{"id":160,"date":"2010-05-07T09:59:52","date_gmt":"2010-05-07T13:59:52","guid":{"rendered":"https:\/\/extension.umaine.edu\/blueberries\/?page_id=160"},"modified":"2022-08-09T08:40:25","modified_gmt":"2022-08-09T12:40:25","slug":"guide-to-efficient-irrigation-of-the-wild-blueberry","status":"publish","type":"page","link":"https:\/\/extension.umaine.edu\/blueberries\/resources\/irrigation\/guide-to-efficient-irrigation-of-the-wild-blueberry\/","title":{"rendered":"631-Guide to Efficient Irrigation of the Wild Blueberry"},"content":{"rendered":"

Fact Sheet No. 631, UMaine Extension No. 2006<\/strong><\/p>\n

\n

Prepared by\u00a0 Jim Hunt, Support Scientist USDA\/ARS, Wayne Honeycutt, Research Leader USDA\/ARS, New England Plant, Soil and Water Lab, Orono, ME and\u00a0 David E. Yarborough, Extension Blueberry Specialist, The University of Maine Cooperative Extension, Orono, ME 04469.\u00a0 April 2009<\/em><\/p>\n

Introduction<\/strong><\/h3>\n
\"Wild<\/a>
Figure 1.<\/strong> Wild Blueberry crop with and without irrigation.<\/figcaption><\/figure>\n

The commercial wild blueberry (Vaccinium angustifolium<\/em>) in Maine is grown on a biennial cycle, in which the prune year following harvest results in vegetative growth and development of floral buds on upright stems.\u00a0 In the following crop year, these buds flower and develop into fruit which is harvested in late summer.\u00a0 Many studies over the years have indicated that supplemental irrigation of wild blueberry during dry periods of this two-year cycle can reduce crop failure and increase profitability by significantly improving both berry yield and quality (Figure 1). Although wild blueberries have been shown to be relatively resistant to drought stress, there is evidence that during very dry periods the plant will be shorter with fewer buds (Figure 2), and in the crop year preferentially direct its resources into vegetative growth at the expense of fruit production. Long-term weather trends indicate that wild blueberries could be expected to get sufficient water in August in only one year out of five.\u00a0 If rainfall is limiting, then irrigating both the non-crop and crop year can significantly increase wild blueberry yield over no irrigation or just irrigating in the crop year.<\/p>\n

\u00a0The goal of irrigation management is to maximize water-use efficiency while maintaining a suitable soil environment for crop growth that is neither too wet nor too dry.\u00a0 Adding insufficient water or postponing irrigation until signs of crop stress are noticeable, can lead to plant injury and reduced yield.\u00a0 Conversely, excess water application results in unnecessary pumping expenses and may lead to leaching pesticides or plant nutrients out of the root zone and into ground or surface waters.<\/p>\n

\"Research<\/a>
Figure 2.<\/strong> Research from the 1950\u2019s showing increase in growth with irrigation<\/figcaption><\/figure>\n

Efficient irrigation management requires being able to effectively forecast crop water needs a few days before the demand becomes critical, and then to apply just enough water to meet those needs.\u00a0 This is relatively simple to do through regular monitoring of crop water use and available soil moisture.\u00a0 The following guidelines illustrate in a step-by-step manner how to improve irrigation efficiency without the need for expensive monitoring equipment.<\/p>\n

Step 1: Estimating Crop Water Usage<\/strong><\/h3>\n

Many experienced growers have an intuitive feel for the water demand of their crop.\u00a0 The traditional \u201crule of thumb\u201d of 1 inch of water per week was shown in a recent four year weighing lysimeter study conducted in Maine to be a fairly accurate estimation for many of the state\u2019s wild blueberry fields.\u00a0 For instance, the study showed that the combined average water use for the months of June through August at a blueberry field in Deblois, ME was about 0.88 inches per week.\u00a0 But, the problem with averages is that they tell only part of the story.\u00a0 The weekly variation associated with this average turned out to be nearly 0.30 inches per week!\u00a0 This means that during the months of June through August, weekly crop water demand at the field varied from less than 0.60 inches to almost 1.20 inches of water.\u00a0 A grower would have to be highly attuned to the daily weather to be able to consistently and accurately predict such wide variations in water demand.\u00a0 Clearly, some easy and reliable means of quantifying crop water demand is required for developing more efficient irrigation practices.\u00a0 In fact, it turns out that crop water demand can be tracked rather easily using weather data.<\/p>\n

Evapotranspiration<\/em> (ET) is a term used by scientists to describe the two closely related processes of water evaporation and plant transpiration that comprise the primary mechanisms by which water moves from the terrestrial environment to the atmosphere.\u00a0 Evapotranspiration represents the crop\u2019s water use.\u00a0 Evapotranspiration is strongly influenced by weather factors such as the amount of overall sunlight, wind speed, air temperature, and relative humidity.\u00a0 All other things being equal, ET rates will be greater on hotter, drier or windier days than on cooler, more humid or calmer days.\u00a0 Specific crop ET rates can be measured directly, but this requires expensive and rather cumbersome research equipment.\u00a0 A quicker and easier way of estimating daily ET rates is based entirely upon the daily weather.\u00a0 These \u201creference<\/em> or potential ET<\/em>\u201d rates, as they are called, are calculated by putting the values of daily weather variables such as total solar flux and maximum and minimum air temperature into a mathematical model known as the Penman-Montieth reference equation. \u00a0Although the derivation of this equation is complex, an easy to use interactive Excel worksheet for determining reference ET and instructions are available from the Wild Blueberry Extension website:<\/p>\n