Another title for this article might be “It’s hard to make a silk purse out of a sow’s ear.”  This doesn’t affect everyone, but I have had enough calls this spring from folks who are looking at commodity prices and have already started the process or are thinking about taking an old pasture or sod field and converting it into either corn or soybeans.  Well maintained ‘new ground’ can yield very well and often has less disease and nematode pressure.  However, it may be impossible to make poor ground into a productive field if compaction or low soil pH cannot be corrected in time for the cropping season or at all.  Input costs must be weighed against realistic yield potential– particularly in fields that have not been limed or fertilized regularly for years.  Soybeans may be a better option than corn in a marginal sod or pasture field.  With fields that have no crop yield history and that have not been managed well in recent years, soybeans would have a lower seed cost, a much lower fertilizer cost and can produce some yield with adequate rainfall under lower fertility conditions (we don’t call them poverty peas for nothing!). 

Some production considerations for soybean or corn planted into sod are listed below:

1. Soil test as soon as possible to assess the fertilizer cost needed to convert the field.  Hay fields are often low in potassium due to removal of the grass but a pasture or sod field may not be as deficient.  In a low test soil, corn requires a minimum of 100-120 lbs K20 while soybeans require 80 lbs per acre.  We don’t soil test for corn nitrogen rate, but a modest corn yield goal of 125 bushel/A would require about 120 lbs N (roughly $68 plus application cost).
2. It is too late to get much benefit from lime this year.  If the soil pH is below 5.6 then lower your yield expectation for that field and manage inputs very carefully.  Commercial agricultural lime takes about two years to provide its full neutralizing benefit in a field.  Working the lime into the ground or using pelletized lime may provide faster initial movement down into the soil or quicker reaction with soil (pelletized lime) but research indicates these practices would make very little impact on soil pH during the first season (i.e. don’t spend extra money on pelletized lime in this situation).  If the field of interest will be used for a crop in 2012 go ahead and apply the ag lime.  Some long-term work at Jackson indicates that when soil pH is very low, spring applied lime can benefit the current crop by reducing levels of aluminum or manganese which may be at phytotoxic levels when soil pH is very low.  
3. Check fields for compaction.  A penetrometer can help determine the depth of a compaction layer.   A compaction layer of 3 to 4 inches may cause problems with root growth and limit water uptake by the crop.     
4. Add molybdenum and a bacterial inoculant to soybean seed.  We have a standing recommendation to include a “moly” treatment with other seed additives in a low pH (<5.6) soil.  Moly helps soil bacteria fix atmospheric nitrogen in nodules on soybean roots and natural soil molybdenum is less available as soil pH decreases.  Rhizobium japonicum bacterial inoculants help supplement native soil bacteria to create root nodules necessary for nitrogen fixation.  Powder or liquid inoculant products that can be added to the hopper box or drill just prior to planting are the least expensive (cost about $1.00/bag seed).  Newer products (Optimize, Vault LVL, Launcher Pro) have an extender that increases the life span of bacteria on the seed but they must be applied by a retailer who does commercial seed treating and cost around $3.00/bag.  Advantages of the commercially applied products is you don’t have to apply and plant on the same date and perhaps more uniform coverage of the bacterial inoculant on the seed.   
5. Check fields early for insect damage and treat quickly if needed.  Consider investing in a higher rate of Poncho or Cruiser insecticide on the seed, particularly if the crop is corn.  Crops planted into sod may take longer to emerge or grow off more slowly due to cool temperatures making them more vulnerable to insect damage.  Above ground insects and cutworms can be managed with an inexpensive foliar insecticide.  However grubs, wireworm and other below ground soil pests can be found in higher numbers in old pasture fields and the standard 250 rate of Poncho or Cruiser may not provide adequate control.  Poncho 1250 can be purchased for an additional $24 per bag (around $10 per acre) which is still much cheaper than the cost of seed to replant a field. 
6. Plant seed at the correct depth and at slightly higher seeding rates to allow for more seed/plant loss.  Some literature recommends increasing corn rates by about 2,000 seeds per acre and soybean rates by about 10,000 seeds per acre.  Corn should be planted at a depth of 2 inches and soybeans at 1.5 inches.  Planters generally do a better job of cutting through sod and placing seed at the correct depth than drills.