242 



plants. It is certain, therefore, that the chief value of the use of lime 

 in agriculture is to be found in some indirect influence, which it exerts 

 upon the soil. Heretofore three special methods have been pointed out 

 in which lime exerts a beneficial influence. In the first place, it pro- 

 foundly affects the physical structure of stiff soils, producing a floccula- 

 tion of the silt, and thus preventing its deposition in individual par- 

 ticles. A well-limed soil is thus apt to be open and porous, and easily 

 tilled. In the second place, the lime exerts a certain soluble influence 

 on undecomposed particles of rock, thus favouring the speedy decom- 

 position and the consequent freeing of the potash and phosphoric acid 

 which they contain. In the third place, the added lime tends to correct 

 any acidity of the soil which may be due to the accumulation and excess 

 of humus, or which may arise from imperfect drainage. 



It must be admitted, however, that one of the chief benefits of the 

 introduction of lime into a soil is derived from the fact that it favours 

 in a high degree the evolution and development of the nitrifying fer- 

 ments. 



The lime which is used for fertilisation is, as a rule chiefly in the 

 form of oxide or hydrate, that is, slacked lime. After its incorporation 

 in the soil, however, both the oxide and hydrate of lime are rapidly- 

 changed to carbonate under the influence of the carbon dioxide (car- 

 bonic acid) which is found in the atmosphere of the soil in notable pro- 

 portions ; in fact, in a much higher percentage than in the air. The 

 soil thus becomes permeated with lime carbonate in a fine state of sub- 

 division, a condition especially well suited to favonr the growth of the 

 nitro-organisms. Hereafter, therefore, in discussing the benefits of the 

 application of lime, this function of it must receive due consideration. 

 It will not be at all surprising if future investigations should establish 

 the fact that this use of lime is of far more importance in agriculture 

 than any of the others above noted. 



SEEDING THE SOIL WITH NITRIFYING ORGANISMS. 



In the previous paragraphs the conditions favouring the development 

 and activity of nitrifying organisms have been briefly set forth, but the 

 presence of all these favouring conditions will prove of no advantage in 

 a soil which is practically sterilised. In such a case, however, if a few- 

 organisms can be supplied, a practically sterilized soil will, after a time, 

 by the natural growth and distribution of nitrifying organisms, become 

 fully impregnated with the nitrifying germs. The question naturally 

 arises, is there any artificial way in which the seeding of the soil may 

 be accelerated ? The answer to this question in undoubtedly affirma- 

 tive. In experiments which have been conducted in this department, 

 and of which notice will be made further on, it has been fully demon- 

 strated that different soils differ in the most marked degree in the num- 

 ber and vitality of the nitrifying organisms which they contain. As a 

 rule, the richer the soil or the more highly fertilized it has been and 

 the more fully cultivated, the greater will be the nnmber of the organ- 

 isms which it contains and the higher the degree of their vitality. It 

 is thus seen that in a field which contains all the elements of fertility, 

 but which by reason of unfavourable conditions, as, for instance, having 

 previously been a swamp or marsh deficient in nitrifying organisms, 

 may be practically sterilised, great benefit may be derived by spreading 



