Establishment of Critical Sap and Soil Nitrate Concentrations using a Cardy Nitrate Meter for Two Carrot Cultivars Grown on Organic and Mineral Soil
2007
Westerveld, S.M. | McDonald, M.R. | McKeown, A.W.
Nitrate (NO₃⁻) meters have been used effectively for crop nitrogen (N) management in many crops, including corn and cabbage. The use of a Cardy NO₃⁻ meter to assess the N status of the carrot crop could improve the utilization of applied N, but critical NO₃-N concentrations are required. Two carrot cultivars were grown on mineral and organic soils over 3 years at five N application rates to establish critical sap and soil NO₃-N concentrations and to identify the effects of soil type and cultivar. Although a yield response to N application occurred on mineral soil in 2 of 3 years, consistent critical sap NO₃-N concentrations could not be established because of variability among years, cultivars, and soil types. Critical soil nitrate concentrations were highly variable, but values of 31 to 36 mg · L⁻¹ NO₃-N could be established for the early sampling date to 30 cm deep. Sap NO₃-N concentrations cannot be used alone for N analysis of carrots, but early-season soil NO₃-N assessment could be useful in adjusting N-fertilization practices.
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