To increase nitrogen (N) use efficiency and reduce water pollution from vegetable production, it is necessary to optimize N management. Fluorescence-based optical sensors are devices that can improve N fertilization through non-destructive field monitoring of crop variables. The aim of this work was to compare the performance of five fluorescence indices (SFR-R, SFR-G, FLAV, NBI-R, and NBI-G) to predict crop variables, as dry matter production, crop N content, crop N uptake, Nitrogen Nutrition Index (NNI), absolute and relative yield, in sweet pepper (Capsicum annuum) crops grown in greenhouse. Fluorescence measurements were periodically made with the Multiplex® 3.6 sensor throughout three cropping cycles subjected to five N application treatments. The performance of fluorescence indices to predict crop variables considered calibration and validation analyses. In general, the five fluorescence indices were strongly related with NNI, crop N content and relative yield. The best performing indices to predict crop N content and NNI at the early stages of the crops (i.e., vegetative and flowering phenological stages) were the SFR indices, both under red (SFR-R) and green (SFR-G) excitation. However, in the final stage of the crop (i.e., harvest stage), the best performing indices were NBI, both under red (NBI-R) and green (NBI-G) excitation, and FLAV. The two SFR indices best predicted relative yield of sweet pepper at early growth stages. Overall, the fluorescence sensor and the fluorescence indices evaluated were able to predict crop variables related to N status in sweet pepper. They have the capacity to be incorporated into best N management practices.

为了提高氮（N）的利用效率，减少蔬菜生产对水体的污染，有必要优化氮管理。基于荧光的光学传感器是可以通过作物变量的非破坏性田间监测来改善施氮量的设备。这项工作的目的是比较五种荧光指数（SFR-R、SFR-G、FLAV、NBI-R 和 NBI-G）的性能，以预测作物变量，如干物质产量、作物 N 含量、作物 N吸收，氮营养指数（NNI），绝对和相对产量，甜椒（辣椒) 温室种植的作物。在经历五次施氮处理的三个种植周期中，使用 Multiplex® 3.6 传感器定期进行荧光测量。荧光指数预测作物变量的性能考虑了校准和验证分析。总的来说，五个荧光指数与NNI、作物N含量和相对产量密切相关。在作物早期（即营养和开花物候阶段）预测作物氮含量和 NNI 的最佳性能指数是 SFR 指数，在红色 (SFR-R) 和绿色 (SFR-G) 激发下。然而，在作物的最后阶段（即收获阶段），表现最好的指数是在红色 (NBI-R) 和绿色 (NBI-G) 激发下的 NBI 和 FLAV。这两个 SFR 指数最能预测早期生长阶段甜椒的相对产量。总体而言，荧光传感器和评估的荧光指数能够预测与甜椒中氮状态相关的作物变量。它们有能力被纳入最佳 N 管理实践。