The fertility thus furnished does not consist so much in the plant food deposited in the soil directly as in that furnished in the successive crops that are grown and fed every year. In Farmers' Bulletin No. 133, published by the United States Department of Agriculture, it is stated that the Wyoming Experiment Station found 44 pounds of nitrogen, 8.27 pounds of phosphoric acid, and 50.95 pounds of potash in one ton of alfalfa. This would mean that in the yield of alfalfa hay from a given area, estimated at four tons per acre for the season, alfalfa would furnish 176 pounds of nitrogen, 33.08 pounds of phosphoric acid, and 203.8 pounds of potash. If this alfalfa were fed upon the farm, it would not only prove a cheap source of protein for feeding, but it would furnish fertility, as stated above, without seriously diminishing the supply of the same in the surface soil, since much of the fertilizing material produced would come from the air and subsoil. The manure thus made, if carefully saved and applied, would thus add materially to the fertility of the land. If, however, the alfalfa were sold, the mineral matter drawn from the cultivable area of the soil and from the subsoil lying under it would be reduced to the extent of the draft made upon these in growing the alfalfa. The direct influence of alfalfa upon the fertility of the land on which it grows is shown in the greatly increased production in the crops which follow alfalfa. This increase is not only marked, but it is frequently discernible for several successive years. But as has been intimated, the benefit that would otherwise accrue from growing alfalfa as a direct means of fertilizing the land is much circumscribed by the long term of years for which it is usually grown. The mechanical effects of alfalfa upon the land are beneficent. It improves the tilth by means of the shade furnished, and the extent to which the roots fill the soil. These in their decay further influence favorably that friability which is so desirable in soils that are cultivated, and as previously stated, the long, deep roots in their decay exercise a salutary influence on drainage. The work of breaking alfalfa fields is frequently laborious, owing to the number and size of the roots. If, however, a plow is used, the share of which has a serrated edge, the roots will be cut or broken off more easily and more effectively. CHAPTER V ALSIKE CLOVER Alsike Clover (_Trifolium hybridum_) takes its name from a parish in the south of Sweden. From there it is probable that it was introduced into England. Linnaeus gave it the name of _hybridum_, imagining it to be a cross between the red and the white varieties. Botanists do not generally hold this view. It is known by various names, as Swedish, White Swedish, Alsace, Hybrid, Perennial Hybrid, Elegant and Pod Clover, but more commonly in America it is spoken of as alsike.