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


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.

Reference has already been made to the tap root which clover sends down

into the soil and subsoil. In the strong varieties this tap root goes

down deeply. When the crop is plowed up, the roots decay, and when they

do, for a time at least, they furnish channels down which the surface

water percolates, if present in excess. Thus it is that clover aids in

draining lands under the conditions named. The channels thus opened do

not close immediately with the decay of the clover roots, hence the

downward movement of water in the soil is facilitated for some time


It has been stated that clovers have more power than some other plants

to gather plant food in the soil. In some instances they literally fill

the soil with their roots. When other plants are sown after the clover

has been broken up they feed richly on the decaying roots of the clover.

Thus it is that clover gathers food for other plants which they would

not be so well able to gather for themselves, and puts it in a form in

which it can be easily appropriated by these. The nitrogen in clover is

yielded up more gradually and continuously as nitrates than it could be

obtained from any form of top dressings that can be given to the land.

In this fact is found one important reason why cereal grains thrive so

well after clover.

Since the roots of clovers act so beneficently on soils, it is highly

important that they be increased to the greatest extent practicable.

Owing to the relation between the growth of the roots of plants and the

parts produced above ground, development in root growth is promoted much

more when the clover is cut for hay than when it is fed off by grazing.

Experiments have also demonstrated that the development of root growth

is much enhanced in medium red clover by taking a second cutting for

hay or seed. They have also demonstrated that more nitrogen is left in

the soil by clover roots after a seed crop than after a crop of hay.

From what has been said, it will be apparent that the extent to which

clovers enrich the soil will depend upon the strength of the growth of

the plants and certain other conditions. It will not be possible to

reduce to figures the additions in plant food which clovers add to the

soil other than in a comparative way. Dr. Voelker has stated that there

is fully three times as much nitrogen in a crop of clover as in the

average produce of the grain and straw of wheat per acre. Dr. Kedzie is

on record as having said that in the hay or sod furnished by a good crop

of clover, there is enough nitrogen for more than four average crops of

wheat, enough phosphoric acid for more than two average crops and enough

of potash for more than six average crops. He has said, moreover, that

the roots and stubble contain fully as much of these elements as hay.

It will also be apparent that where clover grows in good form no cheaper

or better way can be adopted in manuring land, and that in certain areas

the judicious use of land plaster on the clover hastens the renovating

process. It is thought that in some instances the mere loading and

spreading of barnyard manure costs more than the clover and plaster.

Especially will this be true of fields distant from the farm steading.

It is specially important, therefore, that in enriching these, clover

will be utilized to the fullest extent practicable.

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