-74 ANXTTAL RKPORT OF THE Off. Doc. 



any, are so woil situated tliat they can keep up the humus supply 

 iu (heii* soil tlii-ou^i^h the use of barnyard manure alone. They can- 

 not get enough of it. 



Farmers, in the practical working of their farms, have often dis- 

 covered facts and left the exphmation to the scientists. Long years 

 ago tliey found that a clover sod plowed under did, in some way, 

 not only supply the soil with humus, but that it actually increased 

 its productivity through the accumulation of organic nitrogen. 

 How the clover did this was for many years a subject for discus- 

 sion, many farmers imagining that the plants absorbed ammonia 

 from tlie air. In fact, it is not yet proved that plants cannot or 

 can get the use of the ammoniacal gas in the air. Dr. Gray used 

 to say that he could not see why they could not, but admitted that 

 it had never been proved that they did. Tt was not until tlie 

 students of pure science took up the matter that it was discovered 

 that not clover alone, but many other plants of the same botanical 

 order did get the free nitrogen from the air and locate it in the 

 soil in the form of organic matter capable of nitrification. It was 

 found that this work is being done through certain micro-organisms 

 Avhich live parasitically on the roots of some legumes, for it wa« 

 found that unless these were present the legume had no power to 

 get the free nitrogen. It is still a matter of speculation as to 

 what the exact process is through which these microscopic plants 

 get the nitrogen. But for all the purposes of the farmer it is suf- 

 ficient to know that they do, and under what conditions they do get 

 the nitrogen. The wonderful adaptation of the processes of Nature 

 to the needs of humanity is well known h(M'e. It is well known that 

 green plants, as a rule, take nitrogen through their roots only 

 when it is presented in the form of a nitrate of some base iu the 

 soil. It is also known that when the nitrogen has gotten into this 

 form it readily escapes from the soil in the drainage waters. Hence, 

 the importance of the way in which the legumes get and keep the 

 nitrogen. It is not simply an oxydation and formation of nitric acid 

 and, hence, a nitrate left in the soil, but an absorption of the nitro- 

 gen and its location in the organism of tlie plants, where it must 

 subsequently go through the process of decay and be acted upon 

 by the micro-organisms of nitrification before the nitrogen becomes 

 available to plants. This is evidently a provision of Infinite Wis- 

 dom, so that the crops of the succeeding year can get the use of the 

 nitrogen fixed in the soil by the growth of the i)revious season. 

 Were it simply a nitrate left in the soil, tliei-e would be little of 

 it for the next year's crops. 



Learning, through the labors of the men in tlu' labo;alory. the 

 uses of these micro-organisms which live on the roots of Icgunu^ 

 crops, the farmer has at hand the greatest of means for restoring 



