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sphere to leguminous o it will be easy for us to profit by this newly acquired knowledge in order better than before to preserve our lands in a state of suitable fertility. Suppose, for example, that clover, let us say, has been sown with any cereal and that it is left to grow freely, after the harvest; this clover will take a certain quantity of nitrogen from the air, by the help of the nodules on its roots. If this clover is plowed under before the next time of sowing, in the spring or autumn, so as to serve as a green fertilizer, we shall have obtained, with no other expense than the price of the seed, a manure derived wholly from the air of the atmosphere. This practice, first recommended by Ville, has been recently shown by Deherain to have another advantage quite as important. By keeping the surface of the soil in a state of constant evaporation the interpolated cultivation of the clover diminishes the drainage to a notable extent; all the nitrates, which then are formed in large quantities and which would be lost if the earth remained uncovered, are held and assimilated, being rendered insoluble by the vegetation, and when plowed under j augment by so much the more the natural reserves of the soil. This method, whether we consider it as the cultivation of a fallow field or whether we call it “sideration,” “ as proposed by Ville, affords two advantages of primary importance—it prevents in a great measure the losses due to excessive nitrification of the soil in autumn, and restores to the earth a certain quantity of nitrogen which has passed from a gaseous state to the state of organic matter. I do not think it an exaggeration when I say that the gain from this practice alone is "...i. to a strong artificial manuring of the soil, and it may sometimes even attain a value of many i. francs per hectare, which will be realized in subsequent crops. Finally, among other examples of the application of this new knowledge there is a most curious fact which has just been pointed out by Salfeld, in Germany, and which, if proved, will be a further confirmation of the immortal doctrines of Pasteur. After clearing a peat bog situated on the banks of the Ems, on the frontier of Holland, horse beans and vetches were sown. The soil was everywhere enriched with mineral fertilizers, but on one part only of the field a small quantity of good arable earth was spread, in the proportion of about 40 kilograms to the are." The effect of the addition of this latter element was, as it appears, most surprising: under its influence the crop was doubled. This result is, in Salfeld's opinion, similar to the results obtained by Hellriegel and Wilfarth in their laboratory experiments; if this is really so—and it is possible—there will be in the near future a new era, a sort of revolution, so to speak, in practical agriculture. Perhaps the time is not far distant when our farmers will add to the fertilizers of commerce [the so-called soil improvers and complete manures, etc.—C. A.] true culture broths, prepared according to the methods in use in microbic researches, and which will furnish to plants the germs of organisms capable of fixing nitrogen [the nitrogen fixers], or, perhaps, others still, favorable also to their development, and which will cause their crops continually to increase and will finally enrich the soil to the extreme limit of its possible fertility. This would undoubtedly be a vast extension .P that admirable humanitarian work for which we are indebted to Pasteur; but this is anticipation, and I only proposed in this lecture to point out the present state of the question. I shall therefore close by summing up what I have said in a few words. Experiments made by Ville, and repeated and verified by many other observers, have shown us that certain plants, particularly those of the species of the Leguminosae, have taken from the atmosphere a part of the nitrogen that they contain. Berthelot, and also Gautier and Drouin, have shown that the soil alone can to a slight extent enrich itself by means also of a direct fixation of gaseous nitrogen. Berthelot has also shown that this phenomenon corresponds with the development of certain microbes preexisting in the soil; and, finally, i. and Wilfarth have discovered this micro-organism in the nodules on the roots of the Leguminosae. This last work is certainly one of the greatest interest, and does the greatest honor to the physiologists who have succeeded in bringing it to a final result; but it is proper to recognize that the route to be followed had already been marked out by previous researches. The problem was ripe for solution, and it was in our own country— In France—that the great problem of the assimilation of nitrogen had been proposed and in a great part solved, which is no more than was to be expected from so great a center of production and agricultural progress.

a This medical term for atrophy or mortification does not seem quite appro

priate in this case.—C. A. b The are is about 119 square yards, or 100 square meters, or 1,071 square feet.

Professor Frank, of the agricultural institute in Berlin, finds that the tubercles may be removed from the plant without stopping the process of taking nitrogen from the air. Evidently, therefore, the subject has to be investigated still further. (Agr. Sci., Vol. IV, p. 68.)

Frank has also shown that the symbiosis in the tubercles of the Leguminosae is of an entirely different character from that which occurs in the roots of any other plants. Furthermore, when the soil is rich in humus the microbic parasite does no special service to the host, but when the supply of humus is insufficient the microbe symbiont is of the greatest service to the host. (Agr.Sci., Vol. IV, p. 266.)

H. J. Wheeler, of the Rhode Island Experiment Station, gives (Agr.Sci., Vol. IV, p. 55) an account of the work done by Professor Hellriegel at Bernburg, Germany, along the line of investigation conducted by Boussingault and Ville in France, Lawes and Gilbert in England, and W. O. Atwater, of the Storrs School Agricultural Experiment Station. In the present state of the question it may be considered as settled that certain plants are able, if supplied with all the other essential elements, to draw their supply of nitrogen from

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sphere to leguminous plants, it will be easy for us to profit by
newly acquired knowledge in order better than before to pre
our lands in a state of suitable fertility. Suppose, for examples
clover, let us say, has been sown with any cereal and that it is lei
grow freely, after the harvest; this clover will take a certain
tity of nitrogen from the air, by the help of the nodules on its r'
If this clover is plowed under before the next time of sowing, in
spring or autumn, so as to serve as a green fertilizer, we shall l.
obtained, with no other expense than the price of the seed, a mai
derived wholly from the air of the atmosphere.

1

This practice, first recommended by Ville, has been recently sho by Deherain to have another advantage quite as important. Byk ing the surface of the soil in a state of constant evaporation the in polated cultivation of the clover diminishes the drainage to a nota extent; all the nitrates, which then are formed in large quantities a which would be lost if the earth remained uncovered, are held a. assimilated, being rendered insoluble by the vegetation, and w plowed under will augment by so much the more the natural resery of the soil.

This method, whether we consider it as the cultivation of a fali field or whether we call it “sidération," a as proposed by VT affords two advantages of primary importance—it prevents in a gr: measure the losses due to excessive nitrification of the soil in autu and restores to the earth a certain quantity of nitrogen which passed from a gaseous state to the state of organic matter. I do think it an exaggeration when I say that the gain from this prac1 alone is equivalent to a strong artificial manuring of the soil, and may sometimes even attain a value of many hundred francs per 1; tare, which will be realized in subsequent crops.

Finally, among other examples of the application of this knowledge there is a most curious fact which has just been point out by Salfeld, in Germany, and which, if proved, will be a fur confirmation of the immortal doctrines of Pasteur. After clea a peat bog situated on the banks of the Ems, on the frontier of! land, horse beans and vetches were sown. The soil was everyt? enriched with mineral fertilizers, but on one part only of the fie small quantity of good arable earth was spread, in the proportis about 40 kilograms to the are.

The effect of the addition of this latter element was, as it app most surprising; under its influence the crop was doubled. result is, in Salfeld's opinion, similar to the results obtaine Hellriegel and Wilfarth in their laboratory experiments; if th. really so—and it is possible—there will be in the near future a new a sort of revolution, so to speak, in practical agriculture.

Perhaps the time is not far distant when our farmers will a: the fertilizers of commerce [the so-called soil improvers and com manures, etc.-C. A.] true culture broths, prepared according to methods in use in microbic researches, and which will furnis plants the germs of organisms capable of fixing nitrogen [the gen fixers], or, perhaps, others still, favorable also to their der

a This medical term for atrophy or mortification does not seen quite in priate in this case.—C. A.

• The are is about 119 square yards, or 100 square meters, or 1,071 square

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e deposited in the pots in which the plants ater the abundance of tubercles the more ind the greater the gain in nitrogen. The

wir by the legumes explains why they act as Sci., Vol. IV, p. 22.)

iments by A. Petermann on yellow lupins or concludes that the physiological rôle of exaggerated. They can not be the only

gen, although their presence may explain mospheric nitrogen is most marked in the ate further shows that sodium nitrate is not

lupins. The trouble in its use results is very soluble and is soon washed down of the roots, which must then draw their re by means of the microbic organisms.

loss and gain of nitrogen by the soil as of special crops. He sowed grass and two others without any crop. The gain d in the soil in one year–March, 1888, to ws: With no crop the soil gained at the

ectare per year, with the grass crop 394 Lover crop 904 kilograms. On the other Lnitrogen removed from the soil by the

case as follows: No crop, 85; grass, 5; IV, p. 325.)

the air, either directly or indirectly, by means of minute organisms now generally termed microbes. These microbes can be communicated by direct inoculation from one plant to another that has been previously free from them. Experiments are in progress as to the possibility of cultivating these microbes artificially, and when this has been accomplished successfully it will mark a great step toward the solution of the question as to the plant's method of obtaining nitrogen, and not only that, but a great step toward success in agriculture, since every one will be able to inoculate his own plants, and thus immensely stimulate the yield of crops. T. Leone has shown that a great number of germs obtain their nitrogen more easily by decomposing the nitrates, and only when these salts are used up do they begin to nitrify the ammoniacal compounds, and after that possibly attack the free nitrogen of the air. He has also shown that these take the nitrogen as a gas from the nitric acid in the nitrates and do not convert it into ammonia. (Agr. Sci., Vol. V, p. 82.) Leone also shows that the phenomena of nitrification and denitri- th fication occur alternately according to the relative amount of nutri

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ment and number of bacteria present in the water. The manuring of of soil, therefore, gives rise to a cycle of phenomena, nitrification being M first arrested and the nitrates and nitrites reduced until a maximum o formation of ammonia is attained, when nitrification again com- kil mences. The destruction of the nitrates and nitrites in the soil is ha complete or partial according as the supply of manure is abundant o

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or otherwise. (Agr.Sci., Vol. V, p. 107.)
The experiments made in Europe by Boussingault, Hellriegel, and
others as to the method by which plants obtain the nitrogen from the
atmosphere have been repeated and extended by C. D. Woods, of the
Storrs School Agricultural Experiment Station. His results are
summarized as follows:
(1) Peas, alfalfa, serradella, lupine, probably clover, and appar-
ently all leguminous plants, have the power of acquiring large quanti-
ties of nitrogen directly from the air during their growth. There
is no doubt that the free nitrogen of the air is thus acquired by these
plants. This acquisition has something to do with the tubercles on
the roots of these plants, but the details of the process are still to be
solved. The cereals, oats, etc., with which experiments have been
brought to completion, do not have this power of acquiring nitrogen
from the air, nor do they have such tubercles as are formed on the roots
of the legumes. They get their nitrogen from the nitrates or nitrogen-
ous fertilizers. The tubercles on the roots of the legumes may be formed
either after or entirely without the addition of solutions or infusions
containing micro-organisms, and a plausible supposition is that when
such infusions are not furnished the spores of the organisms were

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