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sphere to leguminous plants, 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 will 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 "sidération," a 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 equivalent to a strong artificial manuring of the soil, and it may sometimes even attain a value of many hundred 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 develop

a This medical term for atrophy or mortification does not seem quite appropriate in this case.-C. A.

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

ment 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 of 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 Leguminosa, 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, Hellriegel and Wilfarth have discovered this micro-organism in the nodules on the roots of the Leguminosa.

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.

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 Leguminosa 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

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 example, clover, let us say, has been sown with any cereal and that it is le grow freely, after the harvest; this clover will take a certain q 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 ¦ obtained, with no other expense than the price of the seed, a ma derived wholly from the air of the atmosphere.

This practice, first recommended by Ville, has been recently sho by Deherain to have another advantage quite as important. By k ing the surface of the soil in a state of constant evaporation the i.. polated cultivation of the clover diminishes the drainage to a not 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 reserv of the soil.

a

This method, whether we consider it as the cultivation of a fa.. field or whether we call it "sidération," as proposed by V affords two advantages of primary importance-it prevents in a gr measure the losses due to excessive nitrification of the soil in autur 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 pract alone is equivalent to a strong artificial manuring of the soil, and may sometimes even attain a value of many hundred francs per i 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 poi. out by Salfeld, in Germany, and which, if proved, will be a fu confirmation of the immortal doctrines of Pasteur. After clea a peat bog situated on the banks of the Ems, on the frontier of 1 land, horse beans and vetches were sown. The soil was everyw enriched with mineral fertilizers, but on one part only of the fi small quantity of good arable earth was spread, in the proporti 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 obtain Hellriegel and Wilfarth in their laboratory experiments; if t' 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 co manures, etc.-C. A.] true culture broths, prepared according to methods in use in microbic researches, and which will furni plants the germs of organisms capable of fixing nitrogen [the gen fixers], or, perhaps, others still, favorable also to their de

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

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

[graphic]

Professor Fra the tubercles m process of t subject has to he p. 68.)

Frank has Leguminose occurs in the

soil is rich in

the host, but en
symbionti
p. 266.)

H. J. W
(Agr. St. W
Hellriegel at
conducted in Bo
in England and
Experiment Sta
considered a
all the other

e deposited in the pots in which the plants ater the abundance of tubercles the more nd 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 ogen, although their presence may explain mospheric nitrogen is most marked in the Te 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 ere 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 ed 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 over crop 904 kilograms. On the other of nitrogen 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 denitrification occur alternately according to the relative amount of nutriment and number of bacteria present in the water. The manuring of soil, therefore, gives rise to a cycle of phenomena, nitrification being first arrested and the nitrates and nitrites reduced until a maximum formation of ammonia is attained, when nitrification again commences. The destruction of the nitrates and nitrites in the soil is complete or partial according as the supply of manure is abundant 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 apparently all leguminous plants, have the power of acquiring large quantities 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 nitrogenous 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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