Pre-sidedress Soil Nitrate Test Is Effective for Fall Cabbage

in HortScience
Authors:
Joseph R. HeckmanPlant Science Department, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520

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Thomas MorrisDepartment of Plant Science, P.O. Box U-4067, University of Connecticut, Storrs, CT 06269

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J. Thomas SimsDepartment of Plant and Soil Science, University of Delaware, Newark, DE 19717

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Joseph B. SieczkaLong Island Horticultural Research Laboratory, Cornell University, 3059 Sound Avenue, Riverhead, NY 11901

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Uta KrogmannEnvironmental Sciences Department, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901-8551

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Peter NitzscheRutgers Cooperative Extension of Morris County, P.O. Box 900 Court House, Morristown, NJ 07963-0900

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Richard AshleyDepartment of Plant Science, P.O. Box U-4067, University of Connecticut, Storrs, CT 06269

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The pre-sidedress soil nitrate test (PSNT) was evaluated in 27 fields in New Jersey, 6 in Connecticut, 5 in Delaware, and 2 on Long Island in New York for its ability to predict whether sidedress N is needed to grow fall cabbage (Brassica oleracea var. capitata) as a double crop. Soil NO3-N concentrations measured on 20 field sites on the day of transplanting and 14 days after transplanting indicated that NO3-N concentrations over this time period increased, and that residues from the previous crop were not causing immobilization of soil mineral N. The relationship between soil NO3-N concentration measured 14 days after transplanting and relative yield of marketable cabbage heads was examined using Cate-Nelson analysis to define the PSNT critical level. Soil NO3-N concentrations ≥24 mg·kg-1 were associated with relative yields >92%. The success rate for the PSNT critical concentration was 84% for predicting whether sidedress N was needed. Soil NO3-N concentrations below the PSNT critical level are useful for inversely adjusting sidedress N fertilizer recommendations. The PSNT can reliably determine whether fall cabbage needs sidedress N fertilizer and the practice of soil NO3-N testing may be extendable to other cole crops with similar N requirements.

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