The influence of diatomite rock on humus substances of sod-podsolic soil in conditions of agro ecosystems and physical-chemical mechanism of their interaction

The paper provides an assessment of physical and chemical changes of humus substances in the sludge-colloidal fraction, isolated from the sod-podsolic sandy loamy soil, during its interaction with the diatomite rock of the Inzen deposit in conditions of agro ecosystem of the Nizhny Novgorod Region. The experience was a 3-year (2015-2017) microfield experiment, laid down on one of the fields of «Elitkhoz». The diatomite was added to soil once during the summer season of 2014 in doses of 3, 6 and 12 t/ha, on which winter wheat, barley and peas were subsequently grown (varieties are zoned in the Volga-Viatskiy Region). Each year, upon completion of crop cultivation, a silo-colloidal fraction was isolated from selected soil samples by the Kachinsky gravimetric method and analyzed on an IR-Fourier-spectrometer, determining absorption spectra in frequency range of 4000-400 cm-¹. In soil samples the content of specific organic substance (humus) was also determined by the Thurin method with spectrophotometric termination. The studies revealed that interaction of diatomite with the organic soil matrix resulted in organosilanes RnSiH4-n (930 cm-¹), organosilanes oxygen-free Si-CH3 (1253 cm-¹) and oxygen-containing compounds Si-O-CH3 (1110 cm-¹), as well as siloxane bonds of Si-O-Si (570 cm-¹). The obtained facts directly indicate formation of silicon-containing organo-mineral complexes in sludge-colloidal fraction and participation of silicon in their formation. It is evident that an active diatomite represented by various silicon acids (HnSiOm) was involved in formation of these bonds. The use of diatomite has helped to maintain content of humus substances in soil at the control level, which can also confirm effects of interaction of silicon substances with organic part and, as a result, prevent its degradation. Based on the obtained results and analysis of scientific literature, a mechanism is proposed for possible physical-chemical interaction of active silicon substances with an organic component of the sludge-colloidal fraction of the sod-podsolic soil, which consists in polymerization of silicon on organo-mineral complexes (bonds -Si-O-Si-), as well as in interaction of the hydrolyzed part of humus substances with silicon with subsequent formation of organosilanes, which are subsequently connected with an organic Si-O-CH3 matrix. Due to the fact that organic matter of soils is involved in the formation of ecological stability of soil cover the established effects make it possible to speak about the increase of agro ecological stability of humus substances in sod-podsolic soil due to the use of diatomite rocks.