Cover Crops on Special Crops Land
More than 450,000 acres of Manitoba farmland is used to grow special crops such as potatoes, sugar beets and pulse crops. This land is generally light-textured and very prone to wind erosion. Complicating the issue is the fact that special crops produce very little crop residue to protect the soil.
Wind erosion does more than remove valuable topsoil. It also removes the organic matter that holds the soil together and retains soil moisture, while improving its tilth and structure. Soils that have lost much of their organic material become even more susceptible to wind erosion. Organic matter also provides a kind of nutrient bank, releasing nutrients for crop use.
The best way to protect erosion-prone soils is to use a complete management system including shelterbelts, annual barriers, proper residue management and crop rotations. Cover crops are an important component of the system.
Consider a Cover Crop
The sole purpose of a cover crop is to protect the bare, erosion-prone land from the wind. They are usually seeded after the harvest of a low-residue crop such as potatoes or in the spring to protect the soil until the new crop has grown enough to protect the land. Fall rye is the most commonly-used cover crop, although other cereals such as wheat, barley, and oats are also used.
A fall cover crop must grow enough before freeze-up to provide protection to the soil. The latest recommended seeding date for fall cover crops will vary depending on the weather, but used September 15 as a general guideline.
Fall rye is often left for harvest the next summer - as part of the crop rotation. If you are planning to allow fall rye to survive as a crop the following spring, adjust your seeding deadline accordingly.
It's A Fact
Cover crops have the added benefit of capturing snow over the winter to enhance moisture conditions in the spring. One foot of snow collected equals approximately one inch of water.
Establishing Fall Cover Crops
Fall cover crops are best suited for potato land or pulse crops. Sugar beets are harvested too late in the year for a cover crop to become established.
Option One: Seed With A Fertilizer Broadcaster Prior To Harvest
This method can work well on potato fields because of the significant amount of soil disturbance associated with the harvest. The cover crop seed is incorporated by the potato harvester and the operation used to anchor the potato vines after harvest.
Seeding Rate - 2 bushels/acre because some seed will remain on the surface and some will be buried too deep to germinate.
Advantages
- uses moisture brought to the surface by the potato harvest
- relatively fast operation
- early seeding allows the cover crop more time to establish before freeze-up
- don't have to take valuable time during harvest to seed
Disadvantages
- Requires a higher rate of seed application than post-harvest seeding
Option Two: Seed After Harvest
On potato fields, seed the cover crop within 12 hours of the harvest to take advantage of the moisture brought up by the harvesting operation. Some operators seed their cover crops at the end of each day of harvesting. A press drill is preferred because of better packing and fewer problems dealing with potato vines. Hoe drills and air seeders have a tendency to plug up with vines.
On pulse crop fields, cover crops may be seeded with any one of a variety of seeders but packing is important to obtain a good seed-to-soil contact in soil that is likely to be dry. In-line packers are the most efficient.
Seeding Rate - 3/4 to 1 bushel/acre
Advantages
- drilling the seed into the soil rather than broadcasting it results in better germination and allow lower seeding rates on potato land, it uses moisture brought up by harvesting
Disadvantages
- dealing with potato vines
takes more time and horsepower than broadcasting seed
Option Three: Seed Cover Crops From An Aircraft Prior To Harvest
Seeding cover crops with an aircraft can be effective and economical, especially where large areas of land are involved. Costs per acre for seeding from the air are comparable to other methods when considering the operator's time, operating costs, and wear and tear on machinery.
Advantages
- Time. The producer doesn't use valuable time seeding and a lot of acreage can be seeded in a short time.
Disadvantages
- Uneven distribution of seed among hills and furrows may be a problem.
Anchoring Potato Vines
If potato vines are not anchored, they will roll up and blow away. Use a disc with two-thirds of the discs removed to anchor vines. Have it set up for burying the vines, not for tillage. Travel slowly - about 3 miles/hr - in same direction as the rows or diagonal to them. The operation will leave some cover and ridge the soil.
Using a vine chopper attachment on the potato harvester eliminates the need to anchor the vines.
Removing a Fall-planted Cover Crop
Normally, a cover crop will be killed by frost before it grows too much to be a problem. However, if the cover crop's use of soil moisture and the potential amount of straw on the field the following spring are becoming concerns, use a herbicide to kill it.
Fall rye may be left until spring, then burned off with a herbicide either before seeding a new crop or pre-emergence.
Planting the New Crop
Direct seed the new crop into the cover crop residue. In the case of fall rye, burn off the new growth before seeding or immediately after seeding.
Spring Cover Crops
Since potatoes and pulse crops are most often seeded into cereal stubble as a part of crop rotation, wind erosion is generally not a major concern in the year of establishment. However, sugar beet production poses special problems.
Sugar beets are generally seeded into bare, pulverized soil. It takes up to six weeks before the new crop is thick enough to provide protection for the soil supporting it. Wind blown soil can act like a sand blaster to bombard young plants and cause damage, cutting or shearing them off in extreme cases.
A cover crop of wheat or other cereals should be seeded as early as possible in the spring, prior to planting beets. Cereals will emerge quickly and provide protection to the soil. The beets can be planted directly into the growing crop later. The cover crop will also protect the young beets from the wind. Remove the cover crop with the appropriate herbicide once the beets are at the four-leaf stage.
