If you are planting oats or other small grain alone, without a nurse crop, "plant the small grains as soon as soil conditions permit," advises Brian Lang, Iowa State University Extension crop specialist at Decorah, Iowa. Preference is to seed these crop before mid-April. After mid-April, we lose an average of 10% yield per week, and after May 1 about 15% per week, he says.
In general, the earlier the small grains are planted, the better the test weight and yield. This is largely due to flowering occurring prior to the hot part of summer. Small grains germinate just a few degrees above freezing, but development is slow. If plants develop leaves above ground, the leaves may be frosted, but the growing point is protected below.
However, if soil temperatures fall into the 20s after plants have germinated, significant damage can occur. Seeding rates should be about 30 seeds per square foot, says Lang. Thatâ€™s about 3 bushels per acre for oats and 2 bushels per acre for barley. Adjust the rate upwards based on percent germination and planting conditions. For a reference, see ISU Extension publication PM-1497, Small Grain Production for Iowa www.extension.iastate/edu/Publications/PM1497.pdf. (This link requires your computer to have a free copy of Adobe Acrobat Reader. Click HERE for a copy.)
Planting small grains with alfalfa
While small grains can be planted in March, this is considered too risky for alfalfa, says Lang. Alfalfa germinates at about 48 degrees F. Soil temperatures in March are in the mid-30s or less, but that is for a 4-inch depth. Alfalfa is planted in the upper one-half inch of soil.
Current daytime temperatures could cause the upper inch of soil to reach temperatures causing alfalfa to germinate. Once alfalfa germinates, it doesnâ€™t take long for it to emerge its cotyledons above ground, which would then be susceptible to freezing air temperatures (low to mid-20s to kill the exposed cotyledons).
This doesnâ€™t happen very often, notes Lang. But if it does, those plants will not grow back. Most alfalfa plantings should be held off until closer to mid-April. This is on the later end of the optimal planting window for small grain production, notes Lang, but is your priority to grow small grains or alfalfa?
What about planting forage grasses?
Grasses can be planted "early" like oats. Most grass seeds are small enough to flow through the small seed boxes of grain drills, however, smooth bromegrass is does not. Bromegrass is usually put in with the oats for establishment.
If this is the case, seed the oats shallow (one-quarter to one-half inch deep), advises Lang. Thatâ€™s because of the recommended seeding depth for bromegrass. If seeded at typical oat seeding depth (1 to 1.5 inches), the bromegrass is seeded too deep and establishment could be very severely limited.
The oats can usually still establish okay at the shallow seeding depth. The question is: What is the priority? To establish oats or brome?
For seeding technique, remember that seed depth (one-fourth to one-half inch deep) and seed-soil contact are very critical for good establishment, notes Lang.
The dryer the soil the more important is seed-soil contact. Planters should either have press wheels (best) or be followed with a cultipacker (preferred over a harrow) or harrow (still works well) to improve seed-soil contact, says Lang.