7/2/2013 - By Harrell's

Volatilization is the loss of gaseous ammonia to the atmosphere and is represented by the following reaction:

 No doubt, we have all heard the term, but I wonder how much we actually appreciate its potential impact on our fertility program.  Figure 1 depicts the influence of various N sources on volatilization.  As you can see, volatilization can be as high as 40% of the applied N from urea and 25% from sulfur-coated urea.  Did you flinch?  Probably not, so let me say that again….. volatilization can be as high as 40% of the applied N!!!  That means that if you applied 1 lb of N, only 0.6 lbs has the chance of entering the turf!  If you just paid $4.00 for a gallon of gasoline and the attendant laughed and told you that only about ½ of that gallon actually entered the gas tank, wouldn’t you be just a little upset!?!

Figure 1. Total cumulative N loss due to NH3 volatilization over a 10 day period as affected by N source, Exp. 1. Columns with different letters are significantly different from each other at 0.05 AN, ammonium nitrate, S-coated urea.

So is there anything we can do to reduce N loss from volatilization?  Absolutely!  The first step is to use an N source known to produce little to no volatilization, such as the 4 products in figure 1 with a “B” above their bar.  The remaining option is to include an additive which reduces volatilization by inhibiting the reaction written at the beginning of this article.  To date, only 2 urease inhibitors have been evaluated on turfgrass and their activity documented.  They are: NBPT chemically known as [N-(n-butyl) thiophosphoric triamide] and PPD known as (phenyl phosphorodiamidate).  Numerous compounds claim to reduce volatility, however, as you can see in Figure 2, only the one containing a documented urease inhibitor proved to have an influence.

Figure 2.

For those interested, the below references discuss N volatilization in more detail.

References:

• Goos, R. Jay. 2011. Nitrogen Fertilizer Additives, Which Ones Work? North Central Extension-Industry Soil Fertility Conference. Vol. 27. Des Moines, IA.
• Knight, E.C., E.A. Guertal, and C.W. Wood. 2007. Mowing and Nitrogen Source Effects on Ammonia Volatilization from Turfgrass. Crop Science 47:1628-1634.