We have taken notice of volunteer wheat which is one of the factor of mixed foreign plants in barley feild.
Two experimental items were designed. 1) To investigate the grain sizes of falling wheat (lost grains) at combine harvesting, which relate to the germination and growing ability in the field. 2) To make clear the persistence of volunteer wheat under tilling condition.
The results are as follows,
1) Falling grains (lost grains) at combine harvesting with good operating condition were 7.6kg/10a. Seventy five percent of falling grains had grain sizes of>2.4mm, which would be ripend well.
2) Emergence rate of volunteer wheat grains was changing, as high rate at immediately after they fell on the ground and low rate in summer, and high rate again in fall.
3) It showed high emergence rate until the next spring when the grains had been buring at 20cm depth. Shallow depth buring grains showed high rate at immediately after they fell, but low rate in the next spring.
4) Buring wheat grains soon after they fell will help volunteer wheat plants to persist.
5) The number of volunteer wheat plants was the biggest in where the field was plowed soon after wheat grains fell in summer and plowed again in fall.

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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.

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