Variations in Low Temperature Adaptability of Nitrifiers in Acid Soils

Nitrification of NH 4 ‐N, added as (NH 4 ) 2 HPO 4 to acid soils representative of three southeastern physiographic regions, was studied under controlled conditions at 6 and 32C following amendments to minimize differences among soils in reaction and certain major elements. At 32C, nitrification of the applied NH 4 approached completion in all soils, except the Tifton, by the 10th day irrespective of the region of origin. At 6C, however, patterns of nitrate accumulation were comparable among soils within a defined physiographic region but distinctly different to that of soils from other regions. Since these data were suggestive of variation in microbial adaptation, soils representative of regions of contrasting climate and elevation were further studied. Results from various treatments, such as cross inoculation, sterilization, and stimulation of initial nitrifying population, in either whole or “synthetic soil,” provide evidence that the activity of a soil nitrifying flora subjected to wide temperature variation, is a function of the metabolic adaptation of the organisms to the climate of origin.