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 $159/ha ($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.

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

Computing gravitational waves from slightly nonspherical stellar collapse to black hole: Odd-parity perturbation

Nonspherical stellar collapse to a black hole is one of the most promising gravitational wave sources for gravitational wave detectors. We numerically study gravitational waves from a slightly nonspherical stellar collapse to a black hole in linearized Einstein theory. We adopt a spherically collapsing star as the zeroth-order solution and gravitational waves are computed using perturbation theory on the spherical background. In this paper we focus on the perturbation of odd-parity modes. Using the polytropic equations of state with polytropic indices $n_p=1$ and 3, we qualitatively study gravitational waves emitted during the collapse of neutron stars and supermassive stars to black holes from a marginally stable equilibrium configuration. Since the matter perturbation profiles can be chosen arbitrarily, we provide a few types for them. For $n_p=1$, the gravitational waveforms are mainly characterized by a black hole quasinormal mode ringing, irrespective of perturbation profiles given initially. However, for $n_p=3$, the waveforms depend strongly on the initial perturbation profiles. In other words, the gravitational waveforms strongly depend on the stellar configuration and, in turn, on the ad hoc choice of the functional form of the perturbation in the case of supermassive stars.Comment: 31 pages, accepted for publication in Phys. Rev. D, typos and minor errors correcte