i7s6 The Cornell Reading-Courses 



The soil is a great natural resource and its proper conservation is a 

 problem of public concern. 



The soil is productive just in proportion to its ability to meet the needs 

 of plants for their best growth. These needs are diverse, including food, 

 water, oxygen, heat, light, physical support, and sanitation. With one 

 exception — light — these requirements are largely met by the mechanism 

 and the constitution of the soil. This is accompHshed by three inter- 

 acting properties of the soil — ■ its physical nature, its chemical constitu- 

 tion, and its biological activity. Each of these properties has many 

 variations, which react on and largely affect the other two; so that the 

 maintenance of fertility — the ultimate rational aim of all agriculture — 

 presents an exceedingly complex array of problems. In farm practice 

 the soil is changed for the better or for the worse by a variety of treat- 

 ments, such as manuring, applications of lime, tillage, drainage, and 

 fertilizers. Intelligent soil management involves the treatment of the 

 soil by the most convenient and economic methods, so that the desired 

 change in its character will resvdt. The findings of the laboratory must 

 be translated into terms of farm practice and reduced to the simplest 

 form for the guidance of the busy tiller of the soil, taking into account 

 the normal nature of the soil, the requirements of plants, and the limita- 

 tions of farm practice. 



The diagram on the preceding page represents, by a succession of courses 

 built into the form of a monument, the essential factors in a fertile soil. 

 The conditions represented by these courses are arranged, beginning at 

 the base, in the order of their breadth of influence on the properties of 

 the soil. They are also arranged so that one set of conditions will con- 

 tribute most to the efficiency of the conditions represented by succeeding 

 courses. Every person, in proceeding to improve his soil, should, so 

 far as is practicable, eliminate the need of these treatments in the order 

 suggested, so that the highest efficiency of the soil and the greatest benefit 

 from the treatments and materials applied may be realized. In order to 

 understand the reasons for the arrangement of the means of soil improve- 

 ment in the order given, and to know when as well as how to apply them 

 to a particular soil, it is essential that one have a considerable knowledge 

 of the nature of the soil, of its modes of formation, of the many inter- 

 acting properties of moisture, ventilation, food supj^ly, temperature, and 

 biological characters, and of the ways by which these are controlled. 

 No sim.ple rules will suffice. The variety of soils is so great that each 

 farmer must to a large degree decide what is the best method of managing 

 his particular soil, in the light of the principles involved. The preliminary 

 statement in this lesson, together with the introductory diagram, perhaps 

 as nearly as is possible summarizes the principles involved in the main- 

 tenance of permanent fertility of the soil. It has been well said by 



