除草劑對覆地植被及水土保育之影響

袁秋英 蔣慕琰

台灣省農業藥物毒物試驗所公害防治系

摘 要

台灣為多山的海島，山坡地面積有97萬餘公頃。本省坡地主要農作物為果樹，多屬小規模經營，栽培管理常依賴人工作業。近20年來除草劑新產品之不斷被開發，目前已有16種藥劑登記於果園，用於長短期間不同或針對某特定雜草之防除。化學藥劑除草為目前果園最常使用之雜草防治方法，然而藥劑使用不當或過度噴施非選擇性殺草劑，極易造成土壤之裸露，對於廣大坡地之水土保育是一嚴重問題。嘉磷塞及巴拉刈為本省使用最普遍之萌後除草劑；二者皆為非選擇性藥劑有全面防除之效果。嘉磷塞之藥效持續性長，暖季施藥後40 ~ 50日，土表呈現50 ~ 60 %之裸露狀態。巴拉刈之藥效持續性短，施藥後一個月，再生長之草本植物即形成90 %以上之覆蓋率。冷季施用嘉磷塞及巴拉刈之有效防治期相近似；施藥後三個月，草本植物之覆蓋率僅50 %。經常性使用同一種除草劑，易造成草相之變遷，導致毛穎雀稗、細梗絡石、野塘蒿等耐、抗性植物的滋生。萌前殺草劑以達有龍之藥劑殘效期長，施藥後5個月，地被植物之覆蓋率仍低於20 %，亦即有80 %以上之土表呈裸露狀態，其次為草脫淨、克草及復祿芬等，三福林的藥劑殘效期短，施藥後一個月，地被植物之覆蓋率即為20 %，施藥後3個月，其覆蓋率已達95 %，無顯著土壤裸露現象。目前果園的栽植已由早期的平台階段發展為山邊溝方式，水土保育與環境安全性有賴坡地果園內覆地植被之建立及維持。經由初步試驗篩選出丁基拉草、施得圃、滅蘇民等萌前藥劑，一方面可防除雜草，另一方面可保留鵝兒腸、菁芳草、闊葉鴨舌癀舅等理想之地被植物，此等藥劑適時之應用，具有協助草生栽培之特殊功效。然而如何適當的利用殺草劑發展本土性之草生栽培，以及建立符合環境需求之果園雜草管理體系，是今後仍需努力之目標。

關鍵詞：除草劑、覆地植被、水土保育

Chemical Management of Ground-covering Vegetation for Mountain Farmland in Taiwan

Yuan, Chou-Inn and Mou-Yen Chiang

Plant Toxicology Department

Taiwan Agricultural Chemicals and Toxic Substances Research Institute

Abstract

With limited lowland area, mountains farming constitute an important part agri- culture in Taiwan. Tea, betel nut, summer vegetables, and various kinds of orchards are primarily produced on hilly land and on steep mountains up to 2,000 m above sea level. Soil preservation is essential for sustainable use of farmland in mountain areas. For the last decade, glyphosate and paraquat are heavily used in these farms. Unrestrained use of non-selective herbicides results in kill of both weeds and benefi- cial ground –covering vegetation, and subsequent the exposure of venerable land to torrential rainfall and soil erosion. The ideal management system thus should consid- er both weed control and maintenance of vegetative ground coverage. Non-chemical weeding methods commonly used in lowland areas are often unsuitable for mountain farmlands; Major limitations include labor shortage, small and uneven farm, inade- quate infrastructure, economic competitiveness. Improvement of chemical control is more promising to provide a workable solution. We have evaluated different pre- and post –emergence herbicides for performances on selectivity, impact on flora, effective period, seasonal variation in activity. Data on weeds and other herbaceous species are surveyed for wide-spread mountain farm land. Non-selective chemicals and adequate preemergence herbicide will be integrated to weed out harmful species and to assist the establishment of beneficial species for ground-coverage.

Key words: Herbicide, Ground-covering vegetation, Soil preservation.