726 PRINCIPLES OF SOIL MICROBIOLOGY 



inoculation of the soil with cellulose cleccmposing bacteria have any 

 effect. 



Mutterlein 32 suggested placing one or two pieces of filter paper of a 

 uniform weight (10 grams) at various depths of soil, then, after 2 to 3 

 weeks, removing the paper from the soil and weighing the residue; 

 the loss in weight of the paper was taken as an index of the cellulose- 

 decomposing capacity of the soil. 



Niklewski 33 added cellulose to the soil and measured the carbon 

 dioxide produced by a soil thus treated. In addition to cellulose, 1 

 gram K 2 HP0 4 , 1 gram MgS0 4 , 8 grams CaC0 3 , and (NH 4 ) 2 S0 4 were 

 added to 8 kgm. of soil. He found that the decomposition of cellulose 

 is chiefly controlled by the presence of available nitrogen in the soil. 

 The greater the amount of cellulose added or present in the soil, the 

 quicker does the nitrogen need set in. Nitrogen fixing organisms were 

 thought to play only a secondary role in normal soils, since cellulose is 

 very slowly decomposed in normal soils without the addition of avail- 

 able nitrogen. This would not be the case if nitrogen-fixing organisms 

 were active, as when glucose is added. When only 0.125 per cent 

 cellulose was added to a loess soil, containing 0.15 per cent nitrogen, a 

 nitrogen need could be observed. The greater the amount of cellulose 

 added, the greater was the evolution of C0 2 up to a certain concentra- 

 tion, 1.5 per cent giving at first less C0 2 than 1.0 per cent cellulose. 

 When the available nitrogen is exhausted, the curve soon falls to a 

 certain level depending upon the rapidity of decomposition of the 

 nitrogenous substances in the soil and the rate with which the nitro- 

 gen becomes available. The addition of 0.0125 per cent ammonium 

 sulfate greatly stimulated cellulose decomposition; this amounted to 

 about 1 gram of (NH 4 )2S0 4 in the case of soil, and 2 grams of the 

 ammonium salt in the case of sand, for every 10 grams of cellulose. 

 Larger amounts of nitrogen acted injuriously; this injurious action 

 may be later overcome. 



On comparing the evolution of carbon dioxide, with and without 

 the addition of a nitrogen salt, Niklewski suggested calculating the 

 available nitrogen in the soil from the amount of cellulose decomposed, 

 as indicated by the evolution of C0 2 . In the case of loess soil, with a 

 total of 0.150 per cent nitrogen, 0.040 per cent nitrogen was found to 



32 Mutterlein, C. Studien ttber die Zersetzung der Zellulose im Dilngen und 

 im Boden. Inaug. Diss., Leipzig. 1913. 



33 Niklewski, B. Bodennakteriologische Beobachtungen als Mittel zur 

 Beurteilung von Boden. Centrbl. Bakt., II, 32: 209-217. 1912. 



