UNITED STATES DEPARTMENT OF AGRICULTURE 
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| BULLETIN No. 355 
Contribution from the States Relations Service 
A. C. TRUE, Director 
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Washington, D. C. 
April 13, 1916 
EXTENSION COURSE IN SOILS. 
By A. R. Wettson, Professor of Soils, University of Wisconsin, and H. B. Hendrick, 
Assistant in Agricultural Education, States Relations Service. 
CONTENTS. 
Lesson I. Origin, formation, and com- 
position of soils 
II. The soil and plant growth 
III. Physical properties of the soil. 
IV. The water supply of the soil... 
V. Soil temperature and drainage. 
VI. The nitrogen supply of the 
soil 
Page. 
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 bulletin 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 utilize 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 small 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 in 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 examinations through the leader 
and corrects and returns the papers. 
21862°— Bull. 355—16 1 
