Bayesian approach in agrochemical surveys

In the scheme of agrochemical surveys, sampling is one of the most costly stages. The use of a priori information about the distributions of properties (Bayesian approach) allows one to reduce the number of samples to be taken by 5–10% without deteriorating the accuracy of the estimation. The maintenance of regional soil-mapping databases is a necessary condition for applying the Bayesian approach.     

Peculiarities of detritus profile morphogenesis in insufficiently studied ecosystems of the Okhotsk Sea region

Grouping of detritus profiles based on detailed analysis of the structures of more than 500 sections and using statistical methods was conducted for the first time. A new name, “detritus profile,” which allows one to consider litter itself, as well as peaty and peat formations in the same coordinate system, was suggested. The wide diversity of the detritus profile structure is explained by the specific character of their development in conditions of frost and mountain relief. It was established that humus and humic horizons are invariant and do not correlate with other subhorizons due to their greater age as compared with upper horizons, thus detecting their independence. Interrelation of detritus profile types with forest types and peculiarities of transformation of organic substances was demonstrated.     

Spatial distribution of clay minerals in agrochernozems of erosional and denudational plains in the Stavropol region

The distribution pattern of the fine fractions (<1.0 and 1?C5 ??m) and the mineralogical composition of the agrochernozems formed on the erosional-denudational plains of the Stavropol region have been studied. Erosion and denudation caused the redistribution of the fine material within the catena with its maximal accumulation on the lowermost part of the slope. The same processes favored the formation of surface deposits slightly differing in the composition of the principal mineral phases, i.e., complex disordered mixedlayered micas-smectites with varying combinations of micaceous and smectite layers in crystallites and di- and trioctahedral hydromicas. Imperfect kaolinite and magnesium-ferric chlorite are accompanying minerals. An increase in the amount of mixed-layered minerals with smectite layer is observed down the profile. In addition to the mentioned minerals, the individual smectite and clinoptilolite, which are components of Tertiary deposits, are identified in the lower parts of the agrochernozem profiles. The fine-silt fractions consist of (in decreasing order) di- and tri-octahedral micas, quartz, feldspars, plagioclase, and an admixture of phyllosilicates (kaolinite, chlorite, and mixed-layered chlorite-smectites). The maximal amount of the fine fraction, as well as the maximal amount of mica in it, is registered in the soils in the lower part of the slope. The phyllosilicates are decomposed in this fraction in the upper horizons. The seven-year-long application of mineral fertilizers intensified the peptization of the soil mass in the arable horizons, which increased the content of clay particles in them. A more contrasting distribution of the mixed-layered formations in the profiles, a considerable decrease in their reflection intensities, an increase in the structural disorder of the minerals, and a certain increase in the content of the fine-dispersed quartz are observed.     

Pedodiversity on Soil Maps at the District Level

Eurasian Soil Science - The analysis of soil maps for three districts of Bryansk oblast demonstrates that the rank distributions of polygon areas for low soil taxonomic units on these maps have a...     

Spatial variability in the distribution of particle-size fractions in agrogray soils and agrogray soils with the second humus horizon

The degree of spatial variability in the distribution of particle-size fractions has been determined for agrogray soils of an experimental field of Bryansk Agricultural Academy. The degree of spatial variability is close to the analytical error; for comparing different plots, particle-size distribution analysis has to be performed in two-three replicates. If the particular sets of data (e.g., data sets on the content of clay in the upper and lower parts of the plow horizon) are used, the statistical probability of differences increases. Cluster analysis can be used for the initial grouping of particle-size distribution data.     

Electrical resistivity of arable gray forest soils

The electrical resistivity of gray forest soils and gray forest soils with a second humus horizon was studied in the Bryansk Opol’e region. The dependence of electrical resistivity on the soil’s organic content, moisture, and bulk density was found. It was concluded that the supply of organic matter in the upper layer (50 cm) can be estimated in wet conditions using the equation C_supply = 2.7ER + 34.3 (t/ha).     

Minerals in the three-component combination of agrochernozems in the Kamennaya Steppe

Properties and mineralogy of fine fractions separated from agrochernozems forming a three-component noncontrasting soil combination in the Kamennaya Steppe have been characterized. The soil cover consists of zooturbated (Haplic Chernozems (Clayic, Aric, Pachic, Calcaric)), migrational-mycelial (Haplic Chernozems (Clayic, Aric, Pachic)), and clay-illuvial (Luvic Chernozems (Clayic, Aric, Pachic)) agrochernozems. All the soils are deeply quasi-gleyed because of periodical groundwater rise. The mineralogy of the fraction <1μm includes irregular mica–smectite interstratifications, di- and trioctahedral hydromicas, imperfect kaolinite, and magnesium–iron chlorite. The profile distribution of these minerals slightly varies depending on the subtype of spot-forming soils. A uniform distribution of clay minerals is observed in zooturbated agrochernozem; a poorly manifested eluvial–illuvial distribution of the smectite phase is observed in the clay-illuvial agrochernozem. The fractions of fine (1–5 μm) and medium (5–10 μm) silt consist of quartz, micas, potassium feldspars, plagioclases, kaolinite, and chlorite. There is no dominant mineral, because the share of each mineral is lower than 35–45%. The silt fractions differ in the quartz-to-mica ratio. The medium silt fraction contains more quartz, and the fine silt fraction contains more micas.     

Dynamics of bulk composition of gray forest soil under agricultural treatment

It is shown that the bulk composition of the plow layer of gray forest easy-loamy soil in forests under agricultural treatment is enriched with phosphorus, calcium, and molybdenum. For these elements, no differences are found between different types of treatment. The trends for zinc and copper have opposite results under different types of treatment.     

Quantitative method for comparing soil maps and cartograms

This paper describes how the overall accuracy coefficient and kappa index are used to estimate the similarity of soil maps. Comparison of two detailed maps built by two independent groups of researchers has shown their coinciding by only 60%. The causes of this noncoincidence are discussed.     

Assessing the role of the relief in the spatial variability of agriculturally important soil properties for intensively cultivated agricultural land

An intensively cultivated field of 0.4 ha (sod-podzolic soils) shows considerable variability of agriculturally important soil properties, the rank and direction of the highest variation of which occurred to be close. Therefore, the factor that determines the variation is anthropogenic. The influence of the morphometric characteristics of the relief on the variability of soil properties was described by the multiple linear regression equation. The strongest impact of the relief falls on the thickness of the surface horizon (up to 40%); for pH and the mobile phosphorus content this figure is only 10–15% and decreases with depth, while for mobile potassium it increases with depth.