A question that is often asked is, "Can we seed winter wheat into pea stubble?" The standard answer is "Nope." Does that stop producers from seeding winter wheat into pea stubble? Nope. So, Ducks Unlimited Canada decided some research needed to be conducted that would evaluate the suitability of various stubbles for winter wheat production.
Drs. Byron Irvine and Doug Derksen, from the Ag Canada Research Centre at Brandon, undertook the project 3 years ago. The objectives of the research were to study the effect various stubbles had on winter wheat yields and to evaluate the impact of weeds on winter wheat yields.
In order to reduce risk to the winter wheat seedlings, the winter wheat must be seeded early in the fall. That means the field in which it's to be seeded must be harvested early. Traditionally, winter wheat is seeded into barley and spring seeded canola stubbles. With the introduction of fall seeded canola and its potential to be in the bin one to two weeks earlier than spring seeded canola, it was included in the rotation. Since peas are often the first crop harvested, they, too, were included in the rotation.
Two different rotations were designed and each was established at 2 sites, each with a different soil type and different weed populations. The first rotation was pulse-canola-cereal; the second was pulse-cereal-canola. Winter wheat yields have done well in all cases. The peas have averaged 40-50 bu/ac which Dr. Irvine describes as respectable for the area. The dormant seeded or fall seeded canola has not fared so well.
In the 3 years of the project, the dormant seeded canola has run into some real problems. In two of the three falls, the weather was wet and warm into mid-November enabling the canola to germinate and begin growth. In the third fall, 4 inches of rain were received just before freeze-up. As Dr. Irvine mused, "Is this just a run of bad luck or is dormant seeded canola just not suited to Manitoba?"
On the clay-loam site, the winter wheat out-yielded the spring wheat by 50% but on the loam site, winter wheat yielded only 25% better than the spring wheat. In describing the differences in yield, Dr. Irvine said it isn't because the winter wheat is so great, it's just that the spring wheat is such a poor competitor against the weeds. The number of weeds, in winter wheat, at the loam site was almost 10 times the number at the clay-loam site in some years. As Dr. Irvine points out, no two fields are alike. While the clay-loam site had many more weeds, most of them were broad leafs so they were relatively easy to control in the winter wheat. No wild oat herbicide was applied at either site on the winter wheat.
In terms of pea following winter wheat and spring wheat, Dr. Irvine indicated that the pea yields were just about identical on both stubbles.
So what does it all mean? After only 3 years of study, it is still unclear if it is feasible to routinely plant winter wheat and pea stubble. The researchers are still very much interested in the effect of pea stubble on winter survivability of winter wheat. They and researchers at Melfort and Indian Head, with the help of Ducks Unlimited Canada, will be expanding the scope of the study to develop a more accurate indication of the amount of snow trapped and retained by the pea stubble. Other crops, such as silage and alfalfa, may also produce stubble suitable for planting winter wheat in a timely manner if snow can be managed effectively. No doubt producers will continue to seed winter wheat into peas, especially in years where the harvest is late. While this practice will likely increase the risk of stand loss due to low snow cover, it remains to be seen if the reward is greater than the risk. In just a few years, Drs. Irvine, Derksen, Lafond and Kutcher will be able to provide a better estimate of the risk associated with that practice.
For more information on this project, contact Dr. Byron Irvine at (204) 726-7650 or birvine@em.agr.ca or Dr. Doug Derksen at (204) 726-7650 or derksen@em.agr.ca