為(wei)了(le)及時預防(fang)草害(hai)，對于即將播種或者移栽前后的(de)大白菜大田，應(ying)(ying)分別進行化學除草，技術上應(ying)(ying)掌握如下(xia)要點。

第一，播后苗前選好除草劑。播種之后出苗之前，一(yi)可(ke)畝用(yong)72%異丙甲(jia)(jia)(jia)草(cao)(cao)(cao)(cao)(cao)(cao)胺(an)(an)(an)(an)乳(ru)油(you)(you)70毫(hao)(hao)升(sheng)(sheng)(sheng)或(huo)25%胺(an)(an)(an)(an)草(cao)(cao)(cao)(cao)(cao)(cao)磷乳(ru)油(you)(you)150~200毫(hao)(hao)升(sheng)(sheng)(sheng)、50%丁草(cao)(cao)(cao)(cao)(cao)(cao)胺(an)(an)(an)(an)乳(ru)油(you)(you)75~100毫(hao)(hao)升(sheng)(sheng)(sheng)、敵(di)草(cao)(cao)(cao)(cao)(cao)(cao)胺(an)(an)(an)(an)乳(ru)油(you)(you)150~200毫(hao)(hao)升(sheng)(sheng)(sheng)、50%禾草(cao)(cao)(cao)(cao)(cao)(cao)丹(dan)乳(ru)油(you)(you)100~125毫(hao)(hao)升(sheng)(sheng)(sheng)、50%乙草(cao)(cao)(cao)(cao)(cao)(cao)胺(an)(an)(an)(an)乳(ru)油(you)(you)60毫(hao)(hao)升(sheng)(sheng)(sheng)、33%二甲(jia)(jia)(jia)戊靈乳(ru)油(you)(you)100毫(hao)(hao)升(sheng)(sheng)(sheng)，分別兌清(qing)(qing)水(shui)50公(gong)斤噴灑于(yu)大(da)田(tian)土(tu)表，能防除旱稗(bai)、莎(sha)草(cao)(cao)(cao)(cao)(cao)(cao)、牛筋草(cao)(cao)(cao)(cao)(cao)(cao)等雜(za)草(cao)(cao)(cao)(cao)(cao)(cao)，防效在90%以上。如果(guo)大(da)田(tian)中單子(zi)葉、雙子(zi)葉雜(za)草(cao)(cao)(cao)(cao)(cao)(cao)混合生長，可(ke)選用(yong)35%除草(cao)(cao)(cao)(cao)(cao)(cao)醚乳(ru)油(you)(you)250~300毫(hao)(hao)升(sheng)(sheng)(sheng)，加(jia)(jia)上60%丁草(cao)(cao)(cao)(cao)(cao)(cao)胺(an)(an)(an)(an)乳(ru)油(you)(you)70~80毫(hao)(hao)升(sheng)(sheng)(sheng)，或(huo)者加(jia)(jia)上72%異丙甲(jia)(jia)(jia)草(cao)(cao)(cao)(cao)(cao)(cao)胺(an)(an)(an)(an)60毫(hao)(hao)升(sheng)(sheng)(sheng)，兌清(qing)(qing)水(shui)50公(gong)斤噴于(yu)土(tu)表，有良好的兼治雜(za)草(cao)(cao)(cao)(cao)(cao)(cao)的效果(guo)。雜(za)草(cao)(cao)(cao)(cao)(cao)(cao)種類多、密度大(da)的田(tian)塊，還(huan)可(ke)在播種前每(mei)畝用(yong)10%草(cao)(cao)(cao)(cao)(cao)(cao)甘膦水(shui)劑0.7公(gong)斤，兌清(qing)(qing)水(shui)40公(gong)斤噴施，5天后雜(za)草(cao)(cao)(cao)(cao)(cao)(cao)枯死(si)再整地播種。

第二，栽前栽后選好除草劑。選用(yong)(yong)(yong)育苗(miao)移栽的(de)大(da)(da)白(bai)(bai)菜，移栽之前，可(ke)(ke)畝(mu)用(yong)(yong)(yong)48%敵草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)200毫(hao)(hao)(hao)升(sheng)(sheng)或24%果爾乳(ru)(ru)油(you)(you)(you)50~80毫(hao)(hao)(hao)升(sheng)(sheng)、50%乙草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)80~100毫(hao)(hao)(hao)升(sheng)(sheng)、50%敵草(cao)(cao)(cao)胺(an)可(ke)(ke)濕(shi)(shi)性粉(fen)劑80~100克(ke)、20%敵草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)150毫(hao)(hao)(hao)升(sheng)(sheng)，分(fen)別(bie)兌(dui)清(qing)(qing)水50公(gong)斤噴(pen)(pen)于(yu)土表，均對(dui)雜草(cao)(cao)(cao)有(you)良(liang)好的(de)防(fang)治效(xiao)(xiao)果。大(da)(da)白(bai)(bai)菜移栽之后(hou)雜草(cao)(cao)(cao)出苗(miao)前，可(ke)(ke)畝(mu)用(yong)(yong)(yong)25%胺(an)草(cao)(cao)(cao)磷乳(ru)(ru)油(you)(you)(you)20毫(hao)(hao)(hao)升(sheng)(sheng)、48%敵草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)150~200毫(hao)(hao)(hao)升(sheng)(sheng)、用(yong)(yong)(yong)60%丁草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)130~150毫(hao)(hao)(hao)升(sheng)(sheng)、二甲戊靈(ling)乳(ru)(ru)油(you)(you)(you)100毫(hao)(hao)(hao)升(sheng)(sheng)，分(fen)別(bie)兌(dui)清(qing)(qing)水50公(gong)斤，在(zai)大(da)(da)白(bai)(bai)菜行間定向噴(pen)(pen)于(yu)土表，均有(you)較好的(de)防(fang)效(xiao)(xiao)。對(dui)于(yu)移栽之后(hou)大(da)(da)白(bai)(bai)菜大(da)(da)田(tian)的(de)雜草(cao)(cao)(cao)幼苗(miao)，可(ke)(ke)畝(mu)用(yong)(yong)(yong)10.8%高(gao)效(xiao)(xiao)吡(bi)(bi)氟乙草(cao)(cao)(cao)靈(ling)乳(ru)(ru)油(you)(you)(you)50~60毫(hao)(hao)(hao)升(sheng)(sheng)或15%精吡(bi)(bi)氟禾(he)草(cao)(cao)(cao)靈(ling)乳(ru)(ru)油(you)(you)(you)50~60毫(hao)(hao)(hao)升(sheng)(sheng)，兌(dui)清(qing)(qing)水40公(gong)斤噴(pen)(pen)施(shi)。還可(ke)(ke)用(yong)(yong)(yong)禾(he)草(cao)(cao)(cao)克(ke)加(jia)丁草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)混合施(shi)用(yong)(yong)(yong)，即每畝(mu)禾(he)草(cao)(cao)(cao)克(ke)乳(ru)(ru)油(you)(you)(you)30毫(hao)(hao)(hao)升(sheng)(sheng)加(jia)60%丁草(cao)(cao)(cao)胺(an)乳(ru)(ru)油(you)(you)(you)50~60毫(hao)(hao)(hao)升(sheng)(sheng)，兌(dui)清(qing)(qing)水50公(gong)斤噴(pen)(pen)施(shi)。移栽的(de)大(da)(da)白(bai)(bai)菜幼苗(miao)成活后(hou)，每畝(mu)可(ke)(ke)用(yong)(yong)(yong)48%氟樂(le)靈(ling)乳(ru)(ru)油(you)(you)(you)150~200毫(hao)(hao)(hao)升(sheng)(sheng)或50%撲草(cao)(cao)(cao)凈可(ke)(ke)濕(shi)(shi)性粉(fen)劑75~120克(ke)，兌(dui)清(qing)(qing)水75~100公(gong)斤噴(pen)(pen)霧噴(pen)(pen)濕(shi)(shi)土表，噴(pen)(pen)后(hou)再用(yong)(yong)(yong)齒(chi)耙深鋤土表2~3厘(li)米，以防(fang)揮發。

第三，注意施藥質量。區(qu)別不(bu)同雜草(cao)選(xuan)好對(dui)應(ying)的除草(cao)劑；嚴格按照劑量(liang)(liang)濃度(du)調配藥液；土壤(rang)濕潤時抓緊施(shi)藥，土壤(rang)干燥的先(xian)灌水后施(shi)藥，施(shi)藥遇雨應(ying)重噴；已(yi)出苗(miao)定苗(miao)或已(yi)移栽的大(da)白菜(cai)要選(xuan)擇定向噴施(shi)；有機質含量(liang)(liang)高(gao)的土壤(rang)適當提高(gao)用藥量(liang)(liang)，沙質土壤(rang)適量(liang)(liang)降(jiang)低藥量(liang)(liang)。