CLOVERS AND HOW TO GROW THEM
BY THOMAS SHAW
Author of "Forage Crops Other than Grasses," "The Study of Breeds," "Soiling Crops and the Silo," "Animal Breeding," "Grasses and How to Grow Them," etc.
NEW YORK ORANGE JUDD COMPANY 1906
COPYRIGHT, 1906 By ORANGE JUDD COMPANY
TO ALL PERSONS WHO ARE OR MAY BE INTERESTED IN THE GROWING OF CLOVERS THIS WORK IS MOST RESPECTFULLY DEDICATED BY THE AUTHOR
St. Anthony Park, Minn. 1906
In preparing this work, the chief sources of information beyond the author's experience and observation have been the bulletins issued by the various experiment stations in the United States and discussions in the Agricultural Press.
For the illustrations the author is indebted to Professor A. M. Soule of the experiment station of Tennessee, Professor H. H. Hume of the experiment station of Louisiana and Mr. W. T. Shaw of the experiment station of Oregon.
THE AUTHOR'S PREFACE
Some books have been written on Clover in the United States, and as far as they go they serve a good purpose. Many references and discussions have also appeared in various bulletins and reports issued by the experiment stations. These have proved helpful not only in the States in which they have been issued, but also in other States where the conditions are similar. But no book or bulletin has yet appeared which discusses the growth of clovers as applicable to all parts of the United States and Canada. Nor has any been issued which takes up the subject in orderly and consecutive sequence. It is evident, therefore, that there is not only room for a book which will cover the ground with at least measureable fulness, but also in concise and orderly succession, but there is great need for it. It has been the aim of the author to write such a book.
Only those varieties of clover are discussed at length which are possessed of economic value. The treatment of the subjects is virtually the same as was adopted in writing the book on "Grasses and How to Grow Them." Some references are made to the history, characteristics and distribution of each variety. These are followed by discussions with reference to soil adaptation; place in the rotation; preparing the soil; sowing; pasturing; harvesting for hay; securing seed; and renewing the stand.
The book is intended, in some measure at least, to meet the needs of the students of agriculture, with reference to the plants discussed and also of all who are concerned in the tilling of the soil.
St. Anthony Park, Minn. 1906
TABLE OF CONTENTS
CHAPTER I. PAGE. Introductory 1
CHAPTER II. General Principles for Growing Clovers 6
CHAPTER III. Medium Red Clover 57
CHAPTER IV. Alfalfa 114
CHAPTER V. Alsike Clover 194
CHAPTER VI. Mammoth Clover 218
CHAPTER VII. Crimson Clover 238
CHAPTER VIII. White Clover 258
CHAPTER IX. Japan Clover 279
CHAPTER X. Burr Clover 291
CHAPTER XI. Sweet Clover 300
CHAPTER XII. Miscellaneous Clovers 316
LIST OF ILLUSTRATIONS
FIG. PAGE. 1 Alsike Clover—Frontispiece. 2 Medium Red 61 3 Alfalfa 115 4 Field of Alfalfa 171 5 Alsike 195 6 Crimson 239 7 White 259 8 Japan 281 9 Sweet 301 10 Sainfoin 318 11 Beggar Weed (Flower and Seed Stems) 339 12 Beggar Weed (Root System) 341
In this book all the varieties of clover will be discussed that have hitherto been found of any considerable value to the agriculture of America. Varieties that are of but little value to the farmer will be discussed briefly, if discussed at all. The discussions will be conducted from the standpoint of the practical agriculturist rather than from that of the botanist. It is proposed to point out the varieties of clover worthy of cultivation, where and how they ought to be cultivated, and for what uses.
Definition of Clover.—According to Johnson's Encyclopaedia, clover or trefoil is a plant of the genus Trifolium and the family Leguminosae. The Standard Dictionary defines it as any one of several species of plants of the genus Trifolium of the bean family Leguminosae. Viewed from the standpoint of the American farmer it may be defined in the collective sense as a family of plants leguminous in character, which are unexcelled in furnishing forage and fodder to domestic animals, and unequaled in the renovating influences which they exert upon land. The term Trefoil is given because the leaves are divided into three leaflets. It is also applied to plants not included in the genus, but belonging to the same order.
The true clovers have their flowers collected into roundish or oblong heads and in some instances into cone-shaped spikes. The flowers are small and of several colors in the different varieties, as crimson, scarlet, pink, blue, yellow and white, according to the variety, and some are variously tinted. The stems are herbaceous and not twining. The seeds are inclosed in pods or seed sacks, each of which contains one, two and sometimes, but not often, three or four seeds. The plants have tap roots, and in some varieties these go far down into the subsoil. The roots are also in some varieties considerably branched.
Varieties.—At least twenty varieties, native or naturalized, are found in Great Britain; more than twelve varieties belong to the United States. The more valuable varieties found in this country have been introduced from Europe, unless it be the small white clover (Trifolium repens). Viewed from the standpoint of the agriculturist the varieties that are most generally useful include medium red clover (Trifolium pratense), alfalfa (Medicago sativa), alsike (Trifolium hybridum), mammoth (Trifolium magnum), crimson (Trifolium incarnatum) and small white (Trifolium repens). The varieties which flourish only in the South include the Japan (Lespedeza striata) and the burr clover (Medicago denticulata). Sweet clover (Melilotus alba), sometimes called Bokhara, which will grow equally well North and South, is worthy of attention because of its power to grow under hard conditions, in order to provide honey for bees and to renovate soils. Other varieties may render some service to agriculture, but their value will not compare with that of the varieties named.
The most valuable of the varieties named in providing pasture, include the medium red, the mammoth, the alsike and the small white. The most valuable in providing hay are the medium red, alfalfa and alsike. The most valuable, viewed from the standpoint only of soil renovation, are the medium red, mammoth, alsike, crimson, Japan and sweet. The most valuable in producing honey accessible to tame bees, are the small white, alsike and sweet.
Distinguishing Characteristics.—Clovers differ from one another in duration, habit of growth, persistence in growth, their power to endure low or warm temperatures, and ability to maintain a hold upon the soil. Of the varieties named, alfalfa, the small white and alsike varieties are perennial. That most intensely so is the first variety named. The medium red and mammoth varieties are biennial, but sometimes they assume the perennial quality. Sweet clover is biennial. The crimson, Japan and burr varieties are annual.
Some varieties, as alfalfa, crimson and sweet clover, are upright in their habit of growth. Others, as the small white and the burr, are recumbent. Others again, as the medium red, alsike and mammoth, are spreading and upright. The alfalfa and medium red varieties grow most persistently through the whole season. The sweet, small white and alsike varieties can best endure cold, and the sweet, Japan and burr varieties can best endure heat. The small white, Japan, burr and sweet clovers stand highest in ability to maintain a hold upon the soil.
The minor points of difference are such as relate to the shape and color of the leaves, the tints of shade that characterize the leaflets, the shape and size of the heads and the distinguishing shades of color in the blossoms.
The characteristics which they possess in common are the high protein content found in them, the marked palatability of the pasture and hay, unless in the sweet and burr varieties, the power which they have to enrich and otherwise improve soils, and the honey which they furnish.
Plan of Discussion.—Chapter I., that is, the present chapter, as already indicated, is introductory, and outlines the nature, scope and plan of the work. Chapter II. deals with the general principles and facts which relate to the growing of clovers. A close study of these will, in the judgment of the author, prove helpful to those who engage in growing any of the varieties of clover discussed in the book. Chapters III. to XI. inclusive treat of individual varieties, a chapter being devoted to each variety. It has been the aim of the author to discuss them in the order of the relative importance which they bear to the whole country and to devote space to them accordingly.
The following varieties are discussed and in the order named: Medium Red clover, Alfalfa, Alsike, Mammoth, Crimson, Small White, Japan, Burr and Sweet. All of these varieties will be found worthy of more or less attention on the part of the husbandmen in the various parts of this continent.
Chapter XII. is devoted to a brief discussion of miscellaneous varieties which have as yet been but little grown in this country, or of varieties of but local interest. The former are Sainfoin (Onobrychis sativa), Egyptian clover (Trifolium Alexandrianum), yellow clover (Medicago lupulina), Sand Lucerne (Medicago media), and a newly introduced variety of Japanese clover (Lespedeza bicolor). These may prove more or less valuable to the agriculture of the United States when they have been duly tested, a work which as yet has been done only in the most limited way. The latter include Florida clover (Desmodium tortuosum), more frequently called Beggar Weed, Buffalo clover (Trifolium reflexum), and Seaside clover (Trifolium invulneratum). These may be worthy of some attention in limited areas where the conditions are favorable, but it is not likely that they will ever be very generally grown. They are dwelt upon rather to show their small economic importance and with a view to prevent needless experimentation with plants possessed of so little real merit.
SOME GENERAL PRINCIPLES WHICH APPLY TO THE GROWING OF CLOVERS
In growing clovers, as in growing other crops of the same species, which embrace several varieties, certain features of management will apply more or less to all of these in common. It will be the aim to point out the chief of these in the present chapter.
Adaptation in Clovers.—Adaptation in the varieties of clover considered will be more fully given when discussing these individually, but enough will be said here to facilitate comparisons. Clover in one or the other of its varieties can be grown in almost all parts of the United States and Canada. Speaking in a general way, the medium and mammoth varieties can be grown at their best between parallels 37 deg. and 49 deg. north latitude. Alfalfa has special adaptation for mountain valleys of the entire West, but it will also grow in good form in parts of all, or nearly all, the other States. Alsike clover grows in about the same areas as the common and mammoth varieties, but it may also be grown further North, owing to its greater hardihood. Crimson clover has highest adaptation to the States east of the Allegheny Mountains and west of the Cascades, but will also grow in the more Central States south, in which moisture is abundant. Small white clover will grow in any part of the United States or Canada in which moisture is sufficiently present. Japan and burr clover grow best south of parallel 37 deg. and east of longitude 98 deg.. Sweet clover will grow in all the States and provinces of the United States and Canada, but has highest adaptation for the Central and Southern States.
With reference to adaptation to soils, medium and mammoth clover grow best on upland clay loam soils, such as have sustained a growth of hardwood timber, and on the volcanic ash soils of the Western mountain valley. Alfalfa flourishes best on those mountain valley soils when irrigated, or when these are so underlaid with water as to furnish the plants with moisture. Alsike clover has much the same adaptation to soils as the medium and mammoth varieties, but will grow better than these on low-lying soils well stored with humus. Crimson clover has highest adaptation for sandy loam soils into which the roots can penetrate easily. Small, white clover has adaptation for soils very similar to that of alsike clover. Japan clover and burr clover will grow on almost any kind of soil, but on good soils the growth will, of course, be much more vigorous than on poor soils. Sweet clover seems to grow about equally well on sandy loams and clay loams, but it has also much power to grow in stiff clays and even in infertile sands.
Place in the Rotation.—All the varieties of clover discussed in this volume may be grown in certain rotations. Their adaptation for this use, however, differs much. This increases as the natural period of the life of the plant lessens and vice versa. Consequently, the medium red variety, the mammoth, the crimson, the Japan and the burr varieties stand high in such adaptation. The alsike, living longer, is lower in its adaptation, and alfalfa, because of its long life, stands lowest in this respect. The small, white variety is almost invariably grown or found growing spontaneously along with grasses, hence no definite place has been or can be assigned to it in the rotation. Sweet clover being regarded by many as a weed has not had any place assigned to it in a regular rotation, although in certain localities it may yet be grown for purposes of soil renovation. (See page 306.)
All these crops are leguminous without any exception. This fact is of great significance where crops can be rotated. They have power to gather nitrogen from the air and store it in the soil in tubercles which form on their roots, in all soils in which they produce a vigorous growth. This fact indicates where they should come in the rotation. They should be grown with a view to gather food for other crops made to follow them, which have not the same power. They should, therefore, be made to precede such crops as the small cereals, corn, the sorghums, the millets and cotton. But since these clover plants have the power to bring nitrogen from the air, it must not be supposed that they will grow with sufficient vigor in soils destitute of this element. They must be able to appropriate enough from the seed soil to give them a good start before they can draw nitrogen from the air, hence, though they may be made to follow almost any kind of crop, it may sometimes be necessary to apply some nitrogenous fertilizer before they will make a vigorous growth.
The clovers, unless in the case of some of the smaller varieties, are more commonly sown to provide hay than pasture in the first crops obtained from them. The value of the hay is increased or lessened in proportion as weeds are present. To insure cleanliness in the hay crop, therefore, the system which aims to sow clover seed on land to which clean cultivation has been given while growing on them a cultivated crop, as corn or field roots, meets with much favor. The mechanical condition of the soil immediately after growing these crops also favors the vigorous growth of the young clover plants, more especially when they are sown upon the surface of the land after some form of surface cultivation, rather than upon a surface made by plowing the land after cultivation has been given to it, but to this there may be some exceptions.
Clover in some of its varieties is frequently grown from year to year in orchards and for the two-fold purpose of gathering food for the trees and providing for them a cover crop in winter. The medium red and crimson varieties are preferred for such a use. The latter is the more suitable of the two, since it does not draw on soil moisture needed by the trees, owing to the season at which it is grown. Enough of the seed of these crops may be allowed to mature to re-seed the land from year to year, and thus keep it producing. The clover plants 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 sowing 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 reduced, otherwise the coarse parts may rake up in the hay. It is better applied in the autumn or early winter than in the spring, as then more of the plant food in it has reached the roots of the clover plants, and they have also received benefit from the protection which it has furnished them in winter.
In a great majority of instances, soils are sufficiently well supplied with the more essential elements of fertility to grow reasonably good crops of clover, hence it has not usually been found necessary to apply commercial fertilizers to stimulate growth, as in the growing of grasses. In some instances, however, these are not sufficiently available, especially is this true of potash. Gypsum or land plaster has been often used to correct this condition, and frequently with excellent results. It also aids in fixing volatile and escaping carbonates of ammonia, and conveys them to the roots of the clover plants. It is applied in the ground form by sowing it over the land, and more commonly just when the clover is beginning to grow. The application of 50 to 200 pounds per acre has in many instances greatly increased the growth, whether as pasture, hay or seed. The following indications almost certainly point to the need of dressings of land plaster: 1. When the plants assume a bluish-green tint, rather than a pea-green, while they are growing. 2. When the plants fail to yield as they once did. 3. When young plants die after they have begun to grow in the presence of sufficient moisture. 4. When good crops can only be grown at long intervals, as, say, 5 to 8 years. It has also been noticed that on some soils where gypsum has long been used in growing clover the response to applications of the plaster is a waning one, due doubtless to the too rapid depletion of the potash in the soil.
Potassic fertilizers give the best results when applied to clovers, but dressings of phosphoric acid may also be helpful. Applications of muriate or sulphate of potash or kainit may prove profitable, but on many soils they are not necessary in growing clover. Wood ashes are also excellent. They furnish potash finely divided and soluble, especially when applied in the unleached form. When applied unleached at the rate of 50 bushels per acre and leached at the rate of 200 bushels, the results are usually very marked in stimulating growth in clover.
Seasons for Sowing.—Clovers are more commonly sown in the springtime in the Northern States and Canada than at any other season and they are usually sown early in the spring, rather than late. On land producing a winter crop, as rye or wheat, they can be sown in a majority of instances as soon as the snow has melted. That condition of soil known as honeycombed furnishes a peculiarly opportune time for sowing these seeds, as it provides a covering for them while the land is moist, and thus puts them in a position to germinate as soon as growth begins. Such a condition, caused by alternate freezing and thawing, does not occur on sandy soils. Where it does not so occur, sowing ought to be deferred until the surface of the ground has become dry enough to admit of covering with a harrow. As in sowing the seeds of certain grasses good results usually follow sowing just after a light fall of snow, which, as it melts, carries the seed down into the little openings in the soil. But there are areas, especially in the American and Canadian northwest, where in some seasons the young clover plants would be injured from sowing the seed quite early. This, however, does not occur very frequently. When sown on spring crops, as spring wheat, barley and oats, the seed cannot, of course, be sown until these crops are sown. The earlier that these crops are sown the more likely are the clovers sown to make a stand, as they have more time to become rooted before the dry weather of summer begins. In a moist season the seed could be safely sown any time from spring until mid-summer, but since the weather cannot be forecast, it is considered more or less hazardous to sow clovers in these northern areas at any other season than that of early spring. If sown later, the seed will more certainly make a stand without a nurse crop, since it will get more moisture. If sown later than August, the young plants are much more liable to perish in the winter.
In the States which lie between parallels 40 deg. and 35 deg. north, and between the Atlantic and the 100th meridian west, clover seeds may be sown in one form or another from early spring until the early autumn without incurring much hazard from winter killing in the young plants, but here also early spring sowing will prove the most satisfactory. The hazard from sowing in the summer comes chiefly from want of sufficient moisture to germinate the seed.
In the Southern States the seed is sown in the early spring or in the autumn. If sown late, the heat of summer is much against the plants. Seeds sown in the early autumn as soon as the rains come will make a good stand before the winter, but there are some soils in the South in which alternate freezing and thawing in winter, much more frequent than in the North, would injure and in some instances destroy the plants.
In the Western valleys where irrigation is practiced, clover seeds may be sown at any time that may be desired, from the early spring until the early autumn. The ability to apply water when it is needed insures proper germination in the seed and vigor in the young plants.
Methods of Sowing.—Clover seed may be sown by hand, by hand machines, and by the grain drill, with or without a grass-seed sowing attachment. These respective methods of sowing will be discussed briefly here, but since they are practically the same as the methods to be followed in sowing grass seeds, and since they are discussed more fully in the book "Grasses and How to Grow Them" by the author, readers who wish to pursue the subject further are referred to the book just named.
When clovers are sown by hand, usually but one hand is used. Enough seed is lifted between the thumb and two forefingers of the right hand to suffice for scattering by one swing of the same. On the return trip across the field the seed should be made to overlap somewhat the seed sown when going in the opposite direction. In other words, the seed is sown in strips or bands, as it were, each strip being finished in one round. Some sowers, more expert at their work, sow with both hands and complete the strip each time they walk over the field. When the ground is plowed in lands of moderate width the furrows will serve to enable the sower to sow in straight lines. Where the sowing is done on land sown to grain by the drill, the drill marks may be made to effect the same result. When sown on light snows, the foot-marks will serve as guides. In the absence of marks it will be necessary to use stakes to guide the sower. Four stakes are used, two of which are set at each end of the field, and these are moved as each cast is made. At each round made over the field, from 12 feet to 15 feet may be sown by the sower who sows only with one hand. The sower with two hands will accomplish twice as much.
A comparatively still time should be chosen for sowing the seed by hand, more especially when grass seeds, which are usually lighter, are sown at the same time. In hand sowing much care is necessary in scattering the seed, so that each cast of the seed will spread evenly as it falls, leaving no bare spaces between the cast from the hand or between the strips sown at one time. Hand sowing, especially in the Western States, is in a sense a lost art, owing to the extent to which machine sowing is practised; nevertheless, it is an accomplishment which every farmer should possess, since it will oftentimes be found very convenient when sowing small quantities of seed, and in sowing seeds in mixtures which cannot be so well sown by machines.
Hand machines are of various kinds. Those most in favor for ordinary sowing consist of a seeder wheeled over the ground on a frame resembling that of a wheelbarrow. It sows about 12 feet in width at each cast of the seed. It enables the sower to sow the seed while considerable wind is blowing and to sow it quite evenly, but it is not adapted to the sowing of all kinds of grass and clover mixtures, which it may be desirable to sow together, since they do not always feed out evenly, owing to a difference in size, in weight, in shape and in the character of the covering.
When clover seed is sown with the grain drill, it is sometimes sown separately from grain; that is, without a nurse crop, and is deposited in the soil by the same tubes. But it is only some makes of drills that will do this. Clover seed, and especially alfalfa, may be thus sown with much advantage on certain of the Western and Southern soils, especially on those that are light and open in character, and when the seed is to be put in without a nurse crop. Eastern soils are usually too heavy to admit of depositing the seed thus deeply, but to this there are some exceptions.
When sown with a nurse crop, the seed is in some instances mixed with the grain before it is sown. In some instances it is mixed before it is brought to the field. At other times it is added when the grain has been put in the seed-box of the drill. This method of sowing is adapted to certain soils of the Western prairies and to very open soils in some other localities, but under average conditions it buries seeds too deeply. There is the further objection that they all grow in the line of the grain plants and are more shaded than they would be otherwise. Nevertheless, under some conditions this method of sowing the plants is usually satisfactory.
One of the most satisfactory methods of sowing clover seeds along with a nurse crop is to sow the clover with a "seeder attachment;" that is, an attachment for sowing small seeds, which will deposit the same before or behind the grain tubes as may be desired. The seed is thus sown at the same time as the grain, and in the process is scattered evenly over the surface of the ground. These seeder attachments, however, will not sow all kinds of clover and grass mixtures any more than will hand-sowing machines do the same.
Depth to Bury the Seed.—The depth to bury the seed varies with the conditions of soil, climate and season. Clover seeds, like those of grasses, are buried most deeply in the light soils of the prairie so light that they sink, so as to make walking over them unusually tiresome when working on newly plowed land, and in other instances so light as to lift with the wind. On such soils the seeds may be buried to the depth of 2 to 3 inches. On loam soils, a covering of 1 inch or less would be ample, and on stiff clays the covering may even be lighter under normal conditions.
Clover seeds are buried more deeply in dry than in moist climates, and also more deeply in dry portions of the year than when moisture is sufficient. While it may be proper in some instances to scatter the seeds on the surface without any covering other than is furnished by rain or frost, it will be very necessary at other seasons to provide a covering to insure a stand of the seed.
When clover seed is sown on ground honeycombed with frost, no covering is necessary. When sown on winter grain in the spring, the ground not being so honeycombed, covering with the harrow is usually advantageous. When sown on spring crops and early in the season, it may not be necessary to cover the seed, except by using the roller, even though the seed should fall behind the grain tubes while the grain crop is being sown, or should be sown subsequently by hand. In other instances the harrow should be used, and sometimes both the roller and the harrow. Under conditions such as appertain to New England and the adjacent States to Ontario and the provinces east and to the land west of the Cascade Mountains, clover and also grass seeds do not require so much of a covering as when sown on the prairie soils of the central portion of the continent.
Sowing Alone or in Combinations.—Whether clover seed should be sown alone or in combination with the seeds of other grasses will depend upon the object sought in sowing it. When sown to produce seed, it is usually sown without admixture, but not in every instance; when sown to produce hay, it is nearly always sown in mixtures, but to this there are some exceptions; when sown to produce pasture, it is almost invariably sown with something else; and when sown to enrich the land, it is, in all, or nearly all, instances, sown without admixture.
When sown primarily to produce seed, there are no good reasons why timothy and probably some other grasses may not be sown with medium red and mammoth clover, when pasture is wanted from the land in the season or seasons immediately following the production of seed.
The presence of these grasses may not seriously retard the growth of the clover plants until after they have produced seed, and subsequently they will grow more assertively and produce pasture as the clover fails. Moreover, should they mature any seed at the same time that the clover seeds mature, they may usually be separated in the winnowing process, owing to a difference in the size of the seeds. But timothy should not be sown with alsike clover that is being grown for seed, since the seeds of these are so nearly alike in size that they cannot be separated.
When hay is wanted, the practice is very common of sowing timothy along with the medium red, mammoth and alsike varieties of clover. Timothy grows well with each of these; supports them to some extent when likely to lodge; matures at the same time as the mammoth and alsike clovers; comes on more assertively as the clovers begin to fail, thus prolonging the period of cropping or pasturing; and feeds upon the roots of the clovers in their decay.
Next to timothy, redtop is probably the most useful grass to sow with these clovers, and may in some instances be added to timothy in the mixtures. Some other grasses may also be added under certain conditions, or substituted for timothy or redtop. In certain instances, it has also been found profitable to mix certain of the clovers in addition to adding grass seeds when hay is wanted. The more important of these mixtures will be referred to when treating of growing the different varieties in subsequent chapters. When growing them, the aim should be to sow those varieties together which mature about the same time. The advantages from growing them together for hay include larger yields, a finer quality of hay, and a more palatable fodder.
In the past it has been the almost uniform practice to sow alfalfa alone, but this practice is becoming modified to some extent, and is likely to become more so in the future, especially when grown for pasture.
When sown to produce pasture, unless for one or two seasons, clover seed is sown in various mixtures of grasses in all or nearly all instances. The grasses add to the permanency of the pastures, while the clovers usually furnish abundant grazing more quickly than the grasses. Several of them, however, are more short-lived than grasses usually are, hence the latter are relied upon to furnish grazing after the clovers have begun to fail. In laying down permanent pastures, the seed of several varieties is usually sown, but in moderate quantities. The larger the number of the varieties sown that are adapted to the conditions, the more varied, the more prolonged and the more ample is the grazing likely to be.
When clovers, except the crimson variety, are sown for the exclusive purpose of adding to the fertility of the land, they are usually sown along with some other crop that is to be harvested, the clover being plowed under the following autumn or the next spring. These are usually sown without being mixed with other varieties, and the two kinds most frequently sown primarily to enrich the land are the medium red and crimson varieties. The former grows more quickly than other varieties, and the latter, usually sown alone, comes after some crop already harvested, and is buried in time to sow some other crop on the same land the following spring.
Sowing with or without a Nurse Crop.—Nearly all varieties of clover are usually sown with a nurse crop; that is, a crop which provides shade for the plants when they are young and delicate. But the object in sowing with a nurse crop is not so much to secure protection to the young plants as to get them established in the soil, so that they will produce a full crop the following season. Two varieties, however, are more commonly sown alone. These are alfalfa and crimson clover.
Alfalfa is more commonly sown alone because the young plants are somewhat delicate and easily crowded out by other plants amid which they are growing. Because of the several years during which alfalfa will produce crops when once established, it is deemed proper to sacrifice a nurse crop in order to get a good stand of the young plants. The other clovers are usually able to make a sufficient stand, though grown along with a nurse crop. In some situations alfalfa will also do similarly, as, for instance, where the conditions are very favorable to its growth. Crimson clover is more commonly sown alone for the reason, first, that it is frequently sown at a season when other crops are not being sown; second, that it grows better without a nurse crop; and third, that if grown with a nurse crop the latter would have to be used in the same way as the clover.
Some have advocated sowing clovers without a nurse crop under any conditions. Such advocacy in the judgment of the author is not wise. It is true that in some instances a stand of the various clovers is more certainly assured when they are sown without a nurse crop, but in such situations it is at least questionable if it would not be better to sow some other crop as a substitute for clover. But there may be instances, as where clover will make a good crop of hay the year that it is sown, when sowing it thus would be justifiable. In a majority of instances, however, it will not make such a crop, because of the presence of weeds, which, in the first place, would hinder growth, and in the second, would injure the quality of the hay.
The nurse crops with which clovers may be sown are the small cereal grains, as rye, barley, wheat and oats. Sometimes they are sown with flax, rape and millet. They usually succeed best when sown along with rye and barley, since these shade them less and are cut earlier, thus making less draft on moisture in the soil and admitting sunlight at an earlier period. Oats make the least advantageous nurse crop, because of the denseness of the shade, but if they are sown thinly and cut for hay soon after they come into head, they are then a very suitable nurse crop. One chief objection to flax as a nurse crop is that it is commonly sown late. The chief virtue in rape as a nurse crop is that the shade is removed early through pasturing. The millets are objectionable as nurse crops through the denseness of the shade which they furnish and also because of the heavy draught which they make on soil moisture. Peas and vetches should not be used as nurse crops, since they smother the young clover plants through lodging in the advanced stages of their growth.
Amounts of Seed to Sow.—The amounts of clover seed to sow are influenced by the object sought in sowing; by combinations with which the seeds are sown, and by the relative size of the seeds. The soil and climate should also be considered, although these influences are probably less important than those first named.
When clovers are sown for pasture only, or to fertilize the soil speedily and to supply it with humus, the largest amounts of seed are sown. But for these purposes it is seldom necessary to use more than 12 pounds of seed per acre. These amounts refer to the medium red and mammoth varieties, which are more frequently used than the other varieties for the purposes named. They also include the crimson sown usually to fertilize the soil. When sown to provide seed only, 12 pounds per acre of the medium red, mammoth and crimson varieties will usually suffice. Half the quantity of alsike will be enough, and one-third the quantity of the small white, or a little more than that. Whether alfalfa is grown for seed, for hay or for pasture, about the same amounts of seed are used; that is, 15 to 20 pounds per acre. When sown with nurse crops and simply to improve the soil, it is customary to sow small rather than large quantities of seed, and for the reason that the hazard of failure to secure a stand every season is too considerable to justify the outlay. From 4 to 5 pounds per acre are frequently sown and of the medium or mammoth variety.
When the mammoth and medium varieties of clover are sown for hay with one or two kinds of grass only, it is not common to sow more than 6 to 8 pounds of either per acre. The maximum amount of the seed of the alsike required when thus sown with grasses may be set down at 5 pounds per acre. These three varieties are chiefly used for such mixtures. With more varieties of grass in the mixtures, the quantities of clover seed used will decrease. When clovers are sown with mixtures intended for permanent pastures, it would not be possible to name the amounts of seed to sow without knowing the grasses used also, but it may be said that, as a rule, in those mixtures, the clovers combined seldom form more than one-third of the seed used.
The seeds of some varieties of clover are less than one-third of the size of other varieties. This, therefore, affects proportionately, or at least approximately so, the amounts of seed required. For instance, while it might be proper to sow 12 pounds of medium or mammoth clover to accomplish a certain result, less than one-third of the quantity of the small white variety would suffice for the same end.
The influences of climate and soil on the quantities of seed required are various, so various that to consider them fully here would unduly prolong the discussion. But it may be said that the harder the conditions in both respects, the more the quantity of seed required and vice versa.
Pasturing.—When clover seed is sown in nurse crops that are matured before being harvested, the pasturing of the stand secured the autumn following is usually to be avoided. Removing the covering which the plants have provided for themselves is against their passing through the winter in the best form. In some instances the injury proves so serious as to result in a loss of all, or nearly all, the plants. The colder the winters, the less the normal snowfall and the more the deficiency of moisture, the greater is the hazard. But in some instances so great is the growth of the clover plants that not to graze them down in part at least would incur the danger of smothering many of the plants, especially in regions where the snowfall is at all considerable.
But when the seed is sown alone or in mixtures of grain and even of other grasses in the spring, grazing the same season will have the effect of strengthening the plants. This result is due chiefly to the removal of the shade that weeds and other plants would furnish were they not thus eaten down, but it is also due in part to the larger share of soil moisture that is thus left for the clover plants. Pasturing clover sown thus should be avoided when the ground is so wet as to poach or become impact in consequence. Unless on light, spongy soils which readily lose their moisture, such grazing should not begin until the plants have made considerable growth, nor should it be too close, or root development in the pastures will be hindered.
It would not be possible to fix the stage of growth when the grazing should begin on clover fields kept for pasture subsequent to the season of sowing. The largest amount of food would be furnished if grazing were deferred until the blossoming stage were reached and the crop were then grazed down quickly. But this is not usually practicable, hence the grazing usually begins at a period considerably earlier. In general, however, the plants should not be grazed down very closely, or growth will be more or less hindered.
Grazing clover in the spring and somewhat closely for several weeks after growth begins, has been thought conducive to abundant seed production. This result is due probably to the greater increase in the seed heads that follow such grazing. This would seem to explain why clover that has been judiciously grazed produces even more seed than that clipped off by the mower after it has begun to grow freely.
In nearly all localities the grazing of medium red clover, and even of mammoth clover, somewhat closely in the autumn of the second year, is to be practised rather than avoided. These two varieties being essentially biennial in their habit of growth will not usually survive the second winter, even though not grazed, hence not to graze them would result in a loss of the pasture.
With nearly all kinds of clover there is some danger from bloat in grazing them with cattle or sheep while yet quite succulent, and the danger is intensified when the animals are turned in to graze with empty stomachs or when the clover is wet with dew or rain. When such bloating occurs, for the method of procedure see page 95. The danger that bloat will be produced is lessened in proportion as other grasses abound in the pastures.
Harvesting.—All the varieties of clover, except alfalfa, are best cut for hay when in full bloom. Here and there a head may have turned brown. If cut earlier, the crop is difficult to cure, nor will it contain a maximum of nutriment. If cut later it loses much in palatability. Alfalfa should be cut a little earlier, or just when it is nicely coming into bloom, as if cut later the shedding of the leaves in the curing is likely to be large.
All clovers are much injured by exposure to rain or dew. They will also lose much if cured in the swath, without being frequently stirred with the tedder; that is, it will take serious injury if cured in the swath as it fell from the mower. If cured thus, it will lose in aroma and palatability, through the breaking of leaves and, consequently, in feeding value. To avoid these losses, clover is more frequently cured in the cock. When cured thus, it preserves the bright green color, the aroma and the tint of the blossoms, it is less liable to heat in the mow or stack and is greatly relished by live stock when fed to them.
To cure it thus, it is usually tedded once or twice after it has lost some of its moisture. It is then raked as soon as it is dried enough to rake easily, and put up into cocks. When the quantity to be cured is not large caps are sometimes used to cover the cocks to shed the rain when the weather is showery. These are simply square strips of some kind of material that will shed rain, weighted at the corners to keep them from blowing away. The clover remains in the cocks for two or three days, or until it has gone through the "sweating" process. Exposure to two or three showers of rain falling at intervals while partially cured in the swath or winrow will greatly injure clover hay.
When the area to be harvested is large, clover is sometimes cured in the swath. When thus cured it is stirred with the tedder often enough to aid in curing the hay quickly. It is then raked into winrows and drawn from these to the place of storage. In good weather clover may be cured thus so as to make fairly good hay, but not so good as is made by the other method of curing. It is much more expeditiously made, but there is some loss in leaves, in color and in palatability.
Some farmers cure clover by allowing it to wilt a little after it is cut, and then drawing and storing it in a large mow. They claim that it must be entirely free from rain or dew when thus stored. This plan of curing clover has been successfully practised by some farmers for many years; others who have tried it have failed, which makes it evident that when stored thus, close attention must be given to all the details essential to success.
Clover may also be cured in the silo. While some have succeeded in making good ensilage, in many cases it has not proved satisfactory. The time may come when the conditions to be observed in making good silage from clover will be such that the element of hazard in making the same will be removed. In the meantime, it will usually be more satisfactory to cure clover in the ordinary way.
Grasses cure more easily and more quickly than clovers. Consequently, when these are grown together so that the grasses form a considerable proportion of the hay, the methods followed in curing the grasses will answer also for the clovers. For these methods the reader is referred to the book "Grasses and How to Grow Them" by the author. The influence that grasses thus exert on the growing of clovers furnishes a weighty reason for growing them together.
Storing.—Clovers are ready to store when enough moisture has left the stems to prevent excessive fermentation when put into the place of storage. Hay that has been cured in the cock is much less liable to heat when stored so as to produce mould, than hay cured in the swath or winrow. The former has already gone through the heating process or, at least, partially so. Some experience is necessary to enable one to be quite sure as to the measure of the fitness of hay for being stored. When it can be pitched without excessive labor it is ready for being stored, but the unskilled will not likely be able to judge of this accurately. If a wisp is taken some distance from the top of the winrow or cock and twisted between the hands, if moisture exudes it is too damp, and if the hay breaks asunder readily it is too dry. When no moisture is perceptible and yet the wisp does not break asunder, the hay is ready to be drawn. Care must be taken that the wisp chosen be representative of the mass of the hay. To make sure of this, the test should be applied several times.
Where practicable the aim should be to store clover hay under cover, owing to the little power which it has to shed rain in the stack. This is only necessary, however, in climates with considerable rainfall during the year and where irrigation is practised, as in the mountain States clover hay may be kept in the stack without any loss from rain, and it can be cured exactly as the ranchman may desire, since he is never embarrassed when making hay by bad weather. When storing clovers, the time of the day at which it is stored influences the keeping qualities of the hay. Hay stored at noontide may keep properly, whereas, if the same were stored while dew is falling it might be too damp for being thus stored.
Much care should be taken in stacking clover hay that it may shed rain properly. The following should be observed among other rules of less importance that may be given: 1. Make a foundation of rails, poles or old straw or hay that will prevent the hay near the ground from taking injury from the ground moisture. 2. Keep the heart of the stack highest from the first and the slope gradual and even from the center toward the sides. 3. Keep the stack evenly trodden, or it will settle unevenly, and the stack will lean to one side accordingly. 4. Increase the diameter from the ground upward until ready to draw in or narrow to form the top. 5. Aim to form the top by gradual rather than abrupt narrowing. 6. Top out by using some other kind of hay or grass that sheds the rain better than clover. 7. Suspend weights to some kind of ropes, stretching over the top of the stack to prevent the wind from removing the material put on to protect the clover from rain.
Feeding.—The clovers furnish a ration more nearly in balance than almost any other kind of food. If the animals to which they are fed could consume enough of them to produce the desired end, concentrated foods would not be wanted. They are so bulky, however, relatively, that to horses and mules at work, to dairy cows in milk and cattle that are being fattened, to sheep under similar conditions, and to swine, it is necessary to add the concentrated grain foods, more or less, according to the precise object. But for horses, mules, cattle, sheep and goats that are growing subsequent to the weaning stage, and for mature animals of these respective classes not producing, that is, not yielding returns, a good quality of clover hay will suffice for a considerable time at least without the necessity of adding any other food.
It is considered inferior to timothy as a fodder for horses. This preference is doubtless owing largely to the fact, first, that clover breaks up more and loses more leaves when being handled, especially when being transported; and second, that clover is frequently cured so imperfectly as to create dust from over-fermentation or through breaking of the leaves, because of being over-dried, and the dust thus created is prejudicial to the health of these animals. It tends to produce "heaves." This may in part be obviated by sprinkling the hay before it is fed. When clover is properly cured, it is a more nutritious hay than timothy, and is so far preferable for horses, but since timothy transports in much better form, it is always likely to be more popular in the general market than clover. The possibility of feeding clover to horses for successive years without any evils resulting is made very apparent from feeding alfalfa thus in certain areas of the West.
Clover hay is specially useful as a fodder for milk-producing animals, owing to the high protein content which it contains. Dairymen prefer it to nearly all kinds of fodders grown, and the same is true of shepherds. When very coarse, however, a considerable proportion of the stems is likely to be left uneaten, especially by sheep. Because of this it should be the aim to grow it so that this coarseness of stem will not be present. This is accomplished, first, by growing it thickly, and second, by growing the clovers in combination with one another and also with certain of the grasses.
Clovers are especially helpful in balancing the ration where corn is the principal food crop grown. The protein of the clover crop aids greatly in balancing the excess of carbo-hydrates in the corn crop, hence much attention should be given to the production of clovers in such areas.
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.
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 subsequently.
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.
Clover as a Weed Destroyer.—Where clover is much grown, at least in some of its varieties, it becomes an aid in reducing the prevalence of many forms of weed growth. It is thus helpful in some instances, because of the number of the cuttings secured; in others because of its smothering tendencies, and in yet others because of the season of the year when it is sown and harvested or plowed under, as the case may be.
Alfalfa and medium red clover are cut more frequently than the other varieties and, therefore, because of this, render more service than these in checking weed growth. The former is cut so frequently as to make it practically impossible for most forms of annual weed life to mature seed in the crop. The same is true of biennials and also perennials. But there are some forms of perennial weeds which multiply through the medium of their rootstocks that may eventually crowd alfalfa. Medium red clover is usually cut twice a year, hence, in it annuals and biennials cannot mature seed, except in exceptional instances, and because of the short duration of its life, perennials have not time to spread so as to do much harm.
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.
The cause being known, the remedy is not difficult. It is to grow clover less frequently on such soils. Sufficient time must be given to enable more of the inert potash in the subsoil to become available. Another way would be to apply potash somewhat freely to these soils, and subsoil them where this may be necessary.
It is thought that clover sickness is as yet unknown in the United States and Canada, although its presence had sometimes been suspected in some sections where clover has been much grown. This does not mean that it may not yet come to this country. Should the symptoms given above appear on soils on which clover has been grown frequently and for a long period, it would be the part of wisdom to take such indications as a hint to grow clover less frequently in the rotation.
Possible Improvement in Clovers.—Some close observers have noticed that there is much lack of uniformity in the plants found growing in an ordinary field of clover, especially of the medium red and mammoth varieties. Many of the plants vary in characteristics of stem, leaf, flower and seed; in the size and vigor of the plants; in the rapidity with which they grow; and in earliness or lateness in maturing. So great are these differences that it may be said they run all the way from almost valueless to high excellence. Here, then, is a wide-open door of opportunity for improving clover plants through selection. This question has not been given that attention in the past which its importance demands.
There may be a difference in view as to all the essential features of improvement that are to be sought for, but there will probably be agreement with reference to the following in desirable varieties: 1. They will have the power to grow quickly and continuously under average conditions. This power will render them valuable as pasture plants in proportion as they possess it. 2. They will produce many stems not too coarse in character. This will affect favorably the character of the hay and will also have a bearing on increase in the production of seed. 3. There should be an abundance of leaves. Such production will affect favorably palatability in the pasture and also in the hay. 4. The blossoms should be so short that the honey which they contain may be accessible to the ordinary honey bee. The importance of this characteristic cannot be easily overestimated. It would not only tend to a great increase in seed production through the favorable influence which it would have on fertilization, but it would greatly increase the honey harvest that would be gathered every year, and 5. They should be possessed of much vigor and hardihood; that is, they should have much power to grow under adverse conditions, as of drought and cold. The person who will furnish a variety of red clover possessed of these characteristics will confer a boon on American agriculture.
Bacteria and Clovers.—The fact has long been known, even as long ago as the days of Pliny, and probably much before those days, that clover, when grown in the rotation, had the power to bring fertility to the soil. This fact was generally recognized in modern agriculture and to the extent, in some instances, of giving it a place even in the short rotations. But until recent decades, it was only partially known how clover accomplished such fertilization. It was thought it thus gathered fertility by feeding deeply in the subsoil, and through the plant food thus gathered, the root system of the plants were so strengthened in the cultivated surface section of soil as to account for the increased production in the plants that followed clover. According to this view, the stems and leaves of the plants were thus equally benefited and, consequently, when these were plowed under where they had grown these also added plant food to the cultivated portion of the soil, in addition to what it possessed when the clover seed which produced the plants was sown upon it. In brief, this theory claimed that fertility was added by the clover plants gathering fertility in the subsoil and depositing it so near the surface that it became easily accessible to the roots of other plants sown after the clover and which had not the same power of feeding so deeply. This theory was true in part. The three important elements of plant food, nitrogen, phosphoric acid and potash, were and are thus increased in the soil, but this does not account for the source from which the greater portion of the nitrogen thus deposited in the soil was drawn, as will be shown below.
It was also noticed that when the seed of any variety of clover was sown on certain soils, the plants would grow with more or less vigor for a time and then they would fail to make progress, and in some instances would perish. It was further noticed that if farmyard manure was applied freely to such land, the growth made was more vigorous. Yet, again, it was noticed that by sowing clover at short intervals on such soils, the improvement in the growth of the plants was constant. But it was not understood why clover plants behaved thus under the conditions named. It is now known that ill success at the first was owing to the lack of certain micro-organisms, more commonly termed bacteria, in the soil, the presence of which are essential to enable clover plants to secure additional nitrogen to that found in the soil and subsoil on which to feed. When manure was applied, as stated above, the clover plants secured much or all of their nitrogen from the manure. Bacteria were introduced in very limited numbers at first, it may be through the medium of the seed or in some other way, and because of an inherent power which they possess to increase rapidly in connection with continued sowing of clover at short intervals, they came at length to be so numerous in the soil as to make possible the growth of good crops of clover where these could not be thus grown a few years previously.
Careful observers had noticed that certain warty-like substances were found attached to the roots of clover plants, and that the more vigorously the plants grew, the larger and more numerous were these substances, as a rule. It was thought by many that these warty substances, now spoken of as nodules, were caused by worms biting the roots or because of some unfavorable climatic influence or abnormal condition of soil. It is now known that they are owing to the presence of bacteria, whose special function is the assimilation of free nitrogen obtained in the air found in the interstices; that is, the air spaces between the particles of soil. This they store up in the nodules for the use of the clover plants and also the crops that shall follow them.
The nodules in clover plants vary in size, from a pin head to that of a pea, and they are frequently present in large numbers. Bacteria are present within them in countless myriads. They gain an entrance into the plant through the root hairs. The exact way in which benefit thus comes to the clover plants is not fully understood, but it is now quite generally conceded that the nitrogen taken in by these minute forms of life is converted into soluble compounds, which are stored in the tissues of the roots, stems and leaves of the plants, thus furnishing an explanation to the increased vigor. It cannot be definitely ascertained at present, if, indeed, ever, what proportion of the nitrogen in clover is taken from the air and from the soil, respectively, since it will vary with conditions, but when these are normal, it is almost certain that by far the larger proportion comes from the air. But it has been noticed that when soil is freely supplied with nitrogen, as in liberal applications of farmyard manure, the plants do not form nodules so freely as when nitrogen is less plentiful in the soil. The inference would, therefore, seem to be correct, that when plants are well supplied with nitrogen in the soil they are less diligent, so to speak, in gathering it from the air. In other words, clover plants will take more nitrogen from the air when the soil is more or less nitrogen hungry than when nitrogen abounds in the soil. And yet the plants should be able to get some nitrogen from the soil in addition to what the seed furnishes to give them a vigorous start.
This power to form tubercles, and thus to store up nitrogen, is by no means confined to clovers. It is possessed by all legumes, as peas, beans and vetches. It is claimed that some of these, as soy beans, cow peas and velvet beans, have even greater power to gather nitrogen from the air and store it in the soil than clover, since the nodules formed on the roots of these are frequently larger. In some instances, on the roots of the velvet bean they grow in clusters as large as an ordinary potato. With reference to all these leguminous plants it has been demonstrated that under proper conditions good crops may be grown and removed from the soil and leave it much richer in nitrogen than when the seed was sown. It is thus possible by sowing these crops at suitable intervals to keep the soil sufficiently supplied with nitrogen to grow good crops other than legumes, adapted to the locality, without the necessity for purchasing the nitrogen of commerce in any of its forms. They may be made to more than maintain the supply of nitrogen, notwithstanding the constant loss of the same by leeching down into the subsoil in the form of nitrates, and through the more or less constant escape of the same into the air in the form of ammonia, during those portions of the year when the ground is not frozen.
They will do this in addition to the food supplies which they furnish, hence they may be made to supply this most important element of fertility, and by far the most costly when purchased in the market, virtually without cost. The favorable influences which these plants thus exert upon crop production is invaluable to the farmer. They make it possible for him to be almost entirely independent of the nitrogen of commerce, which, at the rate of consumption during recent years, will soon be so far reduced as to be a comparatively insignificant factor in its relation to crop production. It is possible, however, and not altogether improbable, that by the aid of electricity a manufactured nitrate of soda or of potash may be put upon the market at a price which will put it within reach of the farmer. The power of legumes to increase the nitrogen content in the soil should allay apprehension with reference to the possible exhaustion of the world's supply of nitrogen, notwithstanding the enormous waste of the same in various ways.
The more common sources of loss in nitrogen are, first, through the leeching of nitrates into the drainage water; second, through oxidation; third, through the use of explosives in war; and fourth, through the waste of the sewerage of cities. When plant and animal products are changed into soluble nitrates, they are usually soon lost to the soil, unless taken up by the roots of plants. When vegetable matter on or near the surface of the ground is broken down and decomposed, in the process of oxidation, there is frequently much loss of nitrogen, as in the rapid decomposition of farmyard manure in the absence of some material, as land plaster, to arrest and hold the escaping ammonia. Through explosives used in war there is an enormous vegetable loss of nitrogen, as nitrate salts, which should rather be used to preserve and sustain life than to destroy it. The waste of nitrogen through the loss of sewerage is enormous, nor does there seem to be any practicable way of saving the bulk of it.
In many soils the germs which produce nodules are present when clovers are first grown on them. But where they are not present, the clover plants have no more power to gather nitrogen than wheat or other non-leguminous crops. But since in other soils they are almost entirely absent, how shall they be introduced? The process of introducing them is generally referred to as a process of inoculation, and soils when treated successfully are said to be inoculated.
Three methods have been adopted. By the first, as previously indicated, the grower perseveres in sowing clover at short intervals in the rotation. He may also add farmyard manure occasionally, and thus, through the inherent power of multiplication in the bacteria, they increase sufficiently to enable the land to grow good crops. By the second method, inoculating is effected through soil which is possessed of the requisite bacteria; and by the third, it is effected through the aid of a prepared product named nitragin.
When fields are to be inoculated by using soil it is obtained from areas which have grown clovers successfully quite recently, and which are, therefore, likely to be well filled with the desired bacteria. In some instances the seed is mixed with the soil and these are sown together. To thus mix the seed with the soil and then sow both together broadcast or with a seed drill is usually effective, and it is practicable when minimum quantities of soil well laden with germs are used. In other instances the soil containing germs is scattered broadcast before or soon after the seed is sown. Considerable quantities of earth must needs be applied by this method.
It should be remembered that each class of legumes has its own proper bacteria. Because of this, inoculation can only, or at least chiefly, be effected through the use of soils on which that particular class of legumes have grown, or which are possessed of bacteria proper to that particular species. In other words, bacteria necessary to the growth of vetches will not answer for the growth of clovers, and vice versa. Nor will the bacteria requisite to grow medium red clover answer for growing alfalfa. In other words, the bacteria proper to the growth of one member of even a family of plants will not always answer for the growth of another member of the same. But in some instances it is thought that it will answer. The study of this phase of the question has not yet progressed far enough to reflect as much light upon it as could be desired. It is certainly known, however, that alfalfa will grow on soils that grow burr clover (Medicago maculata) and sweet clover (Melilotus alba), hence the inference that soil from fields of either will inoculate for alfalfa.
Nitragin is the name given by certain German investigators to a commercial product put upon the market, which claims to be a pure culture of the root tubercle organism. These cultures were sold in the liquid form, and it was customary when using them to treat the seed with them before it was planted. Their use has been largely abandoned, because of the few successes which followed their use compared with the many failures. But it is now believed that these cultures can be prepared and used so as to be generally effective and without excessive cost to the grower.
In preparing cultures it has been found that by gradually reducing the amount of nitrogen in the culture of media, it is possible to increase the nitrogen fixing power in these germs from five to ten times as much as usually occurs in nature. It is now known that the bacteria thus grown upon nitrogen free media retain high activity if carefully dried and then revived in liquid media at the end of the varying lengths of time. Some absorbent is used to soak up the tubercle-forming organisms. The cultures are then allowed to dry, and when in that condition they can be safely sent to any part of the country without losing their efficacy. It is necessary to revive the dry germs by immersing them in water. By adding certain nutrient salts the bacteria are greatly increased if allowed to stand for a limited time—as short, in some instances, as 24 hours. The culture thus sent out in a dry form, and no larger than a yeast cake, may thus be made to furnish bacteria sufficient to inoculate not less than an acre of land. It is stated that the amount of inoculating material thus obtained is only limited by the quantity of the nutrient water solution used in increasing the germs, so that the cost of inoculating land by this process is not large. The culture may be applied by simply soaking the seed in it, by spraying the soil, or by first mixing the culture into earth, spreading it over the field and then harrowing it. Inoculations thus tried under the supervision of the United States Department of Agriculture have proved quite successful.
Where any legume is extensively grown surrounding soils come to be inoculated through the agency of winds and water. The increase brought to the yield of plants on various soils runs all the way from a slight gain to 1000-fold. And when soil is once inoculated it remains so for a long time, even though the proper legume should not be grown again on the same soil.