The Effects of NH3 on Seed Corn Germination

Behavior of NH3 in the Soil

• According to the University of Minnesota Extension website, pure ammonia is very corrosive containing up to 82 percent nitrogen and weighing about five pounds per gallon. It is used as a raw material in the manufacture of urea ammonium nitrate, urea, and ammonium nitrate; all of which are used as fertilizers supplying nitrogen for plant growth. In agriculture, NH3 is used as a source of nitrogen for corn. Because it has a high affinity for water, NH3 is injected into the soil, where it readily combines with water to become ammonia hydroxide; further breaking down to ammonium ions. In the absence of water, NH3 does not completely convert to ammonium hydroxide, especially at the source of injection. Injury to corn seedlings occurs when the growing roots come into contact with this "pocket" of NH3. Conversion of NH3 to less toxic forms fails to occur in drier coarse textured soils; therefore, adequate moisture is necessary.

Effect of NH3 on Corn Seed Germination

• Because ammonia is applied under pressure into the soil, it quickly expands into gaseous form and spreads out about 6 inches diameter from point of application, notes the University of Minnesota Extension website. The website continues to note that if corn is planted immediately following NH3 application, substantial injury occurs and final plant density is reduced. According to the University of North Dakota website, this problem is more prominent in dry coarse textured soils than wet soils. Injury to seedlings can also occur if NH3 applications are too shallow and corn is planted right on top of the injected band. The University of Minnesota Extension website notes that affected seedlings also exhibit phosphorus deficiency due to few or damaged roots available for nutrient uptake.

Other Sources of NH3.

• Most nitrogen fertilizers like urea, ammonium nitrate and liquid nitrogen easily convert to NH3 forms that can potentially injure corn seedlings. The University of Oklahoma website notes that urea is high on the list because it can change into ammonium carbonate that quickly turns into NH3. Ammonium nitrate fertilizers may contain up to 50 percent ammonium compounds that can easily convert to NH3 and harm tender seedling roots. Liquid nitrogen materials usually contain different proportions of nitrate, ammonium ions, ammonia, urea and water, notes the University of North Dakota website. Potential for seedling injury exists depending on the proportion of ammonia and any environmental factors that may favor conversion of ammonium into NH3. Use of "nitrification inhibitors" is recommended by the University of Minnesota Extension website, to reduce potential injury to roots by NH3.