Evaluation of the Dualex for the Assessment of Corn Nitrogen Status

ABSTRACT

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.

Keywords:

• SPAD
• Dualex
• nitrogen status
• sensitivity
• comparison

ACKNOWLEDGMENTS

The authors would like to thank Elisabeth Fortier, Edith Fallon, Noura Ziadi, Stéphanie Jacquet, Marcel Tétreault, Landry and Associate's Farm, the summer student crew and the L'Acadie Experimental farm. This work was supported by the GAPS program of Agriculture and Agri-Food Canada.

Notes

^a Results are from experiment at St-Valentin. Applied N dose are 0 kg N ha^{− 1} applied during the crop growth cycle, 30 kg N ha^{− 1} at sowing + 0 kg N ha^{− 1} for topdressing, 30 kg N ha^{− 1} at sowing + 52.5 kg N ha^{− 1} for topdressing, 30 kg N ha^{− 1} at sowing + 105 kg N ha^{− 1} for topdressing and 30 kg N ha^{− 1} at sowing + 157.5 kg N ha^{− 1} for topdressing, respectively. Topdressing was made on 42 DAS.

^b The number in the parenthesis is the days before (−) or after (+) topdressing.

∗ and

∗∗ indicate significance at 5% and 1% levels, respectively.

^a Results are from experiment at L'Acadie. Topdressing was made on 47 DAS.

^b Data is the mean of four replications.

^a Results are from experiment at St-Valentin. Applied N dose 0, 30, 82.5, 135 and 187.5 are no N applied during the crop growth cycle, 30 kg N ha^{− 1} at sowing + 0 kg N ha^{− 1} for topdressing, 30 kg N ha^{− 1} at sowing + 52.5 kg N ha^{− 1} for topdressing, 30 kg N ha^{− 1} at sowing + 105 kg N ha^{− 1} for topdressing and 30 kg N ha^{− 1} at sowing + 157.5 kg N ha^{− 1} for topdressing, respectively. Topdressing was made on 42 DAS.

^b The number with “+” in the parenthesis is the number of days after topdressing.

^c Data is the mean of all four replications.