Abstract
The writers studied the behaviours of simazine and atrazine in the dormant turf (Zoysia matrella) in early spring, and the following results were obtained.
(1) These triazine herbicides were applied at 200g (la) in 200l (10a) of water to the turf which was 5 cm in plant height.
Simazine was much adsorbed onto the dead leaves of the turf and was not detected in the thatch layer under the turf leaves. But when simazine was applied on the turf after the removal of dead leaves or after cutting the leaves at 5mm from the ground, it was much distributed in the thatch and very little in the soil under the thatch layer.
Atrazine was not adsorbed onto the leaves so much as simazine, and was detected in the thatch. When atrazine was applied to the turf after the removal of dead leaves or cutting the leaves at 5mm from the ground, it was distributed in the thatch and about 2.5 cm in soil under the thatch layer.
(2) These triazine herbicides were applied to the turf at 200g (10a) in 100l, 200l or 400l (10a) of water with or without surface active agent (SAA) .
Simazine was much adsorbed onto the turf leaves when it was applied with small amount of water (100l), and simazine adsorbed onto the leaves was not easily desorbed with water. But its adsorption onto the leaves decreased with larger volume of water, such as 200l or 400l (10a) .Its adsorption onto the leaves increased with adding of SAA.
Atrazine was not adsorbed onto the leaves so much as simazine even in the case of small volume of spray water. But the amount of atrazine adsorbeb onto the leaves applied with large volume of water (200l or 400l) was much smaller than that of atrazine applied with small volume of water. The amount of atrazine adsorbed was also small when applied without adding SAA.
(3) The thatch and the soil collected from the turf area were applied with these triazine herbicides, and then young rice plants were cultured in these mediums.
The phytotoxicities of these two herbicides in the thatch were about 1/2 to the toxicities in the soil.
Their phytotoxicities in the sterilized thatch were 3 times higher than in the non-sterilized thatch, but the toxicities in the sterilized soil were about twice higher than in the non-sterilized soil.
(4) The amount of atrazine onto the thatch was about 8 times larger than that of atrazine adsorbed onto the soil. Atrazine adsorbed onto the thatch was not inactivated, but it was gradually desorbed with water, so the organic matter of the thatch plays an important role in the adsorption and desorption or these herbicides.
