High nitrogen rates are important to field-grown cotton ( L.) for recovering from stresses such as light restriction and alleviating its negative impact on yield. However, there is little information on its influence on fiber quality after shading. The objective of this study was to examine fiber quality responses to nitrogen fertilization of shaded cotton. Cotton plants were exposed to a 42 % reduction in global radiation for 16–25 days during early flowering, and fertilizer with different N rates in the Center-West (Primavera do Leste - PL and Chapadão do Sul - CS) and Southeast (Itapeva - IT) Brazil. Four N rates were used in PL and IT, and 3 N rates and an early (FM 906GLT) and a late-cycle (FM 983GLT) cotton cultivar were used in CS. Fiber quality from bolls taken from entire plots (nonportioned plants) and from the lower, middle, and upper thirds of the canopy (portioned plants) was assessed. The lack of interaction in most analyses indicated shading and nitrogen effects on fiber quality as independent. Shading resulted in occasional effects on micronaire, strength, length, length uniformity, and short fiber index. Micronaire of nonportioned plants decreased in response to N inputs, wherein values at the maximum N rate were lower than those at the minimum one by 5.21 % and 7.91 % in PL and IT, respectively. Increasing N rates also decreased micronaire in all canopy portions in IT and the lower third in CS but had nonconclusive effects on other fiber properties. Fiber length and strength were generally greater in the late-maturing cultivar, which had higher micronaire readings in the lower third of the canopy and lower readings in the upper canopy compared with the early cultivar. In conclusion, shading during early flowering has limited and inconsistent effects on cotton fiber quality. Conversely, N fertilization leads to more predictable results, so higher N rates increase the risk of heightened immature fiber percentage. The findings of this work provide new insights into how nitrogen fertilization management affects cotton fiber quality. Future research should consider other management techniques, such as the timing of the crop termination, to avoid the occurrence of low micronaire.

中文翻译：

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了解田间种植的遮荫棉的纤维质量：氮肥的影响


高施氮量对于田间种植的棉花（L.）从光照限制等胁迫中恢复并减轻其对产量的负面影响非常重要。然而，关于其对遮光后纤维质量的影响的信息很少。本研究的目的是检查遮荫棉花的纤维质量对施氮肥的反应。棉花植株在开花早期 16-25 天暴露在全球辐射减少 42% 的环境中，并在中西部（Primavera do Leste - PL 和 Chapadão do Sul - CS）和东南部（Itapeva - CS）施用不同氮含量的肥料。 IT）巴西。 PL 和 IT 中使用 4 种氮肥，CS 中使用 3 种氮肥以及早熟 (FM 906GLT) 和晚熟 (FM 983GLT) 棉花品种。对取自整个地块（未分份的植物）和冠层下、中、上三分之一（分份的植物）的棉铃的纤维质量进行了评估。大多数分析中缺乏相互作用表明遮光和氮对纤维质量的影响是独立的。遮光偶尔会对马克隆值、强度、长度、长度均匀度和短纤维指数产生影响。未分配植物的马克隆值随氮输入而下降，其中最大施氮量时的马克隆值比最小施氮量时的PL和IT值分别低5.21%和7.91%。增加施氮量还降低了 IT 中所有冠层部分和 CS 中下三分之一的马克隆值，但对其他纤维性能没有决定性影响。与早熟品种相比，晚熟品种的纤维长度和强度普遍较高，其冠层下三分之一的马克隆值读数较高，而冠层上部的读数较低。 总之，开花初期的遮荫对棉纤维质量的影响有限且不一致。相反，施氮会导致更可预测的结果，因此较高的施氮量会增加未成熟纤维百分比增加的风险。这项工作的结果为氮肥管理如何影响棉纤维质量提供了新的见解。未来的研究应考虑其他管理技术，例如作物终止的时间，以避免低马克隆值的发生。