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Wet conditions hurt soybean standsBy Jennifer Bremer Soybean stands are the biggest challenge that farmers face in 2007 according to Iowa State University soybean extension agronomist Palle Pedersen. "The problem is that we have had too much rain. soybeans don't like the wet conditions," he said to a group of attendees at a Bayer CropScience Field Day at Gustafson Research Farm near Redfield, Iowa on June 6. When the soybeans emerged they turned yellow and were struggling to survive, which he said indicates a problem with the root systems. He said the last year that was similar to this one was 2003, when it was wet early and the turned off dry, which lead to problems with soybean aphids. "If the stand does not improve, we could see a significant yield loss this year," Pedersen said. "Ninety-five percent of yield loss in soybeans in Iowa is from below the ground. This can be mostly related to disease and nematodes." All producers must realize that each field needs to be managed separately. The factors that need to be taken into consideration in each field include the soybean cultivar, soil type, soil fertility, rotational crop history, tillage practice, weed and insect management, seedling management, seed treatment and climate. Seed treatments have changed a lot in the past 10 years. Pedersen said 10 years ago only two percent of the seed would be treated and now 40 percent of seed is treated. While the treatment can help prevent some seed problems there are other factors that affect soybeans including problems with seed quality, planters, or weather. Pedersen said the damp conditions have also led to some root rot in soybean fields. "Diseases prefer cool, damp conditions and root health is very important and management of the seed bed is key in preventing diseases," he said. The root diseases are hard to treat so Pedersen suggested being sure the seedbed is in proper condition at planting time. The soil should be dry and warm. The yield potential is increased dramatically if conditions are ideal and under those type of conditions the plant is less vulnerable for other problems too. He also suggested a lower seeding rate for a better stand. "At a higher seeding rate there is too much competition and a higher mortality rate," he said. Another suggestion for a better stand is planting in 15-inch rows. He admitted that 30-inch rows look good early, but less mortality is seen in 15-inch rows. Seed treatments are a good insurance against diseases. Research continues on seed treatments and improvements continue as well. Insect problems are some of the easiest to manage, according to Pedersen. Early planting can increase yield potentials, but can also increase the number of bean leaf beetles feasting on the plants. "Having a good established stand is the most important factor in raising high yielding soybeans," he said. "Planting at the optimum time and at the optimum rate will help establish the root system that is so important in a healthy soybean plant." Jennifer Bremer can be reached by phone at 641-938-2342 or by e-mail at jbremermaj@hotmail.com.
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