The Effect of Anhydrous Ammonia on Nitrification and the Microbiological Population in Sandy Soils 1

Anhydrous ammonia was applied to Arredondo loamy fine sand and Lakeland fine sand at rates of 100 and 250 pounds of nitrogen per acre. In all soils the numbers of fungi were decreased. The numbers of bacteria and actinomycetes were increased except for a period not longer than 3 days after application, on the neutral soil, during which time they were decreased. A more detailed study of the zone of retention showed that both the numbers of fungi and bacteria were decreased on the first day. This decrease occurred in both acid and neutral soil. On the tenth day the numbers of fungi were still markedly reduced, whereas the numbers of bacteria had increased to 6 to 25 times those in the check soil. The changes in the microbiological population were noticeable while high concentrations of ammonia were present and were restricted to a 3-inch zone centered on the injector row; this corresponded to the zone in which most of the ammonia was retained. From a total population standpoint, none of the changes noted are likely to permanently disturb the ecological balance in the soil. The drastic reduction in numbers of fungi in the anhydrous ammonia-treated soil indicated that there may be a possibility of it being used as a fungicidal agent in soil. Compared to ammonium sulfate, anhydrous ammonia nitrified more rapidly in the slightly acid soils and less rapidly in the neutral soil. This may be of practical significance in choosing between these two fertilizer materials.