Studies on nitrogen application for clayey gley paddy soil in ultra early drainage cultivation of rice [Oryza sativa] plant

The heavy clayey gley paddy soil that is low permeability distributes widely in the Hokuriku district. This field is expected to be utilized also for upland crops; we call mulch-purpose field. This low permeability, however, hampers the productivity of the upland crops in a low level. Ordinarily, it needs 2 or 3 years to complete the well-drained structure of subsoil of this field with all existing techniques. The block rotation system is introduced extensively in Hokuriku district, but short period of upland field can not alternate sufficiently to upland soil condition, bringing the productivity of upland crops in low level. Therefore, development of upland soil condition in this field is urgently necessary for increasing the productivity of upland crops. For this reason, by the introduction of ultra early drainage cultivation system of rice, we expect the soil drying at the rice cultivation stage before alternation to upland field. We investigated on the physical and chemical change of the soil for introducing the ultra early drainage cultivation system, and the influence to rice growth by applying of nitrogen. Further more, we grasped the influence to quality of the rice grain, and clarified the management system of nitrogen application in the ultra early drainage cultivation of rice