Chlorophyll and nitrate meters as nitrogen monitoring tools for selected vegetables in Southern Ontario




Westerveld, S. M.
McKeown, A. W.
McDonald, M. R.
Scott-Dupree, C. D.

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International Society of Horticultural Science


With the introduction of nutrient management legislation in the province of Ontario there is a need to evaluate methods to improve the nitrogen (N) use efficiency of vegetable production. The effectiveness of the Horiba ‘Cardy’ Model C-141 nitrate (NO3) meter and Minolta SPAD-502 chlorophyll meter for determining N status were evaluated and compared to traditional laboratory N analysis in onions, carrots, and cabbage grown on both organic soil in the Holland/Bradford Marsh, Ontario and mineral soil near Simcoe, Ontario in 2000 and 2001. Nitrogen was applied at 0, 50, 100, 150, and 200% (cabbage and carrots) and 0, 100, and 200% (onions) of the rates recommended by the Ontario Ministry of Agriculture, Food, and Rural Affairs for each crop and soil type. At three times during the growing season, NO3-N levels in sap from recently mature plant material and in soil were assessed using a Cardy NO3 meter, chlorophyll readings were taken from mature leaves with the SPAD meter, and soil and tissue samples were collected and submitted for laboratory N and NO3-N analysis. Soil NO3-N readings from the Cardy NO3 meter were highly correlated with laboratory soil NO3-N results for all mineral soil plots in both years and on organic soil when suitable procedures were developed in 2001. Cardy sap NO3-N readings were correlated with laboratory NO3-N results in the majority of sampling dates for the three crops. SPAD chlorophyll meter readings correlated less with laboratory results, except for cabbage in 2001 when readings were highly correlated with laboratory results. The Cardy NO3 meter can be used to monitor the N status of onions, carrots, and cabbage. The SPAD chlorophyll meter could be suitable for cabbage N monitoring but had limited usefulness for N monitoring of onions and carrots under these conditions


Ontario Crops Research Centre - Bradford: Research Publications


Cabbage, Carrots, Onions, SPAD, Cardy, Nutrient management