage from agricultural land can contribute to
the growth of toxic blue-green algae, fish deaths, and
a drastic reduction in the quality of affected water bodies
Synthetic- and Bio-polymer use for runoff water quality management in irrigated agriculture
Get PDFLow 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
Changes in bicarbonate-extractable inorganic and organic phosphorus by drying pasture soils
Get PDFSoils are commonly dried in the laboratory prior to the determination
of P fractions, but this can profoundly influence the results.
We investigated the impact of soil drying on bicarbonate-extractable
inorganic and organic P in 29 permanent lowland pasture soils from
England and Wales (total C 29-80 g C kg -1 soil, day 219-681 g kg-1
soil, pH 4.4-6.8) by extracting soils at approximate field moisture
capacity and after air-drying at 30°C for 7 d. Air-drying increased the
mean bicarbonate-extractable inorganic P from 14.8 to 22.5 mg P
kg-1 soil, and the mean bicarbonate-extractable organic P from 17.4
to 25.7 mg P kg-' soil. Proportional increases for individual soils
following drying were between 11 and 165% for inorganic P, and
between -2 and 137% for organic P, being greatest in soils with low
P concentrations. The results are unlikely to influence tests for plant-available
P, because these are derived from analyses of air-dried
samples, but have important implications for attempts to relate bicarbonate-extractable
P fractions to processes operating under field conditions
Phosphorus-31 nuclear magnetic resonance spectral assignments of phosphorus compounds in soil NaOH-EDTA extracts
Get PDFSoil P composition can be conveniently determined in alkaline
extracts using solution 31P nuclear magnetic resonance (NMR) spectroscopy,
but spectral assignments are based on fragmentary literature
reports of model compounds in various extraction matrices. We report
solution 31P NMR chemical shifts of model P compounds, including inorganic
phosphates, orthophosphate monoesters and diesters, phosphonates,
and organic polyphosphates, determined in a standardized soil
P extractant (0.25 M NaOH and 0.05 M EDTA). Signals from nucleic
acids (DNA –0.37 ppm, RNA 0.54 ppm) and phospholipids (phosphatidyl
choline 0.78 ppm, phosphatidyl serine 1.57 ppm, phosphatidyl ethanolamine
1.75 ppm) could be differentiated in the orthophosphate diester
region, and were identified in a sample of cultured soil bacteria. Inorganic
and organic polyphosphates could be differentiated by the presence
of a signal at –9 ppm from the a phosphate of organic polyphosphates.
Some orthophosphate diesters, notably RNA and phosphatidyl
choline, degraded rapidly to orthophosphate monoesters in NaOH-EDTA
although DNA, other phospholipids, and orthophosphate monoesters
were more stable. Changes in probe temperature had a marked
influence on signal intensities and the relative magnitude of signals
from orthophosphate monoesters and inorganic orthophosphate, and
we suggest that solution 31P NMR spectroscopy of soil extracts be
performed at 20°C
Horse preference for alfalfa-grass hay harvested in the afternoon or morning
Get PDFCattle, sheep, and goats, prefer forage cut in
the afternoon to that cut in the morning. This preference has
been attributed to the presence of more sugar in the afternoon
than morning forage. However, no quantitative studies have
been reported for horse responses. We chose to test horses'
preference for afternoon (PM) vs. morning (AM) cut alfalfa-grass
hay grown in southeastern Montana. Mixed alfalfa-grass
(alfalfa = 15 % bloom) was cut on 5 July 2002 at 1900
hr and again the next morning at 0700 hr using a swather with
conditioner. Hay was air dried for 24 h and baled into 300 kg
round bales. Bales were placed on palettes, tarped, and
stored in a metal hay shed. Hay consisted of 70% Grimm
alfalfa and 30% Fairway crested wheatgrass. Five kg of both
hays (AM- and PM - cut) were offered ad libitum to each of
five American Quarter horses for 10 minutes during the
morning and afternoon. Both feeding order and position of
feed buckets were randomized at each feeding. Dry matter
intake was determined by weighing before and after feeding.
Four samples of each bale were dried in a convection oven
(60° C) and ground into a fine powder. One gram of
powdered hay was combined with nine milliliters of distilled
water, boiled for five minutes, and vacuum filtered through
Whatman #1 qualitative paper. Sugars in the filtrate were
determined using a hand held Bausch and Lomb 400SD
refractometer having range of 0 - 60% . Data were tested with
analysis of variance. Horses preferred the PM-cut hay by
eating twice as much of the PM - as of the AM -cut hay (P =
0.001). The sugar concentration was 170 mg/g greater in the
extract from the PM -cut than from AM-cut hay (P = 0.04).
Horses are able to identify forage having greater sugar
concentrations and will eat larger quantities of this hay
The efficacy of polyacrylamide to reduce nutrient movement from an irrigated field
Get PDFIrrigation-induced erosion contributes to elevated sediment and nutrient concentrations in irrigation return-flow
water. Polyacrylamide (PAM) is an effective flocculent widely used to reduced soil erosion. We hypothesized PAM would
reduce transport of sediment and nutrients in surface irrigation water flowing over soil. We measured nutrients in irrigation
inflow and runoff water and total and extractable nutrients in sediment transported from agricultural fields. Treatments
were: (1) PAM application and no PAM (control), (2) three flow rates (7.5, 15.0, and 22.5 L min- 1), (3) distance along the
furrow (1 m below the inflow point and 40 m down furrow), and (4) time during irrigation (0.5, 3.5, and 6.5 h after initial
inflow). After irrigation water flowed 40 m, water flowing in furrows receiving PAM treatments reduced the NO3-
concentration in runoff by 85% and the total P concentration in water by 90% compared to runoff water in furrows without
PAM, regardless of flow rate. Mass export of NH4 +, NO3-, dissolved reactive phosphorus (DRP), total P, K, Ca, Mg, Fe, Mn,
Cu, B, and Zn in untreated irrigation runoff water increased as the flow rate increased from 7.5 to 22.5 L min- 1. Export of
these nutrients, via sediment carried by untreated irrigation runoff water, increased from 2 to 5 fold as the flow rate increased
from 7.5 to 22.5 L min-1. After water flowed 40 m, transport of these extractable nutrients was reduced from 10 to 40 fold in
PAM-treated furrows. With proper application, PAM reduces nutrient loss from furrow-irrigated agricultural fields,
protecting surface water and groundwater quality
Weed seed transport and weed establishment as affected by polyacrylamide in furrow-irrigated corn
Get PDFPolyacrylamide (PAM) has been used successfully to reduce erosion and increase
infiltration on nearly a half million hectares of United States irrigated farmland. PAM is a potent
and environmentally safe flocculent that greatly accelerates separation of suspended solids from
water. It also improves particle cohesion, stabilizing soil structure. We hypothesized that in
irrigation furrows, PAM prevents loss of weed seed and might affect weed establishment and
management practices. We grew corn (Zea mays L.) in plots without herbicides, or that were
treated with either Eradicane ® (EPTC + dichlormid) or Dual ® II (S-Metolachlor) and irrigated in
furrows that had either no PAM, or that were treated either with 10 g m- 3 (io kg ML-1 or 10 ppm)
dissolved PAM during water advance, or with PAM applied as a powder patch at the furrow head.
As in previous studies, erosion was greatly reduced with PAM and infiltration was increased.
PAM use also reduced runoff loss of weed seeds (barnyardgrass, kochia, redroot pigweed,
common lambsquarters, and hairy nightshade) 62% to 90%. Interactions of herbicide
treatments and PAM on erosion, infiltration, and weed seed loss were related to the mulching
effect of weed vegetation. PAM is an effective and environmentally safe means of reducing weed
seed distribution in furrow irrigation water while simultaneously reducing erosion and increasing
infiltration in weed-free crop production