Influence of nitrogen forms and ph in the correction of iron deficiency in sunflower

Abstract

The objective was to evaluate the effect of using a nutrient solution with acid, ammonium nitrate and foliar application of acid solution in sunflower plants with iron deficiency. The experiment was performed with the culture of sunflower (Sungro 393) in slow growth of the Laboratory of Plant Nutrition, University of Cordoba, Spain. Initially the plants were cultivated for 11 days in pots containing 0.5 L of nutrient solution (40 mM Fe). Then the plants were subjected to stress, renewing with the same nutrient solution, decreasing the concentration of 5 mM Fe and adding 15 mM NaHCO₃ and CaCO₃ 0.5 g L^-1. In plants with iron deficiency, was submitted to five treatments, consisting of (a) control without Fe, maintaining the same nutrient solution before (b) nitrate nutrient solution with 2 mM Ca (NO₃)₂, (c) nutrient solution with ammonium 2 mM (NH₄)₂SO₄ (d) nutrient solution with dilute HCl, pH 3.5 (e) spraying the leaves with 0.5 mM H₂SO₄ and with five replications. We conducted assessment of indirect measurement of chlorophyll and the measured pH value of the nutrient solution, from 0, 2, 5 and 7 days after treatment application and at last assessment was conducted on the foliar analysis by determining the Fe and total plant dry matter. The use of ammonium nutrient solution decreased the pH of nutrient solution and increased the leaf content of iron and the SPAD value of leaves, eliminating the visual symptoms of iron deficiency in sunflower. The use of ammonium in nutrient solution for seven days, was more effective in correcting iron deficiency in sunflower plants, compared with nitrate and with dilute acid at pH 3.5 and acidic leaf.