MANURE. 161 



The product was as 79 to 74 over the unmanured. The 

 same ground being again sowed with wheat and salts as 

 before prepared, yielded the second year, as 90 to 70 over 

 the unmanured. Two seasons seem therefore necessary to 

 the full efficacy of sulphate of ammonia on limed soils. 



That nitrogen measures the value of manures, is proved 

 also by nitrate of soda. Here soda, the base, also acts ; but 

 if nitrate of soda be used in unequal doses, then the product 

 is nearly in direct ratio to the nitrogen employed. 



Now on the same field on which Kuhlmann performed his 

 experiments, which are above related, he tried at the same 

 time nitrate of soda in two proportions, at the rate of 240 

 and 120 lbs. per acre. 



The yield of hay over unmanured soil was, for 

 240 lbs. nitrate soda, 1550 lbs. per acre. 

 120 " ** 784 " 



This is in direct ratio of the nitrogen employed. If now 

 the effect of nitrate of soda is compared with sal-ammoniac 

 or bone-liquor, it is seen that the addition of the soda base 

 has given the nitrogen great activity. The combination has 

 given the plant power to absorb a greater quantity of food 

 from earth and air, than either the nitrogen or the base 

 singly could have effected. 



The yield has been for every 100 parts of nitrogen used, 

 40.056 parts of hay ; nearly double that produced J)y a 

 simple ammoniacal salt, and four times that which an equal 

 amount of nitrogen ordinarily produces. 



These fjcts prove the strength of the principle adopted for 

 estimating the relative value of manures. No manure, no 

 salt, no combination of salts, gives full vigor to vegetation, 

 while nitrogen is absent. Nitrogen not only measures, but 

 gives the value to manures. It has been asserted, on high 

 authority, that nitrogen in animal manure is always in a 



