Mathematical Models for Controlling Wetted Soil Masses Forming under the Practice of Water Added Corn seeding

摘要

As one China specific practice, the practice of water added seeding is simple, convenient and cheap to adopt and its most important strength is that it is suitable for developing countries to adopt it. In order to increase penetration depth and reduce evaporation of irrigation water with the conventional practice of water added seeding, get rid of white pollution caused by plastic film mulching, and determine the appropriate parameters of wetted soil masses for effective irrigation use efficiency in light of soil conditions and droughts, especially downward depth and horizontal distances of irrigation water infiltration into soil, the authors successfully developed the practice of water added seeding integrating soil clod formation by loosening. Upon the adoption of the practice in soil tillage, soil clods ranging within 10～20mm in size will form and brace against each another to create porous spaces among them, so that irrigation water quickly moved down through porous spaces upon the action of gravity. And in the meantime, when they meet irrigation water, the clods will quickly break up, thereby not affecting seed germination and seedling emergence of corn. The study established the mathematical models for wetted soil masses occurring with the practice of water added seeding and then verified them by experimentation. Where the soil loosening techniques, holing methods, soil water content, horizontal distance and downward depth of added water infiltration required after water adding were obtained, the appropriate added water rate per seeding hole and loosened soil depth could be calculated by adopting the proposed mathematical model. As a result, the study made it feasible to simply and effectively manage the parameters of irrigation water wetted soil spaces, thereby helpful to realize the two targets of drought fighting and water saving that the conventional practice of water added seeding intended to realize.