3Y0 HANDY-BOOK OF HUSBANDRY. 



likewise the different ayers 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 i lb. of ammonia there were 

 3,492° 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 half 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 

 conformity 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 nitro- 

 genous 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 evi- 

 dence, 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, do not much advance the true theory of certain 

 agricultural practices. It is only by carefully investigating subjects 

 like the one under consideration that positive proofs are given 

 showing the correctness of intelligent observers in the fields. 

 Many years ago I made a great many experiments relative to the 

 chemistry of farm-yard manure, and then showed, among other 

 particulars, that manure, spread at once on the land, need not there 

 and then be plowed in, inasmuch as neither a broiling sun nor a 



