136 



On the Growth of Wheat Year after Year. 



hardened below ; and then the treasures of heaven will still, in- 

 deed, fall on its lap, to be carried off again by the parching winds 

 and the scorching sun ; — but, open the bosom of the earth for 

 their reception, and richness and fertility will follow. 



It is for this reason I look upon the plan of intervals as so im- 

 portant. They are, indeed, my mainstay, — the very support, 

 nay, the building up of my system. For, by the frosts of winter, 

 first of all, then by the dry winds and showers of spring, and after- 

 wards by frequent stirring, they become so pulverized and porous, 

 that the organic elements of fertility contained in the atmosphere 

 gain easy admittance, and are there retained ; a small portion for 

 the benefit of the searching rootlets of the growing plant, the 

 larger supply for the future crop. 



I dare not, with certainty, claim the free nitrogen of the air as 

 my helper in the process of fertilization, though thus much has 

 been proved : — Under ordinary circumstances, gaseous nitrogen 

 has shown but little tendency to combine with other bodies ; 

 but, on trial, nitrogen mixed with excess of hydrogen and burned 

 at a jet, produced water and nitric acid. On another trial, pure 

 nitrogen passed over a mixture of charcoal powder and carbonate 

 of potass, produced potassium in quantity. Future trials may 

 produce further discoveries. And surely," says Dr. Fownes,'"'' 

 the chemical energies at work in a living plant are, to say the 

 least, equal in power to those which we have under our control 

 in the laboratory." And certainly, I may add, where the state of 

 the soil affords an easy access to the roots of the plant, the sup- 

 position is not groundless, that the free nitrogen of the air may 

 take its part in bringing the grain of wheat to perfection. 



Then, with regard to the inorganic food required by the wheat. 

 By a gradual exposure of the subsoil in the intervals, I provide a 

 constant supply of this. I have little to contend with here ; the 

 question bemg not so much a question of sufficiency as of ex- 

 pense. For, hear Mr. Way upon this point. " Allowing," he 

 says, "a certain and considerable yearly diminution of the mineral 

 elements of fertility in the land, we have yet, so to speak, an 

 almost infinite supply of these bodies in the soil itself, provided 

 we knew how we might economically avail ourselves of it. This — 

 the item of expense — is, after all, the turning point." 



Now, let us see what is the expense of turning up these trea- 

 sures with the spade. Let us place the cost of hand-labour 

 against the comparatively ineffectual process of the plough. Say 

 there are three ploughings for wheat, as is the case in this neigh- 

 bourhood on soil like mine. That, at seven inches deep and 12^. 

 the acre, will be 865. ; and the time occupied will be three days.j 



* Prize Essay " On the Food of Plants," in vol. iv. of this Journal. 



f Adjoining my four-acre piece of wheat described at the opening of the paper. 



