36 



gives up to the drainage water 211b. of nitric nitrogen per acre per 

 annum, enough to produce a 15 bushel crop of wheat, although 

 neither manure nor crop residues have been added during the whole 

 of the period. If the curve showing the rate of fall continued its 

 present course and without further slowing down, no less than 150 

 years would be needed for exhaustion of the nitrogen.. 



So far as can be ascertained, the nitrogen lost from the soil 

 appears wholly as nitrate in the drainage water. From the top 

 9 inches of the 20in. and 60in. gauges, the nitrogen lost has been 

 respectively 1,124 and 1,1721b. per acre. The nitric nitrogen in 

 the drainage water amounts to 1,247 and 1,2001b. per acre in the 

 two gauges. These figures are arrived at by adding together the 

 ^vhole of the nitrate found and such estimated amounts as are 

 possible for the first seven years before regular determinations 

 were made, deducting nitrogen introduced by rain. The subsoil 

 is left out of account, but evidence is adduced to show that it contri- 

 buted little, if anything, to the nitrate in the dr'ainage water. 



There is no indication of fixation of nitrog-en or loss of 

 gaseous nitrogen. The soil is, however, now- very poor in organic 

 matter. 



The amount of nitrate washed out is closely related to the 

 rainfall and to a less extent to the sunshine of the preceding 

 summer. 



It is difficult to account for the slow rate of removal of nitro- 

 gen from the soil unless one introduces into the ordinary cycle 

 some new element acting as a kind of immobiliser, absorbing 

 nitrates or ammonia as they are produced and giving them up 

 again later on. The case would be met if one supposed that some 

 of the soil organisms, such as alga?, bacteria, fungi, etc., assim- 

 ilated nitrates or ammonia and on their death were themselves 

 decomposed, giving rise ultimately to nitrates again. On this 

 view the nitrogen compounds of the soil would be supposed to 

 break down w-ith formation of ammonia and then nitrate, but only 

 a portion, and not the whole, of this nitrate is liable to loss or 

 assimilation by plants : the remainder would be taken up by 

 organisms, temporarily immobilised, but re-formed on the death 

 and dissolution of the organisms, when again part would be thrown 

 out of the cycle and reabsorbed. 



X. D. J. Matthews. '' Tlie Dete}'}}ii}iation of Ammonia in 

 Soil.'" Journal of Agricultural Science, 1920. \^ol. X. 

 pp. 72-85. 



An aeration method for determining the quantity of ammonia 

 in the soil with more accuracy and in shorter time that hitherto, it 

 being possible to recover 99.5% of added ammonia as against a 

 recovery of 50-60% by the older methods. For details the paper 

 must be consulted.^- 



The results of application to natural soils is to confirm the 

 older conclusion that ammonia is present in minimal quantities 

 only, but it now becomes possible to follow accurately the changes 

 that occur when stubble or green manure are ploughed in, or when 

 ammoniacal fertilisers are added to the soil. 



•Or Soil Conditions and Plant Growth, 4th. ed, 1921. p. 349. 



