Converting Sod to Grain Crops Fact Sheet - April 2007
Converting Sod to Grain Crops: The RIGHT Way Fact Sheet
The Big Decision...
Converting idle or set aside acres to cropland is an endeavor that should be
planned carefully, especially when that land is considered Highly Erodible Land
Truth be told, a healthier soil has developed beneath that existing grassland
or prairie vegetation. Erosion has been controlled; water quality has been
enhanced; the movement of sediment, fertilizer, and chemicals has been reduced.
The protective vegetative cover (grass) has also provided significant wildlife
habitat. This begs the question: Does converting that land back into crop
production mean losing all those stewardship benefits? No. All it takes is
proper planning and good management.
Landowners considering converting prairie or pasture back into cropland,
should consider these items:
- The crops and rotations you want to plant; proper fertilizer, pH, and
pest management planning.
- The tillage system you’ll use on each crop - For fertilizer and pest
management application times and methods.
- Areas on your farm that should remain and be maintained in existing
vegetation–grassed waterways, field borders/turn strips, filter strips, and
severely eroded areas too steep or poor for crop production.
- The impacts this decision will have on resources--soil erosion, soil
quality, water quality, and wildlife habitat.
- Economic impacts of land returned to crop production--costs as well as
- Impacts of cropping on time and labor demand, equipment, and other
Crops and Rotation Options
On land subject to erosion, the best crops are those
that produce large amounts of crop residue like corn, sorghum, or small grains
or crops that form a dense canopy like drilled soybeans, small grains, or
alfalfa/clover hay. Residue protects the soil surface. Corn is a good crop to
follow idle land operations if nutrient and pH levels are adequate. Recent data
indicate soybeans may also be a good crop for the first year after the
conversion, but if they have not been previously grown in the field, inoculate
seeds with Rhizobia to provide nitrogen.
Consult with local NRCS/SWCD staff to find a crop
rotation that controls soil erosion and maintains the benefits of increased
organic matter, soil structure, and increased water infiltration. Land involved
in USDA’s Conservation Reserve Program (CRP) may meet some requirements of
USDA’s National Organic Program certification. Learn more about the
certification process at:
No-till is the preferred method when converting grassland to cropland. Research
indicates grass-legume sod results in significant soil quality improvements,
namely in organic matter levels, structural stability, total pore space, and
soil infiltration rates. These improvements result in soil that is in better
condition to grow plants. Research shows equal yields in corn and soybeans sown
by both no-till operations and plowing. Tillage, however, can eliminate soil
health improvements in as little as one year. Tillage oxidizes organic matter
quickly, reducing the structural stability of soil aggregates and natural pore
space. The loss of organic matter also reduces availability of plant nutrients.
Soils in pasture or prairie are ideal for no-till methods because they lack some
of the conditions (compaction and crusting) that limit no-till success in
excessively tilled soils.
It’s crucial to know current soil fertility levels before planting. Soils on
idle land are much different than soils that have been cropped regularly over
the last decade. If possible, soil tests should be taken 1 to 2 years before the
ground is returned to production in order to provide ample time to apply lime
and fertilizer required for new crops. Generally, phosphorus and potassium
levels will have changed very little since the land was established to grass.
Soil pH levels under grass and prairie tend to revert to native soil levels
prior to agricultural production. In no-till areas where soil test levels are
low, consider applying starter fertilizer when planting corn. Starter fertilizer
has not shown benefits when planting soybeans. Take soil samples at a depth of 7
Since tillage is not used in a no-till system, lime is often over applied. This
can result in a high surface pH which causes herbicide failure and/or carryover.
An early soil test allows application of limestone to adjust pH levels to 6.0 to
6.5 since it takes approximately 6 months for lime to increase soil pH levels.
Most limestone application rates are based on incorporation depth, therefore,
apply 1/2-1/3 recommended amounts unless the laboratory has already adjusted
your lime needs based on needs of a no-till system. Monitor soil pH of the top 2
inches because very low or high pH levels can interfere with herbicide
performance or cause carry-over crop damage.
Because very little legume remains in most grasslands after 10 years, little, if
any, nitrogen (N) credit can be taken. NRCS suggests following Illinois Agronomy
Handbook recommendations to determine N needs.
Research shows that placing N below the soil surface results in consistently
higher yields in no-till because N fertilizers that contain urea volatilize when
surface-applied. However, NBPT, a urease inhibitor, allows broadcast application
of urea with lesser concern of N volatilization.
Phosphorous and Potassium
If you plan to use no-till methods and P and/or K is low, use starter fertilizer
and consider deep banding. Refer to current University of Illinois
When bringing grassland into crop production, landowners must manage for pests
of all kinds—weeds and insects.
Research in Illinois and other Midwestern states has shown consistent perennial
grass weed control from a combination fall plus spring herbicide application
program. This has been found successful especially for tougher to control cool
season grasses such as smooth bromegrass and orchard grass. However, regional
differences in grass control can be noted.
Cool season grass control with translocated herbicides, such as glyphosate,
should be applied at certain growth stages to be effective. The growth stages
where glyphosate will be most effective are: in the spring at boot stage or late
fall before the first killing frost, when perennial plants store food reserves.
For central and northern Illinois, a combination of fall plus spring application
is preferable over spring only treatment. The combination treatment offers more
effective control and is lower in cost than a spring only treatment since spring
only applications require higher herbicide rates. Southern Illinois producers
can use either program, as an earlier spring growing season allows cool season
grasses to reach boot stage prior to corn planting.
Glyphosate in the fall (late September, early October, before a killing frost
occurs), followed by glyphosate in the spring (on grass at least 8”-10” in
height) provides good control of cool season grasses. Ammonium sulfate added at
the rate of 17 lbs./100 gallons water can improve control.
Fall glyphosate rates of 1-2 lbs. ai/acre are recommended. Some research
shows that mowing in July prior to fall spraying significantly increases
perennial grass control. Perennial broadleaf weeds could be a major weed
problem. Producers should scout existing fields for invading perennials such as
milkweed, ironweed, hemp dogbane, trumpetcreeper, brambles, trees/shrubs, etc.
Treat perennial broadleaf weeds in the fall. Adding a hormone herbicide such as
2, 4-D or dicamba to the glyphosate improves control of perennial broadleaves.
Hormone type broadleaf herbicides can reduce control of perennial grasses by
antagonizing the glyphosate at lower glyphosate rates. Higher rates of
glyphosate should also be used in the fall where contact herbicides such as
paraquat are planned for spring burndown. Spot treat grassland areas of with a
2x rate to provide improved control of woody perennial broadleaves.
Spring treatments of glyphosate or paraquat plus atrazine can be used where
planting corn or milo in fields fall treated with glyphosate. Orchard grass and
smooth bromegrass are difficult to control with a spring only treatment,
therefore higher burndown herbicide rates are required. It may or may not be
recommended to tank mix residual herbicides with spring glyphosate applications.
Like fall applications, adding a hormone type herbicide will improve control of
broadleaf weeds. Where used, observe the label specified interval before
planting sensitive crops such as soybeans.
Regardless of your tillage system, wireworms, white grubs, seedcorn maggot and
beetle, and billbugs may present a problem in corn planted into sod. Wireworm
bait stations should be used to determine if corn seed protection is necessary.
Consult current University of Illinois recommendations.
Several soil insecticides are labeled for wireworm control. In addition to
wireworms, white grub control may also be needed. Consult soil insecticide
labels for pest species. A labeled soil insecticide will protect the seed and
the corn plant. A planter box seed treatment will provide wireworm protection to
the seed; however, it will not protect the corn plant.
Common stalk borer and armyworm may sometimes infest converted corn fields.
Armyworms overwinter as partially grown larvae, but adult moths may migrate into
Illinois each spring. Those converted fields that were fall treated with a
herbicide will not be attractive sites for armyworm moths to lay eggs.
Adult Stalk borer moths actively lay eggs in late August and September. The
insect overwinters as an egg. After eggs hatch in spring, partially grown stalk
borer larvae will infest corn as they out grow their previous weed host. If
present, scouting corn during May/June is necessary to identify their movement.
Insecticide treatment is effective only if larvae are outside host plant.
Several management options are available for stalk borer: Plant soybeans, since
they are not a very suitable host or burn down the cover early enough that newly
hatched larvae do not have any host to feed on, and die from starvation.
Finally, an insecticide treatment, properly timed, will be effective as larvae
migrate into the corn plant.
Black cutworm moths can lay eggs in residue. Scout emerging corn for cutworm
damage and treat if cutworm damage exceeds 3% and cutworms are still present.
Consult current University of Illinois recommendations.
Vole populations can sometimes reach high levels in undisturbed sods. Scout
converted fields for vole colonies in early spring, prior to corn planting.
Research confirms five or more colonies per acre is the threshold level for
treatment. There are several options available including: alternate feeds, and
habitat modification. Alternate feeding of 4 bushels cracked corn or 2 bushels
whole kernel corn, applied 1-2 days prior to planting will permit seed corn to
emerge and grow beyond damage by voles. Killing of vegetation 30 or more days
prior to planting corn has also shown to be very effective in reducing vole
Insect pests possible in soybeans include seedcorn maggot, white grubs,
wireworms, and possibly grape colaspis. Consult current University of Illinois
recommendations. As with corn, a fall burndown of existing vegetation will
reduce potential insect damage in soybeans. Always follow all label directions
when using insecticides.
Many agricultural areas were enrolled in federal set-aside programs or used as
pasture because they not suitable for crop production. These may be areas
severely eroded, rocky, steep, or have other conditions that make crop
production unprofitable, difficult, or dangerous. These areas should be
identified in the field and left in sod cover for forage production or planted
to trees/shrubs or left idle for wildlife habitat. Other areas that should
remain in sod include steep areas that would be end rows if cropped,
drainageways that need sod cover to prevent gully erosion, and filter strips
along streams or lakes to prevent access by sediment, nutrient, and pesticide
pollutants. If filter strips are established, ensure they are at least 32 feet
wide on flat slopes and 117 feet wide on steep slopes. Consult current pesticide
labels for required set back zones on filter strips or buffers.
Potential effects of converting
CRP acres to crop production
The Farm Service Agency (FSA) administers the Conservation Reserve Program and
converting those lands to crop production prior to the contract expiration date
is not allowed without terminating the contract. These terminations have costs
associated with them, including repayment of annual payments already received,
cost share payments, interest on those payments, and liquidated damages. Contact
your local FSA office for more information.
Natural Resource Impacts
Over the years, the conservation programs and practices Illinois’
conservation farmers use to protect their land and demonstrate stewardship
principles have provided significant natural resource benefits. Soil erosion,
soil quality, water quality, and wildlife habitat have all been positively
affected by the vegetation, grasses, prairies, trees and shrubs state and
federal programs support and maintain. Transitioning these fields back into crop
production will impact each of the following resource concerns. It is important
to consider these impacts as you decide whether to re-engage idle acres back
into agricultural production.
Soil erosion rates will increase when sloping and Highly Erodible Land (HEL)
fields are cropped compared to land maintained in sod. Erosion can be severe.
Soil loss levels depend upon crops grown, tillage and crop residue left on the
soil surface, as well as row direction. No-till provides the best erosion
control in row crops. The use of cover crops and crop rotations that include hay
should be considered. Check with your local NRCS/SWCD office for specific
erosion estimates for different cropping systems. A good rule to follow: To
prevent excessive erosion, leave at least 50’ of sod strips every 200’ on steep
end rows where crop rows direct water to the end rows. Also, do not till through
drainageways as these will erode severely.
Generally, soil quality will decrease with cropping compared to grasslands.
Valuable soil quality benefits can be attributed to increases in organic matter
and pore space for air and water movement and soil structure stability. Soil
quality is the result of land protected and covered in grass vegetation. In
order to maintain soil quality gains, select an appropriate tillage and
management system. Research indicates no-till, cover crops, or a rotation with
hay will best maintain soil quality improvements of idle land planted to row
By returning land to crop production, land is exposed to increased erosion and
chemical use and the potential for water quality problems is increased. Fields
left idle or planted to prairie pastures have dramatically reduced soil erosion
levels and reduced sedimentation of surface water.
Over the years, these areas reduced amounts of chemical fertilizer and
pesticides that reach surface water. Tillage and management decisions directly
impact potential surface water pollution. Using no-till or a rotation with hay
that controls erosion can reduce sediment and chemicals attached to sediment
that reach surface waters. Use of Integrated Pest Management is recommended to
reduce need for pesticides.
Development of a nutrient management plan is recommended because it limits
fertilizer application to no more than is needed for the crop and management
Wildlife species who have made homes in grasslands, pastures, and marginal areas
will be lost if the land is cropped. Over the years, set aside acres provided
habitat for many types of wildlife across Illinois. Cropping this land reduces
habitat available for wildlife food and cover. Recommendations to reduce impacts
on wildlife include:
- use no-till and crops with hay in the rotation,
- maintain seeding on contour buffer strips, end rows,
- maintain grass seedings on waterways,
- leave strips of unharvested crop along the edge of fields for winter
food and cover.
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