Friday, April 19, 2013

Some Truths About Fertilizer

In the aftermath of the tragic fire and explosion in Texas I have heard many half-truths and some outright fallacies about fertilizer. Today I am trying to get the truth out.

First of all, fertilizer is an essential ingredient to modern commercial agriculture. Fertilizer contains concentrated elements that are needed for plants to grow and nitrogen, phosphorus and potassium are the most common. This same fertilizer mixture is also applied to most lawns and gardens across the country to keep them green and growing.

There are three basic forms of fertilizer, each with their own hazards and benefits. I will go over each in turn.

Anhydrous ammonia is the most concentrated form of fertilizer. Is is 82% nitrogen by weight. Anhydrous, as it is commonly known, is stored as a liquid under pressure in those long white tubes that look like a huge salami. At normal atmospheric pressure is is a gas. Farmers transport anhydrous from the plant to the farm in smaller white steel tanks on a trailer and each holds about 1000 gallons.

The benefit of anhydrous is that is is concentrated and requires fewer trips to town to purchase the fertilizer and fewer times refilling. It is usually the least expensive form of nitrogen fertilizer available. Twenty years ago most farmers used anhydrous as their primary form of nitrogen. Today many famers have switched because of the hazards involved.

Anhydrous ammonia can be dangerous if not handled carefully. It will not burn or explode, as has been reported. Since anhydrous ammonia is stored under pressure, if a valve or hose breaks the ammonia will spray into the atmosphere. It is not a poison, but anhydrous ammonia gets very, very cold when going from a liquid under pressure to a gaseous state. It will freeze whatever is in its path, including my father's leg many, many years ago.

Anhydrous ammonia also wants to join with water, that's what anhydrous means, no water. If released near a person the anhydrous ammonia will absorb the water in the eyes and mouth. Too much, too close and it will blind you. But it will not burn or explode and did not cause the Texas explosion.

Liquid fertilizer is a lower concentration of fertilizer stored and shipped in a liquid form. Most common liquid fertilizers used around here are 32-0-0 (32% nitrogen) and 10-34-0 (10% nitrogen and 34% phosphorus). Liquid fertilizer is gaining in popularity because the hazards are much smaller and it is easier to handle. It does require more trips to fertilize our fields.

The hazards of liquid fertilizer are the salts in the liquid. It will burn in a cut or if splashed into an eye. If spilled into a stream it will cause a fish kill, again by too much salt. It would not be the best thing to drink, but it is not a poison. Once again it will not burn or explode.

Dry fertilizer is the medium concentration of fertilizer. It is identical to what is commonly spread on lawns and gardens. When examined closely dry fertilizer resembles little balls. There are many forms of dry fertilizer, some of the most common are 46-0-0 (urea; 46% nitrogen), 11-52-0 (monoammonium phosphate; 11% nitrogen and 52% phosphorus), 0-0-60 (potash; 60% potassium) and 34-0-0 (ammonium nitrate; 34% nitrogen).

These dry ingredients are mixed to create the desired levels of each main ingredient. Dry fertilizer is gaining in usage around here with current prices. It works well with variable rate fertilization, where we only apply how much fertilizer is needed in each area of a field.

Of those listed above none are really dangerous except one. Most are non-flammable and non-explosive. The one exception is ammonium nitrate (34-0-0). It is the main component of ANFO and was used to blow up the Federal Building in Oklahoma City. By itself ammonium nitrate is not going to explode, it needs other components, namely a carbon source and heat and pressure. The carbon source for the Oklahoma City bomb was diesel fuel. Heat and pressure were supplied by a small explosion.

If you want to read of a really bad explosion, Google the Texas City harbor explosion that destroyed the town. This explosion happened on a couple of ships in 1947. Ammonium nitrate fertilizer in cotton bags (carbon) were in a ship that caught fire. Standard practice at the time to extinguish a ship's fire was to seal the compartment and pump in steam (heat and pressure). BOOM.

So what happened in West, Texas this week? We'll probably never know. From reading the accounts of the firefighters and extrapolating from them my guess is this: A fire started in the retail plant. The firefighters thought they had it out. After smoldering for a while it reignited. Some reports say there were propane tanks nearby which would provide the carbon. The wooden building would also provide the carbon. The fire is the source of the heat and pressure.

Can this happen in Lexington or your local town? I would love to say absolutely not, but there is a small chance. All employees of fertilizer plants know how dangerous the products are that they handle every day and they treat them carefully. Reflect that over the 60 plus years of using commercial fertilizer there are only a couple of very bad explosions that have occurred by accident. Here in Lexington the fertilizer plant is in an industrial area and not near any residences.

Final word is that fertilizer is essential for modern agriculture. While there are hazards involved, fertilizer can be handled safely and carefully. Accidents can happen anywhere anytime. We prepare for the worst and expect the best.


  1. I didn't know that Grandpa got 'burned' from anhydrous ammonia!