Purdue News
Purdue News
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March 9, 2001 Soybean seed good, but don't plant too soonWEST LAFAYETTE, Ind. – Seed quality for this year's soybean crop is considerably better than last; however, a Purdue University agronomist says supplies are going to be tight in Indiana. In Iowa and Nebraska, late, dry weather conditions last fall produced poor seed quality. "Because of this problem, supplies of more popular varieties will be tight since seed from the eastern Corn Belt will be needed to fill this shortfall," says Ellsworth Christmas, Purdue Cooperative Extension Service agronomist. Wet conditions in parts of the eastern Corn Belt at harvest last year caused some seed to develop pod and stem blight. This seed can be identified and treated with a fungicide before planting to prevent rotting prior to germination, says Christmas. Early spring weather in recent years has moved some farmers into the field sooner. However, Christmas says soybean physiology and growth habits need to be taken into account. "When considering the soybean plant and Indiana's climate, particularly soil temperature, the optimum planting date most years is between May 5 and May 20," says Christmas. The ideal soil temperature at planting is 65-70 degrees. Christmas says seed will begin to germinate when the soil temperature rises above 50 degrees; however, germination is slow below 60 degrees, and this can lead to problems. "Slow germination places the seed and plant under significant stress, resulting in soilborne disease, poor stands and seed pods that are close to the soil because of shortened internodes, or the distance between two nodes," says Christmas. The warm germination test of soybean seed this year, used to determine the seed's potential to develop a stand, is averaging in the range of 85 percent to 87 percent prior to cleaning. Checking germination and the number of seeds per pound before calibrating drills and planters can prevent overplanting and save farmers money. As spring approaches, farmers also can start thinking about the use of soybean inoculants or the addition of nitrogen-fixing bacteria to improve yields. Within the last seven years, new inoculants used to increase the roots' rhizobium population have been tested in Indiana on higher yielding soybeans. Average soybean yields increased more than a bushel an acre over the test period. "Using the new inoculants costs approximately $2.50 to $3 per acre and would result in a profitable production practice," says Christmas. Purdue experts have been looking at seed and inoculants but also have focused part of their research on row width and drill usage. With support from the Indiana Soybean Board, Christmas is evaluating three different row spacings in the northern, central and southern parts of the state. During the 2000 growing season, the yield response of drills over planters in soybean production showed significant yield results, says Christmas. "Seven and one-half-inch drilled rows yielded over four bushels per acre higher than 30-inch planted rows and two bushels better than 15-inch planted rows," says Christmas. "If a farmer is considering an increase in row spacing from seven and one-half-inch rows to 15, they can expect a two bushel yield reduction." Source: Ellsworth Christmas, (765) 494-6373, echristm@purdue.edu Writer: Jennifer Doup, (765) 494-6682, jdoup@aes.purdue.edu Purdue News Service: (765) 494-2096; purduenews@purdue.edu Related Web site:
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