Chemical characterization of FYM-alkali extract and its efficacy evaluation as Zn-humate
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Date
2004-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The humic and fulvic acid fractions of humic substance extracted from well decomposed FYM were characterized after isolation, purification and lyopholyzation for oxygen containing functional groups and degree of humification (E4/E6). Potentiometric titrations were carried out with different organo metallic (Fe3+, Mn2+, Cu2+, Zn2+) complexes. The efficacy of Zn-organo complexes to supply Zinc was evaluated in a greenhouse experiment with maize crop.
Fulvic acid contained more oxygen but less nitrogen and carbon than humic acid. Higher amount of oxygen containing functional group (COOH) resulted in more acidity (8.7 me/g) and exchange capacity of fulvic acid as compared to humic acid (6.1 me/g). Lower E4/E6 ratio of humic acid (7.19) than fulvic acid (9.67) indicated the more aromatic and condensed nature of humic acid. The potentiometric titration curves of different metal organo complexes followed the same order for both humic and fulvic acids. The drop in pH followed the order Fe3+>Cu2+>Zn2+>Mn2+ which indicated the order of their affinity in complex formation and stability index.
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. Dry matter production was increased with increasing Zn levels. The highest dry matter was produced when critical Zn concentration in plant reached 39 ppm which was reached at the level 10 mg Zn as ZnSO4, 5 mg Zn as Zn-humate, 2.5 mg Zn as Zn-humate-falvate and 1 mg Zn as Zn-falvate per kg soil.