Issue No. 22, Article 7/September 23, 2011
Fall Seeding Issues
With corn and soybean harvest getting underway in much of the southern part of the state, it shouldn't be too difficult to get wheat seeded close to the best time in that part of Illinois. The optimal time to plant wheat ranges from just past mid-September in the northern edge of Illinois to just before mid-October at the southern tip. In the major growing area of southwestern Illinois, wheat should be planted the second week of October. Planting a few days before or after that time is not of concern, but planting 10 days to two (or more) weeks early is not best practice.
Harvest has started very slowly in northern Illinois, however, so getting wheat planted on time there will be a challenge unless it can follow something other than corn for grain or soybean. Planting a week or two late usually doesn't produce a big penalty, but it can lower yields in years when cold weather comes early.
In fall 2010 the wheat crop was planted on time but got off to a slow start due to very dry soils at planting. This may occur again this year, as some areas continue to be very dry. While wheat seed does not need to take up a lot of water to germinate, it does need some. There may be enough water present in soils following harvest, but you need to be careful to get the seed placed so it can take up what water is there. No-till can help, but not if the soil is powder-dry at the depth of seed placement. It's a little risky, but if there is more soil moisture several inches deep than at the surface, some tillage might help bring up enough to allow the seed to germinate. No matter what, make sure the seed is placed uniformly deep and that the planting process produces good seed-soil contact. That can be more difficult in cornstalks than in soybean residue, but either can work as a preceding crop.
Wheat seeding rate trials in recent years have shown that rates should be between 30 and 40 seeds per square foot. The higher number may be appropriate for later planting or in cases, such as planting into very dry soils, where emergence might be late. The point is that late emergence usually lowers the number of tillers per plant, so more plants can help bring shoot numbers up.
One question that has come up recently is about the possibility of planting wheat in 15-inch rows, using a split-row planter. It seems that some see this as a way to convince farmers who no longer have a drill to plant wheat, and some have promoted it as producing higher yields, or maybe equal yields with lower seeding rates. At Ohio State University they have even conducted wheat variety trails at both spacings; there, they grow much of their wheat farther north and sometimes plant soybeans as a relay crop between wheat rows during wheat growth.
I consider 15-inch wheat rows to be roughly equivalent to 40-inch corn rows. That means that we can often get good yields, but under the best conditions we will not maximize yields in the wider rows. I would exhaust every possibility for getting a wheat drill to use before I would consider modifying a set of vacuum plates to use to plant wheat.
There has been some recent publicity about an effort to establish pennycress (Thlaspi arvense) in the fall to be used to produce oil for biodiesel. Pennycress, a member of the mustard family, is essentially a winter annual weed at this point. Some breeding work is underway. Pennycress is probably best seeded in late August or early September, and as a winter annual it produces a plant that stays small into the winter, then bolts in the spring. We have had it in the field the past two years and have not been overwhelmed by the yields, which have usually been less than 1,000 lb per acre. There's not a well-established market for this crop, at least nearby.
Canola is another crop that is seeded in the fall in regions like Illinois where the winter is not too severe. The crop is used mostly for edible oil and has had a small resurgence of interest in recent years. It is also a member of the mustard family, but unlike pennycress it is well developed as a crop. Issues in past trials have included diseases and inadequate winterhardiness. You can expect to harvest canola at or a little after the time that winter wheat is harvested. It can also be difficult to find a market nearby for this crop.--Emerson Nafziger