Wednesday, May 04, 2011
What Questions Do You Have About Anhydrous Ammonia Application?
As many Cornbelt farmers begin their return to the planting activity at hand, glad their farm is not inundated in Mississippi County, Missouri, the typical issues of spring will return to top of mind and one of those is nitrogen application. Many farmers applied anhydrous ammonia last year during the never-ending fall. However, some anhydrous will need to be applied this spring, and you may have some good questions that could help other farmers.
Have you thought about the reason you might apply anhydrous ammonia compared to other forms of nitrogen? University of Illinois fertility specialist Fabian Fernandez says it is the most concentrated source of nitrogen with less weight of fertilizer per unit of nitrogen, along with the flexibility of its application. The following issues are all taken from his recent newsletter.
Here is our first caller, what is your question? What is a good soil-moisture condition for anhydrous ammonia application, and can I apply it deeper to compensate for less-than-ideal conditions?
Dr. Fernandez says the anhydrous ammonia quickly reacts with organic matter in the soil, along with clay particles, free hydrogen ions and particularly the soil moisture, which allows it to usually stay in a 3-5 inch oval around the exit point of the applicator knife. The best soil moisture is 15-20% and variations on either side of that will create some problems with loss. Soil that is too dry will allow the anhydrous ammonia to volatilize and escape the soil. Soil that is too wet will not seal behind the applicator and allow the ammonia to escape. By smelling the ground behind the applicator, one will be able to determine if ammonia is escaping into the air.
And our next caller please. Is applying anhydrous ammonia after every other row as effective as applying it after every row?
That is a very good question and the answer is yes, you can do that without any loss of yield. And in fact there is a lower horsepower demand because of the reduced number of applicator knives being pulled through the ground. There is another advantage to every other row application, since you are applying twice the amount of ammonia in one location that is creating a temporary alkaline zone that inhibits bacterial transformation of the ammonium to nitrate. That situation can be important when the potential is high for N loss from leaching or denitrification.
All right, caller what is your question? How long do I have to wait after anhydrous ammonia application to plant corn?
The only risk to planting is if the seed falls within the application zone, so separation in time and space can avert seedling injury. If soil conditions are ideal and the ammonia is applied at a proper depth and application rate of 100 to 200 pounds per acre, there is little threat to seeds, even if they are planted on top of the retention zone right after the application. However, that is not recommended, and an RTK guidance system would allow the possibility of planting between the application zones. If that is not a possibility a 3-5 day wait is enough to avoid seedling injury.
Back to the phone lines, what is your question? How long after anhydrous ammonia application can I till the soil?
That will really depend on the soil condition and depth of application. Shallow tillage can be accomplished immediately, and that may help seal the applicator knife cracks in the soil. Since the ammonia usually reacts with the soil moisture immediately, even deeper tillage after a couple days will not be a problem, but use the smell test to determine if ammonia is being lost.
Thanks for calling, what is your question? Does anhydrous ammonia application compact soils?
No, that is one of those myths along with anhydrous ammonia reducing soil organic matter, which is does not do either.
We’ve got time for one more call. Does anhydrous ammonia application change chemical conditions in the soil and affect soil microbes?
Good questions, and for the first one, consider the fact that conversion of ammonia to ammonium creates a temporary alkaline condition in the application zone and when the ammonium converts to a nitrate that is an acid forming reaction, so the result is a reduction in soil pH. But the same happens with other forms of nitrogen, not just anhydrous ammonia. Regarding your second question, the ammonia is going to drastically reduce the bacteria and fungi in the application zone, but they grow back after several weeks.
Thanks Dr. Fernandez, and we hope this has answered questions for quite a few farmers.
Summary:
Anhydrous ammonia is released into a retention zone as the applicator knife passes through the soil, with the zone being a 3-5 inch oval if soil moisture and organic content is able to capture it. Shallow tillage will help seal the ground, and deeper tillage is acceptable if the soil moisture conditions are good. Planting can be accomplished right away if the seeds are not located in the retention zone, and the application of ammonia to every other row of corn not only creates beneficial chemistry in the soil, but also reduces horsepower requirements for the application.
Posted by Stu Ellis on 05/04 at 12:00 AM | Permalink
Comments
Posted by: Craig Day at August 6, 2011 10:10PM
Applying anhydrous ammonia when temperatures are 100 deg. F is not a problem as long as you are able to get a good seal behind the knife track, and as you said in your questions, there is good moisture in the soil. With the high temperature one thing that is important to realize is that the tank will develop higher pressure which can cause an application that will not be as uniform (or the rate as accurate) as you would expect. One of the concerns I have with applying anhydrous ammonia at these high temperatures is that we are talking of applications done likely in July or August. At this point most crops are at least at tasseling. Applying anhydrous ammonia to these plants is not only challenging because of the height of the crop, but also because the application itself is going to damage corn roots that by this time have been growing in the row middles for a while. Most importantly, if the crop is already at tasseling or past that stage, the application is too late and will not result in a yield benefit or on the nitrogen being used by the crop.
Posted by: Fabian Fernandez at August 8, 2011 10:10AM
What about applying NH3 when the temperature is over 100 degrees everyday. We do have decent moisture at 4-5 inches and can easily reach this moisture