Using Anhydrous Ammonia

Pure ammonia (NH3) is made up of 82.24 percent nitro-gen (N) and 17.76 percent hydrogen. It has been formed by the combination of N2 gas from the air (a form not available to crops) and hydrogen. The simple compound is called anhydrous ammonia (NH3) : anhydrous meaning "without water. " It is gas but must be stored, transported, and handled under pressure in special containers. When under pressure it is a liquid, looking and flowing like water. Its weight varies with temperature but is approxi-mately 5 pounds per gallon. If liquid NH3 is released on the soil surface it expands rather rapidly into a gas and will evaporate. When evapo-rating, it is actually colorless although it first appears as a white vapor because of heat intake from the air. It has a sharp, pungent odor which serves as its own warning signal to the user in detecting losses during application. Reaction In The Soil Soil application of NH3 takes advantage of the rapid expansion of liquid ammonia into the gaseous form and its tremendous affinity for water. When the liquid is released in the soil, it quickly spreads out to a diameter of about 6 inches depending on the rate applied, soil mois-ture, and soil texture. It dissolves immediately in soil mois-ture and then is no longer a gas. The compound formed is ammonium hydroxide (NH40H) which breaks into two parts: the ammonium ion (NH4) with a plus charge and the hydroxyl ion (OH-), the negative ion. The (NH4) will cling to either the negatively charged clay particles or the soil organic matter. In this form it moves very little. At the immediate point of injection where the NH3 becomes NH40H, the soil pH is temporarily high since the latter compound is strongly alkaline. When bacteria act on the NH4 to convert it to nitrate, H+ ions are released. Thus NH3, over the entire growing season causes a slight reduction in soil pH. Soil organisms are discussed in a later section