RAPE-CAKE COMPARED WITH AMMONIA. 



205 



2. With rape-cake compared ivith sulphate of ammonia 

 upon turnips. Mr Lawes has published the results of compara- 

 tive experiments with these substances applied singly and 

 together, to a crop of Norfolk white turnips, grown upon his 

 farm in Hertfordshire in 1845. They were as follows. (Rape- 

 cake contains about 4J per cent of nitrogen.) 



tons. cwt. 



Tops. Nitrogen applied 



per acre, 

 tons. cwt. lb. 



1. Nothing gave . . 



2. Farm-yard manure, 12 tons, 17 



3. Rape-cake, 8 cwt. . 4 



4 18 cwt. . 9 



5 8 cwt. 



Sulphate of ammonia, 3 cwtJ 

 6. Rape- cake, 18 cwt. 



Sulphate of ammonia, 3 cwt. 

 7. Sulphate of ammonia, 6 cwt. 3 



16 



7 7 

 4 5 



8 9 



8} 



6 



18 

 14 



38 

 80 



110 



152 



142 



a It is interesting to observe how very much larger a pro- 

 portion of tops, compared with the bulbs, the rape-cake produced 

 than any of the other applications, even than the farm-yard dung. 



b But what more particularly concerns our object is the 

 total want of connexion between the comparative weights of 

 tops, or of bulbs, or of both taken together, and those of the 

 nitrogen contained in the different applications. Take, for 

 example, the total weights of the crops, (tops and bulbs,) and 

 the following table shows how much was produced in each 

 experiment by 100 lb. of nitrogen : 



Total produce. Total nitrogen Produce for 100 lb. 



1. 



2. 

 3. 



4. 

 5. 

 6. 

 7. 



Here we see three things deserving of notice ; first, that the 



* In calculating this column, I have not thought it of consequence to deduct 

 from the produce of the dressed portions the small crop yielded by the part to 

 which nothing was applied. 



