these fields aggregating between 9,000 and 10,000 square miles.
While the values which have been given above, expressing the sum total of nitrogen, phosphorus and potassium applied annually to the cultivated fields of Japan may be somewhat too high for some of the sources named, there is little doubt that Japanese farmers apply to their fields more of these three plant food elements annually than has been computed. The amounts which have been given are sufficient to provide annually, for each acre of the 21,321 square miles of cultivated land, an application of not less than 56 pounds of nitrogen, 13 pounds of phosphorus and 37 pounds of potassium. Or, if we omit the large northern island of Hokkaido, still new in its agriculture and lacking the intensive practices of the older farm land, the quantities are sufficient for a mean application of 60, 14 and 40 pounds respectively of nitrogen, phosphorus and potassium per acre, and yet the maturing of 1000 pounds of wheat crop, covering grain and straw as water-free substance, removes from the soil but 13.9 pounds of nitrogen, 2.3 pounds of phosphorus and 8.4 pounds of potassium, from which it may be computed that the 60 pounds of nitrogen added is sufficient for a crop yielding 31 bushels of wheat; the phosphorus is sufficient for a crop of 44 bushels, and the potassium for a crop of 35 bushels per acre.
Dr. Hopkins, in his recent valuable work on “Soil Fertility and Permanent Agriculture” gives, on page 154, a table from which we abstract the following data:
APPROXIMATE AMOUNTS OF NITROGEN, PHOSPHORUS AND POTASSIUM
REMOVABLE PER ACRE ANNUALLY BY
| Nitrogen, pounds. |
Phosphorus, pounds. |
Potassium, pounds. | |
| 100 bush. crop of corn | 148 | 23 | 71 |
| 100 bush. crop of oats | 97 | 16 | 68 |
| 50 bush. crop of wheat | 96 | 16 | 58 |
| 25 bush. crop of soy beans | 159 | 21 | 73 |
| 100 bush. crop of rice | 155 | 18 | 95 |
| 3 ton crop of timothy hay | 72 | 9 | 71 |
| 4 ton crop of clover hay | 160 | 20 | 120 |
| 3 ton crop of cow pea hay | 130 | 14 | 98 |
| 8 ton crop of alfalfa hay | 400 | 36 | 192 |
| 7,000 lb. crop of cotton | 168 | 29.4 | 82 |
| 400 bush. crop of potatoes | 84 | 17.3 | 120 |
| 20 ton crop of sugar beets | 100 | 18 | 157 |
| Annually applied in Japan, more than | 60 | 14 | 40 |
