School of Agriculture and Environment, The University of Western Australia, Perth, WA, Australia.
The UWA Institute of Agriculture, The University of Western Australia, Perth, WA, Australia.
PLoS One. 2019 Feb 1;14(2):e0210219. doi: 10.1371/journal.pone.0210219. eCollection 2019.
No-tillage with stubble retention is a widely used cropping system for its conservation and yield benefits. The no-tillage farming system in southern Australia relies heavily on herbicides for weed management, but heavy crop residues may have a negative impact on the activity of pre-emergent herbicides applied. Any herbicide intercepted by the crop residue may not reach the soil surface without timely rainfall and may dissipate due to volatilisation, photo-degradation and/or microbial activity. Two experiments were carried out to investigate the interception of prosulfocarb, pyroxasulfone, and trifluralin herbicides by wheat residue and retention following simulated rainfall. For the first experiment, there were four simulated rainfall amounts (0, 5, 10, and 20 mm), three intensities (5, 10, and 20 mm h-1) and five application times (immediately after spraying herbicide, 6 h, 1, 7, and 14 days after spraying). In the second experiment, 20 mm of rainfall was applied at 10 mm h-1 in either 4 × 5 mm rainfall events over two days, 2 × 10 mm rainfall events over one day, or a single 20 mm rainfall event, with a no-rainfall control treatment. Bioassays were used to assess the herbicide activity/availability in the soil and remaining on the residue, using cucumber (Cucumis sativus L.) and Italian ryegrass (Lolium multiflorum Lam.) as indicator plants. At higher rainfall amounts, most of the herbicide leached from the stubble into the soil soon after application; more so with rain in one event rather than multiple events. However, the intensity of rainfall had no effect. Pyroxasulfone leached easily from the residue to the soil to potentially offer good weed control, prosulfocarb had an intermediary leaching effect, while only a small amount of trifluralin leached from stubble after rain. Therefore, in no-tillage situations with large amounts of crop residue present on the soil surface, herbicides that leach easily from the residue should be considered, like pyroxasulfone.
免耕留茬是一种广泛应用的种植系统，具有保护和增产的优势。澳大利亚南部的免耕农业系统严重依赖除草剂来管理杂草，但大量的作物残茬可能会对施用于地表的芽前除草剂的活性产生负面影响。如果没有及时降雨，任何被作物残茬截留的除草剂都可能无法到达土壤表面，而且可能会由于挥发、光降解和/或微生物活性而消散。进行了两项实验来研究模拟降雨后小麦残茬对prosulfocarb、pyroxasulfone 和 trifluralin 除草剂的截留及其保留情况。在第一个实验中，有四个模拟降雨量（0、5、10 和 20 毫米）、三个强度（5、10 和 20 毫米/小时）和五个施药时间（施药后立即、6 小时、1 天、7 天和 14 天）。在第二个实验中，以 10 毫米/小时的速度在两天内施 4×5 毫米的降雨事件 4 次、一天内施 2×10 毫米的降雨事件 2 次或施一次 20 毫米的降雨事件，同时设置无雨对照处理。采用生物测定法，利用黄瓜（Cucumis sativus L.）和意大利黑麦草（Lolium multiflorum Lam.）作为指示植物，评估土壤中残留的除草剂活性/可利用性。在较大降雨量下，施药后不久，大部分除草剂从残茬中淋溶到土壤中；在一次降雨中比多次降雨淋溶得更多。然而，降雨强度没有影响。pyroxasulfone 容易从残茬中淋溶到土壤中，从而可能提供良好的杂草控制效果；prosulfocarb 的淋溶效果居中；而 trifluralin 只有少量从雨后的残茬中淋溶出来。因此，在免耕且地表有大量作物残茬的情况下，应考虑那些容易从残茬中淋溶出来的除草剂，如 pyroxasulfone。
