1,237 research outputs found
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
Center-pivot irrigation system for independent site-specific management of water and chemical application
The development of lateral?move and center?pivot irrigation systems equipped for spatially variable water
application and those equipped with an independent chemical application system have largely evolved independently.
Integration of independent site?specific water and chemical application with lateral?move and center?pivot irrigation systems
has received little attention. Increasing the utility of site?specific management technologies added to automated irrigation
systems will increase their cost effectiveness and commercial potential. An independent chemical application system capable
of variable rate application was installed and tested on a 4?span center?pivot irrigation system equipped for variable rate
water application. The chemical application system was assembled using mini?sprinklers and common commercial irrigation
system components. For uniform chemical application, the coefficient of uniformity (CU) values ranged from 84 to 90
providing acceptable application uniformity. For variable rate chemical application, CU values ranged from 79 to 93 and
measured mean area?weighted relative application values were well correlated with target relative application values with
R2 of 0.9 or higher. Field testing of the chemical application system demonstrated that it can be used to effectively apply
spatially variable chemical application concurrent and independent of spatially variable water application
High-order density-matrix perturbation theory
We present a simple formalism for the calculation of the derivatives of the
electronic density matrix at any order, within density functional theory. Our
approach, contrary to previous ones, is not based on the perturbative expansion
of the Kohn-Sham wavefunctions. It has the following advantages: (i) it allows
a simple derivation for the expression for the high order derivatives of the
density matrix; (ii) in extended insulators, the treatment of
uniform-electric-field perturbations and of the polarization derivatives is
straightforward.Comment: 4 page
Spatially distributed control netowork for flow proportional chemical injection with center pivot irrigation
The agricultural production practice of injecting a chemical into an operating irrigation system and applying it
to the field area with the water is known as chemigation. Chemigation is a widely adopted practice with center pivot sprinkler
irrigation. However, the practice of chemical injection at a constant rate with center pivot sprinkler irrigation systems
equipped with an end gun and/or swing?arm corner watering system results in systematic chemical application errors ranging
from 7% to 21% due to systematic changes in system flow rate. Chemical injection proportional to center pivot sprinkler
system flow rate is one approach to reduce systematic chemical application errors. The objective of this project was to test
the feasibility of using real?time monitoring of center pivot sprinkler irrigation system operating status to control chemical
injection rate proportional to calculated system flow rate, thus minimizing systematic chemical application errors. A spatially
distributed control network was developed to facilitate real?time monitoring of end gun and swing?arm corner watering
system operating status and pressure. The spatially distributed control network consisted of three network nodes at specific
locations along a center pivot sprinkler irrigation lateral that used the 480 VAC 3?phase power cable on the center pivot
sprinkler irrigation system as the communication medium. The spatially distributed control network was installed on a
commercial 460?m (1510?ft) long center pivot sprinkler system equipped with an end gun and swing?arm corner watering
system. Performance of chemical injection proportional to calculated flow rate based on real?time center pivot sprinkler
irrigation system operating status was evaluated by injecting Rhodamine WT dye into the center pivot sprinkler irrigation
system water supply and measuring its concentration in the applied water. Mean dye concentration varied by 26% under
constant rate chemical injection and 2% under flow proportional chemical injection due to systematic changes in center pivot
sprinkler irrigation system flow rate. Use of the flow proportional chemical injection system reduced the coefficient of
variability in measured dye concentration of applied water by 54% from 0.100 to 0.046. Use of the spatially distributed control
network for calculating center pivot sprinkler system flow rate eliminates the need for straight sections of unobstructed piping
at the chemical injection site. Display and/or data logging of real?time center pivot sprinkler operating status is an added
benefit of using the spatially distributed control network. This information provides the ability to monitor, diagnose, and
troubleshoot center pivot sprinkler system operation. Commercialization and adoption of the technology could reduce
systematic chemical application errors and facilitate maintenance and operation of center pivot sprinkler irrigation systems
equipped with an end gun and/or swing?arm corner watering system
The combined use of selective deuteration and double resonance experiments in assigning the 1H resonances of valine and tyrosine residues of dihydrofolate reductase
AbstractSelective deuteration is a general solution to the resolution problem which limits the application of double resonance experiments to the assignment of the 1H NMR spectra of proteins. Spin-decoupling and NOE experiments have been carried out on Lactobacillus casei dihydrofolate reductase and on selectively deuterated derivatives of the enzyme containing either [γ-2H6]Val or (α,δ2,ϵ1-2H3]His, [α,δ1,δ2,ϵ1,ϵ2,ζ-2H6]Phe, [α,δ1,ϵ3,ζ2,ζ3,η2-2H6]Trp and [α,ϵ1,ϵ2-2H3]Tyr. When combined with ring-current shift calculations based on the crystal structure of the enzyme, these experiments allow us to assign 1H resonances of Val 61, Val 115, Tyr 46 and Tyr 68
Collector design for measuring high intensity time variant sprinkler application rates
Peak water application rate in relation to soil water infiltration rate and soil surface storage capacity is important in the design of center pivot sprinkler irrigation systems for efficient irrigation and soil erosion control. Measurement of application rates of center pivot irrigation systems has traditionally used tipping bucket rain gauges. Calculation of application rate from tipping bucket rain gauge measurements restricts computed application rate to a discrete multiple of the rain gauge resolution and time interval. This limits the resolution of application rate measurement, especially for time intervals less than 15 minutes. A collector was designed to measure time variant high intensity sprinkler application rates under field conditions with greater resolution than a tipping bucket rain gauge. The collector funnels water into a 50 mm (2 in.) diameter tube providing a depth multiplication factor of 18.26:1. The depth of water in the tube is measured with a low pressure piezo-resistive pressure sensor connected to a differential amplifier circuit. Combination of the depth multiplication factor of the collector and differential amplifier circuit provides a collector resolution of 1.4 mm/mV. A data logger is used to record water depth in the collector tube during an irrigation event. A digital differentiating filter was designed and used to reduce the effect of random electrical noise in the sensor output on calculated application rate. The collector was tested in the laboratory and under field conditions emulating center pivot sprinkler irrigation. For a range in application rates from 15 to 200 mm/h in the laboratory, the maximum collector error was 2.1 mm/h. Collector measured application rate patterns under field conditions were well correlated to simulated application rate patterns using radial application rate profiles for the sprinklers tested. Collector measured peak application rates were not significantly different from those predicted by the Kincaid (2005) model. The collector functioned as designed in field tests and provided an effective and efficient means of measuring high intensity application rates from center pivot irrigation systems under field conditions
Field scale performance of a variable rate sprinkler for variable water and nutrient application
A 3-span linear-move irrigation system was equipped with 32 prototype variable rate sprinklers. Water
application uniformity was measured over a 2.7X range in application rate. The measured application
uniformity was 90% or greater for all water application rates. Variable rate nitrogen application was
evaluated on a 1.1 ha area. Variable rate nitrogen application was within 4% of target application. The
variable rate sprinkler allows variable rate water application with minimal effect on water application
uniformity
Field testing of a variable rate sprinkler and control system for site-specific water and nutrient application
Development and implementation of site-specific sprinkler irrigation management has been limited due to the lack
of variable rate sprinklers. Thirty-two prototype variable rate sprinklers were constructed and field tested on a three-span
linear-move irrigation system. An algorithm was developed for a distributed control network to allow each sprinkler to be
individually controlled in groups of six or seven along the linear-move lateral. Water application uniformity was monitored
over a 36% to 100% range in application rate. Measured application uniformity equaled or exceeded 90%. Variable rate
nitrogen application was monitored over a 1.1-ha area. Measured nitrogen application rate was within 4% of the target
application rate. Results indicate that the prototype variable rate sprinkler and control system allows water and chemical
application to vary over a 36% to 100% range in application rate with minimal effect on water application uniformity
An evaluation of the stimulants and impediments to innovation within PFI/PPP projects
This paper identifies the theoretical stimulants and impediments associated with the implementation of PFI/PPP (Private Finance Initiative/Public Private Partnership) projects. A current defect of this procurement approach is the unintentional constraint upon the innovations incorporated into the development of PFI projects. A critical evaluation of the published literature has been utilized to synthesize a theoretical model. The paper proposes a theoretical model for the identification of potential innovation stimulants and impediments within this type of procurement. This theoretical model is then utilised to evaluate four previously completed PFI projects. These project case-studies have been examined in detail. The evaluation demonstrates how ineffective current procedures are. The application of this model before project letting could eliminate unintentional constraints and stimulate improved innovation within the process. The implementation of the model could improve the successful delivery of innovation within the entire PFI/PPP procurement process
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