Efficacy evaluation of different Zinc-organo complexes in supplying Zinc to Maize (Zea mays L.) plant

The humic and fulvic acid fractions of humic substances were extracted from well decomposed FYM and there after isolated, purified, lyophilized and complexed with zinc. The efficacy of Zn-organo complexes in supplying zinc was evaluated in a glasshouse experiment with maize as the test crop. Zinc concentration in plant increased with increasing Zn level and the highest Zn concentration was observed when Zn was applied as Zn-fulvate at the level of 10 mg Zn kg−1 soil. Dry matter production was increased with increasing Zn level until the attainment of critical zinc concentration of the plant. The highest dry matter was produced when critical Zn concentration in plant reached ≍ 39 mg kg−1 which was attained by the application of 10.0 mg Zn as ZnSO4, 5.0 mg Zn as Zn-humate, 2.5 mg Zn as Zn-humate-fulvate and 1.0 mg Zn as Zn-fulvate kg−1 soil. Irrespective of zinc sources, zinc recovery was as follows: 0.25 mg Zn kg−1 > 0.5 mg Zn kg−1 > 1.0 mg Zn kg−1 > 2.5 mg Zn kg−1 > 5.0 mg Zn kg−1 >10.0 mg Zn kg−1 soil and irrespective of levels, the average zinc recovery by plant from different sources was as follows: Zn-FA> Zn-HA-FA > Zn-HA > ZnSO4. Thus, zinc-fulvate was found as the most efficient in respect of supplying zinc, increasing plant height and total dry matter production followed by zinc-humate-fulvate, zinc-humate and ZnSO4.