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）的运移与持留特性。本研究旨在评估土壤有效水分对除草剂咪唑烟酸+咪唑乙烟酸（imazapyr + imazapic）商品混剂淋溶行为的影响，以及该除草剂在大豆后茬玉米种植中的残留后效。 本试验以淋溶柱（leaching columns）为载体，采用随机区组设计（randomized block design），设置4次重复，采用3×3×2析因试验方案：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为该除草剂商品混剂的施用量，分别为0.00+0.00、52.5+17.5与105+35 g·ha⁻¹；因子C为土壤深度，分别为0~0.3 m与0.3~0.6 m。 在淋溶柱顶部完成大豆播种后，立即喷施除草剂混剂。试验持续120 d后，将淋溶柱剖分为两段，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）。分别于出苗后15 d和30 d（days after germination, 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。 试验结果显示：在70% CC的土壤条件下，咪唑烟酸+咪唑乙烟酸混剂在0~0.3 m土层中的滞留量更高；而在130% CC条件下，该除草剂会向0.3~0.6 m土层发生淋溶，同时导致西瓜植株的生物量积累显著降低。此外，在70% CC的土壤环境中，该除草剂对后茬玉米种植具有残留潜在危害。