Effect of Varying Levels of Nitrogen and Potash on Petiole Nutrient Contents in Thompson Seedless Grape (Vitis Vinifera L.)

Variation in the bloom-time contents of N0₃-N, total N, P, Ca, Mg, Fe, Cu, Mn and Zn in the petioles of four and five year old Thompson Seedless vines receiving 16 combinations resulting from four levels each of N (300, 600, 900 and 1200 kg/ha/year) and K₂0 (0, 500, 1000 and 1500 kg/ha/year) was studied in order to find out the enchancing or depressing effect of applied N and K_aO on other nutrients and and provide a basis for determining the nutrient needs based on petiole analysis. Higher of N application enhanced the Ca, Mg and Mn status of the vines, but reduced the concentration of NO₃-N, total N, P and K in the petioles. Higher levels of applied potash were associated with increased contents of NO₃-N, K and Cu, but with reduced contents of Mg and Fe. A complementary effect of the levels of N and K2O was observed on the petiole Fe contents. Irrespective of the levels of N and K₂0, mutual antagonism was observed between. Antagonistic/synergistic effects are explained through the preferential accumulation of nutrients of the petioles, dilution effect on account of increased growth due to higher levels of nitrogen, isomorphic ionic substitution and neutralisation of charges and base equilibrium constancy in the foliar tissues.