304 ACTIONS OF ARTIFICIAL MANURES 





do not waste it by setting it free as gas, but they convert it 

 into proteins and similar substances out of which their own 

 bodies are constructed ; in these cases also the soda part of 

 the salt is left behind as carbonate. This process is strictly 

 comparable with the production of acid by the action of micro- 

 fungi upon sulphate of ammonia ; in each case the living 

 organism effects a splitting of the salt in order to obtain 

 nitrogen, and it rejects and leaves behind in the soil in the 

 one case the acid part of the salt, in the other the base. 



We are now in a position to sum up the features of this 

 secondary action of nitrate of soda applied to the soil, an 

 action which causes so great an injury to its texture when the 

 land is at all heavy. The bad texture is due to the defloccula- 

 tion of the clay particles, which is brought about by the 

 presence in the soil of a small quantity of dissolved carbonate 

 of soda. The carbonate of soda is formed by the action of the 

 crop plants and of certain soil bacteria upon the nitrate of 

 soda; they take up the nitrogen-containing part of the salt, 

 because nitrogen is an element indispensable to their develop- 

 ment, and leave behind the soda base combined with the 

 carbon dioxide which they excrete. 



The next point of importance is to find both a remedy for 

 the injured tilth of the heavy soil, where nitrate of soda has 

 been too freely applied, and a means of preventing such action 

 in the future. Lime is of no benefit to a soil which has been 

 deflocculated by an alkali like carbonate of soda, because lime 

 is an alkali itself, and would rather tend to make matters 

 worse. The flocculating action of lime on ordinary clay soils 

 only takes place when the lime gets washed into the soil as 

 soluble bicarbonate ; lime itself, when protected from carbon 

 dioxide, has no flocculating action (see Hall and Morison, 

 J. Agric. Sci., 2 (1907), 244). In this particular case the 

 flocculating action of lime would be largely masked by the 

 carbonate of soda which would still remain in the soil. Gypsum 

 .has been used in America as a means of getting rid of carbonate 

 of soda in those unfertile and unworkable soils known as 



