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 One such tip is the importance of keeping pump suction screens, filters, PVC and drip lines free of unwanted materials by flushing regularly and treating with chemicals as needed.Stettler Supply Co. salesman Val Tancredi, who likes to use analogies when describing how drip systems work, said that uncontrolled growth of bacteria and algae is similar to the I-5 freeway on a late Saturday morning when both the Beavers and Ducks are playing at home. “Everything slows up, pretty soon you’re at a standstill. You have a crash. And then you’re plugged.” Tancredi said that all surface water, especially ponds, is much more prone to algae bloom and other microbe buildups than well water. Regardless of the water source, 1 ppm residual chlorine as an oxidizing agent is enough to control bacteria and algae, which virtually “disappear” after treatment. Another important facet of drip irrigation is the scheduling of water applications to avoid plant stress, especially under-watering, Tancredi said. When the latter is allowed to happen past the point where the plant can pull water from the soil through the roots and up the xylem, the damage is often irreversible, Tancredi said. “It may take days to come out of that damage, even if you correct for it immediately.” Under-irrigating with a drip system on heavy clay soils will also cause cracks in the ground, which can’t be “jumped,” as is the case with overhead irrigation, when watering is resumed. Because most blueberries are mounded to provide good drainage, overwatering is not as big of an issue, Tancredi said. However, overwatering raised blueberry beds will contribute to the waste of not only water and leeched agro-chemicals but also time and pump power. Tancredi recommends the installation of moisture sensors at 6-inch to 12-inch intervals in the soil that allow the grower to monitor the amount of water from the crop's feeder roots down to the anchor roots. Another advantage of drip is that these systems are much more energy efficient and run at a much lower water pressure vs. overhead: 20 psi vs. 50 psi. Drip systems are typically 90-95 percent efficient in the application of water where overhead sprinkler systems are 75 percent efficient. Tancredi is no fan of sawdust as mulch for raised beds blueberries. “It’s a triple loser.” First off, “there is no cheap sawdust available.” Secondly, sawdust separates soil particles, thus causing the soil to lose its wicking action. “If you’re going to stay with sawdust, you’d better use overhead sprinklers; drip isn’t going to work.” Finally, decomposing sawdust “demands nitrogen as it decomposes.” While drip system components are engineered for +20 year life cycle a disadvantage of ground level irrigation is “tractor blight” and critter damage, which, fortunately, is easily repaired with new hose and couplings. Unlike overhead sprinkler irrigation, drip systems provide no protection from frost or heat protection by cooling. Drip systems may be complemented with an overhead micro-sprinkler system positioned above the crop to accomplish that. Overhead micro-sprinklers can also be used to disperse chemicals, such as malathion, to control spotted wing Drosophila. Drip irrigation is not difficult, but it is different from traditional sprinkler irrigation. The grower must operate the system to maintain a desired level of soil moisture to eliminate plant stress as a limiting factor to production. The Willamette Valley’s loamy soils do best with the total daily run time applied in two shots, keeping the plant hydrated without deoxygenating the root zone. In heavier soils growers may irrigate alternately or every third day. |
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