With a view to renovate the crop and increase the yields, in some sections, as in the Atlantic States, it has been recommended to top-dress alfalfa fields with farmyard manure every autumn. This, no doubt, would prove very effective, but it would also be very expensive, unless in the neighborhood of large cities. It would be impracticable without neglecting the needs of the other crops of the farm. In the mountain areas of the West, it has been found that the cost of fertilizing with farmyard manure is in the meantime greater than the increased production in the alfalfa is worth, but it may not be always thus, even on these rich lands. Some Eastern growers also apply more or less gypsum. This is generally sown over the fields after the crop has begun to grow in the spring. Renovating alfalfa fields is much more easily and effectively done, as would naturally be expected, in areas where conditions are highly favorable to its growth than where these are only moderately favorable. In some of the mountain valleys instances have occurred in which alfalfa fields have been plowed and sown with oats, with a result, first that a good crop of oats was reaped, and second, that fairly good crops of alfalfa were harvested the following season without re-sowing the field. =Sources of Injury to Alfalfa.=--Chief among the sources of injury to alfalfa, after the plants have become established, are frost in saturated ground, ice, floods, grasshoppers, gophers, dodder, and pasturing by live stock in the late autumn or winter. When it happens that two or three of these act in conjunction, the injury following is just so much more rapid and complete. As has been intimated, where water is excessive, in a climate which in winter or spring is characterized by alternations of freezing and thawing, the plants will either have the roots snapped asunder, or they will be gradually raised out of the ground. This will only happen in soil with a subsoil more retentive than is compatible with well-doing of the highest order in the plants. The danger from this source is greatest during the first winter after sowing the plants, as then the roots are not really established. The only remedy for such a contingency is the draining of the land. Some reference has also been made to injury done through ice, where it collects in low places in land. The destructiveness of the ice depends on its thickness and its nearness to the ground. When it rests upon the ground for any considerable time the plants die. If, however, water intervenes, the plants may live when the submergence is for a limited time. One instance is on record in Onondaga County in New York State, in which alfalfa survived submergence for a considerable period under a thin sheet of water covered by three inches of ice, but when growth came it was for a time less vigorous than normal.