1999 Volume 55 Issue 2 Pages 127-135
As reported by many agronomists, the direct seeding cultivation of rice is thought to be an effective way to reduce the cost of rice production in Japan. However, the rice yield of direct seeding cultivation is generally lower and unstable compared with that from transplanting cultivation. This is mainly due to the unstable establishment of rice seedlings and slow growth during the early growing stage. The two reasons mentioned above are correlated with an appropriate control of water depth under changing weather conditions.
This report describes an automatic irrigation system based on the rice microclimate prediction model (Inoue, 1985). This irrigation system can appropriately control water depth and accordingly the microclimate of direct seeding rice fields using weather data and rice plant data. The feasibility tests of this system were done at two direct seeding rice fields at Yuza-machi, Yamagata Prefecture in 1995 and at Yawara-mura, Ibaraki Prefecture in 1997, respectively.
The results obtained from the above two experiments can be summarized as follows:
The newly developed automatic irrigation system showed good performance in controlling the water depth of direct seeding rice fields during the whole rice growing season. The brown rice yield from the field controlled by this system was 562kg/10a, while neighboring direct seeding rice fields, in which the water depth was controlled manuall, had yields of 492kg/10a and 505kg/10a in 1997. The plant height of the test field with the automatic irrigation system was about 75cm, compared to about 70cm in neighboring direct seeding cultures.
These results show that the newly developed automatic irrigation system was effective in stabilizing the establishment and emergence of rice seedlings, and in promoting subsequent growth in direct seeding cultures.
