Table 2. Leaf petiole fresh sap nitrate-nitrogen and potassium testing guidelines for tomato[1].

.
Fresh Petiole Sap Concentration (ppm)
Development Stage/Time
NO3-N
K
First buds
1000-1200
3500-4000
First open flowers
600-800
3500-4000
Fruits 1-inch diameter
400-600
3000-3500
Fruits 2-inch diameter
400-600
3000-3500
First harvest
300-400
2500-3000
Second harvest
200-400
2000-2500

[1] Adapted from G. Hochmuth, Plant Petiole Sap-testing Guide for Vegetable Crops, Fla. Coop. Ext. Serv. Circ. 1144 (1994).

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