The first step in soil preparation is to eliminate the existing vegetation. All weeds and grasses on the site must be killed by smothering, cultivating, herbiciding or a combination of these techniques. Smothering weeds on small areas is simple, effective and requires no chemicals or special equipment. Cover the soil surface with black plastic, pieces of old rugs, plywood, or a thick layer of newspapers covered with leaves or grass clippings. Leave in place for a full growing season to kill the plants underneath. Weed-free lawns can usually be killed in two months using smothering. If perennial weeds are present, a full year may be required.
If you prefer not to use herbicides, use smothering, smother cropping, or cultivation. A sod cutter, rototiller, a tractor-mounted rototiller, rotovator, or farm implements such as a plow, disk or harrow may be used.
If using herbicides, we recommend a broad spectrum, non-persistent glyphosate-based herbicide, such as “Roundup.” If pernicious perennial weeds such as Canada Thistle, Canada Goldenrod, orsenettle, or woody shrubs and vines are present, it may be necessary to add a broadleaf herbicide and a surfactant to the “Roundup” mixture. ALWAYS READ THE HERBICIDE LABEL, and follow the manufacturer’s instructions.
Lawn Site Preparation
Two simple ways to remove a lawn are 1) to treat it with a broad spectrum, non-persistent glyphosate-based herbicide in early fall or mid-spring, when it is actively growing, or 2) smother it for 2-3 months during the growing season.
In autumn: After the lawn is dead, prairie seed can be machine-planted using a no-till seed drill or hand-broadcast on top of the dead sod. Broadcast seed will work its way down into the soil over winter and germinate the following spring.
For spring seeding: 1) till the dead sod thoroughly to break up the thatch, 2) burn the dead lawn to reduce thatch, making tilling easier, or 3) after herbiciding, remove dead sod using a sod cutter.
To create an instant seedbed without herbicides: Remove the upper 2-3 inches of sod using a sod cutter. Perennial weeds are not likely to be removed by the sod cutting procedure, so they may pose a threat to your planting.
To remove an existing lawn using cultivation: Till the area weekly 2-3 times. If rhizomatious perennial grasses, such as Quackgrass, are present we recommend year-long tilling.
Agricultural Fields Site Preparation
Old agricultural fields that have been left fallow for a year or longer, and have grown up to weeds. An old field usually requires one to two full growing seasons to prepare it properly. Patience at this stage is essential for a successful planting.
Using cultivation only: Cultivate every 2-3 weeks at a depth of 4-5 inches using a harrow, springtooth, or rototiller. Waiting longer than 2-3 weeks will allow weeds to recover. For rhizomatious perennial grasses, cultivating in intervals greater than 2-3 weeks may actually increase their density. Continue for a second year if weeds are not completely eliminated after one year of this treatment. This is a labor-intensive process. Every cultivation cycle brings new weed seeds to the soil surface where they can germinate. Repeated cultivation is not recommended for slopes or other erosion prone areas.
To herbicide an old field: Mow everything down in mid-summer. Allow vegetation to re-grow to a height of about one foot. Apply herbicide in early to mid-September.
The following year, spray herbicide in mid-spring, early to mid-summer, late summer to early fall, and (possibly) mid-autumn. The area must be completely free of perennial weeds prior to seeding. If not, a further spraying will be required the following spring, and the seed can be planted one week after spraying.
Corn, Soybean and Small Grain Fields typically have fewer weeds, requiring less preparation. Fields with few weeds can be sprayed with herbicide once in late spring and seeded a week later. If small grains have been harvested in summer, spray the field once or twice to kill weeds, and seed that fall or the following spring. If perennial weeds are present, proceed as for old fields.
If you are planting many acres of prairie in an agricultural area, you may rent the land to a farmer and have it planted to corn the first year, followed by soybeans the second year. If the farmer uses herbicides, this cropping sequence will eliminate almost all perennial weeds.
CAUTION: DO NOT plant in fields treated with “Atrazine” within 2 years. While some prairie grasses can tolerate low levels of “Atrazine,” flowers cannot tolerate any. “Atrazine” breaks down in 1-3 years, depending upon the soil type, precipitation and the amount applied. If you have a field that you suspect has “Atrazine” carry-over, you may plant a smother crop of corn or sorghum for a year to hold the soil and control unwanted weeds while the “Atrazine” breaks down. Or, spray with “Roundup” three times during the growing season to control weeds. Warm season grasses can tolerate up to two pounds per acre of “Atrazine”. Cool season grasses and prairie wildflowers are killed or severely damaged by this highly toxic herbicide.
Without herbicides: Cultivate repeatedly for a full growing season. After existing vegetation is eliminated, the final seedbed should be leveled using a drag or disc, or the area can be seeded using a no-till prairie seed drill.
Hilly sites: Maintain vegetation and avoid cultivation. Repeated cultivation may create erosion problems. Slopes should be planted immediately following soil preparation. Plant a nurse crop of oats or annual rye with your prairie seeds (please see page 14 for information on ordering nurse crops). For best results, stake a light erosion blanket containing straw or light excelsior over the seeded area. Or, apply 1-2 inches of weed-free straw mulch.
If you are unable to plant your slope immediately, stabilize the soil by planting a cover crop of oats or annual rye. About a week before planting prairie seeds, till or spray with herbicide. In a week you may plant using a no-till seed drill, or, in the fall after herbiciding, scatter seed directly into the dead cover crop for spring germination.
Newly disturbed soils: Areas of bare soil resulting from recent construction may be essentially weed-free, or they may contain various weedy plants and seeds. If the status of recently disturbed soil is unknown, it is best to level the area, plant with a cover crop of annual rye or oats to hold the soil, and observe whether weeds come up. If so, proceed as described above.
A well prepared site is half the battle when establishing a prairie planting. Once established, your prairie will bring you years of enjoyment with a minimum of maintenance!