Good Fruit Grower

February 15

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Irrigation ���Our research found that the link of delayed bud break and vine development to dry winters is real.��� ���Our research found that the link of delayed bud break and vine development to dry winters is real,��� Keller said. In their study, sap flow and composition seemed little affected by soil moisture and soil type when moisture levels were greater than the permanent wilting point. However, bleeding and bud break were not possible when soil moisture was near permanent wilting point. Soil moisture levels 2 percent above permanent wilting point resulted in delayed bud break. Subsequent shoot growth and fruit set increased up to soil moisture levels that were 4 percent below field capacity. Low soil moisture also resulted in abortion of clusters, decreased percentage of fruit set, and increased the incidence and severity of inflorescence necrosis. In both soil types, variation in the soil moisture accounted for about 75 percent of the variation in shoot and internode length, leaf number and size, and total leaf area. The scientists also found that rapid sap flow was correlated with rapid shoot growth. ���We confirmed that after dry winters, vines may be unable to generate adequate root pressure, which leads to malfunction of their hydraulic system,��� Keller reported. In essence, no, or low, bleeding leads to delayed and uneven bud break, stunted shoot growth, slow canopy establishment, aborted flowers, and poor fruit set, he said. Poor shoot growth leads to low yields and, ultimately, to reduced profits. Early season irrigation While a lack of bleeding indicates dry soil and ���Markus Keller potential problems, the remedy is fairly easy���irrigate early. Keller advises growers to know their soil types and water-holding capacity. Loamy soils have higher waterholding capacity but require higher soil moisture levels than sandy soils for grapevine bleeding. This means that even the best soil moisture measurements are useless without knowledge of the soil���s moisture profile. Therefore, growers should also determine the field capacity and permanent wilting point for each soil type. ���Measure soil moisture before bud break and irrigate if the soil is 4 percent below field capacity,��� he recommends. ���Also, monitor vine growth and irrigate if you don���t see bleeding or bud swell despite rising temperatures.��� Early irrigation���filling the top three feet of the soil profile to 3 percent below field capacity���may prevent dieback of young vines and severe crop loss in mature vines. Funding for the research was received through the U.S. Department of Agriculture���s Northwest Center for Small Fruits Research and the Wine Advisory Board/Washington State University. ��� NEW HOLLAND MODIFIED T4040V w/cab Narrowest & Lowest Pro���le Tractor on the Market Call for Details. I saved Burrow big $$ a t s Tracto You wil l too! r. GOOD FRUIT GROWER FEBRUARY 15, 2013 31

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