Clovers and How to Grow Them

by Thomas Shaw

Renewing.—Because of the comparatively short life of several of the most useful of the varieties of clover, no attempt is usually made to renew them when they fail, unless when growing in pasture somewhat permanent in character. To this, however, there may be some exceptions. On certain porous soils it has been found possible to maintain medium red clover and also the mammoth and alsike varieties for several years by simply allowing some of the seed to ripen in the autumn, and in this way to re-seed the land, a result made possible through moderate grazing of the meadow in the autumn, and in some instances through the absence of grazing altogether, as when the conditions may not be specially favorable to the growth of clover.

It is not uncommon, however, to renew alfalfa, by adding more seed when it is disked in the spring, as it sometimes is to aid in removing weeds from the land. The results vary much with the favorableness of the conditions for growing alfalfa or the opposite.

In pastures more or less permanent in character, clovers may be renewed by disking the ground, adding more clover seed, and then smoothing the surface by running over it the harrow, and in some instances also the roller. This work is best done when the frost has just left the ground for a short distance below the surface.

Some kinds of clover are so persistent in their habit of growth that when once in the soil they remain, and therefore do not usually require renewal. These include the small white, the yellow, the Japan, burr clover and sweet clover. In soils congenial to these respective varieties, the seeds usually remain in the soil in sufficient quantities to restock the land with plants when it is again laid down to grass. Nearly all of these varieties are persistent seed producers; hence, even though grazed, enough seed is formed to produce another crop of plants.

Clovers as Soil Improvers.—All things considered, no class of plants grown upon the farm are so beneficent in the influence which they exert upon the land as clovers. They improve it by enriching it; they improve it mechanically; and they aid plant growth by gathering and assimilating, as it were, food for other plants.

All clovers have the power of drawing nitrogen from the air and depositing the same in the tubercles formed on the roots of the plants. These tubercles are small, warty-like substances, which appear during the growing season. They are more commonly formed on the roots within the cultivable area, and therefore are easily accessible to the roots of the plants which immediately follow. Clovers are not equally capable of thus drawing nitrogen from the air, nor are the same varieties equally capable of doing this under varying conditions. The relative capabilities of varieties to thus deposit nitrogen in the soil is by no means equal, but up to the present time it would seem correct to say that relative capability in all of these has not yet been definitely ascertained. With reference to the whole question much has yet to be learned, but it is now certain that in all, or nearly all, instances in which clovers are grown on land, they leave it much richer in nitrogen than it was when they were sown upon the same.

They also add to the fertility of the surface soil by gathering plant food in the subsoil below where many plants feed. They have much power to do this, because they are deep rooted and they are strong feeders; that is, they have much power to take up food in the soil or subsoil. Part of the food thus gathered in the subsoil helps to form roots in the cultivable area and part aids in forming top growth for pasture or for hay. If grazed down or if made into hay and fed so that the manure goes back upon the land the fertility of the same is increased in all leading essentials. This increase is partly made at the expense of the fertility in the subsoil. But the stores of fertility in the subsoil are such usually as to admit of thus being drawn upon indefinitely.

Clovers improve soils mechanically by rendering them more friable, by giving them increased power to hold moisture, and by improving drainage in the subsoil. Of course, they have not the power to do this equally, but they all have this power in degree and in all the ways that have been named.

Clovers send down a tap root into the soil and subsoil as they grow. From the tap roots branch off lateral roots in an outward and downward direction. From these laterals many rootlets penetrate through the soil. When the plants are numerous, these roots and rootlets fill the soil. When it is broken up, therefore, particles of soil are so separated that they tend to fall apart, hence the soil is always made more or less friable, even when it consists of the stiffest clays. The shade furnished by the clover also furthers friability. This friability makes the land easier to work, and it is also more easily penetrated by the roots of plants. The influence on aeration is also marked. The air can more readily penetrate through the interstices in the soil, and, in consequence, chemical changes in the soil favorable to plant growth are facilitated.

The roots of clovers are usually so numerous that they literally fill the soil with vegetable matter. This matter, in process of decay, greatly increases the power of the soil to hold moisture, whether it falls from the clouds or ascends from the subsoil through capillary attraction. The moisture thus held is greatly beneficial to the plants that immediately follow, especially in a dry season and in open soils, and the influence thus exerted frequently goes on, though with decreasing potency, for two, three or four seasons.