158 



sphere to legiiniinous plants, it will be easy for us to profit b^' 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 quan- 

 tity 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 reconnnended by Ville, has been recently shown 

 by Deherain to have another advantage quite as important. By keep- 

 ing the surface of the soil in a state of constant evaporation the inter- 

 polated 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 Ave consider it as the cultivation of a fallow 

 field or whether we call it " sideration," " as proposed by Ville, 

 aifords 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 hec- 

 tare, 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 Hol- 

 land, horse beans and vetOhes 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 Avill 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 improA^ers and complete 

 manures, etc. — C. A.] true culture broths, pre]:)ared according to the 

 methods in use in microbic researches, and which will furnish to 

 plants the germs of organisms capable of fixing nitrogen [the nitro- 

 gen fixers], or, perhaps, others still, favorable also to their develop- 



a This medical term for atrophy or mortification does not seei» quite appro- 

 priate in this case. — C. A. 



6 The are is about 110 square yards, or 100 square meters, or 1,071 square feet. 



