While some producers have plenty of experience with corn, others are more experienced with tobacco, hay or pastures. The general comments below are targeted to both types of producers.
Nitrogen benefit. Land that has been in a grass and/or legume sod for four years will reduce the fertilizer nitrogen requirement by about 25 pounds of N per acre. If that soil has been in sod for five years or more, then fertilizer nitrogen can be reduced by 50 pounds of N per acre.
The vast majority of hay and pasture fields are potassium (K) deficient. Hay removes a lot of K2O from the soil, while pasture fields tend to remove a little less. Without even conducting a soil test, odds are very good that the sod will need about 60 pounds of K2O per acre. Of course, a soil sample provides a much more accurate estimate of what is needed in the field.
Soil test now, or as soon as the soil allows. Fertilizer prices are rising along with corn commodity prices. A soil test spans 20 acres and will cost about $5 to $10 per sample. The fertilizer bill will be well over $1500 for those same 20 acres. A soil test identifies the nutrient deficiencies in the soil and allows you to apply only what fertilizer is needed. Pull about 10 to 20 cores, each 4 inches deep, for a 20-acre area. Mix all of the cores together and from that mix, send in a sample for testing.
Apply potassium, phosphorus and zinc fertilizer according to the soil test recommendations. These applications can be made anytime before planting.
Itís too late for lime this year. If your soil pH comes back low, you can apply agriculture lime, but it will not help much until the 2012 growing season. If you could have applied lime last fall, that would have been ideal. Pelletized lime is marketed as reacting faster with the soil, but it will not react fast enough to help with this season. Save your money and stay with commercial agriculture lime. If your pH is really low (5.5 or less), lower your expectations for yield. Unless you receive an inch of rain every week during the growing season, yields will be reduced.
Control the weeds early and stay aggressive. If at all possible, burndown the sod before you plant corn. Ideally, corn would be planted into ìbrownî remnants of weeds. Either Gramoxone or glyphosate are good options. Gramoxone tends to work a little better than glyphosate at cooler temperatures.
Keep sod waterways. Examine the sod fields and identify low areas where water flows. Many producers spend a lot of money establishing sod waterways. Here is one opportunity to leave them established before you start row-cropping.
Try to stay no-tillage if possible. You will get the most benefit from available nitrogen this way. Water-holding capacity is maximized with no-tillage. Erosion is minimized in no-tillage.
Test for compaction. Many hay and pasture fields have some surface compaction. The next time the fields are saturated with water, walk them with a penetrometer to test for compaction. (Most county extension offices have a penetrometer.) If that compaction is 3 to 4 inches deep, then you may need to do some surface tillage to break up the compaction. A field cultivator or chisel plow is the preferred tillage tool, if tillage is necessary. If the compaction is an inch or less, most no-till planters with sufficient weight can break through that compaction.
Plant a slightly higher seeding rate. Planting into sod, means planting into grubs, wireworms, voles, field mice and other critters. Expect a little more seedling loss and increase the seeding rate by about 2,000 more seeds per acre to compensate. The seeding rate will range from about 32,000 seeds per acre on highly productive fields to about 24,000 seeds per acre on less productive fields.
Place seeds about 1.5 to 1.75 inches deep. The number one failure we have observed in sod-to-corn situations came from shallow seeding depth. In those cases, corn seedlings were more likely to show potassium deficiency, lodge over or have stunted in growth. Get the seeding depth correct. You will pay for it greatly if you do not.
Select a good hybrid. Based on the University of Kentucky trials, there is a huge swing in yield potential from commercial hybrids. Selecting a hybrid with a good track record in the state improves your odds of having a good hybrid and getting good yields. Never ask the seed salesman to “Give me whatever you have.” Do your homework and select good hybrids.
Consider using a seed insecticide. Seed treatments such as Poncho 1250 or Cruiser Extreme 1250 offer enough insecticide to help control grubs and wireworms. If the season is cool and cloudy during germination, a foliar insecticide applied to young plants (1 to 3 fully emerged leaves) could be warranted. The cool, cloudy conditions slow corn growth and favor insect damage. Insect damage is typically more severe in fields with a lot of residue. Bright, sunny conditions favor quicker growth of the young plants and insect damage is less severe most of the time.
Spreading about one bushel of cracked corn per acre is a method for slowing down damage from voles, field mice and other varmints. The animals will eat the cracked corn, first, and are less likely to dig up seeds.
Assuming that the burndown application worked well, there will be some perennial and annual weeds that need to be controlled when the corn is emerging. In general, when weeds emerge with the corn crop, they should not be allowed to get more than 6 inches tall. Herbicide combinations that contain atrazine typically can be applied soon after planting up until the corn reaches 12 inches in height. If the previous field was especially weedy, then another herbicide application may be necessary. Many postemergence herbicides have spray restrictions when corn reaches about V6 to V8 (six to eight fully emerged leaves).
Nitrogen fertilizer can be applied preplant or sidedress on well-drained soils. However, on poorly and somewhat poorly drained soils, a portion of the nitrogen should be sidedressed, if possible. The limit to sidedressing depends on the equipment options. However, most nitrogen sidedress applications go on before corn reaches V4 to V6.
These are some general observations and guidelines for management of soils going from sod to corn. If you have extensive experience in corn production, you know that different fields require different management strategies. If you have less experience with corn production, take the time to ask others with experience. Learn from them. There is tremendous potential for profits from corn this year, but proper management ñand favorable weather – will be critical to attaining those profits. Contact your local county extension agent for more resources and expertise on corn production.