The clovers that are most helpful in smothering weeds are the mammoth, the medium and the alsike varieties. These are thus helpful in the order named. To accomplish such an end they must grow vigorously, and the plants must be numerous on the ground. When grown thus, but few forms of weed life can make any material headway in the clover crop. Even perennials may be greatly weakened, and in some instances virtually smothered by such growth of clover. To insure a sufficient growth of clover it may be advantageous to top dress the crop with farmyard manure sufficiently decayed, and in the case of medium red clover to dress the second cutting with land plaster. If the second growth is plowed under, subsequent cultivation of the surface will further aid in completing the work of destruction. The crimson variety is sown and also harvested at such a time that the influence on weed eradication is very marked. The ground is usually prepared in the summer and so late that weeds which sprout after the clover has been sown cannot mature the same autumn. In the spring it is harvested before any weeds can ripen. When plowed under, rather than harvested, the result is the same. When clover is grown in short rotations, its power to destroy weeds is increased. For instance, when the medium red or mammoth varieties are grown in the three years' rotation of corn or some root crop, followed by grain seeded with clover, the effects upon weed eradication are very marked, if the cultivation given to the corn or roots is ample. Under such a system weeds could be virtually prevented from maturing seeds at any time, especially if the medium variety of clover were sown, and if the stubbles were mown some time subsequent to the harvesting of the grain crop. Such a system of rotation faithfully carried out for a number of years should practically eradicate all, or nearly all, the noxious forms of weed life. =Clover Sickness.=--On certain of the soils of Great Britain and probably on those of other countries in Europe, where clover has been grown quite frequently and for a long period, as good crops cannot be grown as previously, and in some instances the crop is virtually a failure. The plants will start from seed in the early spring and grow with sufficient vigor for a time, after which they will show signs of wilting and finally they die. Various theories were advanced for a time as to the cause before it was ascertained by experiment what produced these results. Some thought they arose from lack of water in the soil, others claimed that they were due to the presence of parasites, which in some way preyed upon the roots, others again attributed them to improper soil conditions. It is now just about certain that they arose from a deficiency of soluble potash in the subsoil. Such, at least, was the conclusion reached by Kutzleb as the result of experiments conducted with a view to ascertain the cause of clover wilt.