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  • Writer's pictureRachel

Stepping Up Your Management Game: Application and Safety Requirements for Anhydrous Ammonia

With your eyes on the finish line, many of you are beginning to look beyond harvest 2018 and to the next step in our management process: nitrogen. Nitrogen is one the most critical applications we make each year. In fact, behind water, nitrogen is often the most critical element necessary for plant growth and reproduction. With that in mind, it is essential that we set ourselves up for a productive growing season starting now. A frequently used nitrogen source is anhydrous ammonia. Anhydrous is one of the more economic sources of nitrogen with a high nitrogen content at a lower cost. It does come with its challenges though, both to application requirements and safety concerns. This week’s blog will walk you through the criteria that make anhydrous so desirable as a nitrogen source, some of the requirements for economic and sustainable application and finally cover some very important safety requirements for working with anhydrous ammonia.

Why Use Anhydrous?

At 82% N, anhydrous is the highest percent nitrogen of all commercial nitrogen sources. It generally tends to be the cheapest as well. Nationwide, from 2000 to 2008, there was a dramatic increase in price, generally corresponding to the increase in natural gas prices during that time frame. From 2008 on, anhydrous prices have been fairly volatile with prices swinging from $499 a ton to $851 a ton. Even so, these prices are often the cheapest per unit of nitrogen.

Image courtesy of University of Illinois

The window of use for anhydrous is often much larger than for other nitrogen sources. This is due to the makeup of the anhydrous. Anhydrous means “without water”. Because the makeup of the chemical has no water, this makes it hygroscopic, or water loving. Anhydrous will bond rapidly with any water it comes in contact with. This both increases its stability and makes it dangerous to work with.

Anhydrous ammonia, or NH3 is a liquid at high pressure, and consequently must be stored under pressure in tanks. As soon as anhydrous is applied to the soil and interacts with water, it is converted into ammonium or NH4+ which is a form useable by the plant. These NH4+ molecules or ammonium are easily bound to the clay and organic matter particles in the soil making it very stable. This process of converting from NH3 to NH4+ does take a little time and will depend heavily on soil temperature, moisture, and pH. The warmer the temperature, the more rapid the conversion. Ideally, you would want a fairly concise conversion from NH3 to NH4+. NH4+ is much more stable than the gas NH3. NH3, if not sealed into the soil well, can escape through the soil and be lost.

Once converted to ammonium, it will stay well bound to the clay and organic matter. It cannot be lost by volatilization, leaching, or denitrification. It can be converted from ammonium to nitrate (NO3-) by the process called nitrification. This is done through the work of microbes. In this form, the nitrogen is much less stable and can be lost in multiple different ways. To keep as much nitrogen as possible, it is best to keep the nitrogen in the NH4+ form as long as possible. Since nitrification is a microbial driven process, the warmer the temperatures, the faster the conversion. Microbes can function down to 32 degrees, but do so at such a slower rate that the effects are nearly negated.

Application Requirements

Because of its dependency on temperature for conversions, temperature plays a large roll in when and where to place anhydrous. To keep as much nitrogen as ammonium as possible, delay applications of anhydrous until colder weather. This will keep the majority of the nitrogen as ammonium and minimize over winter losses. Generally, a threshold of 50 degrees is advised. However, there are some stipulations to that. A consistent soil temperature of 50 degrees is necessary at 4 inches deep. Merely reaching 50 degrees overnight is not enough to keep the ammonium from being nitrified. It must stay below 50 consistently. Additionally, it must not be a prolonged period before the first soil freeze. If that time frame will be long, it is advised to wait until closer to soil freezing.

A downside to fall application is the potential for nitrification to start early in February and March as we start getting some warm days. Many producers feel that this chance is outweighed by the dispersal of the workload. When considering spring applications, with the potential for wet springs, not having all of the nitrogen applied before planting needs to start is a concern. Additionally, fall application can reduce possible soil compaction.

A final consideration involves dryness of the soil. With dry soils, the chance for loss is much greater. This is due to large cracks and air pockets in the soil allowing anhydrous to escape. This can also occur as it is more challenging to get the top sealed over and trap all the anhydrous underground with dry conditions. If this is the case, increase the depth of injection or wait until the soil conditions are more optimal.

Safety Concerns

Because of its hygroscopic nature, anhydrous is EXTREMELY dangerous. Exposure to anhydrous can result in extreme burns, temporary or permanent blindness and even death. It is imperative that farmers follow strict procedures and guidelines to avoid accidental exposure. Most accidents take place around connectors, so be extremely careful when handling these connections. Bleed the hose coupling before disconnecting it, as anhydrous is under extreme pressure. Don’t move any hoses by the valve handle as this could cause one to open unexpectedly.

Avoid situations resulting in pressure buildup. Don’t overfill tanks. Fill tanks only 85% full to allow for expansion. Make sure the tanks are painted fully white to cut down on heat absorption. Park tanks in the shade if at all possible.

Maintain proper protective gear and procedures. Wear long sleeves, protective eyewear and long gloves. Keep an additional 5 gallons of water in the tractor at all times. Water is the only solution for exposure. Keep a squirt bottle of water for flushing eyes. It is recommended for eye, nose and mouth, or skin exposure to apply a constant flushing of water for 15 minutes then seek emergency medical attention. A stream of water the size of a pencil will use up 5 gallons of water in 7.5 minutes. Having additional water on the tractor is imperative to reduce damage as much as possible. “Also, because of the low boiling point of anhydrous, any contact with it can burn by freezing as well as caustic action.” Always wear long sleeves and gloves!

Anhydrous will expand rapidly and sit close to the ground as it leaks. Always have an escape route planned. Work upwind from all hoses and connections in case of a rupture. Always park the tank and applicator when not in use in a location that the wind will blow away from homes and animals. Check over equipment regularly, focusing on hoses and connections. Make sure there are no copper, brass, or galvanized couplings as ammonia will corrode through them.

If there is an accident, work fast. Apply water as quickly and thoroughly as possible. Move the injured party our of direct contact with any leaking anhydrous. If it has come in contact with eyes, eyes will close involuntarily. Force the eyes open to begin flushing them out. Be sure to remove contacts immediately.

Anhydrous can be extremely dangerous, in fact, it is likely the most dangerous chemical on your farm. However, handled with care, it can be an excellent source for nitrogen. Remember, there is ALWAYS time for safety. Take extra time when necessary to prevent catastrophic problems down the road.


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