302 AMMONIA AND NITRIC ACID. 



ammonia were computed as the equivalent ; 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 in exactly the same manner as if they, also, 

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

 results were as follow : — 



Comjiarative experiments at Bogenhausen ivith guano and salts of 

 a7nmonia containing equal quantities of nitrogen. 



Haevest, 1857. — Baeley. 



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 httle higher than that of the un- 

 manured plot; while the plot manured with guano 

 yielded, for the same quantity of nitrogen, 2\ times more 

 corn, and 80 per cent, more straw, than the average crop 

 of the plots manured with salts of ammonia. 



In the subsequent year, this experiment was repeated 

 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 apphed, had borne winter rye, 

 then clover, and then oats, for three years. The oat 

 stubble was broken up and then twice ploughed : on the 



