GREAT DIVERSITY IN NATURE OF SOILS. 



311 



growth of cereal plants, must chiefly depend upon the 

 successful growth of fodder plants. 



The unmanured fields in the Saxon experiments 



It is easily perceived from this table that the quanti- 

 ties of nitrogen which could be obtained from the field 

 and restored in the form of farm-yard manure, bear a 

 proportion not exact but sufficiently well marked, to 

 the crops of clover produced by the field ; and there 

 can be no doubt that the farmer who takes the right 

 way to make his fodder plants thrive, obtains at the 

 same time the means of enriching his arable soil with a 

 surplus of nitrogenous food for his corn-plants. 



We do not mean to imply that in every possible case 

 the farmer must renounce the idea of supplying to his 

 land ammonia from other quarters ; for soils vary so 

 very much in their nature, that even though we can 

 assert that by far the greater proportion of them may 

 not require a restoration of nitrogenous food, yet this 

 will not hold good for all without exception. In a soil 

 rich in lime and humous materials, in consequence of 

 the process of decay going on, a certain quantity of the 

 ammonia fixed in the earth is converted into nitric acid, 

 which is not retained by the soil, but is conveyed into 

 the lower layers in the form of salts of lime 'or mag- 

 nesia. Under certain circumstances, this loss may 

 amount to much more than is compensated by the at- 

 mosphere, and for such fields a supply of ammonia will 

 always be useful. The same holds good for certain soils 

 which have not been tilled for many years, and in 



