INVESTIGATIONS ON THE PRODUCTION OF PLANT FOOD. 181 



small amount of material one uses in the laboratory and the limited 

 time available for an investigation. 



Table showing Losses of Nitrogen from Cultivated Soils, Broadbank 

 Wheat Field, 47 years, 1865-1912. 





Rich Soil (2) 

 lb. to the acre. 



Poor Soil (3) 

 lb. to the acre. 



N. in Soil, 1865 

 N. added in manure \ 

 rain (51b.) seed (2lb.) / 



■175% = 4340 



9730 



•105% = 2720 

 330 



N. expected in 1912 

 N. found in 191 2 



I4070 

 •245% = 5730 



305 0 



•103% = 2510 



Loss from Soil 

 N. in crops 



83-IO 

 255 J 



540 



750 



Balance being dead loss 

 Annual dead loss 



5790 

 123 



— 2IO 



— 5 



When a difficulty of this sort arises the method adopted is to 

 study parallel cases where the action is more pronounced. Two of 

 these are being studied in some detail : the loss from a sewage bed 

 and the loss from a manure-heap. Sewage presents a particularly 

 interesting case, because here the loss is actually utilized as a means 

 of sewage disposal, and the sewage chemist tries to encourage it 

 just as strenuously as the agricultural chemist is trying to stop 

 it. Indeed the situation is not altogether devoid of humour, for 

 the community on the one hand spends many thousands of pounds 

 in destroying nitrogen compounds in its sewage works, and on 

 the other spends many thousands of pounds in purchasing nitrogen 

 compounds for its soils. It was to find some way of bridging this 

 difficulty that the Hon. Rupert Guinness came forward and enabled 

 us to secure at Rothamsted the services of Mr. E. H. Richards, 

 late of the Sewage Commission investigations, to make a systematic 

 study of these losses. At Rothamsted we have selected the manure- 

 heap because of its special agricultural and horticultural importance ; 

 in France, Muntz and Laine took the sewage-bed. For a long time 

 it was uncertain whether the gaseous nitrogen arose direct from the 

 proteins by a process analogous to combustion or whether it was formed 

 by decomposition of the nitrates. The problem is not yet- solved, 

 but the evidence is steadily accumulating against the combustion 

 hypothesis, and so far as it goes it indicates that the nitrogen passes 

 safely through the ammonia stage but gets lost afterwards. If this 

 turns out to be correct, an interesting method of reducing the loss, if 

 not of preventing it altogether, will become possible. It is obvious 

 that if the ammonia (or the nitrate into which it is converted) is 

 absorbed by the plant it cannot give rise to gaseous nitrogen in 

 the soil, and therefore the loss will be eliminated by arranging the 



