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Double Cropping Soybeans

Winter wheat harvest is now well underway. With higher commodity prices and lots of soil moisture there is renewed interest in double cropping soybeans after wheat. A number of early harvested wheat fields have already been seeded to soybeans. Double cropping is not generally practiced in Ontario, because our growing season is too short and there is often insufficient moisture in mid-summer to establish the crop. This year moisture is adequate in most regions. Double cropping soybeans has been attempted with limited success in Essex and Kent counties when wheat came off early. This year the wheat has not come off early so the likelihood of success is relatively small unless September weather ends up being unusually warm. In Southwestern Ontario it's possible to achieve a 20-30 bu/ac crop if planting on July 1st and everything else going right. However, the 30 bu/acre yield potential on July 1st drops approximately 1 bu/ac/day. Attempting to double crop after July 15th has little chance of success unless there is a very long fall. If double cropping is attempted consider the following points:

• The low yield potential of such a late planted crop means that input costs must be kept at a minimum. The keys to a successful soybean double crop are adequate moisture and a long, open fall.
• Harvest wheat as early as possible. Every day counts. Spread chaff and straw evenly. Aim for an 8- 12" stubble height - this helps to ensure stem elongation for higher bottom pod height without impeding early growth.
• If there is no moisture to a depth of 2.5 inches, plant at 1.5 inches and wait for rain. Success will be rain dependent. If conditions are extremely dry, do not attempt to double crop. Most double crop failures can be attributed to beans being planted into dry conditions.
• In fields where soybean diseases are a major problem, double-cropping will make those problems worse. Consider the rotational implications.
• Control weeds in wheat, either before planting or before emergence of soybeans. Also, plan the herbicide program to control volunteer wheat.
• Plant in narrow rows with high seeding rates. Aim for 250,000 seeds/acre in 7.5 inch rows. The quicker a full canopy is achieved the better.
• Choose tall, small seeded varieties;
  • In greater than 2800 CHU areas choose a
    variety close to full maturity
  • In areas with less than 2800 CHU's choose a variety with slightly lower CHU's than full season. Choosing very short day maturities (<2500) is not a good option. Short season soybeans planted very late will not yield well because the plants will not grow tall enough. Full season beans will provide greater height and better pod set. Due to the photo period effect a full season bean will not mature significantly later than a short day bean.
• There is no crop insurance for such a late planted crop