Soybean Growers continued from page 1 to be quite effective in controlling some of the main problem weeds in Pennsylvania, such as johnsongrass and Canada thistle.      Curran and M.S. candidate Wade Esbenshade are investigating methods of controlling burcucumber, an increasingly troublesome weed, in soybeans. The Pennsylvania Soybean Promotion Board funded a study on the effects of row spacing and tillage on burcucumber control. "The results show that row spacing has little effect on burcucumber control and that establishment of the weed is much reduced in no-till fields," says Curran. "This probably occurs because the seeds need sufficient seed-to-soil contact to germinate, which they don't get in no-till fields. So the message to farmers is to use no-till in fields where burcucumber is prevalent." In fact, the research shows that farmers gain an advantage using a post-emergent herbicide (Roundup in Roundup Ready or Synchrony in STS soybeans) in a no-till field because a single in-crop application of pesticide usually will suffice for the whole growing season.      Last year, the Pennsylvania Soybean Promotion Board funded a cooperative effort between Curran and Peggy Wagoner at the Rodale Institute to identify the most effective methods of weed control in organically grown food-grade soybeans. Currently, this is one of the biggest limitations to growing organic soybeans. Curran and Wagoner are studying the influence of planting date on the amounts of weeds present. "About 80 percent of weeds in Pennsylvania germinate	between May 1 and June 15," says Curran. "The initial temptation may be simply to plant soybeans later, but the yield potential decreases the later in the growing season the seeds are sown. Our research indicates that in central Pennsylvania, June 1 is about the latest planting date that will provide a solid yield while still reducing the amount of weeds present."      Curran and Wagoner are also examining the optimum schedule for weed removal from organic soybeans. Other than cultural control techniques such as changing planting date and crop rotation, mechanical control, consisting of rotary hoeing and cultivation, is really the only options for these fields. This is usually first done shortly after planting and repeated throughout the growing season. Curran and Wagoner have set up a yield comparison experiment in which each test plot receives up to four rotary hoeings and mechanical cultivations per growing season. Summer '99 was the first field season for that experiment so results are not yet available.      Food-grade organic soybeans would be an attractive market if some of the weed control issues could be solved. Soybeans of this grade sold for $18 to $22 per bushel in 1998 and about $15 per bushel this year. Typical yields can be greater than 40 bushels per acre if good weed control is achieved. Conventionally grown soybeans used for oil or animal feed sold for less than $4 per bushel, and food-grade conventional beans sold for about $6 per bushel. Food-grade beans contain more protein than conventional beans, but yields may be slightly lower.	Because soybeans are a nitrogen-fixing crop, farmers generally do not apply nitrogen fertilizer to these fields. However, Doug Beegle, professor of agronomy, and John Yocum are running an experiment to determine whether soybean plants that receive an application of nitrogen just prior to the reproductive phase of the life cycle (about four weeks after planting) produced higher yields. "The theory is that during this period, the plants may need nitrogen more quickly than they can fix it," says Beegle. He and Yocum ran the test both at the Agronomy farm near State College and at Landisville in Lancaster County. The experiment examined the influence of till versus no-till and early (around May 1) vs. late (late May / early June) planting on the effectiveness of the N application. The first season of data showed that the N application had no effect on soybean yield, regardless of the planting date or tillage status. However, as expected, the yield from the early planting was higher.      Finally, we have already featured research by Barbara Pennypacker, associate professor of agronomy, on methods of controlling soybean white mold (Focus on Research, Winter 1999). The department will continue to strive toward the goals of determining optimal management conditions for crops grown in Pennsylvania and getting word out to farmers.      Hatley can be reached by e-mail at oeh2@psu.edu and by phone at (814) 863-1013. Yocum's e-mail address is jyocum@psu.edu and his phone number is (717) 653-4728. Curran is at wsc2@psu.edu, (814) 863-1014 and Beegle is at dbb@psu.edu, (814) 863-1016.