When 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 systems 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.
“We can do better by increasing the amount of biology in our soil by putting some diversity into the system.”
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 Washington 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.”
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.”
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.
Many fruit growers have meters to measure the Brix level of their fruit, but Omeg also measures the Brix level of leaf sap, which he says is an easy and cheap way to assess the health of the foliage.
“The job of leaves is to produce sugars, and the healthier a tree is, and the healthier the leaves on the tree, the more sugars they’re producing,” he said.
He also has a Firmtech machine to measure the size and firmness of cherries, which are the two most important fruit quality parameters. However, the most important sampling growers do is with their own eyes, he said. It’s easy to get busy and forget to check the results if you put on a new spray or a different rate of fertilizer, so Omeg sets an alarm on his phone calendar to remind him.
He’s tried many different soil stimulants from as far away as Maine or the Great Lakes and found dramatic differences in how they perform. A locally manufactured liquid fish hydrolysate from Pacific Gro, LLC, has been one of the most beneficial.
“A high oil-content product seems to work better for me on my farm in my growing conditions,” he said, noting that salmon-based products work well. A liquid crab hydrolysate from Pacific Gro made from fish and crab shells provides a good boost of calcium, which is one of the key elements in fruit firmness.
These treatments work well in weak blocks, he stressed, but he does not see the benefit in blocks that are already doing well.
In a trial he conducted with Skeena, the fish fertilizer treatment significantly increased fruit size, with 25 percent of the cherries treated with the fish product being 8½ row, compared with 17 percent of the control cherries. The proportion of 9-row cherries also increased. Omeg said the difference might have been enough for his packer to do an 8½-row pack.
Compaction of soil in the drive row caused by tractors limits the ability of tree roots to grow in that area. Omeg said he uses an AerWay cultivator to aerate the soil. Its blades make divots about eight inches deep, providing channels for water, air, and fertilizer. He usually applies fertilizer immediately after using the tool.
Omeg’s been planting a seed mix including daikon tillage radish, instead of managing a permanent seed cover crop, in order to stimulate biological activity. The radish dies in the winter, opening up large channels for water and air infiltration and allowing other species to come in.
“The more species of plants you have in your cover crop, the better the response is going to be because biological diversity is increased in the soil,” he said.
Omeg hopes to collaborate with Lynn Long, Oregon State University extension educator in The Dalles, on a trial to look at the benefits to tilling the cover crop biomass into the soil versus leaving it on top. He uses a rotary spader to incorporate the green manure, rather than a rotary tiller, to avoid soil compaction.
Omeg used to write off compost as being too expensive, but a couple of years ago he decided he should try it out. He concluded that, like fish products, it had little effect on healthy blocks but was worth the high cost of application in blocks that had been struggling. After only two years, soil tilth and fruit size and firmness were improving.
In his trials in a young Regina orchard, he tested compost applied at rates of a quarter of an inch, a half of an inch, and one inch in depth and found an improvement in fruit size in the half-inch treatment compared with a quarter-inch, but no further improvement by going up to an inch. •