American farmers are facing potential nitrogen (N) fertilizer supply problems for the 2001 spring season. This year, you may need to switch to an N fertilizer source you are not familiar with. But, with good management, strategic planning, common sense and partnership with MFA, this issue can be adequately addressed.

The air you breathe contains approximately 79 percent N and is the origin of most inorganic N fertilizers. Nonleguminous plants cannot utilize this gaseous N. The process to convert atmospheric N into usable fertilizer is as follows:

Air (N₂, O₂) + Natural Gas (CH₄) + Heat, Pressure and Catalyst » Anhydrous Ammonia (NH₃) + Carbon Dioxide (CO₂)

All other major N fertilizers, except ammonium sulfate (industrial byproduct), use anhydrous ammonia as the base N source for manufacturing. From the above equation, it is obvious nitrogen fertilizer manufacturing requires a high-energy input. In fact, 85 percent of anhydrous ammonia production cost is energy. The major issue concerning N supply is the cost of natural gas in the United States. It is important to note that other uses of natural gas (industry, heating, etc.) take priority and can tolerate higher prices compared to fertilizer production. This has forced the shutdown of many U.S. N manufacturing facilities and moved them to places like Trinidad and Saudi Arabia where natural gas prices are lower (less than 10 percent of the U.S. cost).

The loss of U.S. manufacturing facilities has put more stress and cost into the transportation and distribution components of N fertilizers. Anhydrous ammonia is difficult to transport. Lower total N analysis materials such as ammonium nitrate and urea ammonium nitrate solution require high per unit N transportation and storage costs. Another cost issue is the high import duties that may be placed on N materials, especially ammonium nitrate.

Agronomically, how does the N situation affect you? Basically, if you can obtain the products you prefer in 2001, use them. But those who use ammonium nitrate, anhydrous ammonia or urea ammonium nitrate solution should be prepared to use other N products, specifically urea.

How does urea compare to ammonium nitrate? They are both quality N materials that have been used for decades. However, both have agronomic strengths and weaknesses. Under warm soil conditions, especially moist soils that are experiencing windy, drying-out conditions, urea can undergo a volatilization process where its N is converted to a gas and lost to the atmosphere. Once incorporated into the soil through tillage or rainfall, this problem is eliminated. With our cropping conditions, urea-N volatility losses range from 0 to 30 percent. If managed properly, we can keep this N loss minimal.

Many producers feel ammonium nitrate is superior to urea for pasture and hay application. They often cite a faster "green-up" with ammonium nitrate compared to urea. This may be true occasionally because urea must convert to plant-available ammonium (a process that takes a few days) before it becomes plant available. But just as often the leachable nitrate component of ammonium nitrate moves through the soil system or denitrifies (soil microbial conversion of nitrate to gaseous nonplant-available N) as the soil/plant system experiences spring rainfall. For late-winter/early spring fertilization, there is no difference in efficacy between ammonium nitrate and urea. The volatilization process requires several days of warm temperature with no incorporating rainfall. This combination occurs rarely in our region before mid-May. Therefore, for spring topdress on winter wheat, pasture or hay ground, there is little difference between urea and ammonium nitrate.

The two problems concerning urea occur with late-spring through midfall application onto pasture or hay ground and surface broadcast application onto no-till corn or milo fields. How can you address these issues? With no-till corn, there are a few options. I would first recommend a nondisturbing knife application of anhydrous ammonia, if available. Apply the anhydrous ammonia as soon as possible to avoid supply bottlenecks and the busy spring season. If anhydrous ammonia is not available, apply urea on dry soil as close to planting as possible, including postemergence. Try to time the urea application within a few days prior to an incorporating rainfall. Another option is to apply higher N rates (20 to 40 additional pounds of N per acre) when using urea compared to ammonium nitrate. Depending on the premium paid for ammonium nitrate, this option may be economical.

The bottom line is we have dealt with fertilizer shortages in the past, and we will see them again in the future. There are many factors to consider when developing an N fertilizer management plan. As always, MFA is poised to help you through any potential fertilizer supply problems. Please visit with MFA field personnel prior to the spring rush so we can all be prepared for the 2001 field season.