LEACHING AND CARRYOVER FOR SAFRINHA CORN OF THE HERBICIDES IMAZAPYR + IMAZAPIC IN SOIL UNDER DIFFERENT WATER CONDITIONS

ABSTRACT Soil moisture can alter the transport and permanence of pre-emergent herbicides. The objective of this work was to evaluate the influence of water availability in the soil on the leaching of a commercial mixture of the herbicides imazapyr + imazapic, as well as the carryover effect of this herbicide in corn planted in succession to soybean. The experiment was carried out in leaching columns in a randomized block design with 4 replications. A 3x3x2 factorial scheme was used, with factor A being the irrigation (130%, 100% and 70% of field capacity (CC)), factor B the doses of the commercial mixture of the herbicides imazapyr + imazapic (0.00+ 0.00; 52.5 + 17.5 and 105 + 35 g ha-1) and factor C at soil depth (0-0.3 m and 0.3-0.6 m). Soybean sowing was performed at the top of the columns and immediately after herbicide mixture was applied. After 120 days the columns were opened, generating two sections, where corn (Zea mays) and the other watermelon (Citrullus lanatus) were sown as a bioindicator of herbicide residue. The fluorescence parameters of chlorophyll a at 15 and 30 days after germination (DAG) and shoot dry matter accumulation at 30 DAG were evaluated. There was greater retention of the herbicide imazapyr + imazapic at a depth of 0-0.3m at 70% CC condition and leaching at a depth of 0.3-0.6m at 130% CC condition, with a reduction in the mass accumulation of watermelon plants. The herbicide has a carryover potential for corn cultivation in soils maintained at 70% CC.

摘要 土壤水分可改变苗前除草剂（pre-emergent herbicides）的运移与残留持久性。本研究旨在评估土壤水分有效性对咪唑烟（imazapyr）+咪唑烟酸（imazapic）商用混配除草剂淋溶行为的影响，以及该除草剂在大豆后茬玉米田中的残留后效。试验采用随机区组设计（randomized block design），设置4次重复，以淋溶柱（leaching columns）为载体开展实验，采用3×3×2三因子试验方案：因子A为灌溉水平（分别为田间持水量（field capacity, CC）的130%、100%与70%）；因子B为该商用混配除草剂的施用量（0.00+0.00、52.5+17.5与105+35 g ha⁻¹）；因子C为土壤土层深度（0~0.3 m与0.3~0.6 m）。在淋溶柱顶部播种大豆，施药后立即完成该混配除草剂的喷施。试验开展120 d后剖开淋溶柱，分为两段土层，分别种植玉米（*Zea mays*）与西瓜（*Citrullus lanatus*）作为除草剂残留的生物指示物（bioindicator）。分别于玉米出苗后15 d与30 d（DAG）测定叶绿素a荧光参数，并于出苗后30 d测定地上部干物质积累量。结果表明：在70% CC处理下，咪唑烟+咪唑烟酸更多残留于0~0.3 m土层；而在130% CC处理下，该除草剂更多淋溶至0.3~0.6 m土层，同时导致西瓜植株生物量积累降低。在70% CC的土壤条件下，该除草剂对后茬玉米种植存在残留风险潜力。