130 TALKS ON MANURES. 



get a good crop of clover, if you will keep the sheep off of the land 

 this fall. But I do not see what you mean by the clover-plants 

 finding food enough for 40 bushels of wheat, while in point of 

 fact, if you had sown the field again to wheat this fall, you would 

 not, as you say, probably get more than 12 or 15 bushels of wheat. 



" He means this,'* said the Doctor. " If he had sown the land 

 to wheat this fall, without manure, he would probably not get 

 over 15 bushels of wheat per acre, and yet you both agree that the 

 land will, in all probability, produce next year, if mown twice, 

 three tons of clover-hay per acre, without any manure. 



" Now, if we admit that the clover gets no more nitrogen from 

 the rain and dews, and from the atmosphere, than the wheat will 

 get, then it follows that this soil, which will only produce 15 bush- 

 els of wheat per acre, does, in point of fact, contain plant-food 

 enough for 40 bushels of wheat, and the usual proportion of straw. 



" The two crops take up from the soil as follows : 



Phosphori: acid. fbtash. Nitrogen. 



15 bushels wheat and straw lOHbs. 1H Ibs. 22 Ibs. 



3 tons clover-hay 33 " 1 U " 150 " 



" These facts and figures," continued the Doctor, " arc worth 

 looking at and thinking about. Why can not the wheat get as 

 much phosphoric acid out of the soil as the clover ? " 



"Because," said the Deacon, "the roots of the clover go down 

 deeper into the subsoil than the roots of wheat." 



" That is a very good reason, so far as it goes," said I, " but 

 does not include all the facts. I have no sort of doubt, that if I 

 had sown this land to wheat, and put on 75 Ibs. of nitrogen per 

 acre, I should have got a wheat-crop containing, in grain and 

 straw, 30 Ibs. of phosphoric acid. And so the reason I got 15 

 bushels of wheat per acre, instead of 40 bushels, is not because 

 the roots of wheat do not go deep enough to find sufficient soluble 

 phosphoric acid." 



" Possibly," said the Doctor, " the nitrogen you apply may ren- 

 der the phosphoric acid in the soil more soluble." 



" That is true," said I ; " and this was the answer Licbig gave to 

 Mr. Lawes. Of which more at some future time. But this an- 

 swer, like the Deacon's, does not cover all the facts of the case ; 

 for a supply of soluble phosphoric acid would not, in all proba- 

 bility, give me a large crop of wheat. I will give you some facts 

 presently bearing on this point. 



" What we want to find out is, why the clover can get so much 

 more phosphoric acid, potash, and nitrogen, than the wheat, from 

 the same soil ?" 



