Good Fruit Grower

December 2011

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Cover crop choice takes time and research Expect several years of trial and error to find best crop. by Geraldine Warner grower has on-farm trials in which he planted different cover crops between orchard rows. The cover crops are cut during the growing season with a special mower that directs the clippings into the tree rows to form a mulch. The primary goal is have the legumes provide nitrogen A The ladino clover cover crop thrived for the first two years but has begun to decline. for biomass grown in the alley that is then mowed and blown onto the tree row to form a thin mulch layer, orchard manager Amos Kukes reported during a visit to the orchard this spring organized by the Natural Resources Conservation Service. The mulch can improve tree growth, suppress weeds, add organic matter to the soil, and conserve water. Morgan planted his first trial in May 2008, in a mature orchard, seeding directly into the grass drive alley with a pple growers who are experimenting with grow- ing a nitrogen source in the alleys of their orchards are finding that not all cover crops are equal. Warren Morgan, a Quincy, Washington, four-foot-wide no-till drill. He planted alfalfa, jumbo ladino clover, kura clover, and birdsfoot trefoil, all peren- nial legumes. In some areas, the alleys were sprayed with herbicide before seeding to reduce the competition from weeds. Growth was affected by the shade that the trees cast on the alleys and by tractor traffic, which some plants withstood better than others. David Granatstein, sustainable agriculture specialist with Washington State University, said it takes a number of years to figure out the benefits and drawbacks of the various types of cover crops, and there's a lack of research in this area. "What we see in year one or two may be really different than in years three, four, and five," he said. Biomass • The alfalfa was quick to grow and produced the greatest amount of biomass of all the cover crops. The alfalfa tended to grow tall and spindly (probably due to shade), and might work well mixed with other shorter- growing crops, such as clover, to provide a two-tier cover crop with even more biomass, Granatstein suggested. Alfalfa can serve as habitat for pests such as thrips and lygus bugs, but if rows are mowed alternately, the pests generally move from one row to the next, rather than into the trees. • The ladino clover produced a good, weed-free stand INC. Representing Over 30 Leading Nurseries in the U.S. and Europe 1-800-421-4001 CALL US FIRST FOR THE LARGEST SELECTION OF TREES AND ROOTSTOCKS AVAILABLE 2013 & 2014 CONTRACTS STILL AVAILABLE FOR CHERRIES & APPLES Tel: 503-538-2131 Fax: 503-538-7616 54 DECEMBER 2011 GOOD FRUIT GROWER FREE early on, but started to decline by year three, possibly because rodents were eating it. Although some cover crops provide habitat for beneficial insects, they can also attract pests, and rodents are a big concern, Granatstein said. • The kura clover was the slowest to become estab- lished, and was barely visible the first year. However, by year three, it had dramatically increased its growth and started to move out towards the tree rows. "Can we wait that long?" Granatstein wondered. "Or can we plant it with something else as a nurse crop?" A drawback of kura is that the seed is not that easy to find. Granatstein said he got the idea of planting it from experiments done in the Midwest in field crops and obtained the seed from Wisconsin. Kura also seemed attractive to rodents. • The trefoil takes a little longer to get growing in the spring, but it equaled alfalfa in biomass by year three. The seed is easy to obtain. There are a number of varieties, but good information on which ones are better suited to an orchard setting is lacking. Nitrogen The mulch under the trees should be light and actively decomposing, Granatstein said. He sampled the cover crops and soil in 2009 and 2010 to assess the nitrogen contribution of the plant material. The alfalfa leaf tissue contained 4.1 percent nitrogen, compared with 3.9 for the ladino, 3.4 for the trefoil, 3.1 for the kura, and 2.3 for grass. The alfalfa also had a relatively low carbon-to-nitrogen ratio of 10.6, making it quicker to decompose. Ladino clover had a ratio of 11.2, trefoil 13.0, kura clover 14.9, and grass 18.8. Granatstein estimates that the alfalfa, which produced close to 3,000 pounds of biomass per acre over the first three years of the trial, was providing about 33 pounds per acre of available nitrogen to the trees each year. Services are to growers New Item: Windbreak Hybrid Willow [Stonewall™] Available geraldine warner

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