LOG IN
plant chlorophyll meter, leaf sensor
Conversion of atLEAF CHL units

atLEAF CHL to SPAD units/Total chl



atLEAF CHL value: SPAD units: Total chl:
mg/cm2



The conversion to SPAD units is performed according to the calculations of Zhu, Tremblay, and Liang (9). The total chlorophyll content of leaves is obtained by converting the atLEAF CHL values in SPAD and considering the relationship among chlorophyll content and SPAD units given by the following referenced authors (1)...(10).



(1) Richardson A.D., Duigan S.P., and Berlyn G.P., 2002. An evaluation of noninvasive methods to estimate foliar chlorophyll content. New Phytol. 153
(2) Pinkard E.A., Patel V., and Mohammed C., 2006. Chlorophyll and nitrogen determination for plantation-grown Eucalyptus nitens and E. globulus using a non-destructive meter. For. Ecol.Manage. 223
(3) Schaper H. and Chacko E.K., 1991. Relation between extractable chlorophyll and portable chlorophyll meter readings in leaves of eight tropical and subtropical fruit tree species. J. Plant Physiol. 138
(4) Monje O.A. and Bugbee B., 1992. Inherent limitations of nondestructive chlorophyll meters - a comparison of 2 types of meters. Hortscience 27
(5) Uddling J., Gelang-Alfredsson J., Piikki K., and Pleijel H., 2007. Evaluating the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings. Photosynth. Res. 91
(6) Murillo-Amador B., Avila-Serrano N.Y., Garcia-Hernandez J.L., Lopez-Aguilar R., Troyo-Dieguez E., and Kaya C., 2004. Relationship between a nondestructive and an extraction method for measuring chlorophyll contents in cowpea leaves. J. Plant Nutr. Soil Sc. 167
(7) Coste S., Baraloto C., Leroy C., Marcon É., Renaud A., Richardson A.D., Roggy J.C., Schimann H., Uddling J., Hérault B. 2010 Assessing foliar chlorophyll contents with the SPAD-502 chlorophyll meter: a calibration test with thirteen tree species of tropical rainforest in French Guiana. Ann. For. Sci. 67
(8) Ruiz-Espinoza F.H., Murillo-Amador B., García-Hernández J.L., Fenech-Larios L.; Rueda-Puente E.O.; Troyo-Diéguez E., Kaya C., Beltrán-Morales A. 2010 Field evaluation of the relationship between Chlorophyll content in basil leaves and a portable Chlorophyll meter (spad-502) readings Journal of Plant Nutrition x
(9) Zhu J., Tremblay T., and Liang Y. 2012 Comparing SPAD and atLEAF values for chlorophyll assessment in crop species Can. J. Soil Sci. 92
(10) Richardson A.D. , Duigan S.P. and Berlyn G. P. 2002 An evaluation of noninvasive methods to estimate foliar chlorophyll content New Phytologist 153


atLEAF CHL units to wheat N fertilizer/Protein

atLEAF CHL value: N fertilizer (lb/acre) : N fertilizer (kg/ha) :

Protein concentrat. % :

Wheat N fertilizer to atLEAF units

N fertilizer (lb/acre) : atLEAF CHL value:

N fertilizer (kg/ha) : atLEAF CHL value:


Wheat Protein concentration (%) to atLEAF units

Protein Concentration(%) : atLEAF CHL value:



The conversions are obtained following:

  • 2013-2014 Research Report to the California Wheat Commission
    Calibrating In-field Diagnostic Tools to Improve Nitrogen Management for High Yield and High Protein Wheat in the Sacramento Valley
    PI: Mark Lundy, UC Cooperative Extension Agronomy Advisor

    • see also:

  • Presentation: In-field plant monitoring as a tool for N management in small grains
  • Proceedings: In-field plant monitoring as a tool for N management in small grains
  • Managing N fertilizer to optimize protein and yield in California wheat



    • atLEAF CHL units to corn N fertilizer


    High-Nitrogen Reference Value Chlorophyll Meter Test Method


    Average field atLEAF CHL value:
    High-N reference atLEAF CHL value:
    Nitrogen Recommendation  lbs N/A

    Alternative Two-Step Chlorophyll Meter Test Method (No High-N Reference Area)

    Interpretation of chlorophyll meter readings in fields with a recent history of manure or a forage legume without a high-N reference plot




    Average field atLEAF CHL value:
    Nitrogen Recommendation

    The formulas are taken from Penn State extension, Agronomy Facts 53, The Early Season Chlorophyll Meter Test for Corn. Recommendation is obtained by converting the atLEAF CHL to SPAD units for corn as per Zhu, Tremblay, and Liang (9).



    atLEAF CHL value and in-season N application rate

    Take the average atLEAF CHL reading of the corn in the area of interest and the average atLEAF CHL reading of the reference strip closest to that area.


    Average field atLEAF CHL value:
    Average reference strip atLEAF CHL value:
    Nitrogen Recommendation

    The formulas are taken from Iowa State University, University extension, In-Season Sensing for Nitrogen Stress in Corn. Recommendation is obtained by converting the atLEAF CHL to SPAD units for corn as per Zhu, Tremblay, and Liang (9).


    We cannot guarantee the validity of conversions provided or be held responsible for any errors that have been made.