286 AMMONIA AND NITRIC ACID. 



( = 3 '75 Ibs.) of ammonia were computed as the equiva- 

 lent ; and each of the other four plots received exactly 

 the same quantity of ammonia, in the salt of ammonia 

 employed for manure. 



It is clear that if an increased crop was obtained by 

 means of the guano, and if this was due to the amount 

 of its nitrogen, then each of the other four plots, having 

 received the same quantity of nitrogen, must necessarily 

 be affected exactly in the same manner as if they, also, 

 had been manured with 20 Ibs. of the same guano. The 

 results were as follow : 



Comparative experiments at Bogenhausen with guano and salts 

 of ammonia containing equal quantities of nitrogen. 



HARVEST, 1857. BARLEY. 



Grain. Straw, 



grammes. Ibs. grammes. grammes. 



Manured with 5880=13 carbonate of ammonia. . 6335 16205 



" 4200= 9 nitrate 8470 16730 



" 6720=14| phosphate " 7280 17920 



6720=14| sulphate " 6912 18287 



" 20 lbs. = 24f av. guano 17200 33320 



Unmanured 6825 18375 



Although each of the four plots had received the 

 same quantity of nitrogen, still their respective crops 

 did not correspond ; on the whole, the crop from the 

 plots manured with salts of ammonia, corn and straw 

 together, was in each case very little higher than that 

 of the unmanured plot ; while the plot manured with 

 guano yielded, for the same quantity of nitrogen, 2-J- 

 times more corn, and 80 per cent, more straw, than the 

 average crop of the plots manured with salts of am- 

 monia. 



In the subsequent year, this experiment was re- 

 peated in a similar manner in the same district with 

 winter wheat. The field chosen, and to which six 

 years previously farm-yard manure had been applied, 

 had borne winter rye, then clover, and then oats, for 

 three years. The oat stubble was broken up and then 

 twice ploughed : on the 12th September, 1857, the seed 



