2.5 67.0
Lime 3.5 5.5
Magnesia 11.5 2.9
Potash 30.0 13.0
Soda, chloride of sodium,
oxide of iron, sand, etc. 2.0 4.8
----- -----
Total 100.0 100.0
===== =====

"The mean produce of wheat, per acre, may be estimated at 25 bushels,
which, at 60 lbs. per bushel, gives 1,500 lbs.; and as the weight of the
straw is generally twice that of the grain, its produce will be 3,000
lbs. According, therefore, to the preceding data, there will be carried
away from the soil:

In 1,500 lbs. of the grain 25 lbs. of mineral food,
(in round numbers).
In 3,000 lbs. of the straw 150 lbs. of mineral food,
(in round numbers).
---
Total 175 lbs.

"On the average of the analyses, it will be found that the composition
of these 175 lbs. is as follows:

------------------------------+-----------+-----------+----------
| In the | In the |
| grain. | straw. | Total.
+-----------+-----------+----------
Phosphoric acid | 12.5 lbs. | 7.5 lbs. | 20.0 lbs.
Sulphuric acid | 0.1 " | 4.0 " | 4.1 "
Carbonic acid | | |
Silica | 0.6 " |100.5 " |101.1 "
Lime | 0.9 " | 8.2 " | 9.1 "
Magnesia | 2.9 " | 3.0 " | 5.9 "
Potash | 7.5 " | 19.5 " | 27.0 "
Soda, chloride of sodium, | | |
oxide of iron, sand, etc. | 0.5 " | 7.3 " | 7.8 "
+-----------+-----------+----------
| 25. lbs. |150. lbs. |175. lbs.
------------------------------+-----------+-----------+----------

"The total quantity of ash constituents carried off the land, in an
average crop of wheat, thus amounts to only 175 lbs. per acre, whilst a
good crop of clover removes as much as 672 lbs.

"Nearly two-thirds of the total amount of mineral in the grain and straw
of