914 research outputs found
Relationship Between Foliage Temperature and Water Stress in Potatoes
Field studies were conducted in southern Idaho to evaluate the
possibility of using thermal infrared measurements of potato foliage to
detect soil water deficits. Concurrent measurements of foliage-air temperature
differences (Tf-Ta), leaf water potential (?leaf) and vapor pressure
deficit (VPD) were obtained from differentially-irrigated Russet Burbank
and Kennebec potatoes during the 1982 and 1983 growing seasons. Foliage-air
temperature differences for well-watered potatoes were linearly related
to VPD. Differences in Tf-Ta values between stressed and well-watered
potatoes were relatively small in the early morning when evaporative demand
was low. However, severe soil water deficits caused afternoon Tf-Ta
values to rise as much as 8.0 C above non-stressed levels under conditions of
high VPD.
Foliage-air temperature differences and VPD data were used to construct
a plant water stress index (PWSI) which reflected the rise in Tf-Ta,
above non-stressed levels at a given VPD. The PWSI was linearly related to
depressions in ?leaf caused by moderate to severe soil water deficits.
However, the PWSI did not increase significantly above non-stressed values
unless the soil matric potential ?soil fell below – 70 kPa (centibars). Since
potatoes are normally irrigated before ?soil falls below – 60 kPa, it appears
that foliage temperature measurements cannot be used to effectively
schedule irrigation for this crop
Potato
Soil erosion is a serious agricultural problem. Most of the available literature
on the subject concerns nonirrigated cropland where natural precipitation
and snowmelt water produce the forces needed to erode soil and transport
sediment. Most of the water providing those forces for erosion on irrigated
land is that applied by humans to supply water to growing crops. The purpose
of this chapter is to provide a review of irrigation-induced soil erosion
and to supply some insight into its hazards and control
Comparison of site-specific and conventional uniform irrigation management for potatoes
Site-Specific Irrigation Management (SSIM) can be defined as irrigation management (depth, timing) based on
crop need to defined sub-areas of a field referred to as management zones. Implementation of SSIM will require additional
irrigation system hardware, labor, and information on soil and/or plant water status in each management zone. Costs
associated with these additional requirements will need to be offset by increased receipts from improved crop yield and quality
in order for the technology to be adopted by producers. The potential for SSIM to increase crop yield, quality, and economic
return has not been evaluated in field studies. Crops such as potatoes, for which yield and quality are highly sensitive to soil
water availability, are most likely to show an economic benefit from site-specific irrigation management. A two-year field
study was conducted to evaluate the potential for SSIM to increase yield and quality of potatoes relative to Conventional
Uniform Irrigation Management (CUIM). Near real-time soil water content was used to schedule irrigations under both
irrigation management treatments. Field average water application was nearly the same for the irrigation management
treatments, 503 mm (19.8 in.) in 2001 and 445 mm (17.5 in.) in 2002. In both study years, tuber yield distributions trended
4% greater under site-specific irrigation management but were not significantly different (p < 0.05). Total tuber yield per
unit of water applied from irrigation and precipitation was 4% greater in 2001 and 6% greater in 2002 under SSIM. Based
on a local tuber quality adjusted potato processing contract price structure, the trend in gross income averaged across the
field site was 65/acre) greater with SSIM. This increase in gross income is likely about half the actual cost of
commercial site-specific irrigation technology. The required 3- to 5-year crop rotation for potato disease management means
that the site-specific irrigation system needs to be mobile or an economic benefit must also be realized from other crops in
the rotation. The economic benefit of SSIM needs to be increased or realized for other crops in the rotation for it to be an
economically viable technology in potato production systems in Idaho
U of Idaho and USDA-ARS Progress Report: Potassium management in irrigated potato systems of Southern Idaho
An initial survey (Fig. 1) was completed for southern Idaho to correlate soil test K levels with % K
concentrations in potato petioles. Twenty-eight fields were sampled across the major production
areas of the state during potato bulking. A positive correlation (R = 0.66) was observed between
soil test K (stK) levels and petiole K concentrations. The K values ranged from 105 ppm stK to
almost 600 stK. Petiole K % ranged from 7.5% to 12%. The present Univ. of Idaho critical
value for Russet Burbank is set at about 7%. Unfortunately this value has not been completely
substantiated because of insufficient low stK sites
Potato Irrigation Management
Potato yield and quality are sensitive to both excess and deficit soil water. This sensitivity, coupled with a relatively shallow root zone and medium- to coarse -textured soils common in many production areas, makes economically efficient irrigated potato production challenging. Potato is grown under all types of irrigation systems worldwide, but irrigation systems capable of light, frequent, uniform water application are best. Optimum potato irrigation management requires a working knowledge of soil water relations and irrigation system characteristics. This chapter introduces both in the context of potato production in arid areas of the Pacific Northwest U.S. General guidelines and irrigation management aids are presented along with examples for implementing quantitative irrigation management of potato in an arid environment
Interaction and flocculation of spherical colloids wetted by a surface-induced corona of paranematic order
Particles dispersed in a liquid crystal above the nematic-isotropic phase
transition are wetted by a surface-induced corona of paranematic order. Such
coronas give rise to pronounced two-particle interactions. In this article, we
report details on the analytical and numerical study of these interactions
published recently [Phys. Rev. Lett. 86, 3915 (2001)]. We especially
demonstrate how for large particle separations the asymptotic form of a Yukawa
potential arises. We show that the Yukawa potential is a surprisingly good
description for the two-particle interactions down to distances of the order of
the nematic coherence length. Based on this fact, we extend earlier studies on
a temperature induced flocculation transition in electrostatically stabilized
colloidal dispersions [Phys. Rev. E 61, 2831 (2000)]. We employ the Yukawa
potential to establish a flocculation diagram for a much larger range of the
electrostatic parameters, namely the surface charge density and the Debye
screening length. As a new feature, a kinetically stabilized dispersion close
to the nematic-isotropic phase transition is found.Comment: Revtex v4.0, 16 pages, 12 Postscript figures. Accepted for
publication in Phys. Rev.
Gram Yield and Yield Components of Spring Wheat Genotypes at Different Moisture Regimes
Yield and developmental characteristics of crop genotypes grown at different levels of water availability are often used to select genotypes that are adapted to variable moisture environments. Field studies were conducted at Aberdeen. Idaho, USA in 1992 and 1993 to evaluate the effects of varying moisture supply on grain yield and yield components of spring wheat genotypes. In both years, 12 spring wheat (Triticum aestivum L.) genotypes were grown under three irrigation levels (well-watered. moderate water-stress and severe water-stress) imposed during the periods from mid-tillering to anthesis with a line source sprinkler irrigation system. Grain yield and yield components (spikes m-2, spikelets spike-1, kernels spikelet-1, kernels spike-1, and kernel weight) were used to evaluate the genotypic response to water stress. Overall, water stress caused a reduction in grain yield and yield components. Genotypes exhibited a large year-to-year variation in their ranks for grain yield. Medium-tall growing genotypes (IDO 367. lDO 369 and Rick) generally produced high yields under water stress conditions in 1992 (relatively dry year), while short -medium genotypes (WPB 926. Yecora Rojo and Pondera) produced high yields under water stress conditions in 1993 (relatively wet year). Chris and Serra were the lowest yielding genotypes under water stress conditions in both years. Under moderate stress conditions. 100 367 and Yecora Rojo had consistently high yields. Genotypic yield differences under water stress conditions were primarily related to the differences in the numbers of spikes m". Therefore, a tendency for high plasticity for Spikes per unit area could be used to select wheat genotypes for improved drought tolerance
Defect structures and torque on an elongated colloidal particle immersed in a liquid crystal host
Combining molecular dynamics and Monte Carlo simulation we study defect
structures around an elongated colloidal particle embedded in a nematic liquid
crystal host. By studying nematic ordering near the particle and the
disclination core region we are able to examine the defect core structure and
the difference between two simulation techniques. In addition, we also study
the torque on a particle tilted with respect to the director, and modification
of this torque when the particle is close to the cell wall
Defect structures in nematic liquid crystals around charged particles
We numerically study the orientation deformations in nematic liquid crystals
around charged particles. We set up a Ginzburg-Landau theory with inhomogeneous
electric field. If the dielectric anisotropy varepsilon_1 is positive, Saturn
ring defects are formed around the particles. For varepsilon_1<0, novel "ansa"
defects appear, which are disclination lines with their ends on the particle
surface. We find unique defect structures around two charged particles. To
lower the free energy, oppositely charged particle pairs tend to be aligned in
the parallel direction for varepsilon_1>0 and in the perpendicular plane for
varepsilon_1<0 with respect to the background director . For identically
charged pairs the preferred directions for varepsilon_1>0 and varepsilon_1<0
are exchanged. We also examie competition between the charge-induced anchoring
and the short-range anchoring. If the short-range anchoring is sufficiently
strong, it can be effective in the vicinity of the surface, while the director
orientation is governed by the long-range electrostatic interaction far from
the surface.Comment: 10 papes, 12 figures, to appear in European Physical Journal
Potato cultivar response to seasonal drought patterns
The ability to minimize potato yield and quality losses due to drought can be greatly improved by understanding the relative responses of different cultivars to seasonal variations in water supply. To address this need, we initiated a two year field experiment to determine the responses of the six potato cultivars to different seasonal drought patterns, including 1) full season irrigation at 100% ET, 2) irrigation at 100% ET terminated during late bulking , 3) full season irrigation at 70% ET , 4) irrigation at 70% ET terminated during late bulking , and 5) a gradual reduction in irrigation from 100% ET during tuber initiation through early bulking, to 70% ET during mid-bulking, and 50% ET through late bulking. GemStar Russet and Ranger Russet, two medium-late maturing cultivars, generally produced the highest yields across the range of drought treatments, but both were fairly sensitive to changes in drought severity. Alturas, a late maturing cultivar, produced relatively high yields with full irrigation, but exhibited the greatest sensitivity to increasing drought severity, particularly when severe late-season water deficits were imposed. Yields for the early maturing cultivar Russet Norkotah were relatively low overall, but it was the least sensitive to changes in drought severity, particularly when late season drought was imposed. Russet Burbank produced comparatively high total yields across the range of drought treatments, but U.S. No. 1 yields were substantially reduced by each seasonal drought pattern. However, it was less sensitive to changes in drought severity than GemStar Russet, Ranger Russet and Alturas. Total and U.S. No. 1 yields for Summit Russet were low for each drought treatment and it exhibited intermediate sensitivity to changes in drought severity. GemStar Russet had the highest water use efficiency based on U.S. No. 1 yield
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