You will find in the practical exercises many suggestions as to experiments that you can make with your class or with individual members. Do not neglect this first-hand teaching. It will be a delight to your pupils. In many cases it will be best to finish the experiments or observational work first, and later turn to the text to amplify the pupil's knowledge.
Although the book is arranged in logical order, the teacher ought to feel free to teach any topic in the season best suited to its study. Omit any chapter or section that does not bear on your crops or does not deal with conditions in your state.
The United States government and the different state experiment stations publish hundreds of bulletins on agricultural subjects. These are sent without cost, on application. It will be very helpful to get such of these bulletins as bear on the different sections of the book. These will be valuable additions to your school library. The authors would like to give a list of these bulletins bearing on each chapter, but it would soon be out of date, for the bulletins get out of print and are supplanted by newer ones. However, the United States Department of Agriculture prints a monthly list of its publications, and each state experiment station keeps a list of its bulletins. A note to the Secretary of Agriculture, Washington, D.C., or to your own state experiment station will promptly bring you these lists, and from them you can select what you need for your school.
AGRICULTURE FOR BEGINNERS
CHAPTER I
THE SOIL
SECTION I. ORIGIN OF THE SOIL
The word soil occurs many times in this little book. In agriculture this word is used to describe the thin layer of surface earth that, like some great blanket, is tucked around the wrinkled and age-beaten form of our globe. The harder and colder earth under this surface layer is called the subsoil. It should be noted, however, that in waterless and sun-dried regions there seems little difference between the soil and the subsoil.