Evaluation of the dualex for the assessment of corn nitrogen status

The Dualex is a new leaf-clip instrument that can be used to monitor corn nitrogen (N) status. It is based on the measurement of polyphenolics (Phen), which are secondary metabolites affected by stress factors. The purpose of this study was to compare Dualex to SPAD (chlorophyll meter), the latter having been used for several years in monitoring crop N status. As well, the interest of combining Dualex and SPAD information in Chl/DUAD (ratio of SPAD to Dualex reading on adaxial side), Chl/DUAB (ratio of SPAD to Dualex reading on abaxial side), and Chl/Phen (ratio of SPAD to the sum of DUAD and DUAB) ratios were considered. Significantly positive and negative correlations with corn leaf N concentration were found for SPAD and Dualex, respectively. Successful N status diagnosis could be achieved with either Dualex or SPAD for corn within 21 days after topdressing while the Dualex lost sensitivity at later stages. Dualex measurements could be limited to leaves abaxial side or adaxial side, instead of adaxial + abaxial sides, with no inconvenience. Among all parameters considered, the combined ratios with SPAD (Chl) and Dualex readings, Chl/DUAD, Chl/DUAB, and Chl/Phen were strongly related to applied N dose at all samplings dates, and found the most sensitive and robust through the season. Copyright © Taylor & Francis Group, LLC.