Plate 5. Alfalfa: Effect of Bacteria from Alfalfa and from Sweet Clover.Pot 1.—No bacteria.Pots 2 and 3.—Bacteria from alfalfa.Pots 4 and 5.—Bacteria from sweet clover.The four series of photographs were taken five, six, seven and eight weeks from time of planting, respectively.
Plate 5. Alfalfa: Effect of Bacteria from Alfalfa and from Sweet Clover.
Pot 1.—No bacteria.
Pots 2 and 3.—Bacteria from alfalfa.
Pots 4 and 5.—Bacteria from sweet clover.
The four series of photographs were taken five, six, seven and eight weeks from time of planting, respectively.
From these investigations we thus have conclusive evidence that infected sweet clover soil can be used for the inoculation of alfalfa fields, the bacteria of the two plants acting the same. The infected soil may be obtained from any place where the sweet clover is found growing with abundance of tubercles on its roots. The soil may be collected to a depth of three or four inches and scattered over the alfalfa field at the rate of 100 pounds or more to the acre. It is well to scatter the infected soil at about the time the alfalfa is seeded, and harrow it in with the alfalfa seed, although it may be applied some days or even some weeksbefore seeding time, and probably it would be all right to apply the infected soil the fall before, for it is known that the bacteria will live in soil for several months, even though the soil be placed in sacks and allowed to become quite dry.
Investigations have shown that 100 pounds of thoroughly infected soil to the acre is sufficient to produce a very satisfactory inoculation within one year from the time it is applied. Of course, somewhat heavier applications may well be made if it can be done at small expense. The infected soil need not be applied with any high degree of uniformity, but special care should be taken that the higher places and watersheds are not missed in scattering it over the field. If a few square yards, or even square rods, should be missed on the slopes or lower land, it would make but little difference, as the bacteria will be washed over such places from the higher land.
After the soil becomes somewhat dry it is easily scattered by hand from the wagon or from a sack which one can carry. Sometimes it is applied by means of an end gate seeder or a fertilizer drill, or it could be spread by a manure spreader with an application of manure.
The question naturally arises whether there is not danger of getting some sweet clover seed with the infected sweet clover soil, and thus of getting sweet clover mixed with the alfalfa in the field.
In the writer’s opinion there is little or nothing to fear in this matter. In the first place, the amount of sweet clover seed thus obtained would be very small, probably none at all, if one were careful to scrape off the vegetable matter, and perhaps a half inch of earth before collecting the infected soil (most of the bacteria are probably between one-half inch and six inches in depth, as most of the tubercles develop and decay between those depths); second; it is doubtful if a small amount of sweet clover hay would lessen the value of alfalfa hay in the least, for stock frequently eat small amounts of sweet clover of their own choice even when it is nearly mature, and if it is cut while still quite immature and tender it makes quite satisfactory hay, so much so that in some sections of the United States, particularly in the South, sweet clover is regularly seeded on fields and cut for hay, and it is found to be a valuable and very nutritious feed, the live stock eating it in large quantities, and with apparent relish, after they have acquired a taste for it; third, sweet clover is not known as a bad weed in the fields or meadows, even where it has been a common roadside plant for many years, and, being naturally a biennial plant, if it were cut down every five or six weeks, as we commonly cut alfalfa during the season, it would almost certainly die out after a few years while alfalfa, a perennial plant, would continue to live.
Only one instance has come to the writer’s attention where alfalfa has been growing for several years with sweet clover growing in thefield or fence rows beside it. This is on the farm of Mr. D. S. Mayhew, of Mercer County, Illinois, who writes as follows regarding the matter:
“Will say that the sweet clover has made no headway in my meadow, as it did not go to seed, on account of my cutting it so often. The sweet clover got into the alfalfa in the seed when I sowed it. I do not think it will do any harm in a meadow, but I believe it would do harm in a pasture if it wasn’t cut down as stock will not eat the sweet clover.”
“Will say that the sweet clover has made no headway in my meadow, as it did not go to seed, on account of my cutting it so often. The sweet clover got into the alfalfa in the seed when I sowed it. I do not think it will do any harm in a meadow, but I believe it would do harm in a pasture if it wasn’t cut down as stock will not eat the sweet clover.”
Of course if sweet clover should get into the field and persist in growing, and if it were found to injure the alfalfa appreciably or markedly, we can always resort to plowing the ground up and growing corn or other crops, thus obtaining some benefit from the leguminous crop for its fertilizing value, and at the same time completely eradicating the sweet clover, but leaving the soil well infected with alfalfa bacteria ready to serve in case alfalfa should be again seeded within a few years.
In general agriculture in Illinois, whether it be grain farming or ordinary livestock farming, the growing of legumes is absolutely essential as a part of any economic system which shall maintain the fertility of the soil; and for the successful growing of legumes the presence and assistance of the proper species of nitrogen-gathering bacteria are also absolutely essential. These facts being granted, it certainly follows that when sowing any legume on land, where the same legume has never been grown before, or perhaps where it has not been successfully grown within recent years, we should always consider the matter of inoculation; and, unless there is good reason to believe that the soil has been inoculated by the washing from other higher lying land where these bacteria are known to be present or by applications of manure made from that legume, or by some other such incidental means; or unless there is evidence that the bacteria are carried with the seed in sufficient quantity to effect a satisfactory inoculation (as appears to be the case with the cowpea), then we should inoculate the soil directly with the specific bacteria required by the legume which we desire to grow.
While some Illinois soils are becoming deficient in phosphorus and in lime, especially in the southern part of the state, and while phosphorus[8]and ground limestone can be applied to such soils with marked benefit and profit, especially for the growing of legumes, there is abundant evidence that one of the dominant causes for the failure or unsatisfactory growth of some of our most valuable legumes, and on some soils the sole cause of failure, is the absence of the proper nitrogen-gathering bacteria.
There is no reason to believe that any of the different species of nitrogen-gathering bacteria will live in the soil for more than a fewyears[9]in the entire absence of any legume upon which they naturally live, and the accumulating evidence strongly indicates that the bacteria which are present in places in our soils, such as the red clover bacteria, now found abundantly in many places in the state, especially in northern and central Illinois, the cowpea bacteria more common in southern Illinois, and the alfalfa or sweet clover bacteria, which are becoming prevalent in some sections—that all these have been, and are being, gradually introduced and extended almost entirely by mere chance. Of course if the wagon-wheel, which carries the mud along the road, carries with it sweet clover seed from one place to another, it may also carry the sweet clover bacteria which live on the sweet clover roots.
It now seems absurd to suppose that there were red clover bacteria in Illinois soil before red clover itself was grown on Illinois soil, unless the same bacteria live also upon some other legume which was native to our soils. There is some evidence that the vetch bacteria are native to our soil, possibly living upon the native wild vetches. At any rate, tubercles commonly develop on vetch roots without artificial inoculation. Investigations are in progress to ascertain whether the notorious failure of crimson clover in Illinois may not be due in part, at least, to the absence of the proper bacteria. (It has been stated by some writers that the bacteria of crimson clover and those of red clover are identical, but we already have some reason to doubt the accuracy of this statement.)
[1]It should be remembered that there are ten essential elements of plant food each of which is of equal importance to the plant, for if the plant is deprived of any one of the ten essential elements it is impossible for it to develop and mature. Carbon has no market value as plant food because the plant obtains carbon in the form of carbon dioxid, a gas which is present everywhere in the atmosphere and which the plant inhales through its leaves. Both hydrogen and oxygen are without market value because they are the elements which compose water, a liquid compound which plants absorb through their roots. Calcium, magnesium, iron, and sulfur have no market value as elements of plant food because they are present in practically all soils in abundance as compared with the amounts required in plant growth. The three elements nitrogen, phosphorus, and potassium, do have market values, because they are required by plants in very considerable quantities, and they are present in most soils in rather limited amounts, and when the available supply of any one of these elements becomes too much reduced in a soil the crop yield also becomes reduced. For further information regarding the use of these elements of plant food on Illinois soils, see Circular No. 68, “Methods of Maintaining the Productive Capacity of Illinois Soils.”[2]Technically this first step is preliminary to, and not a part of, nitrification.[3]Among the scientists who were prominent in making these discoveries regarding the action of bacteria in the fixation of atmospheric nitrogen were Hellriegel, Willfarth, and Nobbe in Germany, Atwater in America, Lawes and Gilbert in England, and Boussingault and Ville in France.[4]It may be well to call attention to the fact that there are numerous instances where two different kinds of plants live together in intimate partnership relation. If only one of the two plants receives benefit from this relationship or association, then the plant receiving the benefit is celled a parasite. Thus the mistletoe is a parasite upon the elm or gum or other tree on which it lives. The mistletoe draws its nourishment from the tree. The tree is injured rather than benefited by the mistletoe. Dodder is also a parasitic plant, living upon other plants, except during the early part of its growth. Ticks and lice are common examples of animal parasites living upon other animals.In some cases a relationship exists which is not parasitic but symbiotic. The term symbiosis, which is commonly used by biologists to define this relationship, means living together in mutual helpfulness. The association of bees and flowers may serve to illustrate this mutual helpfulness, although this is not an example of intimate symbiosis. Thus the bees obtain their food from the flowers and, in turn, the flowers, many of them, are incapable of producing seed or fruit unless the pollen is carried from the male flower to the female flower by bees or other agencies. It is well known that plant lice and ants are mutually helpful.Likewise the association of nitrogen-gathering bacteria and leguminous plants is a relationship of mutual helpfulness and this is one of the best illustrations of what is meant by symbiosis. The legume furnishes a home for the bacteria and also furnishes in its juice or sap most of the nourishment upon which the bacteria live. The bacteria, on the other hand, take nitrogen from the air contained in the pores of the soil, and cause this nitrogen to combine with other elements in suitable form for plant food which is then given up to the legume for its own nourishment.Another illustration of remarkable parasitism, if not, indeed, one of true symbiosis, is found in the common lichens living upon rocks and trees. The lichen is not a single plant, but two plants—an alga, which lives upon the wood or stone, and a fungus which lives upon the alga. Algæ also live in the free state separate from fungi, and the present opinion of botanists seems to be that when the two are associated in the form of lichens this association is not detrimental, but rather beneficial, to the alga, as well as to the parasitic fungus. If this is true, then it is another case of true symbiosis. (There is reason to believe that the fungus has some power to feed upon atmospheric nitrogen, and then to furnish combined nitrogen to the alga upon which it lives.)In the symbiosis of leguminous plants and nitrogen-gathering bacteria we have a partnership or relationship of immeasurable value to agriculture. Here is a class of plants (legumes) that are capable of consuming or utilizing nitrogen in quantities larger than could possibly be obtained from ordinary soils for any considerable length of time. They have no power in themselves of taking nitrogen from the atmosphere, and to them the symbiotic relation with this low order of plants (the nitrogen-gathering bacteria) is especially helpful, and for the best results it is absolutely necessary.[5]There are some noteworthy exceptions to this rule (see following pages for illustration), and there is some evidence that, by a comparatively long process of breeding, or evolution, the bacteria which naturally live upon one kind of legume may gradually develop the power to live upon a distinctly different legume to which they were not at first adapted. Of course this process of forcing bacteria to live upon a legume to which they are not naturally adapted has little or no practical value because it is unnecessary if there is a species of bacteria which naturally lives upon the same legume. On the other hand, if, by any such process of breeding, or evolution, a species of nitrogen-gathering bacteria could be developed which could live on a non-leguminous plant, as corn, for example, it would be of incalculable practical value. As yet the efforts of bacteriologists, working on this problem, have given only negative results, so far as known to the writer.[6]In this connection attention is called to the fact that the so-called “spot disease” of alfalfa, which is not uncommon in the western states, especially during wet seasons, became somewhat prevalent in Illinois in 1903. When the effect of this disease becomes marked, the leaves turn yellow and growth is retarded. If this occurs the alfalfa should be clipped. This is the only effective remedy known to be practicable. Seeding alfalfa with a light nurse crop is gaining favor in Illinois.[7]Some of these observations have already been reported in the agricultural press. (See, for example, the Breeders’ Gazette, September 9, 1903, page 391, and September 16, 1903, page 442.)[8]Steamed bone meal is the most economical and satisfactory form of phosphorus for use on Illinois soils, unless ground rock phosphate (not acid phosphate) shall prove to be still more economical. Experiments to determine this are in progress.[9]Just how long the bacteria will live in a soil without a leguminous crop upon which they can feed is not definitely known. Certainly they live for two or three years, but probably not more than five or six years. Further investigation is needed to establish the length of time the different kinds of bacteria may remain in the soil under different conditions.
[1]It should be remembered that there are ten essential elements of plant food each of which is of equal importance to the plant, for if the plant is deprived of any one of the ten essential elements it is impossible for it to develop and mature. Carbon has no market value as plant food because the plant obtains carbon in the form of carbon dioxid, a gas which is present everywhere in the atmosphere and which the plant inhales through its leaves. Both hydrogen and oxygen are without market value because they are the elements which compose water, a liquid compound which plants absorb through their roots. Calcium, magnesium, iron, and sulfur have no market value as elements of plant food because they are present in practically all soils in abundance as compared with the amounts required in plant growth. The three elements nitrogen, phosphorus, and potassium, do have market values, because they are required by plants in very considerable quantities, and they are present in most soils in rather limited amounts, and when the available supply of any one of these elements becomes too much reduced in a soil the crop yield also becomes reduced. For further information regarding the use of these elements of plant food on Illinois soils, see Circular No. 68, “Methods of Maintaining the Productive Capacity of Illinois Soils.”
[1]It should be remembered that there are ten essential elements of plant food each of which is of equal importance to the plant, for if the plant is deprived of any one of the ten essential elements it is impossible for it to develop and mature. Carbon has no market value as plant food because the plant obtains carbon in the form of carbon dioxid, a gas which is present everywhere in the atmosphere and which the plant inhales through its leaves. Both hydrogen and oxygen are without market value because they are the elements which compose water, a liquid compound which plants absorb through their roots. Calcium, magnesium, iron, and sulfur have no market value as elements of plant food because they are present in practically all soils in abundance as compared with the amounts required in plant growth. The three elements nitrogen, phosphorus, and potassium, do have market values, because they are required by plants in very considerable quantities, and they are present in most soils in rather limited amounts, and when the available supply of any one of these elements becomes too much reduced in a soil the crop yield also becomes reduced. For further information regarding the use of these elements of plant food on Illinois soils, see Circular No. 68, “Methods of Maintaining the Productive Capacity of Illinois Soils.”
[2]Technically this first step is preliminary to, and not a part of, nitrification.
[2]Technically this first step is preliminary to, and not a part of, nitrification.
[3]Among the scientists who were prominent in making these discoveries regarding the action of bacteria in the fixation of atmospheric nitrogen were Hellriegel, Willfarth, and Nobbe in Germany, Atwater in America, Lawes and Gilbert in England, and Boussingault and Ville in France.
[3]Among the scientists who were prominent in making these discoveries regarding the action of bacteria in the fixation of atmospheric nitrogen were Hellriegel, Willfarth, and Nobbe in Germany, Atwater in America, Lawes and Gilbert in England, and Boussingault and Ville in France.
[4]It may be well to call attention to the fact that there are numerous instances where two different kinds of plants live together in intimate partnership relation. If only one of the two plants receives benefit from this relationship or association, then the plant receiving the benefit is celled a parasite. Thus the mistletoe is a parasite upon the elm or gum or other tree on which it lives. The mistletoe draws its nourishment from the tree. The tree is injured rather than benefited by the mistletoe. Dodder is also a parasitic plant, living upon other plants, except during the early part of its growth. Ticks and lice are common examples of animal parasites living upon other animals.In some cases a relationship exists which is not parasitic but symbiotic. The term symbiosis, which is commonly used by biologists to define this relationship, means living together in mutual helpfulness. The association of bees and flowers may serve to illustrate this mutual helpfulness, although this is not an example of intimate symbiosis. Thus the bees obtain their food from the flowers and, in turn, the flowers, many of them, are incapable of producing seed or fruit unless the pollen is carried from the male flower to the female flower by bees or other agencies. It is well known that plant lice and ants are mutually helpful.Likewise the association of nitrogen-gathering bacteria and leguminous plants is a relationship of mutual helpfulness and this is one of the best illustrations of what is meant by symbiosis. The legume furnishes a home for the bacteria and also furnishes in its juice or sap most of the nourishment upon which the bacteria live. The bacteria, on the other hand, take nitrogen from the air contained in the pores of the soil, and cause this nitrogen to combine with other elements in suitable form for plant food which is then given up to the legume for its own nourishment.Another illustration of remarkable parasitism, if not, indeed, one of true symbiosis, is found in the common lichens living upon rocks and trees. The lichen is not a single plant, but two plants—an alga, which lives upon the wood or stone, and a fungus which lives upon the alga. Algæ also live in the free state separate from fungi, and the present opinion of botanists seems to be that when the two are associated in the form of lichens this association is not detrimental, but rather beneficial, to the alga, as well as to the parasitic fungus. If this is true, then it is another case of true symbiosis. (There is reason to believe that the fungus has some power to feed upon atmospheric nitrogen, and then to furnish combined nitrogen to the alga upon which it lives.)In the symbiosis of leguminous plants and nitrogen-gathering bacteria we have a partnership or relationship of immeasurable value to agriculture. Here is a class of plants (legumes) that are capable of consuming or utilizing nitrogen in quantities larger than could possibly be obtained from ordinary soils for any considerable length of time. They have no power in themselves of taking nitrogen from the atmosphere, and to them the symbiotic relation with this low order of plants (the nitrogen-gathering bacteria) is especially helpful, and for the best results it is absolutely necessary.
[4]It may be well to call attention to the fact that there are numerous instances where two different kinds of plants live together in intimate partnership relation. If only one of the two plants receives benefit from this relationship or association, then the plant receiving the benefit is celled a parasite. Thus the mistletoe is a parasite upon the elm or gum or other tree on which it lives. The mistletoe draws its nourishment from the tree. The tree is injured rather than benefited by the mistletoe. Dodder is also a parasitic plant, living upon other plants, except during the early part of its growth. Ticks and lice are common examples of animal parasites living upon other animals.
In some cases a relationship exists which is not parasitic but symbiotic. The term symbiosis, which is commonly used by biologists to define this relationship, means living together in mutual helpfulness. The association of bees and flowers may serve to illustrate this mutual helpfulness, although this is not an example of intimate symbiosis. Thus the bees obtain their food from the flowers and, in turn, the flowers, many of them, are incapable of producing seed or fruit unless the pollen is carried from the male flower to the female flower by bees or other agencies. It is well known that plant lice and ants are mutually helpful.
Likewise the association of nitrogen-gathering bacteria and leguminous plants is a relationship of mutual helpfulness and this is one of the best illustrations of what is meant by symbiosis. The legume furnishes a home for the bacteria and also furnishes in its juice or sap most of the nourishment upon which the bacteria live. The bacteria, on the other hand, take nitrogen from the air contained in the pores of the soil, and cause this nitrogen to combine with other elements in suitable form for plant food which is then given up to the legume for its own nourishment.
Another illustration of remarkable parasitism, if not, indeed, one of true symbiosis, is found in the common lichens living upon rocks and trees. The lichen is not a single plant, but two plants—an alga, which lives upon the wood or stone, and a fungus which lives upon the alga. Algæ also live in the free state separate from fungi, and the present opinion of botanists seems to be that when the two are associated in the form of lichens this association is not detrimental, but rather beneficial, to the alga, as well as to the parasitic fungus. If this is true, then it is another case of true symbiosis. (There is reason to believe that the fungus has some power to feed upon atmospheric nitrogen, and then to furnish combined nitrogen to the alga upon which it lives.)
In the symbiosis of leguminous plants and nitrogen-gathering bacteria we have a partnership or relationship of immeasurable value to agriculture. Here is a class of plants (legumes) that are capable of consuming or utilizing nitrogen in quantities larger than could possibly be obtained from ordinary soils for any considerable length of time. They have no power in themselves of taking nitrogen from the atmosphere, and to them the symbiotic relation with this low order of plants (the nitrogen-gathering bacteria) is especially helpful, and for the best results it is absolutely necessary.
[5]There are some noteworthy exceptions to this rule (see following pages for illustration), and there is some evidence that, by a comparatively long process of breeding, or evolution, the bacteria which naturally live upon one kind of legume may gradually develop the power to live upon a distinctly different legume to which they were not at first adapted. Of course this process of forcing bacteria to live upon a legume to which they are not naturally adapted has little or no practical value because it is unnecessary if there is a species of bacteria which naturally lives upon the same legume. On the other hand, if, by any such process of breeding, or evolution, a species of nitrogen-gathering bacteria could be developed which could live on a non-leguminous plant, as corn, for example, it would be of incalculable practical value. As yet the efforts of bacteriologists, working on this problem, have given only negative results, so far as known to the writer.
[5]There are some noteworthy exceptions to this rule (see following pages for illustration), and there is some evidence that, by a comparatively long process of breeding, or evolution, the bacteria which naturally live upon one kind of legume may gradually develop the power to live upon a distinctly different legume to which they were not at first adapted. Of course this process of forcing bacteria to live upon a legume to which they are not naturally adapted has little or no practical value because it is unnecessary if there is a species of bacteria which naturally lives upon the same legume. On the other hand, if, by any such process of breeding, or evolution, a species of nitrogen-gathering bacteria could be developed which could live on a non-leguminous plant, as corn, for example, it would be of incalculable practical value. As yet the efforts of bacteriologists, working on this problem, have given only negative results, so far as known to the writer.
[6]In this connection attention is called to the fact that the so-called “spot disease” of alfalfa, which is not uncommon in the western states, especially during wet seasons, became somewhat prevalent in Illinois in 1903. When the effect of this disease becomes marked, the leaves turn yellow and growth is retarded. If this occurs the alfalfa should be clipped. This is the only effective remedy known to be practicable. Seeding alfalfa with a light nurse crop is gaining favor in Illinois.
[6]In this connection attention is called to the fact that the so-called “spot disease” of alfalfa, which is not uncommon in the western states, especially during wet seasons, became somewhat prevalent in Illinois in 1903. When the effect of this disease becomes marked, the leaves turn yellow and growth is retarded. If this occurs the alfalfa should be clipped. This is the only effective remedy known to be practicable. Seeding alfalfa with a light nurse crop is gaining favor in Illinois.
[7]Some of these observations have already been reported in the agricultural press. (See, for example, the Breeders’ Gazette, September 9, 1903, page 391, and September 16, 1903, page 442.)
[7]Some of these observations have already been reported in the agricultural press. (See, for example, the Breeders’ Gazette, September 9, 1903, page 391, and September 16, 1903, page 442.)
[8]Steamed bone meal is the most economical and satisfactory form of phosphorus for use on Illinois soils, unless ground rock phosphate (not acid phosphate) shall prove to be still more economical. Experiments to determine this are in progress.
[8]Steamed bone meal is the most economical and satisfactory form of phosphorus for use on Illinois soils, unless ground rock phosphate (not acid phosphate) shall prove to be still more economical. Experiments to determine this are in progress.
[9]Just how long the bacteria will live in a soil without a leguminous crop upon which they can feed is not definitely known. Certainly they live for two or three years, but probably not more than five or six years. Further investigation is needed to establish the length of time the different kinds of bacteria may remain in the soil under different conditions.
[9]Just how long the bacteria will live in a soil without a leguminous crop upon which they can feed is not definitely known. Certainly they live for two or three years, but probably not more than five or six years. Further investigation is needed to establish the length of time the different kinds of bacteria may remain in the soil under different conditions.