EXPERIMENTS WITH SALTS OF AMMONIA. 285 



These experiments are worth notice in the history 

 of agriculture, because they show what statements could 

 be laid before farmers^ at a time when ignorance of first 

 principles did not yet permit scientific criticism. 



With regard to the influence of ammonia and salts 

 of ammonia there was instituted in the years 1857 and 

 1858, on the part of the General Committee of the Agri- 

 cultural Society of Bavaria, a series of comparative 

 experiments in the district of Bogenhausen, as to the 

 operation of guano, and various salts of ammonia con- 

 taining an equal amount of nitrogen, the results of 

 which are decisive. 



The experiments were conducted upon a field (a 

 loam) which had gone through the usual rotation, and 

 which, with ordinary farm-yard manure, had borne rye 

 and then oats twice successively. Of eighteen plots in 

 this field, each 1914 square feet in area, four were ma- 

 nured with salts of ammonia, and one with guano, one 

 plot remained unmanured. 



As a starting point for estimating the quantity of 

 manure to be employed, it was assumed that 400 Ibs. 

 of guano per acre English ( = 493 Ibs. avoir.) corre- 

 spond to the full measure of farm-yard manure usually 

 applied. According to this proportion, 20 Ibs ( = 24f 

 Ibs. avoir.) of guano were reckoned for the area in 

 question. 



The samples of good Peruvian guano selected were 

 previously analysed, and in 100 parts a quantity of 

 nitrogen was found corresponding to 15*39 of ammonia. 

 As a general rule, only one-half of the nitrogen in 

 guano is present as ammonia ; the other half appears 

 as uric acid, guanine, &c., of the operation of which 

 upon the growth of plants little or nothing, as we have 

 before observed, is known. But it was assumed that 

 the nitrogen in these other substances was just as oper- 

 ative as that in the ammonia, and the quantum of the 

 various salts of ammonia (which were likewise analysed 

 previously to ascertain exactly their amount of ammonia) 

 was reckoned in accordance with this assumption. Ac- 

 cordingly, for the above 20 Ibs. of guano, 1719 grammes 



