Abstract
Laboratory experiments were carried out to study the influence of surface soil hardness, ponding water depth, mass and dimensions of coated seeds, falling height on seed penetration depth of sprayed direct seeding of rice plants which is one of the most important direct seeding methods. As the result, 1) Because of water resistance under inundation condition, to obtain appropriate seed penetration depth, surface soil must be too soft when puddled soil are not yet settled down. 2) By the same reason, seed penetration depth can be increased by the mass of seed coating or falling height only when surface soil is very soft and ponding water depth is not so deep. 3) For the reasons stated above, it is necessary to obtain appropriate seed penetration depth in sprayed direct seeding of rice plants as seeding into puddled soil surface soil just after puddling.
