Cassava (Manihot esculenta Crantz, Euphorbiaceae), an important source of food for millions of people in the world, is distributed mainly in Asia, Africa, Latin America, and the Caribbean. Weeds are important biotic constraints on cassava production, and herbicide application can provide effective weed control in this crop. However, the different possibilities of herbicide selectivity (factors associated and not associated with the plants) must be studied before implementation. The aim of this study was to evaluate the effects of the combination of different pre-emergence herbicides and two stem cutting planting systems (vertical and horizontal) on phytotoxicity and several agronomic traits of the cassava crop. The experiment was conducted through a factorial arrangement in a completely random design in Corrientes, Argentina. The factors studied were planting systems (horizontal and vertical position), weed control methods (hoeing or application of diuron, S-metolachlor, pendimethalin or clomazone, 625; 1920; 900 and 1000 g a.i. ha−1, respectively), and cropping seasons (2018–2019 and 2019–2020). The following variables were measured: phytotoxicity, plant height, relative plant stand, total weight of tuberous roots per plant, starch concentration of tuberous roots, and starch production per ha. The highest precipitations occurred in the 2018–2019 cropping season. The vertical planting system in combination with herbicides showed lower phytotoxicity values and higher values of plant height, starch concentration, and starch production per ha than the horizontal planting system. The highest phytotoxicity values were recorded with the application of diuron combined with the horizontal planting system and in the 2018–2019 season, with a 33.33% decrease in relative plant stand compared to the use of hoeing. Starch concentration remained unchanged with the use of clomazone and pendimethalin, whereas the effect of these herbicides on starch production varied with the cropping season, decreasing only in 2019–2020. Starch production was significantly lower with the use of S-metolachlor (up to 55.29% in 2018–2019) and of diuron (up to 60.57% in 2019–2020) than with the use of hoeing. In conclusion, phytotoxicity values were higher for the horizontal planting system than for the vertical system. The herbicide with the highest phytotoxic effect on the cassava crop was diuron; the effect increased when combined with the horizontal planting system in the cropping season with higher rainfall. This work provides the basis for integrated weed management concerning the use of herbicides and their selectivity according to planting systems for cassava crops.

中文翻译：

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木薯 （Manihot esculenta Crantz） 出苗前除草剂的选择性及其与插茎种植系统的关系


木薯 （Manihot esculenta Crantz， Euphorbiaceae） 是世界上数百万人的重要食物来源，主要分布在亚洲、非洲、拉丁美洲和加勒比地区。杂草是木薯生产的重要生物限制因素，除草剂的应用可以为这种作物提供有效的杂草控制。然而，在实施除草剂之前，必须研究除草剂选择性的不同可能性（与植物相关和无关的因素）。本研究的目的是评估不同出苗前除草剂和两种切茎种植系统（垂直和水平）的组合对木薯作物植物毒性和几个农艺性状的影响。该试验是在阿根廷科连特斯通过完全随机设计的因子安排进行的。研究的因素是种植系统（水平和垂直位置）、杂草控制方法（锄草或施用敌草隆、S-异丙甲草胺、二甲戊灵或氯马宗，625;1920;分别为 900 和 1000 g a.i. ha-1）和种植季节（2018-2019 年和 2019-2020 年）。测量了以下变量：植物毒性、株高、相对株株分、每株块茎根总重、块茎根的淀粉浓度和每公顷的淀粉产量。2018-2019 年农作物季节降雨量最高。与水平种植系统相比，垂直种植系统与除草剂结合使用的植物毒性值较低，而株高、淀粉浓度和每公顷淀粉产量值较高。敌草隆与水平种植系统相结合的应用记录了最高的植物毒性值，在 2018-2019 季节，为 33。与使用锄草相比，相对植株减少 33%。使用氯马酮和二甲戊灵后，淀粉浓度保持不变，而这些除草剂对淀粉生产的影响随种植季节而变化，仅在 2019-2020 年下降。与使用锄草相比，使用 S-异丙甲草胺（2018-2019 年高达 55.29%）和敌草隆（2019-2020 年高达 60.57%）的淀粉产量明显较低。总之，水平种植系统的植物毒性值高于垂直系统。对木薯作物具有最高植物毒性作用的除草剂是敌草隆;在降雨量较高的种植季节与水平种植系统相结合时，效果会增强。这项工作为杂草综合管理提供了基础，包括除草剂的使用及其根据木薯作物种植系统的选择性。