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  • Author or Editor: W.R. Stevenson x
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The Wisconsin potato crop is managed intensively through multiple inputs of pesticide, fertilizer, and irrigation. Beginning in 1979, a multidisciplinary team at the Univ. of Wisconsin developed an effective Integrated Pest Management Program to address key management decisions associated with this crop. The program fostered the development of several private IPM businesses and continues to help increase the acceptance of IPM technology by the potato industry. Results of component and integrative research, funded by industry, state, and federal sources, provided the essential ingredients for development of computer software now used for managing the potato crop on ≈ 70,000 acres (28,330 ha) of potatoes in a multistate area. The software helps growers determine the need for and timing of critical crop inputs. By reducing or eliminating unneeded pesticide and irrigation applications, the software helps to improve overall production efficiency. Industry adoption of this software is providing the impetus for development of more comprehensive software that includes additional aspects of potato production as well as the production of crops grown in rotation with potato.

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To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential has proven to be a useful index of stress in a number of fruit tree species. Day-to-day fluctuations in stem water potential under well-irrigated conditions are well correlated with midday vapor-pressure deficit, and, hence, a nonstressed baseline can be predicted. Measuring stem water potential helped explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In almond, stem water potential was closely related to overall tree growth as measured by increases in trunk cross-sectional area. In cherry, stem water potential was correlated with leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once stem water potential dropped to between −1.5 to −1.7 MPa. In pear, fruit size and other fruit quality attributes (soluble solids, color) were all closely associated with stem water potential. In many of these field studies, systematic tree-to-tree differences in water status were large enough to obscure irrigation treatment effects. Hence, in the absence of a plant-based measure of water stress, it may be difficult to determine whether the lack of an irrigation treatment effect indicates the lack of a physiological response to plant water status, or rather is due to treatment ineffectiveness in influencing plant water status. These data indicate that stem water potential can be used to quantify stress reliably and guide irrigation decisions on a site-specific basis.

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