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的迁移与持留特性。本研究旨在评估土壤水分有效性对市售烟嘧磺隆+甲氧咪草烟（imazapyr + imazapic）复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。本试验采用随机区组设计，设置4次重复，以淋溶柱开展研究，采用3×3×2三因素析因试验方案：因素A为灌溉水平（分别为田间持水量（field capacity, CC）的130%、100%和70%），因素B为该复配除草剂的施用量（0.00+0.00、52.5+17.5 g·ha⁻¹和105+35 g·ha⁻¹），因素C为土壤土层深度（0~0.3 m与0.3~0.6 m）。试验于淋溶柱柱顶进行大豆播种，随后立即施加该除草剂复配药剂。120 d后将淋溶柱剖开，分为两段土层，分别播种玉米（Zea mays）与西瓜（Citrullus lanatus）作为除草剂残留的生物指示作物，测定出苗后15 d与30 d的叶绿素a荧光参数，以及出苗后30 d的地上部干物质积累量。结果表明，在田间持水量70%的水分条件下，烟嘧磺隆+甲氧咪草烟更多滞留于0~0.3 m土层；而在130%田间持水量条件下，该药剂更多淋溶至0.3~0.6 m土层，同时导致西瓜植株生物量积累降低。在田间持水量维持70%的土壤中，该除草剂对后茬玉米种植存在残留后害风险。