PREDICTION OF NITROGEN FERTILIZATION FOR ‘KYOHO’ GRAPEVINE USING SIMPLIFIED NITRATE COLORING INDICATOR

With high N absorption from soil and rapid translocation of N to shoots and fruit, ‘Kyoho’ grapevines (Vitis labruscana) are apt to grow vigorously and to fail floral bud differentiation as well as have poor berry set.
A nitrate coloring indicator (NCI) comprised of 14g sulfanilic acid, 2g – naphthylamine, 10g MnSO₄ • H₂O, 100g BaSO₄, 7.5g citric acid and deionized water (mixed reagents 1 : water 5, w/v) was prepared by absorption of the reagent solution on to Toyo filter paper #6, and then freeze-dried.
The NCI was available to test the nitrate levels of leaf petioles and vineyard soil extracts.
The NCI was sensitive over the 1 to 250ppm nitrate-N range in concentration within 1 to 2 minutes after reaction.
A leaf petiole extract diluted with 10 times the volume of deionized water had optimal nitrate-N at 50 to 70ppm (500 to 700ppm as actual concentration) and changed the NCI paper from white to pink color : Nitrate deficiency resulted in a colorless response as less than 5ppm, while a dark red color indicated excessive nitrate such as more than 200ppm (2,000ppm as actual concentration) in petioles.
In a test of a soil extract diluted with 5 times the volume of deionized water, optimal nitrate-N ranges occured at pale pink color which indicated 10 to 20ppm of nitrate (50 to 100ppm as actual concentration). It was possible to predict how much N fertilizers should be supplied to vineyard by using this test at full bloom.

III International Symposium on Mineral Nutrition of Deciduous Fruit Trees

W.S. Kim

Vitis labruscana, nutrition, diagnosis, nitrogen, color chart

https://doi.org/10.17660/ActaHortic.1997.448.59