Role of post-harvest residue in developing thermal properties of humic acids in the soils of different types
2009
Debska, B., University of Technology and Life Sciences, Bydgoszcz (Poland) | Drąg, M., University of Technology and Life Sciences, Bydgoszcz (Poland) | Tobiašova, E., Slovak Univ. of Agriculture in Nitra (Slovak Republic)
The aim of the present paper was to determine parameters of thermal decomposition of humic acids of the soils of different types with no additives and when mixed with post-harvest residue before and after 360 days of incubation. The research was based on a model incubation experiment carried out at the Dept. of Pedology and Geology of the Slovak Agricultural University in Nitra. Plant residue (mixtures of aerial parts and roots) of corn (K), oilseed rape (Rz), sunflower (SI), potato (Zm) and rye (Z) were mixed in the ratio 10:1 with the following soil samples: Haplic Luvisol (Lo), Chernozem (Hh), Haplic Arenosol (Re) and Haplic Gleysol (Ge) and the mixtures were incubated at 25 deg C and 60% of field water capacity. The plant-soil mixtures were analyzed prior the experiment and after 360 days of incubation. Humic acids were separated from the control soil (without plant residue), and plant-soil mixtures before and after incubation with the standard Schnitzer method. Thermal properties were determined with the use of the Derivatograph C (MOM, Hungary). Samples of 40 mg humic acids were mixed with Al2O3 (1:9) and heated in the air at the rate of 3.3 deg C per min. The results of thermal analysis showed that parameters of thermal decomposition of humic acids were determined both by the soil type and by the properties of post-harvest residue introduced into soil. The process of decomposition of post-harvest residue was connected with, e.g. a decreased value of the parameter corresponding to the burning heat of humic acids. Low values of parameter Z were due to the presence of non-decomposed lignin and cellulose structures in the molecules of humic acids.
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