E. J. RlTSSKLL AND H. B. HUTCIIINSON 



123 



Barnfield 



Little Hoos Field 



Nitrogen 



•112 °/, 

 •178 % 



Loss on ignition 



3-969 % 

 4-572 °/„ 



CaCO, 



3-409 °/„ 

 3-159 °/o 



The chemical investigation was directed mainly to the nitrogen 

 compounds, annnonia, nitrates, complex and unstable nitrogen com- 

 pounds, and humus. The soil was picked over, passed through a 3 mm. 

 sieve, and put up in quantities of 800 grams into large bottles. These 

 were then divided into four sets : to each bottle in one set was added 

 40 grams of toluene, which was allowed to remain in the soil during 

 the whole of the experimental period ; a second set also received the 

 same amount of toluene, but at the end of three days the soil was 

 spread out till the toluene evaporated ; a third set was heated to 98° C. 

 for 3 hours, and the fourth was left untreated as control. After these 

 various treatments the water content of the soil was brought up to 

 15 per cent. Precautions were taken to prevent reinfection, and the 

 bottles were kept plugged with cotton-wool to admit air ; they were 

 stored in a cupboard at about 15° C. At suitable intervals a bottle 

 was taken from each set and the determinations above referred to 

 were made. 



§ 15. Changes in the amount of ammonia and of nitrate present. 

 The determination of ammonia in soils is complicated by two factors 

 which, however, act in opposite directions : soil has a remarkable power 

 of retaining ammonia, and, on the other hand, some of the organic com- 

 pounds of the soil are very unstable and readil}' decompose with forma- 

 tion of ammonia. By distilling soil at 12 mm. pressure with water 

 containing 2 per cent, of magnesia in suspension we have succeeded 

 in reducing these sources of error and obtaining quite satisfactory 

 results. 



Although ammonia is the final nitrogenous product of the decom- 

 position of organic matter in the soil it is not the final result of the 

 bacterial activity in the untreated soil, but is at once changed to nitrate. 

 It is therefore necessary to make simultaneous determinations of 

 ammonia and of nitrates. 



The results of two of the experiments are given in Table 2. Soil 1 

 had two years previously received a complete dressing of artificial manure, 

 whilst Soil 2 had been for some years unmanured. 



