322 A3IM0NIA AND NITRIC ACID. 



another question, whether, on the whole, progress in this 

 respect is, or is not, possible in agricultural practice. 



A few considerations only are necessary to bring the 

 farmer to the conviction, which I myself entertain, that if 

 increased production depends upon an augmentation of 

 nitrogenous food in the soil, we must at once renounce 

 all idea of improvement. For my own part, I am much 

 more inclined to beheve, that progress is only possible 

 and attainable if the farmer restricts himself to that 

 store of nitrogen Avhich he can collect upon his own 

 ground, avoiding as much as possible all purchase of 

 nitrogenous food from other quarters. 



On the average, all the experiments of Lawes in 

 England have shown, that for one pound of salts of 

 ammonia in manures^ two pounds of wheat may be 

 reaped. 



These results, we must remember, were obtained from 

 a field in which one acre without manure of any kind 

 was able to yield, for seven years consecutively, 1125 lbs. 

 of corn and 1756 lbs. of straw ; and that all the plots 

 manured with salts of ammonia also received phosphate 

 and sihcate of potash.* 



On an average, Lawes manured his fields with 3 cwt. 

 of salts of ammonia, and thereby he obtained half as 

 much corn again as the unmanured plot yielded. 



We will now assume that the extra crop obtained was 

 exclusively due to the salts of ammonia ; Ave mil further 

 suppose that all soils are inexhaustible in phosphoric 



* On this point Lawes says ('Journal of the Eoyal Agr. Soc. of Eng.,' 

 V. xiv. p. 282), that for the production of one bushel of wheat (=64 to 

 65 pounds, containing 1 pound of nitrogen) which the soil Avas made to 

 yield above its natural power, 5 pounds of ammonia were requisite 

 ( = 16 pounds of sal ammoniac, or 20 pounds of sulphate of ammonia). 

 He adds, however, that in no single experiment did the extra crop 

 obtained correspond to this estimate. 



