Clovers and How to Grow Them

by Thomas Shaw

On upland soils sandy or gravelly in character where the rainfall is much less than normal and where the subsoil is not underlaid with sheet water, alfalfa will not usually succeed, notwithstanding that it may grow well on these soils where the rainfall is normal. On such soils it is not easy to get a stand of the plants, as they are much apt to perish in the dry weather of the first season, but if once established on such soils the plants have much power to grow even where the rainfall is considerably less than normal.

Alfalfa will not grow well in soils naturally wet until they are drained. And when drained it will not grow with normal vigor, on what may be termed slough soils, where the subsoil is far down and covered with a deep covering of vegetable mold. What are termed slough soils in the Western prairies, therefore, are not well fitted for the growth of alfalfa. On these it may not succeed well, when it may grow with much vigor on the adjoining upland. When some wet soils are drained, alfalfa may not succeed well on them for a time and later may grow luxuriantly. This may arise from the lack of time for proper aeration after being drained, or from the want of lime to further correct acidity in the soil, or from the want of the proper bacteria. Notwithstanding that alfalfa will not grow well on undrained lands that are naturally wet, and notwithstanding that it will perish if the roots reach standing water at a distance too near the surface, the best crops by far are usually grown on irrigated lands. This arises, first, from the ability to adjust the supplies of water to meet the needs of the plants, and second, from the congenial character of the soil and subsoil. Next to these the best crops are grown where congenial soils are underlaid with ground water, not too near nor too distant from the surface. On these soils the plants are largely supplied with moisture from the water below ascending on the principle of capillary attraction. How near or how distant such water should be will depend somewhat on subsoil conditions. It would seem correct to say that it ought never to come nearer to the surface than 3 feet, nor should it be more than 20 feet down. The most suitable distance would be, say, 8 to 16 feet. When the roots of alfalfa reach water at too short a depth they will die.

Alfalfa may sometimes be grown satisfactorily on soils subject to overflow, but usually there is hazard in growing it on these. If the overflow occurs comparatively early in the season, if it is not of great depth, if it is of short duration, and if the waters quickly drain out of the subsoil possessed by the alfalfa, it may receive little or no harm from such overflow. Instances are on record wherein ice has formed on alfalfa and yet the plants survived, but such a condition will usually prove fatal to them. But should the overflow take place in hot weather, usually it will injure the plants seriously, and may, indeed, completely destroy them. So great is such hazard, that care must be taken against the application of an excess of irrigating waters under such conditions. Overflow waters that are stagnant are more injurious probably than those that are in motion, owing, it may be, to the less supply of dissolved oxygen in the former.

Soils suitable in themselves, but lying on stiff clay bottoms or underlaid with hard pan within two or three feet of the surface, will not maintain a good stand of alfalfa. The plants in these may grow well for a time, probably a year or two, after which they will fail. The roots are not able to go down to gather food. When the subsoils are simply stiff clays, deep subsoiling, as already intimated, may render much service, but when composed of hard pan this may not be practicable. In moist climates, however, reasonably good crops have been obtained from soils with underlying rock not more than four feet below the surface.

The fact should not be overlooked that soils may have the requisite physical conditions for growing alfalfa, and they may possess in fair supply the essential elements of plant food, and yet alfalfa will not succeed at the first when sown on these, because of the absence of the soil bacteria, the presence of which is essential to the vigorous growth of the plants. Because of this, growers should be slow to conclude that alfalfa will not flourish on the soils on which they sow it until they have first tried to grow it on those soils that have been inoculated with the requisite alfalfa bacteria. For the methods of procedure in such cases see [page 53]. Some persons claim that soils which will grow medium red clover in good form will also grow alfalfa in good form. This does not necessarily follow. While there is much of similarity in the soils suitable for the growth of both, alfalfa may fail on lands that grow red clover luxuriantly until the bacteria proper to alfalfa have been introduced. Soils may be tested for bacteria, and even in winter, by sowing some seed in pots and treating them like well-cared-for house plants. When the plants are 2 to 3 months old, if tubercles are found on the roots, the conclusion would seem safe that such soil does not require inoculation.

Place in the Rotation.—In a certain sense it can scarcely be said of alfalfa that it is a rotation plant, because of the long term of years for which it is grown in an unbroken succession. Nevertheless, in all places it cannot always be maintained for a long term of successive years without renewal. In the Eastern States it is frequently, though not always so crowded by various grasses, that the fields in which it grows are broken up at some period short of ten years, and not infrequently at the end of five or six years. When thus grown, it becomes a rotation plant, though grown in what may be termed long rotations. But even in the West, where, under irrigation, it may be grown for a quarter of a century or even for a longer period without renewal, it may be used when desired in short rotations. In such situations it grows so readily and becomes established so quickly, that the fields may be broken with a view to alternate with other crops at the end of the second year, or of any year subsequently from the sowing of the seed that may be desired. Alfalfa in these soils will serve even better than medium red clover in such situations, since while it is growing, it will produce more hay or soiling food, and consequently should excel the former in the fertility which it makes available.

East of the Mississippi and north of the Ohio River, alfalfa will frequently follow cultivated crops, as corn, potatoes and field roots, and when the fields are broken, it will be followed by crops other than legumes. On many soils the influence which this crop has on relieving the surface soil from excessive moisture, through channels opened into the subsoil by the decaying roots, is so helpful as to considerably stimulate production in addition to the fertilizing influence which it exerts directly. Particularly good crops of corn, the small cereal grains, and even field roots may be grown after alfalfa.

On soils east of the Mississippi and south of the Ohio, the rotation will be somewhat similar. But on Southern soils alfalfa will frequently follow immediately crops especially grown to be plowed under as green manures for the benefit of the alfalfa. These crops include cow peas, soy beans, crimson clover, and to a limited extent, burr clover. It will also be followed frequently by crops of cotton and other non-leguminous plants, the growth of which in the United States is confined to the area now being considered.

In the area west of the Mississippi and east of the semi-arid region beside the mountains, alfalfa may follow the small cereal grains, and may in turn be followed by them and also by millets. It may also follow and precede corn, or the non-saccharine sorghums, where the climatic conditions are suitable for growing the latter.

In the irrigated regions of the West, alfalfa may be made to serve almost any purpose in the rotation that may be desired. By growing it as a rotation crop in these valleys it may be made to furnish the soil indefinitely with supplies of nitrogen and humus. In these soils it may be made to follow directly almost any crop grown on them, and similarly it may be made to precede the growth of almost any crop for which the locality has marked adaptation. Small cereal grains, timothy, vegetables, field roots, potatoes, corn, small fruits and orchards may be profitably grown on buried alfalfa meadows. This does not imply, however, that alfalfa meadows should not, as a rule, be maintained for a long term of years.