03074naa a2200277 a 450000100080000000500110000800800410001902200140006002400270007410000170010124501160011826000090023450007770024352014510102065300130247165300150248465300180249965300290251765300210254670000150256770000240258270000170260670000190262370000180264277301360266010607642020-02-05       2020    bl uuuu     u00u1 u    #d  a1424-82207 a10.3390/s200205092DOI1 aDE SOUZA, R.  aEffect of cultivar on chlorophyll meter and canopy reflectance measurements in cucumber.h[electronic resource]  c2020  aArticle history: Received: 29 November 2019 / Revised: 13 January 2020 / Accepted: 14 January 2020 / Published: 16 January 2020. This article belongs to the Special Issue Proximal Sensing for Nitrogen Management: https://www.mdpi.com/journal/sensors/special_issues/Proximal_Nitrogen Funding information: Funding: This research was funded by Spanish Ministry of Economy and Competitiveness (Project AGL2015-67076-R). RdS was supported by a FPI grant (BES-2016-076706) and FMP by a Ramón y Cajal grant (RYC-2014-15815). Correspongin author: Romina de Souza (rominadesouzai@gmail.com); Rafael Grasso (rgrasso@inia.org.uy); M. Teresa Peña-Fleitas (mtpena.fl@ual.es); Marisa Gallardo (mgallard@ual.es); Rodney B. Thompson (rodney@ual.es); Francisco Padilla (f.padilla@ual.es)  aABSTRACT. Optical sensors can be used to assess crop N status to assist with N fertilizer management. Differences between cultivars may affect optical sensor measurement. Cultivar effects on measurements made with the SPAD-502 (Soil Plant Analysis Development) meter and the MC-100 (Chlorophyll Concentration Meter), and of several vegetation indices measured with the Crop Circle ACS470 canopy reflectance sensor, were assessed. A cucumber (Cucumis sativus L.) crop was grown in a greenhouse, with three cultivars. Each cultivar received three N treatments, of increasing N concentration, being deficient (N1), sufficient (N2) and excessive (N3). There were significant differences between cultivars in the measurements made with both chlorophyll meters, particularly when N supply was sufficient and excessive (N2 and N3 treatments, respectively). There were no consistent differences between cultivars in vegetation indices. Optical sensor measurements were strongly linearly related to leaf N content in each of the three cultivars. The lack of a consistent effect of cultivar on the relationship with leaf N content suggests that a unique equation to estimate leaf N content from vegetation indices can be applied to all three cultivars. Results of chlorophyll meter measurements suggest that care should be taken when using sufficiency values, determined for a particular cultivar. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.  aGenotype  aGreenhouse  aLeaf nitrogen  aProximal optical sensors  aVegetation index1 aGRASSO, R.1 aPEÑA-FLEITAS, M.T.1 aGALLARDO, M.1 aTHOMPSON, R.B.1 aPADILLA, F.M.  tSensors (Switzerland), 2 January 2020, Volume 20, Issue 2, Article number 509. OPEN ACCESS. Doi:  https://doi.org/10.3390/s20020509