Establishment of Critical Sap and Soil Nitrate Concentrations using a Cardy Nitrate Meter for Two Carrot Cultivars Grown on Organic and Mineral Soil

Abstract

Nitrate (NO 3 2 ) meters have been used effectively for crop nitrogen (N) management in many crops, including corn and cabbage. The use of a Cardy NO 3 2 meter to assess the N status of the carrot crop could improve the utilization of applied N, but critical NO 3 -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 NO 3 -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 NO 3 -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 21 NO 3 -N could be established for the early sampling date to 30 cm deep. Sap NO 3 -N concentrations cannot be used alone for N analysis of carrots, but early-season soil NO 3 -N assessment could be useful in adjusting N-fertilization practices.

Timing Nitrogen Applications for Quality Tops and Healthy Root Production in Carrot

“…Only the study at the experiment station in 2001 showed high correlation at late season. Westerveld et al (2003aWesterveld et al ( , 2004, and Westerveld, McDonald, and McKeown (2007b) found that the strongest correlation between tissue samples and petiole sap NO 3 − -N was during early and midseason and it diminished by late season. Just prior to harvest, at the experiment station, total N and sap NO 3 − -N in petioles generally indicated that N uptake and storage in tops responded to N treatments.…”

Topdress strategies and remote sensing for nitrogen management in processing carrots

“…A robust correlation may not be necessary for effective topdress decision support if the minimum action thresholds for petiole nitrate are accurate. However, variation in petiole nitrate values observed across different soils, varieties, and management practices contributes to uncertainty about the suitability of available thresholds without region and variety‐specific calibrations (Westerveld, McDonald, et al., 2003; Westerveld et al., 2007).…”

“…Petiole nitrate values sampled throughout the season are compared to thresholds, prompting topdress N applications when sampled values fall below the threshold (Warncke, 1997). However, due to differences in weather conditions and carrot varieties, the accuracy and generalization of critical threshold values have been questioned, with labor constraints often resulting in relatively small sample sizes within large fields (Selk et al., 2004; Westerveld, McKeown, Scott‐Dupree, et al., 2003; Westerveld et al., 2007). Improving the spatial resolution and completeness of the data as well as reducing the labor required for sampling may improve in‐season N topdressing decisions.…”

Evaluation of a Rapid Field Test Method for Assessing Nitrogen Status in Potato Plant Tissue in Rural Communities in the Bolivian Andean Highlands

“…Conventional nitrate ion selective electrodes are subject to interference by various anions, particularly chlorine (Cl), bicarbonate (HCO 3 ), and nitrogen dioxide (NO 2 ) (Myers and Paul 1968;Onken and Sunderman 1970). Although the Cardy meter may be considered easy to operate and maintain and is an important tool to routinely assess the crop N status during varied stages of plant growth (Westerveld, McDonald, and McKeown 2007), some important factors should be considered with Downloaded by [Oregon State University] at 02:47 27 December 2014 respect to sap analysis. For instance, the plant water status may significantly influence the nitrate status in the same way as the presence or absence of clouds, time of sampling, and tissue portion to be sampled (Hartz et al 1993;Hochmuth 1994;Majić et al 2009).…”