Abstract
(1) The field conditions for using the weeder smoothly in rainy season are as follows.
1) Depth of tilling before seeding is about 5cm —that is shallow—.
2) The field is drained quickly after it stops raining.
3) Paddies are seeded on the small ridge which is about 60cm wide; depth of covering of paddy is about 2.5cm and the surface of the ridge is level.
(2) We could work the weeder on the paddy field —sand loam and loam— from plastic limit to field moisture capacity (d. b. 34%-d. b. 39%). And then, we could work the weeder in three days after a rainfall of 80mm.
(3) The soil moisture of the surface of field decreased quickly after we used the weeder in high soil moisture.
4) By the weeder working, addition of pulverizing, decrease of porous space and sinkage of ridge surface were noticed a little.
(5) The depth of seeds and end of stalk of wild sawa millet was a little shallower than that of rice and resistance for pulling out wild sawa millet was less than that of rice untill 20days after seeding. So, it seemed to be effective to use the weeder by 20 days after seeding.
