The earlier root studies did not pretend to determine the depth to which roots actually penetrate the earth. In recent years, however, a number of carefully conducted experiments were made by the New York, Wisconsin, Minnesota, Kansas, Colorado, and especially the North Dakota stations to obtain accurate information concerning the depth to which agricultural plants penetrate soils. It is somewhat regrettable, for the purpose of dry-farming, that these states, with the exception of Colorado, are all in the humid or sub-humid area of the United States. Nevertheless, the conclusions drawn from the work are such that they may be safely applied in the development of the principles of dry-farming. There is a general belief among farmers that the roots of all cultivated crops are very near the surface and that few reach a greater depth than one or two feet. The first striking result of the American investigations was that every crop, without exception, penetrates the soil deeper than was thought possible in earlier days. For example, it was found that corn roots penetrated fully four feet into the ground and that they fully occupied all of the soil to that depth. On deeper and somewhat drier soils, corn roots went down as far as eight feet. The roots of the small grains,--wheat, oats, barley,--penetrated the soil from four to eight or ten feet. Various perennial grasses rooted to a depth of four feet the first year; the next year, five and one half feet; no determinations were made of the depth of the roots in later years, though it had undoubtedly increased. Alfalfa was the deepest rooted of all the crops studied by the American stations. Potato roots filled the soil fully to a depth of three feet; sugar beets to a depth of nearly four feet. Sugar Beet Roots In every case, under conditions prevailing in the experiments, and which did not have in mind the forcing of the roots down to extraordinary depths, it seemed that the normal depth of the roots of ordinary field crops was from three to eight feet. Sub-soiling and deep plowing enable the roots to go deeper into the soil. This work has been confirmed in ordinary experience until there can be little question about the accuracy of the results.