1,166 research outputs found
A Buried Drain Erosion and Sediment Loss Control System
The lower ends of most furrow irrigated fields have become
convex shaped, meaning the slope progressively increases
from a point 20 to 60 feet from the field end to the
tailwater ditch. This increasing slope is the result of maintaining
tailwater ditches too deep and keeping them cleaned
so runoff from these fields is not restricted. The process of
forming a convex field end continues yearly at an increasing
rate. With each passing year, the slope at the end of the
field becomes greater so that runoff water runs faster and
has more energy to erode. Over many years, large quantities
of soil have been lost from the lower ends of furrow
irrigated fields. Field ends 1.5 to 2.0 feet lower than the furrow
elevation 20 to 60 feet upslope are common. Much of
the soil loss is from the lower ends of fields
A Buried Pipe System for Controlling Erosion and Sediment Loss on Irrigated Land
A new system comprised of a buried pipe, with riser inlets from the
surface at intervals, along the lower end of furrow-irrigated fields was
designed, installed, and evaluated on 21 fields to determine its effectiveness
as an erosion and sediment loss control system for irrigated land.
The system utilizes small sediment collection ponds with the riser inlets
from the buried pipe serving as overflow outlets for the ponds. This
system corrects convex-shaped field ends caused by erosion and solves
an energy related erosion problem common on furrow-irrigated land.
During the first season, these system removed from 80 to 9S% of the
sediment from runoff water and collected from 4.1 to 40.5 Mg ha-Âą
from 12 fields on irrigated land where detailed data were collected. All
systems performed without problems and all convex end problems except
one were corrected the first season. After the convex ends are corrected,
the system continues to reduce sediment loss. This new system eliminates
the tailwater ditch, puts more land into crop production, reduces weed
problems, and prevents the usual problems associated with a wet tailwater
ditch. The buried pipe erosion and sediment loss control system
is a major advance in the control of erosion and sediment loss on irrigated
land
Crop sequences and conservation tillage to control irrigation furrow erosion and increase farmer income
Five years of research show that there are many benefits to conservation tillage
on furrow-irrigated land. Benefits are enhanced when cropping sequences are altered to
accommodate the fewest number of tillage operations over the entire cropping sequence.
Results showed that soil erosion can be reduced 47 to 100 percent, crop yields can be
sustained, and farmer net income can be increased an average of more than $125 ha-1
each year over a 5-year cropping sequence
Furrow Erosion and Sediment Losses on Irrigated Cropland
Sediment losses from furrow erosion on irrigated cropland ranged from 0.5
to 142 metric tons per hectare (0.2 to 63.0 tons/acre) on 49 Idaho fields during one irrigation
season. Field slope varied from 1.0 to 5.0 percent and furrow stream size from 11.3
to 49.9 liters per minute (3.0 to 13.2 gal/min). Erosion increased sharply on row-cropped
fields when slopes exceeded 1.0 percent. Furrow erosion can be reduced by: (a) reducing
furrow stream size when water reaches the furrow ends, (b) avoiding irrigation of row
crops on slopes that are too steep, (c) keeping the tailwater ditch shallow and the water in
it moving slowly, (d) installing tailwater control systems, and (e) alternate-furrow irrigation.
Sediment losses from irrigated lands can also be reduced markedly by planting
vegetative filter strips and using sediment retention basins. Total phosphorus losses were
reduced in proportion to the reduction in sediment losses
Debye screening and Meissner effect in a two-flavor color superconductor
I compute the gluon self-energy in a color superconductor with two flavors of
massless quarks, where condensation of Cooper pairs breaks SU(3)_c to SU(2)_c.
At zero temperature, there is neither Debye screening nor a Meissner effect for
the three gluons of the unbroken SU(2)_c subgroup. The remaining five gluons
attain an electric as well as a magnetic mass. For temperatures approaching the
critical temperature for the onset of color superconductivity, or for gluon
momenta much larger than the color-superconducting gap, the self-energy assumes
the form given by the standard hard-dense loop approximation. The gluon
self-energy determines the coefficient of the kinetic term in the effective
low-energy theory for the condensate fields.Comment: 29 pages, RevTe
Longitudinal gluons and Nambu-Goldstone bosons in a two-flavor color superconductor
In a two-flavor color superconductor, the SU(3)_c gauge symmetry is
spontaneously broken by diquark condensation. The Nambu-Goldstone excitations
of the diquark condensate mix with the gluons associated with the broken
generators of the original gauge group. It is shown how one can decouple these
modes with a particular choice of 't Hooft gauge. We then explicitly compute
the spectral density for transverse and longitudinal gluons of adjoint color 8.
The Nambu-Goldstone excitations give rise to a singularity in the real part of
the longitudinal gluon self-energy. This leads to a vanishing gluon spectral
density for energies and momenta located on the dispersion branch of the
Nambu-Goldstone excitations.Comment: 16 pages, 4 figures, minor revisions to text, one ref. adde
The Effect of Furrow Irrigation Erosion on Crop Productivity
Furrow irrigation erosion redistributes topsoil by eroding upper
ends of fields and depositing sediment on downslope portions causing
a several fold topsoil depth difference on individual fields. This
investigation was conducted to evaluate the effects of this erosion
and deposition process on crop yield and to develop crop yield-topsoil
depth relationships. Studies were conducted on 14 farmer-operated
fields and on field plots with a continuous topsoil depth gradient
from 10 to 66 cm. Severe erosion on the upper ends of fields combined
with tillage has mixed light-colored subsoil with topsoil and
caused these areas to become whitish in color. Crop yields have
sharply decreased on these whitish areas compared to areas where
the topsoil depth is 38 cm, or the original depth. Yields were increased,
but less sharply, where sediment deposition has increased
topsoil depth above 38 cm up to a depth of about 66 cm. Yield-topsoil
depth relationships followed the equation Y = a+b 1nX with
significant correlation coefficients for wheat (Triticum aestivum L.),
sweet corn (Zea mays L.), barley (Hordeum vulgare L.), alfalfa
(Medicago sativa L.), dry beans (Phaseolus sap.) and sugarbeets (Beta
vulgaris L.). Yield decreases per unit loss of topsoil were greatest
for wheat and sweet corn and least for sugarbeets. Yields on whitish
soil areas could not be improved more than indicated by these relationships
by adding additional fertilizer phosphorus or potassium
Furrow Erosion Reduces Crop Yields
Furrow irrigation erosion redistributes topsoil within
fields and causes serious topsoil losses from farms. Erosion
occurs on the upper portions of fields where the
furrow streams are largest and the energy greatest. The
furrow stream must be large enough at the head end of
the furrow to supply sufficient water for infiltration over
the entire furrow length
Furrow irrigation water-quality effects on soil loss and infiltration
Irrigation-induced erosion is a serious problem in the western USA
where irrigation water quality can vary seasonally and geographically.
We hypothesized that source-water electrical conductivity (EC) and
sodium adsorption ratio (SAR = Na/[(Ca + Mg)/2]^0.5, where concentrations
are in millimoles of charge per liter) affect infiltration and
sediment losses from irrigated furrows, and warrant specific consideration
in irrigation-induced erosion models. On a fallow Portneuf silt
loam (coarse-silty, mixed, mesic Durixerollic Calciorthid), tail-water
sediment loss was measured from trafficked and nontrafficked furrows
irrigated with waters of differing quality. Treatments were the four
combinations of low or high EC (0.6 and 2 dS m-1) and low or high
SAR (0.7 and 12 [mmolc L-1]^0.5). Slope is 1%. Twelve irrigations were
monitored. Each furrow received two irrigations. Main effects for
water quality, traffic, and first vs. second irrigations were significant
for total soil loss, mean sediment concentration, total outflow, net
infiltration, and advance time. Average tail-water soil losses were 2.5
Mg ha-1 from low EC/low SAR furrows, 4.5 Mg ha-1 from low EC/
high SAR furrows, 3.0 Mg ha-1 from high EC/high SAR furrows;
and 1.8 Mg ha-1 from high EC/low SAR furrows. Elevating water
EC decreased sediment concentration from 6.2 to 4.6 g L-1, but
increasing SAR increased sediment concentration from 6.2 to 8.7 g
L-1. Net infiltration decreased 14% in high SAR compared with low
SAR treatments. Soil loss increased 68% for second irrigations, and
net infiltration fell 23% in trafficked furrows, but water-quality effects
were the same. Water quality significantly influenced infiltration and
erosion processes in irrigated furrows on Portneuf soils
Influence of irrigation water quality on sediment loss from furrows
Agricultural erosion research has focused on rainfall-induced soil loss, with comparatively little attention to furrow
irrigation-induced erosion. One rationale for this is that rill erosion is mechanistically similar to erosion in irrigated
furrows. However, significant differences exist between the two processes. These are related to soil conditions during
initial stream advance, downstream flow rates, and chemical characteristics of the water stream. The salinity and
sodicity of water in rills are low, owing to its atmospheric origin, whereas, irrigation water quality varies geographically
and seasonall
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