More than 20 years of private and public research on site-specific variable rate sprinkler irrigation (SS-VRI) technology on self-propelled center pivot and linear move irrigation systems has resulted in limited commercial adoption of the technology. Competing patents, liability, and proprietary software have affected industry's willingness to move into a new technology area. Documented and proven water conservation strategies using sitespecific irrigation are quite limited. Marginal costs associated with site-specific technologies are high. Although sales of SS-VRI are increasing, they are primarily being used for Communicated by J. Kijne. Mention of trade names, companies, or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.
a b s t r a c tPrecision irrigation management of wine grape requires a reliable method to easily quantify and monitor vine water status to allow effective manipulation of plant water stress in response to water demand, cultivar management and producer objective. Mild to moderate water stress is desirable in wine grape in determined phenological periods for controlling vine vigor and optimizing fruit yield and quality according to producer preferences and objectives. The traditional leaf temperature based crop water stress index (CWSI) for monitoring plant water status has not been widely used for irrigated crops in general partly because of the need to know well-watered and non-transpiring leaf temperatures under identical environmental conditions. In this study, leaf temperature of vines irrigated at rates of 35, 70 or 100% of estimated evapotranspiration demand (ET c ) under warm, semiarid field conditions in southwestern Idaho USA was monitored from berry development through fruit harvest in 2013 and 2014. Neural network (NN) models were developed based on meteorological measurements to predict well-watered leaf temperature of wine grape cultivars 'Syrah' and 'Malbec' (Vitis vinifera L.). Input variables for the cultivar specific NN models with lowest mean squared error were 15-min average values for air temperature, relative humidity, solar radiation and wind speed collected within ±90 min of solar noon (13:00 and 15:00 MDT). Correlation coefficients between NN predicted and measured well-watered leaf temperature were 0.93 and 0.89 for 'Syrah' and 'Malbec', respectively. Mean squared error and mean average error for the NN models were 1.07 and 0.82• C for 'Syrah' and 1.30, and 0.98 • C for 'Malbec', respectively. The NN models predicted well-watered leaf temperature with significantly less variability than traditional multiple linear regression using the same input variables. Non-transpiring leaf temperature was estimated as air temperature plus 15• C based on maximum temperatures measured for vines irrigated at 35% (ET c ). Daily mean CWSI calculated using NN estimated well-watered leaf temperatures between 13:00 and 15:00 MDT and air temperature plus 15• C for non-transpiring leaf temperature consistently differentiated between deficit irrigation amounts, irrigation events, and rainfall. The methodology used to calculate a daily CWSI for wine grape in this study provided a daily indicator of vine water status that could be automated for use as a decision-support tool in a precision irrigation system.Published by Elsevier B.V.
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 2 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.Resumen Se puede mejorar grandemente la habilidad para minimizar las pérdidas en rendimiento y calidad de papas debido a la sequía, mediante el entendimiento de las respuestas relativas de diferentes variedades a variaciones estacionales en el suministro de agua. Para atender esta necesidad, iniciamos un experimento de campo por dos años para determinar las respuestas de seis variedades de papa a diferentes patrones de sequía estacional, incluyendo, 1) riego completo en el ciclo al 100 % ET, 2) riego al 100 % ET terminando durante el fin de la tuberización, 3) riego durante todo el ciclo a 70 % ET, 4) riego al 70 % ET terminando al final de la tuberización, y 5) reducción gradual de riego de 100 % ET durante la iniciación de la tuberización a lo largo del llenado temprano, a 70 % ET durante la mitad del llenado, y 50 % ET a lo largo de la tuberización tardía. Gem Star Russet y Ranger Russet, dos variedades de intermedias a tardías, generalmente produjeron los rendimientos más altos a lo largo de la amplitud de los tratamientos de sequía, pero ambas fueron muy sensibles a los cambios de la severidad de la sequía. Alturas, una variedad tardía, produjo rendim...
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