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not only gather nitrogen for the fruit trees, but in their decay they increase the power of the soil to retain moisture for the benefit of the trees.
Some varieties of clover may be grown as catch crops, that is, as crops which are grown in addition to some other crop produced the same season. When thus grown, it is usually for purposes of soil improvement rather than to furnish food. The varieties best adapted for this purpose in the Northern States and Canada are the medium red and the crimson, the latter being much more circumscribed in the area where it will grow successfully than the former. When medium red clover is thus grown, it is commonly sown along with one of the small cereal grains, and is buried in the autumn or in the following spring. (See page 75.) The extent of the advantage is dependent chiefly on the amount of the growth made, and this in turn is influenced by the character of the soil, the season and the nurse crop. In certain areas favorable to the growth of clover some good farmers sow clover along with all the small cereal grains which they grow. Crimson clover is usually sown in the late summer after some crop has been reaped and it is plowed under the following spring. (See page 250.)
In the Southern States Japan clover and burr clover will serve the purpose of catch crops better than the other varieties. The former will follow a winter crop (see page 284), and the latter a summer crop. (See page 294.)
Although alfalfa is not usually looked upon as a rotation crop in the Rocky Mountain valleys, it may be made such a crop. In these it grows so vigorously as to fill the soil with its roots in one or two seasons, hence it may be made to rotate profitably with other crops. (See page 135.) In such instances, however, medium red clover would probably answer the purpose quite as well, and possibly better, since the labor of burying it with the plow would be less difficult.
While some varieties of clover may be grown in various rotations and with profit, one of the best of these, where the conditions are favorable, is a three years' rotation. The first year some small cereal grain is grown and clover is sown along with it or, at least, on the same land. The next year the clover is grown for hay or pasture. The third year a crop of corn, potatoes or vegetables is grown, and the following year small cereal grain and clover. The clover may thus be made to furnish nitrogen indefinitely for the other crops, but in some instances it may be necessary to add phosphoric acid and potash.
Preparing the Soil.—Clovers are usually sown with a nurse crop. The exceptions are crimson clover, and in many instances alfalfa. When thus grown, the preparation of soil for the nurse crop will usually suffice for the clovers also. But there may be instances in which it would be proper to give more attention to cleaning and pulverizing the soil to properly fit it for receiving the clover seed. The leading essentials in a seed-bed for clover are fineness, cleanness, moistness and firmness. Ordinarily black loam soils, sandy loam soils, sandy soils, humus soils and the volcanic ash soils of the West are made sufficiently fine without great labor. Clay soils may call for the free use of the harrow and roller used in some sort of alternation before they are sufficiently pulverized. Excessive fineness in pulverization of these soils is also to be guarded against in rainy climates, lest they run together, but this condition is present far less frequently than the opposite.
Cleanness can usually be secured when clovers follow cultivated crops by the labor given to these when the land is not plowed in preparing it for the clovers. In other instances the longer the land is plowed before putting in the seed and the more frequently the surface is stirred during the growing part of the season, the cleaner will the seed-bed be.
In the spring the land is usually sufficiently moist for receiving the seed. In the autumn moisture is frequently deficient. Stirring the surface of the soil occasionally with the harrow will materially increase the moisture content in the soil near the surface, even in the absence of rain. As crimson clover is usually sown in the late summer and alfalfa is frequently sown in the autumn, it may sometimes be necessary to give much attention to securing sufficient moisture to insure germination in the seed.
When clovers are sown in the spring on land which is also growing a winter crop, no preparation is necessary in preparing the land for receiving the seed. On some soils the ground becomes sufficiently honeycombed through the agency of water and frost to put it in a fine condition for receiving the seed. When this condition is not present, the seed will usually grow if sown amid the grain and covered with the harrow.
When clovers are sown on sod land for the purpose of renewing pastures, disking them will prepare them for receiving the seed. The extent of the disking will depend on such conditions as the toughness of the sod and the nature of the soil. Usually disking once when the frost is out a little way from the surface, and then disking across at an angle will suffice, and in some instances disking one way only will be sufficient. On newly cleared lands the clovers will usually grow without any stirring of the land before sowing, or any harrowing after sowing. Clovers that are grown chiefly for pasture, as the small white, the Japan and the burr, will usually obtain a hold upon the soil if scattered upon the surface which is not soon to be cultivated.
Fertilizers.—On certain soils low in fertility and much deficient in humus, it may be necessary to apply fertilizers in some form before clovers will grow vigorously. Such are sandy soils that have been much worn by cropping, and also stiff clays in which the humus has become practically exhausted. In such instances green crops that can be grown on such lands, as rye, for instance, plowed under when the ear begins to shoot, will be found helpful. If this can be followed on the sandy soil with some crop to be fed off upon the land, as corn, for instance, and the clover is sown, successful growth is likely to follow. On clays in the condition named it may not be necessary to grow a second crop before sow
ing clover, since in these soils the lack is more one of humus than of plant food. The application of farmyard manure will answer the same purpose, if it can be spared for such a use.
Other soils are so acid that clovers will not grow on them until the acidity is corrected, notwithstanding that plant food may be present in sufficient quantities. Such are soils, in some instances at least, that have been newly drained, also soils that grow such plants as sorrels. This condition will be improved if not entirely corrected by the application of lime. On such soils this is most cheaply applied in the air-slaked form, such as is used in plastering and in quantities to effect the end sought. These will vary, and can only be ascertained positively by experiment.
Usually it is not necessary to apply much farmyard manure in order to induce growth in nearly all varieties of clover, and after free growth is obtained, it is not usually necessary to supply any subsequently for the specific purpose named. In some soils, however, alfalfa is an exception. It may be necessary to enrich these with a liberal dressing of farmyard manure to insure a sufficiently strong growth in the plants when they are young. Having passed the first winter, further dressings are not absolutely essential, though they may prove helpful.
Farmyard manure applied on the surface will always stimulate the growth of clovers, but it is not common to apply manure thus, as the need for it is greater in growing the other crops of the farm. When thus applied, it should be in a form somewhat