Issue link: http://read.dmtmag.com/i/291333
22 APRIL 15, 2014 GOOD FRUIT GROWER Pay attention to the SOIL W hen Mike Omeg joined his parents on the family orchard in The Dalles, Oregon, it struck him that a tremendous amount of emphasis was being placed on managing tree canopies, but much less on what was happening below ground. Mike and his parents, Mel and Linda, were trying new training sys- tems and new varieties. Trees were spaced as close as 8 feet apart with 14 feet between rows—densities that his grandparents could never have imagined. Omeg said growers tend to think of soil as just something to hold the trees up, and he realized that by not paying attention to the soil, he and his family were missing an opportunity for better income through better management. Soil is an amazing living ecosystem, Omeg said during a presentation at the Washing- ton State Horticultural Association's convention last December. It is full of nutrients, but almost all of them are unobtainable by the tree. It takes microorganisms in the soil to make them available to the tree roots. Many growers still maintain a barren, weedfree strip in their orchard rows, and then they plant another monoculture crop—grass—in the alleys, he noted. "This is, biologically speaking, kind of a barren landscape. We can do better by increasing the amount of biology in our soil by putting some diversity into the system." Mulch During a trip to Australia about 15 years ago, Omeg and his parents saw how cherry growers in the Adelaide area were growing trees on about eight inches of soil on top of granite. They would berm up the soil in the planting rows and put a straw mulch on top. While Australians have plentiful land, water is scarce and the straw helped conserve water. The Omegs had plantings that were being irrigated from wells. When the water dropped off, they started using straw mulch. "What we quickly found was we had a really good response in our trees," Omeg said. "It had to do with improvements in soil quality. Mulches of various kinds provide a tremendous benefit." It's important to monitor the effect of new practices and to keep an untreated check for comparison, Omeg said. He prefers to gather as much data as possible himself rather than send samples to a lab and wait for the results. To assess the physical condition of the soil, he uses a penetrometer—a metal shaft with a spring in it—that is pushed into the soil to measure resistance. "That gives me an idea of how I'm improving soil tilth, which is a really important thing," he said. Soil with good tilth allows movement of water and air in the soil. "The fluffier your soil is, the better." He also applies soil stimulants to kick-start the benefits of the mulch and stimulate biological activity in the soil. "I'm very impatient," he said. "I don't want to wait 15 years to see the benefits. I want to speed up the natural biological processes that are occurring and get them moving faster." Soil respiration Omeg uses the Solvita test to measure the respiration of the soil. The rate of carbon dioxide release is an indication of the microbial activity and is considered an indicator of soil health. The rapid test involves placing a small (but precise) amount of soil in a jar with water with a small probe, or "sign" as Omeg calls it, which turns color based on the carbon dioxide level. His goal is to push respiration to the maximum, though he's not concerned about whether the biological activity involves bacteria, fungi, or protozoa. "I'm going to say I want as many soil organisms as possible so all that microbial activity is breaking down soil nutrients because the tree likes to eat recycled nutrients," he said. A greater focus on the soil can help improve orchard performance, an Oregon cherry grower says. by Geraldine Warner SOILS & Weed Control Mike Omeg plants a seed mix, including the daikon tillage radish, as a cover crop to improve water and air penetration and stimulate biological activity in the soil.