South African lovegrass (Eragrostis plana Nees) is the most important weed of native pastures in southern Brazil. Management options are limited under water-stress conditions, and glyphosate has been the main tool for control. This study compared four salts of glyphosate applied at three growth stages and determined the glyphosate tolerance level. In addition, the performance of ammonium sulfate (AMS) under two soil moisture conditions (50% and 100% of water-holding capacity) and the effect of AMS on absorption and translocation of radiolabeled [14C]glyphosate were evaluated. The potassium salt of glyphosate had the fastest activity across growth stages of E. plana, which is more vulnerable to glyphosate at the panicle initiation stage. Isopropylamine salt was the slowest-acting glyphosate formulation. Younger plants were typically more easily controlled than older plants at the full tillering stage. The addition of AMS increased the level of control of drought-stressed E. plana compared with glyphosate alone by increasing translocation out of the treated leaf and consequently increasing the concentration of glyphosate in the primary culm. These data can be used to plan an effective management program for E. plana that takes into account the developmental stage of desired pasture grass species.

中文翻译：

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硫酸铵提高草甘膦对水分胁迫下南非爱情草（Eragrostis plana）的疗效

南非爱情草 (画笔Nees) 是巴西南部原生牧场中最重要的杂草。在缺水条件下管理选择有限，草甘膦一直是控制的主要工具。本研究比较了在三个生长阶段施用的四种草甘膦盐，并确定了草甘膦耐受水平。此外，硫酸铵（AMS）在两种土壤水分条件下（50%和100%持水量）的性能以及AMS对放射性标记[14C]草甘膦进行了评估。草甘膦钾盐在整个生长阶段的活性最快E.plana，在穗起始阶段更容易受到草甘膦的影响。异丙胺盐是作用最慢的草甘膦制剂。在完全分蘖阶段，较年轻的植物通常比较老的植物更容易控制。AMS 的加入提高了对干旱胁迫的控制水平E.plana与单独使用草甘膦相比，通过增加处理叶片外的转运并因此增加草甘膦在初级秆中的浓度。这些数据可用于规划有效的管理计划E.plana考虑到所需牧草物种的发育阶段。