Jump to Main Content
Temperature as a factor in nitrogen changes in the soil
- Panganiban, E.H.
- Agronomy journal 1925 v.17 no.1 pp. 1-31
- biological activity in soil, temperature, ammonification, nitrification, nitrogen fixation, New York
- The effect of constant and alternating temperatures has been studied in connection with ammonification, nitrification, denitrification and nitrogen fixation, under both aerobic and anaerobic conditions. Studies with ammonification at a constant temperature indicated that ammonification took place between 15 degrees and 60 degrees C., and that at higher temperatures the rate is faster. The thermophilic organisms seem to be very active ammonifiers. Studies in connection with alternating temperatures showed that the degree of variation of alternating temperatures, whether 15 degrees or 5 degrees C., affects the process to the same extent. Studies with nitrification at constant temperature showed that the process took place between 15 degrees and 40 degrees C., and that the optimum temperature in soil cultures is about 35 degrees C., or slightly higher. Alternating the temperatures depressed the process very greatly, although a daily greater degree of variation, say 15 degrees C., seems to counteract this effect. A 10-day or 5-day change of temperature with the same degree of variation gave an entirely different result. With a 10-day change of temperature, the incubation starting at higher and ending at lower temperatures, showed much less nitrate accumulation than when incubated in the reverse order. Denitrification at constant temperature for one week showed that the process took place between 15 degrees and 40 degrees C., and that the optimum temperature in soil cultures lies somewhere between 25 degrees and 30 degrees C. When the incubation period was made two weeks, the results could not be regarded as reliable, for the amount of sugar added, which is necessary for the process, was found to be exhausted after a week of incubation. The determination of the actual amount of nitrates in the presence of dextrose was also studied but was found to be impossible, for a considerable portion of nitrate is lost in the determination. The nitrate lost by denitrification was reduced to ammonia and to albuminoid nitrogen. There was no loss of nitrogen by complete reduction. Studies in connection with alternating temperatures are not satisfactory because the period of incubation, which was one week, was too short. A longer incubation, however, necessitates an increase of the amount of sugar for the organisms, also an increase of the nitrates to be denitrified. An increase of either or both will produce a toxic effect, and the result will be unreliable. A study of nitrogen fixation under both aerobic and anaerobic conditions showed that the process took place between 15 degrees and 40 degrees C., and that the optimum temperature in soil cultures again for both conditions lies between 25 degrees and 30 degrees C. There was a greater fixation under anaerobic than under aerobic conditions. Soil 3 showed this interesting result, and probably Soils 1 and 2 would have shown the same had they not possibly lost nitrogen by denitrification. Determination of probable error indicated that the results are reliable. There are some indications that a soil active in one nitrogen change will be also active in the other nitrogen changes.