Biogenic Catalysis of Soil Formation on Mars?

The high iron abundance and the weak ferric iron spectral features of martian surface material are consistent with nanophase (nm-sized) iron oxide minerals as a major source of iron in the bright region soil on Mars. Nanophase iron oxide minerals, such as ferrihydrite and schwertmannite, and nanophase forms of hematite and goethite are formed by both biotic and abiotic processes on Earth. The presence of these minerals on Mars does not indicate biological activity on Mars, but it does raise the possibility. This work includes speculation regarding the possibility of biogenic soils on Mars based on previous observations and analyses. A remote sensing goal of upcoming missions should be to determine if nanophase iron oxide minerals, clay silicates and carbonates are present in the martian surface material. These minerals are important indicators for exobiology and their presence on Mars would invoke a need for further investigation and sample return from these sites.     

Co-Composting of Soil Heavily Contaminated with Creosote with Cattle Manure and Vegetable Waste for the Bioremediation of Creosote–Contaminated Soil

Mispah form (FAO: Lithosol) soil contaminated with >380 000 mg kg^?1 creosote was co-composted with cattle manure and mixed vegetable waste for 19 months. The soil was mixed with wood chips to improve aeration and then mixed with cattle manure or mixed vegetable waste in a ratio of 4:1. Moisture, temperature, pH, ash content, C:N ratios, and the concentrations of creosote in the compost systems were monitored monthly. The concentrations of selected hydrocarbons in the compost systems were determined at the end of composting. Temperature rose to about 45°C in the cattle manure compost within two months of incubation while temperature in the control and vegetable waste remained below 30°C until the fourth month. Creosote concentration was reduced by 17% in the control and by more than 99% in the cattle manure and vegetable waste compost after composting. The rate of reduction in concentration in the mixed vegetable waste compost was initially lower than in the cattle manure compost. The reduction rate became similar in later months with only small differences towards the end of the composting. The concentrations of selected creosote components were reduced by between 96% and 100% after composting. There was no significant difference in reduction in concentration in both compost systems at p 0.05. Microbial activity correlated with reduction in creosote concentration.     

Three-dimensional Microorganization of the Soil–Root–Microbe System

Soils contain the greatest reservoir of biodiversity on Earth, and the functionality of the soil ecosystem sustains the rest of the terrestrial biosphere. This functionality results from complex interactions between biological and physical processes that are strongly modulated by the soil physical structure. Using a novel combination of biochemical and biophysical indicators and synchrotron microtomography, we have discovered that soil microbes and plant roots microengineer their habitats by changing the porosity and clustering properties (i.e., spatial correlation) of the soil pores. Our results indicate that biota act to significantly alter their habitat toward a more porous, ordered, and aggregated structure that has important consequences for functional properties, including transport processes. These observations support the hypothesis that the soil–plant–microbe complex is self-organized.     

Soil lipase activity – a useful indicator of oil biodegradation

The evaluation of soil lipase activity as a tool to monitor the decontamination of a freshly oil-polluted soil was tested in a laboratory study. An arable soil was experimentally contaminated with diesel oil at 5 mg hydrocarbons g^–1 soil dry weight and incubated with and without fertilization (N-P-K) for 116 days at 20°C. Lipase activity and counts of oil-degrading microorganisms were measured at regular time intervals, and the correlations with the levels of hydrocarbon concentrations in soil were investigated. The residual soil hydrocarbon concentration correlated significantly negatively with soil lipase activity and with the number of oil-degrading microorganisms, independent of fertilization. The induction of soil lipase activity is a valuable indicator of oil biodegradation in naturally attenuated (unfertilized) and bioremediated (fertilized) soils.     

Soil mycoflora from trufflè native areas of Saudi Arabia

Soil fungi of areas in the North-Eastern region of Saudi Arabia where truffles are native were surveyed. Forty-three species of fungi belonging to twenty genera were isolated. Most were recovered from soils underneath or around truffle ascocarps: thirty species from soil under the surface of Tirmania nivea ascocarps, twenty-four from Terfezia boudieri soil and twenty species each from Tirmania pinoyi and Terfezia claveryi soils. Rhizosphere soil of Helianthemum lippi, on the other hand, yielded twenty-four fungal species while only fourteen fungal species were found in soil without vegetation. The total counts of fungi/g soil were highest in soils from the under surface of truffles, followed by rhizosphere soil, with the lowest in soils without vegetation.     

Predicting Soil Salinity with Vis–NIR Spectra after Removing the Effects of Soil Moisture Using External Parameter Orthogonalization

Robust models for predicting soil salinity that use visible and near-infrared (vis–NIR) reflectance spectroscopy are needed to better quantify soil salinity in agricultural fields. Currently available models are not sufficiently robust for variable soil moisture contents. Thus, we used external parameter orthogonalization (EPO), which effectively projects spectra onto the subspace orthogonal to unwanted variation, to remove the variations caused by an external factor, e.g., the influences of soil moisture on spectral reflectance. In this study, 570 spectra between 380 and 2400 nm were obtained from soils with various soil moisture contents and salt concentrations in the laboratory; 3 soil types × 10 salt concentrations × 19 soil moisture levels were used. To examine the effectiveness of EPO, we compared the partial least squares regression (PLSR) results established from spectra with and without EPO correction. The EPO method effectively removed the effects of moisture, and the accuracy and robustness of the soil salt contents (SSCs) prediction model, which was built using the EPO-corrected spectra under various soil moisture conditions, were significantly improved relative to the spectra without EPO correction. This study contributes to the removal of soil moisture effects from soil salinity estimations when using vis–NIR reflectance spectroscopy and can assist others in quantifying soil salinity in the future.     

Spatial Variability of Soil Chemical Properties of a Prairie–Forest Transition in Louisiana

Woody plant expansion, particularly eastern red cedar (Juniperus virginiana L.), has been a major threat to Louisiana calcareous prairies. Previous studies have shown that woody plant expansion into grasslands is associated with an increase in soil heterogeneity. We studied the within site spatial variability and among site differences of surface (0–15 cm depth) soil pH, electrical conductivity (EC), and Mehlich III extractable Ca, Mg, K, Fe and Mn from three remnant prairie-forest associations in Winn Parish, Louisiana. The prairie soil was consistently basic (pH > 7.0) and the forest soil was acidic (pH < 7.0) while the transition soil was neutral (pH = 7.0). A nonparametric statistical test for the equality of medians among sites showed the median values of the soil attributes differed (α = 0.05) except for soil Ca and Fe. The similarity in Ca concentration among sites was attributed to the calcareous parent material common to the three sites. Geostatistical analysis showed that spatial dependence was expressed over a range of 20–30 m for most of the soil attributes considered. Semivariogram shapes were similar among sites, suggesting the greater control of soil parent material on the observed spatial soil pattern. Shorter range of variation emerged only for soil pH when soil data from the forest and transition were deleted, indicating the scaling characteristics of soil pH and its susceptibility to plant induced changes. It is concluded that soil pH can be used as an index to determine prairie-forest boundary, and to access the impact of eastern red cedar on these and similar sites derived from calcareous parent material. Further, results from this study can be used for designing future ecological studies within the prairie by taking the soil spatial variability into account.     

Influence of Drying–Rewetting Frequency on Soil Bacterial Community Structure

Soil drying and rewetting represents a common physiological stress for the microbial communities residing in surface soils. A drying–rewetting cycle may induce lysis in a significant proportion of the microbial biomass and, for a number of reasons, may directly or indirectly influence microbial community composition. Few studies have explicitly examined the role of drying–rewetting frequency in shaping soil microbial community structure. In this experiment, we manipulated soil water stress in the laboratory by exposing two different soil types to 0, 1, 2, 4, 6, 9, or 15 drying–rewetting cycles over a 2-month period. The two soils used for the experiment were both collected from the Sedgwick Ranch Natural Reserve in Santa Ynez, CA, one from an annual grassland, the other from underneath an oak canopy. The average soil moisture content over the course of the incubation was the same for all samples, compensating for the number of drying–rewetting cycles. At the end of the 2-month incubation we extracted DNA from soil samples and characterized the soil bacterial communities using the terminal restriction fragment length polymorphism (T-RFLP) method. We found that drying–rewetting regimes can influence bacterial community composition in oak but not in grass soils. The two soils have inherently different bacterial communities; only the bacteria residing in the oak soil, which are less frequently exposed to moisture stress in their natural environment, were significantly affected by drying–rewetting cycles. The community indices of taxonomic diversity and richness were relatively insensitive to drying–rewetting frequency. We hypothesize that drying–rewetting induced shifts in bacterial community composition may partly explain the changes in C mineralization rates that are commonly observed following exposure to numerous drying–rewetting cycles. Microbial community composition may influence soil processes, particularly in soils exposed to a significant level of environmental stress.     

Can CO2 Fertilization Enhance Phytoremediation of Organic Soil Contamination?

Low efficiency is a key problem confronting the development and application of phytoremediation technology. Based on political pressure to reduce CO₂ emissions in China and the fact that CO₂ is necessary for plant photosynthesis, the effects of captured CO₂ fertilization on phytoremediation of soil di-(2-ethylhexyl) phthalate (DEHP) pollution by C₃ plant (mung bean, Vigna radiata L.) and C₄ plant (maize, Zea mays L.) were investigated. Results showed that DEHP pollution negatively affected the growth and rhizosphere environments of both plants. After CO₂ fertilization, both plants had more biomass (aboveground, belowground, and total dry weight), higher alkaline phosphatase activity, and more microbes with DEHP tolerance in their rhizospheres. Superoxide dismutase activity in leaves of both plants decreased significantly. Microbial community composition in both rhizospheres changed. CO₂ fertilization also increased plant uptake of DEHP, particularly in the roots, and decreased residual DEHP concentrations in the rhizospheres. These effects were more evident in the C₃ than in the C₄ plant. This study indicated that CO₂ fertilization can enhance the phytoremediation process of polluted soil through promoting plant growth, improving the rhizosphere environment, and increasing plant uptake of DEHP, particular in a C₃ plant. CO₂ fertilization could be considered as a measure to enhance phytoremediation.     

Impacts of Environmental Colloids on the Transport of 17 β-estradiol in Intact Soil Cores

Estrogens such as 17-β estradiol (E2) are endocrine-disrupting compounds and can affect the reproductive systems of aquatic organisms. Therefore, it is important to understand the mechanisms of their transport in the environment. E2 and its daughter product estrone (E1) are both strongly adsorbed by soil organic matter and have relatively short half-lives. Reduced contact time with soil makes transport of E2 and E1 in soil more likely. In this study, intact soil cores from three soils representing a range of particle size distribution, structure, and organic matter content were used to compare the transport of E2 with and without the presence of colloidal material fractionated from soil or swine manure. In chemical transport experiments conducted with undisturbed soil columns, E2 and E1 were measured both in solution and attached to suspended solids in column effluent. During the transport experiments, colloids carrying E2 passed through all soils, with the exception of the sandy soil. The presence of colloids decreased the first detection time of E2 in the aqueous phase, was correlated with greater peak E2 concentrations in the effluent of both loamy and clayey soils, but not through the sandy soil, and increased mass fractions of the E2 that was transported.     

Bioremediation of Cadmium-Contaminated Soil through Cultivation of Maize Inoculated with Plant Growth–Promoting Rhizobacteria

A pot experiment was conducted to study the effect of single and co-inoculation of Bacillus mycoides and Micrococcus roseus strains, indigenous to heavy metal (HM)–contaminated soils, on the growth and essential-nutrient and Cd uptake of maize in a soil polluted with 100 and 200 mg Cd kg^?1. Increasing Cd levels significantly decreased shoot and root dry weights, and shoot P, Fe, Zn, and Mn uptake. All bacterial treatments significantly increased biomass and shoot nutrient uptake of plant compared with control in the soil polluted with Cd. Inoculation of plants with B. mycoides and consortium of two bacteria significantly increased, whereas M. roseus significantly decreased, shoot and root Cd uptake, and Cd transfer and translocation factors compared with control in Cd-polluted conditions. The results showed that B. mycoides and consortium of two bacteria had an effective role in phytoextraction and M. roseus was the most effective treatment in phytostabilization of Cd.     

Complementary Models of Tree Species–Soil Relationships in Old-Growth Temperate Forests

Ecosystem-level studies identify plant–soil feedbacks as important controls on soil nutrient availability, particularly for nitrogen and phosphorus. Although site- and species-specific studies of tree species–soil relationships are relatively common, comparatively fewer studies consider multiple co-existing species in old-growth forests across a range of sites that vary in underlying soil fertility. We characterized patterns in forest floor and mineral soil nutrients associated with four common tree species across eight undisturbed old-growth forests in Oregon, USA, and used two complementary conceptual models to assess tree species–soil relationships. Plant–soil feedbacks that could reinforce site-level differences in nutrient availability were assessed using the context-dependent relationships model, whereby relative species-based differences in each soil nutrient diverged or converged as nutrient status changed across sites. Tree species–soil relationships that did not reflect strong feedbacks were evaluated using a site-independent relationships model, whereby forest floor and surface mineral soil nutrient pools differed consistently by tree species across sites, without variation in deeper mineral soils. We found that the organically cycled elements carbon, nitrogen, and phosphorus exhibited context-dependent differences among species in both forest floor and mineral soil, and most often followed a divergence model, whereby species differences were greatest at high-nutrient sites. These patterns are consistent with theory emphasizing biotic control of these elements through plant–soil feedback mechanisms. Site-independent species differences were strongest for pools of the weatherable cations calcium, magnesium, potassium, as well as phosphorus, in mineral soils. Site-independent species differences in forest floor nutrients were attributable to one species that displayed significantly greater forest floor mass accumulation. Our findings confirm that site-independent and context-dependent tree species-soil relationships occur simultaneously in old-growth temperate forests, with context-dependent relationships strongest for organically cycled elements, and site-independent relationships strongest for weatherable elements with inorganic cycling phases. These models provide complementary explanations for patterns of nutrient accumulation and cycling in mixed-species old-growth temperate forests.     

Climatic Control on Plant and Soil δ13C along an Altitudinal Transect of Lushan Mountain in Subtropical China: Characteristics and Interpretation of Soil Carbon Dynamics

Decreasing temperature and increasing precipitation along altitude gradients are typical mountain climate in subtropical China. In such a climate regime, identifying the patterns of the C stable isotope composition (δ¹³C) in plants and soils and their relations to the context of climate change is essential. In this study, the patterns of δ¹³C variation were investigated for tree leaves, litters, and soils in the natural secondary forests at four altitudes (219, 405, 780, and 1268 m a.s.l.) in Lushan Mountain, central subtropical China. For the dominant trees, both leaf and leaf-litter δ¹³C decreased as altitude increased from low to high altitude, whereas surface soil δ¹³C increased. The lower leaf δ¹³C at high altitudes was associated with the high moisture-related discrimination, while the high soil δ¹³C is attributed to the low temperature-induced decay. At each altitude, soil δ¹³C became enriched with soil depth. Soil δ¹³C increased with soil C concentrations and altitude, but decreased with soil depth. A negative relationship was also found between O-alkyl C and δ¹³C in litter and soil, whereas a positive relationship was observed between aromatic C and δ¹³C. Lower temperature and higher moisture at high altitudes are the predominant control factors of δ¹³C variation in plants and soils. These results help understand C dynamics in the context of global warming.     

Isolation of a β-Carotene Over-Producing Soil Bacterium, Sphingomonas sp.

A carotenoid-accumulating bacterium isolated from soil, identified as a Sphingomonas sp., grew at 0.18 h(-1) and produced 1.7 mg carotenoids g(-1) dry cell, among which beta-carotene (29% of total carotenoids) and nostoxanthin (36%). A mutant strain, obtained by treatment with ethyl methanesulfonate, accumulated up to 3.5 mg carotenoids g(-1) dry cell. Accumulation of beta-carotene by this strain depended on the oxygenation of the growth medium, with maximal accumulation (89%) occurring under limiting conditions. Beta-carotene accumulation could be further enhanced by incubating the cells in the presence of glycerol (either not or only slowly assimilated) and yeast extract resulting in an accumulation of 5.7 mg beta-carotene g(-1) dry cell wt. The strain used lactose as carbon source with similar biomass and carotenoid production, providing a viable alternative use for cheese whey ultra-filtrate.     

Dynamics of Inorganic Nitrogen in Nitrate and Glucose-amended Alkaline–saline Soil

Induction of assimilatory NO ₃ ⁻ reduction through the application of an easily decomposable substrate in alkaline–saline soils of the former lake Texcoco (Mexico) resulted in a fast immobilization of NO ₃ ⁻ in excess of N required for metabolic activity and the release of large concentrations of NO ₂ ⁻ and smaller amounts of NH ₄ ⁺ . We postulated that this was regulated by the amounts of NO ₃ ⁻ and glucose added, and affected by the specific characteristics of soil from the former lake Texcoco. This was investigated by spiking soils of different electrolytic conductivity (EC) 56.0 dS m⁻¹ (soil A of Texcoco) and 11.6 dS m⁻¹ (soil B of Texcoco) with different concentrations of NO ₃ ⁻ and glucose while dynamics of CO₂, NH ₄ ⁺ , NO ₂ ⁻ and NO ₃ ⁻ were monitored in an aerobic incubation for 7 days. For comparison reasons (control) an agricultural soil with low EC (0.3 dS m⁻¹) was included as well. In the agricultural soil, 67% of the added glucose mineralized within 7 days, but only 15% in soil A of Texcoco and 20% in soil B of Texcoco. The application of NO ₃ ⁻ to the agricultural soil added with glucose increased cumulative production of CO₂ 1.2 times, 1.5 times in soil A of Texcoco and 1.8 times in soil B of Texcoco. Concentration of NO ₂ ⁻ increased to > 100 mg NO ₂ ⁻ -N kg⁻¹ when 1000 mg glucose-C kg⁻¹ and 500 mg NO ₃ ⁻ -N kg⁻¹ were added to soil A and B of Texcoco, but remained < 3 mg NO ₂ ⁻ -N kg⁻¹ in the agricultural soil. The ratio between the cumulative production of CO₂ and the decrease in concentration of NO ₃ ⁻ was approximately one in soil A and B of Texcoco, but 10 in the agricultural soil after 3 days. It was found that micro-organisms in the alkaline–saline soil of the former lake Texcoco were capable of immobilizing large quantities of NO ₃ ⁻ when an easy decomposable substrate was available in excess of what might be required for metabolic activity while producing large concentrations of NO ₂ ⁻ , but these phenomena were absent in an agricultural soil. In soil of Texcoco, concentrations of NO ₂ ⁻ and NH ₄ ⁺ increased with increased salinity and availability of NO ₃ ⁻ . This ability to remove large quantities of NO ₃ ⁻ under these conditions and then utilize it at a later time might benefit micro-organisms of the N limited alkaline–saline soils of Texcoco.     

Do Botanical Pesticides Alter the Structure of the Soil Microbial Community?

The effects of synthetic pesticides on the soil microbial community have been thoroughly investigated in the past mostly by culture-dependent methods and only few recent studies have used culture-independent approaches for this purpose. However, it should be noted that most of these studies have been conducted in microcosms where the soil microbial community is exposed to unrealistic concentrations of the pesticides, providing an unrealistic exposure scheme for soil microorganism. On the other hand, little is known regarding the potential impact of botanical pesticides on the soil microbial community. Therefore, a laboratory study and a field study were conducted to investigate the effects of synthetic (metham sodium [MS], sodium tetrathiocarbonate [SoTe], and fosthiazate) and botanical pesticides (azadirachtin, quillaja, and pulverized Melia azedarach fruits [PMF]) on the soil microbial community using phospholipid fatty acids (PLFA) analysis. Principal component analysis (PCA) on the results of the laboratory study indicated that the application of PMF resulted in significant changes in the soil microbial community. This was obvious by the proportional increase in the abundance of fatty acids 18:1ω9cis, 18:1ω9trans, which are common in gram-negative bacteria and saprotrophic fungi, and 18:2ω6,9, which is a fungal indicator. This response was attributed to the release of copious amounts of organic carbon and nutrients in the soil by the PMF. On the other hand, MS inhibited fungi and gram-negative bacteria, while fosthiazate and the botanical pesticides quillaja and azadirachtin did not impose significant changes in the soil microbial community. Similar results were obtained by the field study where application of the fumigants MS and SoTe significantly altered the structure of the soil microbial community with the former having a more prominent effect. Fosthiazate imposed mild changes in the soil microbial community, whereas quillaja and azadirachtin again did not show a significant effect. Overall, botanical pesticides, at their recommended dose, did not alter the structure of the soil microbial community compared to synthetic nonfumigant and fumigant pesticides which induced significant changes.     

Soil Drench Treatment with ?-Aminobutyric Acid Increases Drought Tolerance of Potato

The non-protein amino acid β-aminobutyric acid (BABA) is known to be a priming agent for a more efficient activation of cellular defence responses and a potent inducer of resistance against biotic and abiotic stresses in plants. Nevertheless, most of the studies on priming have been carried out in Arabidopsis. In potato, the effect of BABA was demonstrated only on biotic stress tolerance. We investigated the effect of BABA on the drought tolerance of potato and found that soil drenched with BABA at a final concentration of 0.3 mM improves the drought tolerance of potato. Water loss from the leaves of the primed plants is attenuated and the yield is increased compared to the unprimed drought-stressed plants. The metabolite composition of the tubers of the BABA-treated plants is less affected by drought than the tuber composition of the non-treated plants. Nitric oxide and ROS (reactive oxygen species) production is increased in the BABA-treated roots but not in the leaves. In the leaves of the BABA-treated plants, the expression of the drought-inducible gene StDS2 is delayed, but the expression of ETR1, encoding an ethylene receptor, is maintained for a longer period under the drought conditions than in the leaves of the non-treated, drought-stressed control plants. This result suggests that the ethylene-inducible gene expression remains suppressed in primed plants leading to a longer leaf life and increased tuber yield compared to the non-treated, drought-stressed plants. The priming effect of BABA in potato, however, is transient and reverts to an unprimed state within a few weeks.     

Effects of Land-Use Change on Soil Nutrient Dynamics in Amazônia

Over the past several decades, the conversion of native forest to agricultural land uses has accelerated across the Amazon Basin. Despite a growing body of research on nutrient dynamics in Amazonian primary forest and forest-derived land uses, the effects of widespread land-use change on nutrient contents and cycles in soil and vegetation are not well understood. We reviewed over 100 studies conducted in Amazônia over the past 40 years on nutrient dynamics in natural forests and forest-derived land uses (pasture, shifting cultivation, and tree plantations). Our objectives were to compare soil data from land uses across Amazônia and identify any gaps in our present knowledge that might offer direction for future research. Specifically, by analyzing data we tested the following five widely cited hypotheses concerning the effects of land-use change on soil properties compiled from 39 studies in multifactorial ANOVA models; (a) soil pH, effective cation exchange capacity (ECEC), and exchangeable calcium (Ca) concentrations rise and remain elevated following the slash-and-burn conversion of forest to pasture or crop fields; (b) soil contents of total carbon (C), nitrogen (N), and inorganic readily extractable (that is, Bray, Mehlich I, or resin) phosphorus (P_i) decline following forest-to-pasture conversion; (c) soil concentrations of total C, N, and P_i increase in secondary forests with time since abandonment of agricultural activities; (d) soil nutrient conditions under all tree-dominated land-use systems (natural or not) remain the same; and (e) higher efficiencies of nutrient utilization occur where soil nutrient pools are lower. Following the conversion of Amazonian forest to pasture or slash-and-burn agriculture, we found a significant and lasting effect on soil pH, bulk density, and exchangeable Ca concentrations. Unlike the other three land uses studied, concentrations of extractable soil P_i were equally low in both forest and pastures of all age classes, which demonstrates that postburning pulses in soil P_i concentration following a slash-and-burn decrease rapidly after forest-to-pasture conversion, perhaps due to accumulation in organic P fractions. Neither the concentrations nor the contents of total C and N appeared to change greatly on a regionwide basis as a result of forest-to-pasture conversion, but surface soil C:N ratios in 5-year-old pastures were significantly higher than those in older pastures, suggesting changes in the soil concentrations of at least one of these elements with time after pasture creation. Pasture soils did have higher total C and N concentrations than land uses such as annual cropping and secondary forest fallow, indicating that soil C and N maintenance and/or accumulation following forest conversion may be greater in pastures than in these other two land uses. The low concentrations of C and N in shifting cultivation soils appear to persist for many years in secondary forests regenerating from abandoned crop fields, suggesting that the recuperation of soil losses of C and N resulting during no-input annual cropping is slower than previously thought. Soil C, N and P concentrations were strongly related to clay content. Across all land uses, efficiencies of N, P, and Ca use (estimated as the inverse of litterfall N, P, and Ca contents) were not related to the sizes of their soil pools. More work is needed to test and standardize P extraction procedures that more accurately reflect plant availability. Few studies have been conducted to determine the role of organic P fractions and dissolved organic N (DON) in the elemental cycles of both natural and managed systems in this region. In general, we recommend further study of annual and perennial cropping systems, as well as more detailed examination of managed pastures and fallows, and secondary forests originating from various disturbances, since the intensity of previous land use likely determines the degree of soil degradation and the rate of subsequent secondary regrowth.     

Mathematical Modeling of the Dynamics of Plant Mineral Nutrition in the Fertilizer–Soil–Plant System

A numerical simulation of the spatial–temporal dynamics of a multi-parameter system has been developed. The components of this system are plant biomass, the mobile and stationary forms of mineral nutrition elements, rhizosphere microorganisms, and environmental parameters (temperature, humidity, and acidity). Parametric identification and verification of the adequacy of the model were carried out based on the experimental data on the growth of Krasnoufimskaya-100 spring wheat on peat lowland soil. The results are represented by temporal distributions of biomass from agricultural crops and the findings on the contents of the main nutrition elements within the plant (nitrogen, phosphorus, and potassium). An agronomic assessment and interpretation of the results are given.