OGASAWARA Masaru Utsunomiya University, Weed Science Center, Associate Professor, 雑草科学研究センター, 助手 (40194419)
YONEYAMA Koichi Utsunomiya University, Weed Science Center, Associate Professor, 雑草科学研究センター, 助教授 (00114174)
|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1991 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1990 : ¥1,400,000 (Direct Cost : ¥1,400,000)
In turf fields, efficiency of applied herbicides is lower than that in upland fields, mainly due to the deposition of chemicals on turfgrass leaves which cover some of existing weeds and almost all of soil surface. This decrease in the efficiency is more remarkable for soil treatment type herbicides than for foliar treatment type herbicides. Amounts of herbicides retained by turf leaves were affected by herbicide formulation types, spray volume, addition of wetting agents, amount of rainfall, duration between the application and rainfall, and growth stages and plant height of the turfgrass. Lower mowing of the turfgrass, usage of flowables rather than wettable formulations, application with a large volume of water without wetting agent, or watering soil after the spray also decreased the amounts of herbicides retained by the leaves. The addition of a soil-permeation agent to the sprity diminished the amounts of herbicides retained by the leaves and promoted the desorption of herbicides
from tile leaves by rainfall.
In a turfgrass field, residues of herbicides in soil decreased rather rapidly within two weeks after treatment and then gradually. In particular, more rapid decreases of the residues were observed when herbicidies were applied during the warm seasons, whereas 5 - 25 % of the applied dosage were fOLliid even 5 molitlis after the application in autumn.
When herbicides were sprayed in a turfgrass field and in an uncropped field, both have a slope of 15", and a simulated rainfall of 80 mm/hr was applied 6 - 72 hours after the treatment, runoff volume of surface water and amounts of eroding soil were greater in the uncropped field than in the turfgrass field. Less water soluble and more soil absorbable herbicides were transported largely with eroding soil and, on the other hand, more water soluble herbicides were lost with the runoff water. Total amounts of herbicides transported with the runoff water and with the soil erosion were larger in the uncropped field than in the turf field. In both the fields, more water water soluble herbicides appeared to be hardly transported than less water soluble ones. In the cases of simazine and pendimethalin, the loss due to herbicide runoff in the uncropped field seemed not to be affected significantly by their formulation types. However, in the turf field, greater amounts of the herbicides were lost due to the runoff when their flowable products rather than wettable products had been applied.