The properties of humic (HA) and fulvic acids (FA) isolated from a 27-year-old long-term experiment with rice-wheat-cowpea on a Mollisol in northern India were evaluated for elemental composition and functional groups. As compared to fallow, C, H and N decreased, while O increased in the control, but the use of NPK+FYM over the years enhanced the C and N of humic substances. The carboxylic (-COOH) and phenolic-OH groups declined in the control, but improved with NPK+FYM in comparison to fallow. Carboxylic groups (-COOH) contributed about 2–3 times more in HA and 4–5 times more in FA than the respective phenolic-OH groups to the molecular weights of these fractions of soil organic matter. The results suggested the role of integrated nutrient management in maintaining active soil humus over the years.
Campbell, C. A., Zentner, R. P. (1993): Soil organic matter as influenced by crop rotations and fertilization.
Soil Sci. Soc. Am. J.
Zentner R. P. , 'Soil organic matter as influenced by crop rotations and fertilization' (1993) 57Soil Sci. Soc. Am. J.: 1034-1040.
Zentner R. P. Soil organic matter as influenced by crop rotations and fertilizationSoil Sci. Soc. Am. J.19935710341040)| false
Flaig, W., Beutelspacher, H., Reitz, E. (1975): Chemical composition and physical properties of humic substances. pp. 168–174. In: Giesking, J. E. (ed.),
Soil Components Vol. 1. Organic Components
. Springer-Verlag, New York.
Reitz E. , '', in Soil Components Vol. 1. Organic Components, (1975) -.
Reitz E. Soil Components Vol. 1. Organic Components1975)| false
Nand Ram (1995): Long-term effects of fertilizers on crop production and soil properties on a mollisol.
Tech. Res. Bull. 124
. Directorate of Experiment Station, G. B. Pant University of Agriculture and Technology, Pantnagar, India.