C.O.R.N. Newsletter 2010-34

Dates Covered: 
October 12, 2010 - October 19, 2010
Editor: 
Curtis Young

Fall Application of Manure - Points to Consider

With harvest finishing earlier than usual this year, there is more time to think about the application of manure on fields this fall.

With any land application of fertilizer (manure or commercial), it is essential that two principles are adhered to: supplementation is necessary based upon crop need (following soil test) and application is made in such a way to ensure utilization of the nutrients by the crop to minimize environmental impacts. Since the former has been recently discussed (see CORN Newsletter 2010-28), and fall provides some special considerations, the latter will be discussed here.

Manure is often considered a waste product, but it should be treated as a nutrient resource. As such, soil tests should dictate if manure nutrients are applied to the field and just how much is needed. It is convenient and economical from a labor and fuel usage perspective to apply the manure to the field closest to the source, but this is not a sound agronomic or environmental practice.

In addition to soil testing, the manure should also be tested. This allows you to make an informed decision on how much manure to apply (or how much was applied) to a field. The equipment used to apply the manure should also be calibrated so the quantity of manure actually applied can be determined.

Additionally, quantifying the amount of manure that a field receives allows you to take credit for the manure applications when it comes time for commercial supplementation. Manure applications provide all nutrients required for growing plants. You should know approximately how much has been applied, so that you can properly credit nutrients.

With any fertilizer application, it is important to consider runoff potential. Two key factors affect loss potential: nature of the field and weather pattern. Observe setbacks from surface features such as ditches, surface tile inlets, ponds, etc when applying manure or commercial fertilizer. Considerations of field slope and surface residue (high percent residue reduces runoff) will also help minimize potential water quality impacts. Loss potential is greatly increased when rainfall occurs shortly after fertilizer application, thus avoid applications that may coincide with significant rainfall events.

Additional information regarding rates, timing, management considerations and set-back distances, see Chapter 6, Manure Application, of Bulletin 604.

Fall Application of Anhydrous Ammonia - A Good Idea?

With harvest progressing ahead of schedule this fall, and the tough sidedress conditions this previous spring, some folks are considering fall application of anhydrous ammonia to satisfy a good portion of their nitrogen budgets for next spring.  The question is – is this a good idea?  And if you are considering it, how should it be done?

First of all, Ohio State University does not recommend fall applied anhydrous ammonia as a preferred method of nitrogen application.  Our justification is years of field research that shows fall applied anhydrous ammonia can be susceptible to loss and that can result in significant yields decreases.  Just how much yield loss?  As much as 30%.  Our shallow, poorly drained soils with systematic subsurface drainage, cause fall applied anhydrous ammonia application to be riskier for us than our neighbors to the west.  Warm periods in late winter and early spring warm-ups allow ammonia to be nitrified to nitrate that can be lost by leaching (under cool, excessively wet conditions) or by denitification (under warm, excessively wet conditions).

Even though we do not recommend fall applications of anhydrous ammonia, we do provide guidelines if anhydrous ammonia is to be applied.  First and foremost, soil temperatures should be below 50 F.  This will minimize soil microbial activity slowing the conversion of ammonia to nitrate.  Remember, our goal should be to keep ammonia/ammonium in the soil as long as possible because it is not as susceptible to loss as nitrate is.  Consider the use of a nitrification inhibitor.  This is especially critical if soil temperatures are warmer.  The inhibitor will slow the conversion of ammonia to nitrate.  Realize that the inhibitor does not provide inhibition indefinitely, so still try to make applications in cooler soil temperatures.

Remember these guidelines if you are considering applying anhydrous ammonia this fall.

 

Fall Weed Control and Management of Black Cutworm

Last week in this C.O.R.N. newsletter, Mark Loux discussed the advantages of fall herbicide applications.   Along with better weed control in the spring, another benefit is reducing the likelihood of an insect pest that can cause significant damage to corn, the black cutworm.  By helping to provide a weed-free seedbed in the spring, growers remove a preferred egg laying site for adult female moths.  

Black cutworms migrate from southern states in the spring, laying their eggs on perennial weeds in the spring.  Of specific importance is chickweed, which is one weed that Mark mentioned in his article and is a very favorable plant for cutworm oviposition.   Insect movement to corn then occurs when the weeds are killed in the spring with a spring herbicide application and larvae search for other hosts.  Providing a weed free situation in the spring reduces the likelihood of cutworm problems.  When considering the benefits of a fall herbicide application, do not forget the added benefit of black cutworm management. Eliminating weeds in the fall is an excellent preventive tactic to begin your corn insect management for 2011!

 

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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.