THE YEAST OF THE SOIL. 23 



needed, by a rotation of crops or by ploughing in stubble or green 

 crops ? Assuming that the actual plant food in a cord of stable 

 manure is worth on a fertilizer basis, S3 per cord, what is the 

 humus, the remainder of the cord, worth and how much will it 

 cost to haul or freight it, and apply it to one's own soil and crop 

 recjuirements ? 



Plant Food Supply. 



As a manufacturer studying ways and means of supplying the 

 plant food which is required by the intensive methods around 

 Boston, and by wasteful methods in some other sections, I some- 

 times wonder where it is all coming from, and if we can keep up 

 with the demand. Yet, knowing what science has done, and is 

 capable of doing, I have no fear that so far as plant food is concerned 

 (which is only one item in the problem) we shall find the needed 

 supply. Just now, our chief concern are nitrogen and potash. 

 Discoveries will render the nitrogen of the air available, in fact, 

 discoveries have already been made which are claimed to be a 

 commercial success. The bacteriologist, through his study of life 

 of the soil, will also help us in this direction. We are now, through 

 the efforts of the chemist, also utilizing a hundred and one by- 

 products of our industries which a few years ago were thrown away, 

 while new discoveries of phosphoric acid, in the shape of mineral 

 phosphates, are being made all over the world. It only remains 

 now, to find some new source of potash, like that in Stassfurt, 

 Germany, or some feasible way of rendering available, the potash 

 in our feldspar rocks. Then, with the aid of the "yeast of the soil" 

 we shall have rounded out the circle. 



Intensive Agriculture. 



INIarket gardeners and florists are carrying on "intensive agri- 

 culture." They produce abnormal crops and therefore require 

 intensive methods of cultivation and feeding. A potato plant, 

 left to itself and in the state of nature, produces potato balls. Man, 

 by modern methods of cultivation and selection of seed, has changed 



