140 



Power of Soils to absorb Mamire. 



]3y which he supported this practice were principally two. The 

 first, which it is merely necessary to mention, was that by the 

 breaking up and subdivision of the particles of soil, a new and 

 constantly increasing food-yielding surface, or as he himself 

 called it " pasture," was provided for the roots of plants. 



The second argument was, that by the continual opening and 

 loosening of the soil opportunity was given to the air to enter it, 

 and to confer upon it increased fertility. Tull knew not of what 

 nature those atmospheric influences were, for at that time the 

 names of ammonia and carbonic acid were unknown ; but he was 

 nevertheless convinced that the air did exercise some beneficial 

 influence on the soil, and his aim was to court its entrance to the 

 fullest extent. 



Of the system which Tull invented to enable him to carry out 

 his peculiar views, it is not my intention to speak. From time 

 to time that system, more or less modified to adapt it to parti- 

 cular circumstances, has been revived by thinking, intelligent men ; 

 and at the present time a good deal of attention has been attracted 

 to the novel method of wheat-growing practised by the Rev. Mr, 

 Smith, at Lois Weedon, in Northamptonshire. Accounts of this 

 system have appeared in a late number of this Journal and else- 

 where ; and as I have no intention of advocating any system, but 

 simply of examining a principle by the application of the rule 

 and square of scientific truth, I shall merely say that Mr. Smith 

 believes with his great predecessor, Jethro Tull, that on fair aver- 

 age wheat-soils deep and abundant cultivation may more than 

 replace manure. I said before that Mr. Smith has published his 

 own account of his experiments and his views on the subject ; 

 they go much farther than the bare question above propounded, 

 but this is the question to which I limit my present inquiry, 

 namely — Is it likely, on theoretical considerations, that the air 

 and the soil together can by any means be made to yield without 

 the application of manure, and year after year continuously, a crop 

 of wheat of from 30 to 35 bushels per acre ? I confess that I do 

 not see why they should not do so. 



We have seen the power which soils possess of abstracting 

 ammonia from the air — this power is not confined to periods of 

 rain, it is not even limited to the periodical recurrence of dew — 

 so often as air charged with carbonate of ammonia comes into 

 contact with a surface of soil, so often will that soil be enriched 

 by ammonia to the extent to which the air contains it. It is 

 impossible to state numerically the amount of ammoniacal manur- 

 ing which a soil properly prepared might, in 24 hours, or in the 

 course of the year, thus receive, simply because the necessary 

 data are wanting, and v/e can only therefore judge by results. 



