Vol 73, No 1 (2018)

The paper describes approaches assessing the diversity of soils in Russia, as well as algorithms for quantitatively assessing the differentiation of soil bodies and covers. To assess soil diversity (or the degree of differentiation of parent rock materials into soil bodies and soil covers), two indices have been introduced: the vertical differentiation index (Ird) and the spatial lateral differentiation index (Ild (red)). These indices were computed based on the soil cover structure shown on the Soil Map of the Russian Federation on a scale of 1: 2.5 M within the spatial framework of the Map of Soil-Ecological Zoning of the Russian Federation on a scale of 1: 2.5 M. Based on the data obtained, the most complex soil covers and soil profiles on plains were identified at the boundary of the Boreal and Subboreal geographical belts in the zones of soddy-podzolic soils (umbric albeluvisols/umbric podzols) of the southern taiga and gray forest soils (albic luvisols/luvic greyic phaeozems) of deciduous forests characterized by widespread occurrence of dynamically mature soils, as well as in mountainous soil provinces of the Altai and Caucasus.

The features of cesium-137 (¹³⁷Cs) root uptake by spring oat (Avena sativa L.) and lettuce (Lactuca sativa L.) plants have been studied in a model experiment with simulation of radionuclide fallout into undisturbed monoliths of arable chernozems from the Plavsk radioactive spot. An integrated approach using digital autoradiography and γ-spectrometry methods has revealed a uniform pattern of vertical and lateral ¹³⁷Cs distribution in the soil profile and low bioavailability of the radionuclide or root uptake by plants. Certain biological features of the test crops with respect to root uptake of ¹³⁷Cs have been demonstrated: limited translocation of the element into shoots via its relative accumulation in roots for oats and limitation of general root uptake of ¹³⁷Cs into plants, given its uniform distribution between roots and shoots for lettuce.

The effect of amorphous silicon dioxide (SiO₂) on cadmium behavior in the soil–plant system was studied in a field experiment on a flooded paddy soil slightly contaminated by cadmium. The application of amorphous SiO₂ results in a 1.3- to 1.8-fold smaller cadmium accumulation in the aboveground organs of rice and a 1.8- to 2.6-fold decrease in the content of its available compounds, which can be explained by metal sorption on the surface of applied silicon dioxide and by the reaction of monosilicic acid, which forms in the SiO₂ solution, with cadmium. The decrease in cadmium availability is most intensive in the first 2 weeks after SiO₂ application. Amorphous silicon causes a 26.6% increase in rice productivity in the first season and 72.9% in the second. The data obtained testify to the fact that the application rates of traditional mineral fertilizers can be decreased without risk to rice productivity if silicon compounds are used. They should become an integral and important part of implementing the 4R-STRATEGY for fertilizer application and plant nutrition optimization.