The Bio-chemical Activity of Soils

Introduction Many methods have been devised in order to obtain a picture of the relatively broad spectrum of microorganisms present in the soil (Waksman, 1932; Lohnis, 1938 ; Beijerinck, 1946 ; Winogradsky, 1949). Techniques for direct microscopic examination, including contact slide methods, were developed by a number of research workers (Rossi, 1921, 1936; Conn, 1928, 1929 ; Cholodny, 1930; Kubiena, 1932) and have since been used with good results (Jensen, 1935). Studies have also been carried out on the chemical activity of microbes in the soil. Thus the influence of microbes on soil fertility has been examined by Waksman (1922, 1923), Waksman and Dubos (1926), WaGman and Starkey (1923, 1924a, 1924b), van Schuchtelen (1910). The TTC dehydrogenase" activity of these organisms has been examined by Lenhard (1956, 1957), Stevenson (1 959), Roth (1 963, 1964), Hirte (1963) and Schaefer (1963).