UNITED STATES DEPARTMENT OF AGRICULTURE 



^•Vi^'^«-(TU 



%^1 BULLETIN No. 355 



Contribation from the States Relations Service 

 A, C. TRUE, Director 



Washington, D. C. 



Apra 13, 1916 



EXTENSION COURSE IN SOILS. 



By A. R. Whitson, Professor of Soils, University of Wisconsin, SiJid H. B. Hendrick, 

 Assistant in Agricultural Education, States Relations Service. 



CONTENTS. 



Lesson I. Origin, formation, and com- 

 position of soils 2 



II. The soil and plant growth 10 



III. Physic.alpropertiesof thesoil. 17 



IV. The water supply of the soil ... 24 

 V. Soil temperature and drainage. 31 



VI. The nitrogen supply of the 



soil , 



Lesson VII. The phosphorus and potassium 



of soils 47 



VIII. Manures and fertilizers 54 



IX. Soil acidity and liming 62 



X. Management of special soils... 68 



XI. Soil adaptation to crops 80 



XII. Crop rotations and soil fer- 

 tility 84 



GENERAL SUGGESTIONS TO LEADERS. 



Although it is not necessary that the leader of this course shall 

 have had any special training, his work will be easier if he reads at 

 least a lesson ahead of the class work, or, better still, goes more or 

 less rapidly through the whole buUetui in advance. In this way it 

 will be easier for him to make suggestions regarding the practice work 

 in connection with each lesson. 



The references of each lesson have been carefully selected and are 

 thought to be about sufficient to utiUze the remainder of the forenoon 

 after the lesson text has been carefully read and discussed. Where a 

 choice is given between two references, the leader may use his judg- 



NoTE. — This course has been prepared by direct cooperation between the authors and J. M. Stedman, 

 Farmers' Institute Specialist, of the States Relations Service, and is designed to aid agricultural colleges 

 in their extension work. It is intended for the use of smaU groups of farmers assembled as a class to study 

 the subject in a systematic manner with one of their number as a leader. It is adapted for use ia any part 

 of the United States. The agricultural college is to loan the class the reference Library listed in the Appendix 

 and also a set of apparatus and the supplies designated therein. The class meets as often as convenient in 

 a suitable room where tables for exercise work are available. The forenoon is devoted to the lesson and 

 reference work and the afternoon to the exercise work, an entire day being thus consumed for each lesson. 

 At the completion of the course and as often as desired the college conducts examinatio-ns through the leadef 

 and corrects and returns the papers. 



21862°— Bull. 355-16 1 



