Nitrogen (N) is an essential element frequently associated with environmental issues, and the utilization of leaf clip sensors to adjust N fertilization is a technology of interest. This study aimed to evaluate the indices measured with SPAD and Dualex through the bell pepper crop cycle cultivated under different N doses, to identify the ability of the SPAD and Dualex optical sensors to assess N status and establishing the accuracy of the chlorophyll indices as yield estimators. Bell pepper plants were cultivated for 150 days after transplanting (DAT) in slabs fertigated with 6 different N doses divided into 10 bi-weekly applications. The indices SPAD, chlorophyll (CHL), flavonoids (FLV), and nitrogen balance index (NBI) were measured over the cycle on the uppermost mature leaves of each treatment. We determined the N content of these leaves and the final commercial yield. An interaction effect was found between N dose and growth stage. The SPAD and CHL indices were not significantly affected by N dose up to 60 DAT. The FLV and NBI indices show an opposite pattern in response to N dose. We found a strong correlation between the SPAD, CHL, and NBI and the N content in the leaves and between these indices and commercial yield in several evaluated dates. However, we did not observe a significant correlation between commercial yield and FLV. Both leaf clip sensors could predict the N status of the leaves and the commercial yield, improving the correlation as the crop development progressed.

中文翻译：

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近端光学传感器在评估板坯甜椒氮含量和产量中的应用

氮 (N) 是经常与环境问题相关的基本元素，利用叶夹传感器来调整施氮是一项令人感兴趣的技术。本研究旨在评估在不同氮剂量下栽培的甜椒作物周期中用 SPAD 和 Dualex 测量的指数，以确定 SPAD 和 Dualex 光学传感器评估氮状态的能力，并确定叶绿素指数作为产量估计值的准确性. 将甜椒植株在移栽 (DAT) 后在用 6 种不同 N 剂量灌溉的平板中栽培 150 天，每两周施用 10 次。在每个处理的最上层成熟叶片的周期内测量SPAD、叶绿素（CHL）、黄酮类化合物（FLV）和氮平衡指数（NBI）的指数。我们确定了这些叶子的 N 含量和最终的商业产量。发现氮剂量和生长阶段之间存在交互作用。SPAD 和 CHL 指数不受 N 剂量的显着影响，直至 60 DAT。FLV 和 NBI 指数对 N 剂量的反应显示出相反的模式。我们发现 SPAD、CHL 和 NBI 与叶片中的 N 含量以及这些指数与几个评估日期的商业产量之间存在很强的相关性。然而，我们没有观察到商业产量和 FLV 之间的显着相关性。两种叶夹传感器都可以预测叶子的氮状况和商业产量，随着作物发育的进展提高相关性。SPAD 和 CHL 指数不受 N 剂量的显着影响，直至 60 DAT。FLV 和 NBI 指数对 N 剂量的反应显示出相反的模式。我们发现 SPAD、CHL 和 NBI 与叶片中的 N 含量以及这些指数与几个评估日期的商业产量之间存在很强的相关性。然而，我们没有观察到商业产量和 FLV 之间的显着相关性。两种叶夹传感器都可以预测叶子的氮状况和商业产量，随着作物发育的进展提高相关性。SPAD 和 CHL 指数不受 N 剂量的显着影响，直至 60 DAT。FLV 和 NBI 指数对 N 剂量的反应显示出相反的模式。我们发现 SPAD、CHL 和 NBI 与叶片中的 N 含量以及这些指数与几个评估日期的商业产量之间存在很强的相关性。然而，我们没有观察到商业产量和 FLV 之间的显着相关性。两种叶夹传感器都可以预测叶子的氮状况和商业产量，随着作物发育的进展提高相关性。我们没有观察到商业产量和 FLV 之间的显着相关性。两种叶夹传感器都可以预测叶子的氮状态和商业产量，随着作物发育的进展提高相关性。我们没有观察到商业产量和 FLV 之间的显着相关性。两种叶夹传感器都可以预测叶子的氮状况和商业产量，随着作物发育的进展提高相关性。