H. B. Hutchinson 99 



or fungal action are onl}' tardily removed by any base that may be 

 present. 



The gains of nitrogen shown below, although not large, are fairly 

 satisfactory in view of the restricted conditions under which they were 

 obtained. The substances to be tested were previously dried and finely 

 ground and then added in quantities of 0-5 to 1-0 grm. to 10 grm. of fine 

 air-dry soil. These portions were placed in Erlenmeyer flasks and 

 incubated at 30° C. after sufficient water had been added to make the 

 mixture nicely saturated. 



The addition of straw at the rate of 5 per cent, gave the following 



results. 



Total nitrogen 



/- ' ^ 



At After After After 



beginning 30 days 44 days 240 days 



0-5 grm. straw + 10 grm. soil 15-92 mgrm. 17.50 mgrm. 17-71 mgrm. 18-23 mgrm. 



Gain (calculated per grm. straw) — 3-16 „ 3-58 „ 4-62 „ 



Finely ground wheat stubble and elm leaves added at tlie rate of 

 10 per cent, gave relatively lower gains. 



Total nitrogen 



The use of sand and of calcium carbonate, in conjunction with soil, 

 gives better results, possibly on account of better aeration and a more 

 efficient neutralisation of acid products. 



Total nitrogen 



At beginning After 69 days 

 1 grm. straw +5 grms. sand + 5 grms. soil + 1 grm. GaCO, 15-30 mgrm. 21-57 mgrm. 



Gain ' — 6-27 „ 



In comparison with sugar, these plant materials appear to become 

 available for nitrogen fixation much less rapidly, but the final gains agree 

 well with those frequently obtained when sugar is subjected to the action 

 of a mixed bacterial flora. 



Pot Exferiments. With the object of obtaining further information as 

 to the value of plant residues and sugar for the fixation of nitrogen, a 

 number of pot experiments have been carried out, the efiect of the 

 apjjlications being gauged in the first instance by plant growth, and at 

 the close of the experiments by nitrogen determinations. With sugar, 

 starch, and other non-nitrogenous materials, demonstration of their use 



7—2 



