Issue link: http://read.dmtmag.com/i/60127
Irrigation system PROS and CONS E Irrigation ffective irrigation influences the entire growth process of an orchard—the rate of tree growth, utilization of nutrients, and fruit growth and yields. But no sin- gle irrigation system is the answer for everyone, says Carlos Pacheco, an irriga- tion system designer with Growers Supply Company, Ltd., in British Columbia, Canada. The best system for a given orchard No single system is right for everyone. depends on the types of trees, tree spac- ing, and the amount the grower can afford to spend, Pacheco said dur- ing the B.C. Tree Fruit Horticultural Symposium in March. by Geraldine Warner Drip Drip irrigation is the most efficient type of system. It is typically 95 percent efficient, meaning that 95 percent of the water goes where it's needed. Most of the drip irrigation tubing is pressure compen- sated, so that even if a 100-foot long tube is on a slope, the first emitter will put down as much water as the last one. Drip tubing comes with a variety of • Frequent applications and shorter irrigation cycles are required because of the limited wetting zone. • Animals, including coyotes, like to chew on drip irrigation systems. Microsprinklers Microsprinklers are about 85 percent emitter spacings and flow rates. It is often purchased in 1,000-foot coils. Flow rates can be anywhere from 0.3 to 2.0 gallons per hour per emitter, and emitter spacings can range from 12 to 60 inches. The cost is from $125 to $200 per roll, depending on the spacing of the emitters. The closer the emitters, the more expensive it will be, Pacheco said. Advantages of drip include: • Precise application of water • Less incidence of disease • Ability to apply fertilizers through the irrigation lines directly to the trees • Small wetted area minimizes the need for weed control • Can increase the temperature in the orchard, advancing the ripening of apples and grapes • People can work in the orchard on pruning or harvesting while the drip system is running. • Suited to automation Disadvantages of a drip system include: • More susceptible than a sprinkler system to clogging, unless the system includes a good water filter • Emitters and laterals are easily damaged by workers when they're pruning or harvesting or by tractors • Requires intensive management • Effectiveness of water application is difficult to assess. The best way is to dig a hole and look at the soil. 26 APRIL 1, 2012 GOOD FRUIT GROWER One of the advantages of a drip system is less need for weed control because of the smaller wetted area. efficient. As water is thrown out into the atmosphere, some of the water evapo- rates. Because more water is applied more quickly, some of the water will be trans- ported away. Microspinklers have spinning mecha- nisms inside that throw out water in an even pattern. A large variety of micro-sprinklers is available. The flow rates are from 8 to 70 gallons per hour, and water is applied in a radius of 5 to 16 feet. Microsprinklers cost between $1.25 and $2.00 each. Microjets are about 80 percent efficient. They don't have a spinning action to give an even throw. Water comes out of the orifice, reflects off the back plate, and is thrown out. Notches on the back plate determine the cov- erage pattern. Because there are no spinning mecha- nisms, they are a little cheaper than microsprinklers, though Pacheco said he believes they are less efficient. Advantages of microsprinklers include: • Low pumping costs because of low water pressure • Creates a larger wetted area, which keeps the dust down • Efficient use of water • Produces a wider green belt than the drip Disadvantages include: • Higher relative humidity, increasing the risk of disease • Filtration is required. www.goodfruit.com