Good Fruit Grower

April 15

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DNA/RNA fingerprint tests are conducted on the fungi and bacteria in the soil to determine what is happening within the rhizosphere (the area directly around the roots) under the different management systems. Recently, studies have been done to determine potential apple replant disease problems. Mowed grass While vegetation is strongly competitive in peach orchards and in young apple orchards, the mowed grass in this irrigated and fertilized apple orchard only slightly suppressed yield over the long term. "The trees were smaller and less productive early, but they adapted to the competition," Merwin said. Over two decades of observations, yields in the mowed-grass treatment were lower than from the glyphosate- or bark mulch-treated soil, but about equal to those from trees in bare strips treated with preemergence herbicides. "The decomposed mulch at the soil interface was gradually incorporated into the soil and doubled soil organic matter content over the years of treatments." —Ian Merwin "Even though the bark mulch was not mixed into the soil, the decomposed mulch at the soil interface was gradually incorporated into the soil and doubled soil organic matter content over the years of treatments," Merwin said. The preemergence herbicide-treated plots had lower levels of bacteria in the soil, the other three not being significantly different. When levels of fungi in the soils were measured, the grass treatment had higher levels than the others. The bark-mulched soil, in respiration tests, emitted significantly more carbon dioxide, a measure showing elevated microbial activity in the soil. As the experiments go on, Merwin becomes more fascinated with the bark mulch system. It is more expensive to maintain, but the soil becomes more fertile. That can be an advantage, but also a disadvantage if growers need to control tree vigor. "In Europe, they pay growers to sequester carbon," he said. "If they ever do that here, bark mulch is the way to do it." • Glyphosate strips After years of twice-annual treatment with glyphosate, Merwin said, mosses grew on the plots, creating a protective surface blanket that is almost ideal as a ground cover. It protects the soil from erosion, but does not compete with the trees. While the surface tends to be weedy late in the season and during winter, those weeds are like a free cover crop. They are not competitive, and have no significant impact, he said. Preemergence After 15 years had elapsed, the striking result was that the treatment differences became statistically less significant over time. The soil in the preemergence herbicide strips had less phosphorus, less potassium, less manganese, less organic matter, and less cation exchange capacity, but differences were not statistically significant. The preemergence herbicide-treated plots were the most vegetation-free of all the treatments. In the drainage outflow, more nitrate leached from the bare soil than in any of the other systems. Bark mulch Trees in the bark mulch strip treatment became very different as the experiment developed. "After ten years, the trees got larger but not more productive of fruit. The fertility level of the soil rose—maybe too much for apples," Merwin said, adding that it might be an option for growers working on soils with low fertility. That kind of mulch—made of an abundant local resource from hardwood sawmills in northern New York State— created a truly different soil, which contained two to three times the levels of phosphorus and twice the calcium of the others, and almost twice the organic matter. Organic matter content rose to 8.6 percent. The pH was higher—7.2 compared to 6.4 in the other plots—and the cation exchange capacity was 25 percent higher. www.goodfruit.com UNIQUE CHEMISTRY FOR STANDOUT PERFORMANCE. When it comes to protecting your orchard, Delegate® WG insecticide stands alone. Deleg offers proven egate , performance against codling moth — along with other tough pests like Oriental fruit mot , l th, leafrollers, spotted wing drosophila, plum curculio and apple maggot. What sets it apart? A mode of action so unique, it's the only one in its class. That makes Delegate key to any spray rotation program for pome and stone fruit, cranberries, blueberries or grapes. www.DelegateInsecticide.com 800-258-3033 ® Trademark of The Dow Chemical Company ("Dow") or an affiliated company of Dow Always read and follow label directions. ©2013 Dow AgroSciences LLC L38-359-010 (01/13) BR 010-34175 DAAGDELE2059 GOOD FRUIT GROWER April 15, 2013 13

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