482 BOARD OF AGRICULTURE. 



Percentage of nitrogen per acre: 1st 6 inches. 2d 6 inches. 3d G inches. 



lbs. lbs. lbs. 



Excess of nitrogen in an acre of soil 12 inches? J 



deep calculated as ammonia in part of field > 3592^ 

 mown once and then seeded ) 



It will be seen, that not only was the amount of large clover 

 roots greater in the part where clover was grown for seed, but 

 that likewise the different layers of soil were in every instance 

 richer in nitrogen after clover seed than after clover mown twice 

 for hay ; or as it may be expressed : In one acre of soil there were 

 3592 pounds more of ammonia in the land where clover seed was 

 grown than where other clover was made entirely into hay ; or the 

 former part of the same field produced rather more than one-half 

 more of the total quantity of nitrogen yielded by the latter. 



Reasons are given in the beginning of. this paper which it is 

 hoped will have convinced the reader that the fertility of land is 

 not so much measured by the amount of ash-constituents of plants 

 which it contains, as by the amount of nitrogen which, together 

 with an excess of such ash-constituents, it contains in an available 

 form. It has been shown likewise that the removal from the soil 

 of a large amount of mineral matter in a good clover crop, in con- 

 formity with many direct field experiments, is not likely in any 

 degree to affect the wheat crop, and that the yield of wheat on 

 soils under ordinary cultivation, according to the experience of 

 many farmers, and the direct and numerous experiments of Messrs. 

 Lawes and Gilbert, rises or falls, other circumstances being equal, 

 with the supply of available nitrogenous food which is given to the 

 wheat. This being the case, we cannot doubt that the benefits 

 arising from the growth of clover to the succeeding wheat are 

 mainly due to the fact that an immense amount of nitrogenous food 

 accumulates in the soil during the growth of clover. 



This accumulation of nitrogenous plant-food, specially useful to 

 cereal crops, is, as shown in the preceding experiments, much 

 greater when clover is grown for seed than when it is made into 

 hay. This affords an intelligible explanation of a fact long observed 

 by good practical men, although denied by others who decline to 

 accept their experience as resting on trustworthy evidence, because 

 as they say, land cannot become more fertile when a crop is grown 

 upon it for seed which is carried off, than when that crop is cut 

 down and the produce consumed on the land. The chemical points 

 brought forward in the course of this inquiry show plainly that 

 mere speculations as to what can take place in a soil and what not, 



