Off-target paraquat movement to rice has become a major problem in recent years for rice producers in the midsouthern United States. Nitrogen (N) fertilizer is applied to rice in greater quantity and frequency than all other nutrients to optimize rice yield. Two separate field studies were conducted from 2015 to 2018 in Stoneville, MS, to assess whether starter N fertilizer can aid rice recovery from exposure to a sub-lethal concentration of paraquat and to evaluate rice response to different N fertilizer management strategies following exposure to a sub-lethal concentration of paraquat. In both studies, paraquat treatments consisted of paraquat at 0 and 84 g ai ha–1 applied to rice in the two- to three-leaf (EPOST) growth stage. In the starter fertilizer study, N fertilizer at 24 kg ha–1 as ammonium sulfate (AMS) was applied to rice at spiking- to one-leaf (VEPOST), two- to three-leaf (EPOST), or three- to four-leaf (MPOST) growth stages before and after paraquat treatment. In the N fertilizer timing study, N fertilizer at 168 kg N ha–1 was applied in a single four-leaf to one-tiller (LPOST) application or two-, three-, and two four-way split applications. Despite starter N fertilizer applications, paraquat injured rice ≥41%, reduced height 57%, reduced dry weight prior to flooding 77%, delayed maturity 10 d, reduced dry weight at maturity 33%, and reduced rough rice yield 35% in the starter fertilizer study. Similarly, in the N fertilizer timing study, paraquat injured rice ≥45%, reduced height 14%, delayed maturity 10 d, reduced dry weight at maturity 44%, and reduced rough rice yield 50% for all N fertilizer management strategies. Both studies indicate that severe complications in growth and development can occur from rice exposure to a sub-lethal concentration of paraquat. In both studies, manipulation of N fertilizer management did not facilitate rice recovery from early-season exposure to paraquat.

中文翻译：

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水稻暴露于亚致死浓度的百草枯后的氮肥计划

近年来，美国中南部稻米生产商面临的主要问题是百草枯向稻米转移。与所有其他养分相比，向水稻施用氮 (N) 肥料的数量和频率高于所有其他营养素，以优化水稻产量。2015 年至 2018 年在密西西比州斯通维尔进行了两项独立的田间研究，以评估起始氮肥是否有助于水稻从暴露于亚致死浓度的百草枯中恢复，并评估水稻在暴露于百草枯的亚致死浓度。在这两项研究中，百草枯处理由 0 和 84 g ai ha 的百草枯组成–1适用于二至三叶（EPOST）生长阶段的水稻。在起始肥料研究中，N 肥料为 24 kg ha–1因为硫酸铵 (AMS) 在百草枯处理前后的穗到一叶 (VEPOST)、二到三叶 (EPOST) 或三到四叶 (MPOST) 生长阶段施用于水稻。在氮肥时机研究中，氮肥在 168 kg N ha–1在单个四叶到一分蘖 (LPOST) 应用程序或两个、三个和两个四向拆分应用程序中应用。尽管施用了起始 N 肥，百草枯对水稻的伤害 ≥41%，高度降低 57%，淹水前干重降低 77%，成熟延迟 10 天，成熟时干重降低 33%，糙米产量降低 35%肥料研究。同样，在氮肥施肥时间研究中，百草枯对所有氮肥管理策略的水稻伤害≥45%，高度降低 14%，成熟延迟 10 天，成熟干重降低 44%，糙米产量降低 50%。两项研究都表明，水稻暴露于亚致死浓度的百草枯可能会导致生长和发育的严重并发症。在这两项研究中，