practicable for the farmer, for he must remove most of his crops from the field in order that they may be put to the various uses for which they are raised. A study of the formation of the soil, however, suggests two things that he can do to prevent the exhaustion of the fertility. The first is so to treat the soil as to assist and hasten Nature in the process of converting potential plant food into available forms; and to guard against a too complete destruction of the organic matter in the soil. The second is to return to the soil an amount of nitrogen, phosphoric acid and potash equivalent to that removed by the crop. The effect of early spring plowing on the conservation of moisture. The darker plots were plowed earlier than the lighter ones and contained several tons more water per acre CHAPTER VI TILLAGE Tillage Increases Feeding Ground for Roots.The most efficient means of assisting nature in the conversion of unavailable food into forms that the plant leave the minimum amount of work for the harrow, etc. can use is good tillage of the soil. Tillage, in the sense in which it is used here, signifies any operation of stirring and pulverizing the soil by means of plows, harrows, cultivators or any other implement, either before or after the seed is sown. The most noticeable result of tillage is that the soil is made finer, the large lumps being broken up into smaller particles, and in this way Nature's work in the formation of soils is accelerated. Pulverization of the earth is beneficial in many ways. In the first place, loosening the soil makes it easier for the plant roots and root-hairs to penetrate it. Mention has been made of the fact that all soils are composed of grains of greater or less dimensions separated by air spaces. The tender root-hairs must push their way in between these soil-grains, as it is impossible for them to penetrate the solid particles themselves. It must be evident that the more the soil is pulverized the larger the number of the openings between grains, and, consequently, the greater room for root growth. The plant is dependent upon the root-hairs for its. supply of mineral food and, as these hairs grow only between and around the soil grains, it is apparent that they can feed only on the surfaces of these particles. Good tillage increases the amount of surface exposed to the roots by breaking the large lumps into small grains; and the more complete the pulverization the larger the area from which the plant can obtain its food. The rapid increase of surface due to breaking down the lumps of a soil in poor tilth seems almost unbelievable to one who has given the subject no thought. An example will serve to illustrate what is meant: A cube, 2 inches on the side, presents a surface of 24 square inches. If this cube is cut once in each direction 8 cubes are formed, each one inch on a side, giving a total of 48 square inches of surface, so that cutting only once in each direction doubles the amount of surface. Thus, theoretically, a plant should be able to derive twice as much food from the eight small cubes as from the large one. |