Studies on diagnosis of weed damages due to weed competition
Grant-in-Aid for Scientific Research (B).
|Research Institution||KYOTO UNIVERSITY|
KUSANAGI Tokuichi Kyoto University Agriculture Professor, 農学部, 教授 (50205069)
|Project Fiscal Year
1990 – 1992
Completed(Fiscal Year 1992)
|Budget Amount *help
¥5,000,000 (Direct Cost : ¥5,000,000)
Fiscal Year 1992 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1991 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1990 : ¥3,400,000 (Direct Cost : ¥3,400,000)
|Keywords||Weed damage / Weed damage diagnosis / Crop-weed competition / Direct seeded rice / Echinochloa weeds / 雑草害 / 雑草害診断 / 作物-雑草競合 / 水稲直播栽培 / ヒエ属雑草 / 作物ー雑草競合 / 水稻直播栽培 / 雑草の発生予測 / 雑草の発生診断 / 雑草の埋土種子集団|
Studies conducted with objective to obtain fundamental data for the prediction and diagnosis of weed damages in rice included amount of soil-buried weed seeds, their field emergence, the emergence patterns and crop growth and yield in direct seeded rice with and without tillage as well as in transplanted rice. Main results found are as follows:
1. Characteristics of Weed Population relating to Crop-Weed Competition
(1) A large population of soil-buried weed seeds composed mainly of hydrophytic and hygrophytic weeds was still maintained at the experimental field weeds of which had been controlled with continuous applications of herbicides for more than 10 years.
(2) Direct seeded rice was infested with weeds of 40 species of 20 families in total, and the infestation was greater in an increasing order of direct seeded rice without tillage, the one with tillage and transplanted rice. Main weeds were Echinochloa crus-galli var. crus-galli, E. oryzicola, Leptochloa chinensis, Cyperus irria, Eclipta prostrata and Lindernia dubia.
(3) Weeds at direct seeded rice could be grouped into those emerging during unflooded and flooded periods, and were different in ecological characters between two groups.
2. Conditions of Weed Emergence and Weed Damage Diagnosis
(1) Crop yield reduction was 80-95% in direct seeded rice and about 50% in transplanted rice. These values could be related to amount of weed emergence and the species composition.
(2) The duration of weeding required to avoid weed damage was about 60 days after sowing.
(3) Damage by Echinochloa weeds for 70 days after sowing showed higher correlation with plant height of the weeds than with the number of weeds. Crop yield was not reduced by the weeds when they were less than 10 cm in height regardless of the amount of emergence. This result suggested plant height and the amount of emergence of Echinochloa weeds as potential indicators for diagnosis of weed damage or weed control assessment.
Research Output (13results)