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Title: The effect of drying on the microbiological processes in soils
Author: Khalil, Fahmy Khalil
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1929
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(1) Drying considerably reduced the bacterial content of the soil. • • (2) On subsequent moistening and incubation dried soils gave higher counts than permanently moist soils. • • (3) Air drying caused a rapid conversion of ammoniacal to nitrate nitrogen. • • (4) Drying increased the nitrogen fixing capacity of the soil (solution tests). • • (5) Drying increased the ammonifying and nitrifying power of the soil (soil tests). • • (6) No evidence could be obtained in support of the view that the microflora of dried soils is more efficient than that of moist soils. (a) In ammonification and nitrification solution tests moist soil was superior to dried soil when equal quantities of soil were used but when approximately equal numbers of bacteria were introduced, there was no difference in the ammonifying and nitrifying capacity of dried and moist soils. • (b) Inoculation of dried soil with a filtrate from moist soil did not reduce its ammonifying and nitrifying power (soil tests). • (c) The drying of partially sterilised soil (subsequently re- inoculated) increased its ammonifying and nitrifying capacity (soil tests). • • (7) Drying renders the soil organic matter more easily decomposable. (a) The organic matter in dried soil was more rapidly ammonified and nitrified than that in moist soil. • (b) Soils to which organic matter had been added before drying showed greater increases in microbiological activity as a result of drying than soils which had received no addition. • • (8) Treatment of the soil with prussic acid caused more than eighty per cent reduction in bacterial numbers. • • (9) 1'or normal soils, soil extract agar and glycerine nitrate agar gave higher bacterial counts than Thornton's medium. The latter gave the highest counts for soils treated with hydrocyanic acid gas. • • (10) Crystal violet as recommended by Smith does not completely inhibit actinomycetes on glycerine nitrate medium. • • (11) Soil samples taken during winter contained more ammoniacal than nitrate nitrogen. • • (12) Samples obtained while the soil was frozen showed higher bacterial counts than those taken when the soil was not frozen.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available