Abstract
A survey was made on the change of the physical properties of soils tilled by moldboard plow, rotary tiller, trencher and subsoiler with different performances.
The surveyed items of the physical properties were penetration resistance, three phase distribution which are closely related to plant growth and physical stress of crops.
1) Characteristics of the change of penetration resistance. There are three types of change patterns as follows;
(1) The penetration resistance just after tillage was comparatively large and then decreased in the following month with some increase thereafter.
(2) The penetration resistance just after tillage was small and then continuously increased with a high rate.
(3) The penetration resistance just after tillage was small and then gradually increased thereafter.
2) Characteristics of the change of three phase destribution The solid phase ratio decreased by 5 to 20% by tillage. Largest densification with rapse of time was observed for the soils tilled by rotary and followed by moldboard plow, subsoiler and trencher in this order.
