212 



Moiiurittf/ for Hai/ 



portions (100 gms.) of soil witii water and varying amounts of lime, 

 and determining the lime left free after twenty-four hours. 



It was found that the soil of Plot 12 "fixed" practically the whole 

 of the lime applied even when the proportion was as high as two per 

 cent, of the soil used, whilst even in the most favourable case the soil 

 fi.xed practically 1-5 per cent, of its weight of lime In'fore any appreciable 

 surplus of free lime renuiined. The data for a few plots are given 

 in Tal)l(> IX {rf. also Fig. 1). 



Injluence upon Bacterial Activities in Soil. 



The part played by soil bacteria in determining fertility, more 

 particularly by regulating the supply of available plant food, is now 

 common knowledge and need not be enlarged upon. In this connection 

 interest centres mainly round the supply of nitrogen, which is presented 

 by the bacteria first in the form of ammonia and then, if the conditions 

 are favourable, the latter is further converted to nitrates. Under 

 normal conditions this latter change ("nitrification") goes on more 

 rapidly than ammonia production and hence the amount of ammonia 

 present in the soil at a given time is usually exceedingly small. 

 In the case of ordinary arable soils investigated by RusselP the 

 ammonia amounted to only 1-2 parts per million of soil, rising to 3-4 

 parts in the case of rich dunged soils and garden soils. Much higher 

 proportions were found, however, in the soils of the Garforth hay 

 plots here under review, as may be seen in Talile X. 



Table X. Nitrogen as Ammonia and Nitrate in Soils (1911). 



' Rus.<!oll. This Jnnrnnl. 1910. iit. 233. 



