By Dennis Holland, CCA, Pioneer Hi-Bred International, Alburnett, IA
Oct. 18, 2012 -- Many producers in the Midwestern corn-belt are dealing with very dry soil conditions this fall, causing them to question the value of performing the normal activities usually done right after harvesting the crop, such as soil sampling, applying anhydrous ammonia, and fall tillage. This article will address these concerns and provide insight on how to best manage fall field-work in this historical drought.
A good soil sampling program is a very important management tool to employ when raising crops. High commodity prices along with good yield levels in recent years make soil sampling more necessary than ever. However, when soils are abnormally dry, the following considerations need to be made to ensure you are getting accurate soil test results and are interpreting the results appropriately.
Potassium and pH readings being slightly lower would not change management decisions enough to justify delaying soil sampling in fields scheduled to be sampled this fall. The most important consideration to make this fall when determining whether or not to soil sample is the quality of the soil cores. If it is possible to obtain good soil cores with the soil probe, then move forward with sampling plans. Just keep in mind when interpreting lab results that pH and potassium sample results may read slightly lower in dry conditions, so manage accordingly.
Applying anhydrous ammonia in the fall is a popular and economical source of nitrogen for corn crops. For this to be an effective practice, the soil needs to be in the right condition. Applying anhydrous ammonia when soils are too wet, too dry, too cloddy, or too warm can lead to significant chances of losses, causing environmental concerns and wasted input dollars. This fall, some producers are concerned about dry soil conditions and are curious about how to be most successful when making anhydrous applications.
When anhydrous ammonia is injected into the soil, it needs to react with soil moisture to convert to ammonium, which will bind to the clay and organic matter in the soil. So do the soils in the drought-stricken areas of the corn-belt have enough moisture for this conversion to happen? University experts agree that even dry soils contain enough moisture to react with the ammonia. However, extra steps may need to be taken to ensure the slot created by the application knife seals and is not left open allowing the ammonia gas to escape.
Three management considerations need to be made to improve sealing in dry soils – amount of ammonia applied, increasing application depth, and slot closing attachments.
The best way to check for ammonia losses after application is to use your nose. If you can smell a strong ammonia odor a few hours after application, waiting for better conditions would be the best decision. Correctly applying ammonia takes a lot of experience and expertise. Remember to check over your equipment to make sure everything is working properly. No one likes to see light green strips in their fields in the middle of the summer from an ammonia application error!
Tillage works best when soils are dry, but what about when soils are very dry as they are this fall? If the soil is so dry that it breaks up in large chunks and clods, it may be wise to wait until soil conditions improve. However, in many cases, tillage will work just fine and may work better. Dry soils will be easier to fracture than wet soils, breaking up more of the deep compaction caused by wheel traffic when the soil was wetter.
One important consideration worth mentioning is residue management and water conservation. In areas where crops were drought stressed, crop residue will be much less compared to years when yield levels are closer to normal. Therefore, surface tillage to manage residue may not be as necessary, and it may be wise to leave as much residue on the surface as possible to conserve soil moisture and encourage rainfall infiltration.
One popular tool to accomplish deep, compaction busting tillage while leaving the surface relatively undisturbed is the in-line ripper. This tool has large ripper shanks oriented in a straight line to maximize lift and shatter compaction layers while leaving a majority of the crop residue on the soil surface. These tools do an outstanding job of eliminating compaction while still allowing residue to remain on the soil surface.
Managing through a drought can be very difficult and challenging. Different decisions will need to be deployed to best manage the dry soil conditions to optimize yields in 2013. Have a safe and productive fall and winter season, and see you in the fields next spring!