Crimson or Scarlet Clover, a Nitrogen Gatherer.
Cultivating the Legumes.—The present system of green manuring contemplates something in addition to what was formerly gained, for agricultural sciences now recognizes the fact that nitrogen, the most expensive element of fertility, can be taken from the air and added to the plant food in the soil by means of certain plants which have the peculiar habit of regularly forming little tubercles or lumps on their feeding roots. These lumps are to be found on plants in perfect health, and are not parasitical in any hostile sense. The lumps are filled with small living organisms called bacteria, and, hence, have been called bacteroid tubercles. The minute tenants slowly but surely secrete nitrogen, and put it in a form adapted to plant growth.
The plants which bear these root lumps belong to a group called legumes, of which clover, peas, beans, vetches, etc., are familiar examples.
Curiously enough, nearly all the leguminous plants are thus fitted by nature by means of the root lumps to act as soil enrichers, and these plants have, therefore, assumed the highest agricultural significance.
It is well known that such crops as cowpeas, crimson or scarlet clover, common red and pea vine or sapling clover, Soja beans, vetches, etc., can be used to add nitrogen to the soil in commercial quantities. The gain of new material, expressed in money, has been estimated as high as $25 per acre. This, therefore, is the avenue through which the farmer can most economically supply nitrogen to his land. If he will exercise all the economy heretofore suggested in the care of natural manures, and will grow legumes, he will not have much occasion to buy nitrogen in the market.
Grass vs. Clover.—An idea of the great fertilizing value of the leguminous plants as compared with grasses may be obtained by a study of the following analyses from U. S. Farmers' Bulletin No. 16, by Dr. E. W. Allen, on "Leguminous Plants for Green Manuring and for Feeding":
| Fertilizing Value in Crop. | ||||
| Assumed | Per Acre. | |||
| Yield. | ||||
| Per Acre. | Nitrogen. | Phos. Acid. | Potash. | |
| Hay from | Tons. | Pounds. | Pounds. | Pounds. |
| Red top (a grass) | 2 | 23·0 | 7·2 | 20·4 |
| Timothy (a grass) | 2 | 25·2 | 10·6 | 18·0 |
| Red Clover (a legume) | 3 | 62·1 | 11·4 | 66·0 |
| Alfalfa (a legume) | 3 | 65·7 | 15·3 | 50·4 |
| Cowpea (a legume) | 3 | 58·5 | 15·6 | 44·1 |
| Soja bean (a legume) | 3 | 69·6 | 20·1 | 32·4 |
Nitrogen, Phosphoric Acid, Potash.—We have just noted the cheapest source of nitrogen. It can be collected by root tubercles at less than the commercial rate of 14 to 17 cents per pound.
Phosphoric acid can be best secured, if a new supply becomes necessary, in the form of ground bone or in the form of acid phosphate. Either of these articles, if bought from a reliable dealer, is a good and economical thing to use.