Phosphatic 3Ianurcs for Root- Crops. 
39 
In England the application of purely phosphatic manures is 
confined almost exclusively to root-crops. It ma}' not be amiss, 
therefore, to inquire why it is that these manures, as a rule, 
benefit root-crops more than cereals and other crops ? The idea 
naturally suggests itself that turnips or Swedes require more 
phosphoric acid to bring them to perfection than wheat, barley, 
or oats ; and an examination of the ashes of these several crops 
confirms this impression. A given quantity of ash of turnips, 
it is true, contains less phosphoric acid than the same quantity 
of wheat-ash ; but since the total amount of mineral matters or 
ash in a crop of turnips is very much laiger than that in a crop 
of wheat, the amount of phosphoric acid which is removed from 
the soil by the one is a cry much more considerable than that 
taken up by the other. 
Taking the average composition of the ash of turnips, bulbs 
and tops, deduced from the recorded results of numerous expe- 
rimenters, we have in 100 parts — 
Bulbs. Tops. 
Totash 42-0 20-0 
Soda 2-0 3-0 
Magnesia 2-0 1-0 
Lime 11-5 30-0 
Phosphoric acid 9-0 5"0 
Sulphuric acid 11-5 11"0 
Silica 1-0 1-0 
Chloride of sodium G-0 S'O 
Chloride of ]iotasBium .. fi-O 
Carbonib acid lo'O lG-0 
100-0 100-0 
The average composition of the ash of the grain and straw of 
wheat is as follows : — 
Wheat. Straw. 
Phosphoric acid 50"0 S'O 
Sulphuric acid -5 2-7 
Silica 2-5 67-0 
Lime 3-5 5'5 
MagBCsia 11-5 2-0 
Potash 30-0 13-0 
Soda ) ^.g 
Chlorides of potassium and sodium .. ) 
100-0 100-0 
If we suppose the crop of bulbs of the turnips to weigh 20 tons 
per acre and the tops 6 tons, and take the average percentage of 
ash in the bulbs at '70 and that in the tops at 1'7, we remove 
from each acre, in round numbers — 
lbs. 
In the bulbs 314 mineral matter. 
In the tops 228 „ 
542 
