A rapid nitrate sap test for outdoor tomatoes

Trials were conducted with tomatoes over 2 years to evaluate nitrate sap testing and determine desirable sap nitrate values. In addition, desirable values for acetic acid extractable nitrate-N (HOAc-NO₃-N) and total N were determined. There were strong linear correlations between applied N and sap nitrate-N, HOAc-NO₃-N, and to a lesser extent with total N. The desirable sap nitrate value at 6 weeks from transplanting was 880–1180 mg 1^?1 in the first year and 980–1120 mg l^?1 in the second year. The sap nitrate desirable values were generally lower later in the crop growth. The desirable values found in this study for HOAc-NO₃-N and total N were in good agreement with other published data.