232 THE LUKE OF THE LAND 



or vegetable matter in the soil is the most effective fac- 

 tor in soil fertility." The answer to this is that a most 

 luxuriant crop can be grown in pure sand with mineral 

 fertilizers and not a trace of humus. 



The changing attitudes of the Bureau of Soils on 

 soil fertility are represented as follows: A. All soils 

 have sufficient plant food for the production of crops 

 indefinitely. B. The fertility of the soil is affected by 

 toxic principles left in the soil from previous crops. C. 

 The fertility of the soil depends chiefly upon its physi- 

 cal state, and the function of applied fertilizers is not 

 one of nutrition, but one of modification of physical 

 character. D. The fertility of the soil depends chiefly 

 upon the amount of vegetable matter it contains. 



It is to be hoped that in the near future the Bureau 

 of Soils will reach the conclusion which is now held by 

 all prominent scientific investigators in the world, 

 namely, that the fertility of the soil is dependent upon 

 its ability to feed the crop. All factors which affect 

 that ability are factors in soil fertility. 



INCREASING- NITROGENOUS FERTILIZERS. 



In regard to the nitrogenous constituents of the soil, 

 however, happily a discovery has been made which 

 means much to scientific agriculture, namely, the fact 

 that a certain family of plants, the leguminous family, 

 of which the pea, the bean, clover and locust trees, 

 are types, has the remarkable faculty of assimilating 

 atmospheric nitrogen and converting it into nitric acid 

 in a form suitable for plant nutrition. This remark- 

 able phenomenon is due to the fact of bacterial action. 

 The nitrifying bacteria live in connection with the 

 plant itself, being parasites upon the plant roots, and 

 in this symbiotic activity seem capable of directly oxi- 



