Synopsis This text has enjoyed a wide acceptance since its introduction in 1924. This fourth edition has been prepared to include some of the many worth-while additions to our agronomic knowledge and, therefore, to make it still more useful to teachers and students. The many suggestions made by various users of this textbook have been followed closely in making the current revision. The initial chapters, history of American agriculture, replaces beginnings of plant culture of former editions. A new chapter has been added, grassland farming. Rice is covered in a special chapter and placed along with the other grain crops in section II. Many of the former references have been replaced with newer ones that give information more in keeping with the changing times. The basic concept of the very practical outline used in preparing the first edition has been kept. At the same time, however, cognizance has been taken of the wealth of new information that investigators have reported, and many of the chapters, in effect, have been rewritten.