A test of diethyltoluamide (DETA) in protecting animals from the gadfly     

P V Semenov  N P Gomoiunova  A P Korolev 《Veterinariia》1968,45(6):87-89

  相似文献   

Relation between Soil Health, Wave-like Fluctuations in Microbial Populations, and Soil-borne Plant Disease Management     

Ariena H. C. van Bruggen  Alexander M. Semenov  Anne D. van Diepeningen  Oscar J. de Vos  Wim J. Blok 《European journal of plant pathology / European Foundation for Plant Pathology》2006,115(1):105-122

A healthy soil is often defined as a stable soil system with high levels of biological diversity and activity, internal nutrient cycling, and resilience to disturbance. This implies that microbial fluctuations after a disturbance would dampen more quickly in a healthy than in a chronically damaged and biologically impoverished soil. Soil could be disturbed by various processes, for example addition of a nutrient source, tillage, or drying-rewetting. As a result of any disturbance, the numbers of heterotrophic bacteria and of individual species start to oscillate, both in time and space. The oscillations appear as moving waves along the path of a moving nutrient source such as a root tip. The phase and period for different trophic groups and species of bacteria may be shifted indicating that succession occurs. DGGE, Biolog and FAME analysis of subsequent populations in oscillation have confirmed that there is a cyclic succession in microbial communities. Microbial diversity oscillates in opposite direction from oscillations in microbial populations. In a healthy soil, the amplitudes of these oscillations will be small, but the background levels of microbial diversity and activity are high, so that soil-borne diseases will face more competitors and antagonists. However, soil-borne pathogens and antagonists alike will fluctuate in time and space as a result of growing plant roots and other disturbances, and the periods and phases of the oscillations may vary. As a consequence, biological control by members of a single trophic group or species may never be complete, as pathogens will encounter varying populations of the biocontrol agent on the root surface. A mixture of different trophic groups may provide more complete biological control because peaks of different trophic groups occur at subsequent locations along a root. Alternatively, regular addition of soil organic matter may increase background levels of microbial activity, increase nutrient cycling, lower the concentrations of easily available nutrient sources, increase microbial diversity, and enhance natural disease suppression.  相似文献   

Simulations of jets driven by black hole rotation     

Semenov V  Dyadechkin S  Punsly B 《Science (New York, N.Y.)》2004,305(5686):978-980

The origin of jets emitted from black holes is not well understood; however, there are two possible energy sources: the accretion disk or the rotating black hole. Magnetohydrodynamic simulations show a well-defined jet that extracts energy from a black hole. If plasma near the black hole is threaded by large-scale magnetic flux, it will rotate with respect to asymptotic infinity, creating large magnetic stresses. These stresses are released as a relativistic jet at the expense of black hole rotational energy. The physics of the jet initiation in the simulations is described by the theory of black hole gravitohydromagnetics.  相似文献   

Breeding indices when evaluating the genotype of pigs     

V. P. Rybalko  V. V. Semenov  O. L. Tret’yakova  L. V. Kononova  O. V. Pluzhnikova 《Russian Agricultural Sciences》2011,37(1):76-78

A combined index of reproductive qualities (CIRQ) is used for evaluating the reproductive productivity of sows of different genotypes, the index V ₁₀₀ ^* for evaluating young replacement stock, and the index for evaluating fattening qualities. The best crossing variants are revealed as a result of using the index evaluations: Large White of the Grigoropolis-1 type (LW GT) × Early Maturing Meat of the steppe type (EM-1 ST) × Landrace (L); EM-1 ST × (EM-1 ST × L); and L × (EM-1 ST × L).  相似文献   

Modelling the variability of UK sugar beet yields under climate change and husbandry adaptations     

G. M. Richter    A. Qi    M. A. Semenov  & K. W. Jaggard 《Soil Use and Management》2006,22(1):39-47

In the future, UK summers are likely to be warmer and drier. Modelling differential water redistribution and uptake, we assessed the impact of future drier climates on sugar beet yields. Weather was generated for 1961–1990 (BASE) and predictions based on low‐ and high‐emission scenarios (LO, HI) described in the most recent global climate simulations by the Hadley Centre, UK. Distributions and variability of relative soil moisture deficit (rSMD) and yield gap (drought‐related yield loss, YG_dr = 1?actual yield/potential yield), and sugar yield were calculated for different time‐lines using regional weather, soil texture and management inputs. The rSMD is estimated to exceed the senescence threshold with a probability of 75% (2050sLO) to 95% (2080sHI) compared with 65% (BASE). The potential yield loss, YG_dr, is likely to increase from 17% (BASE) to 22% (2050sLO) to 35% (2080sHI). However, increasing potential growth rates (CO₂ × temperature) cause average sugar yields to rise by between 1.4 and 2 t ha^?1 (2050sLO and 2050sHI respectively). Yield variation (CV%) may increase from 15–18% (BASE) to 18–23% (2050s) and 19–25% (2080s). Differences are small between regions but large within regions because of soil variability. In future, sugar yields on sands (8 t ha^?1) are likely to increase by little (0.5–1.5 t ha^?1), but on loams yields are likely to increase from 11 to 13 t ha^?1 (2050sHI) and 15 t ha^?1 (2080sHI). Earlier sowing and later harvest are potential tools to compensate for drought‐related losses on sandy soils.  相似文献   

The Structure of Bacterial and Fungal Communities in the Rhizosphere and Root-Free Loci of Gray Forest Soil     

Semenov  M. V.  Nikitin  D. A.  Stepanov  A. L.  Semenov  V. M. 《Eurasian Soil Science》2019,52(3):319-332

Eurasian Soil Science - The taxonomic composition, abundance, and diversity of bacterial and fungal communities in the rhizosphere loci and bulk mass of the gray forest soil (Eutric Retisol...  相似文献   

Assessment of the Impact of No-Till and Conventional Tillage Technologies on the Microbiome of Southern Agrochernozems     

Nikitin  D. A.  Ivanova  E. A.  Zhelezova  A. D.  Semenov  M. V.  Gadzhiumarov  R. G.  Tkhakakhova  A. K.  Chernov  T. I.  Ksenofontova  N. A.  Kutovaya  O. V. 《Eurasian Soil Science》2020,53(12):1782-1793

Eurasian Soil Science - Quantitative characteristics of microbial communities in southern agrochernozems of the Stavropol region managed with the use of no-till technology and moldboard plowing...  相似文献   

Relationships between the Size of Aggregates,Particulate Organic Matter Content,and Decomposition of Plant Residues in Soil     

Semenov  V. M.  Lebedeva  T. N.  Pautova  N. B.  Khromychkina  D. P.  Kovalev  I. V.  Kovaleva  N. O. 《Eurasian Soil Science》2020,53(4):454-466

Eurasian Soil Science - The distribution of total organic matter (Corg), particulate organic matter (CPOM), and potentially mineralizable organic matter (C0) in mega- (10–5 and 5–2 mm),...  相似文献   

Distribution of transformed organic matter in structural units of loamy sandy soddy-podzolic soil     

B. M. Kogut  M. A. Yashin  V. M. Semenov  T. N. Avdeeva  L. G. Markina  S. M. Lukin  S. I. Tarasov 《Eurasian Soil Science》2016,49(1):45-55

The effect of land use types and fertilizing systems on the structural and aggregate composition of loamy sandy soddy-podzolic soil and the quantitative parameters of soil organic matter has been studied. The contribution of soil aggregates 2–1 mm in size to the total C_org reserve in the humus horizon is higher than the contributions of other aggregates by 1.3–4.2 times. Reliable correlations have been revealed between the contents of total (C_org), labile (C_lab), and active (C₀) organic matter in the soil. The proportion of C₀ is 44–70% of C_lab extractable by neutral sodium pyrophosphate solution. The contributions of each of the 2–1, 0.5–0.25, and <0.25 mm fractions to the total C₀ reserve are 14–21%; the contributions of each of the other fractions are 4–12%. The chemically labile and biologically active components of humic substances reflect the quality changes of soil organic matter under agrogenic impacts. A conceptual scheme has been proposed for the subdivision of soil organic matter into the active, slow (intermediate), and passive pools. In the humus horizon of loamy sandy soddy-podzolic soil, the active, slow, and passive pools contain 6–11, 34–65, and 26–94% of the total C_org, respectively.  相似文献   

Carbon dioxide,methane, and nitrous oxide fluxes in soil catena across the right bank of the Oka River (Moscow oblast)     

M. V. Semenov  I. K. Kravchenko  V. M. Semenov  T. V. Kuznetsova  L. E. Dulov  S. N. Udal’tsov  A. L. Stepanov 《Eurasian Soil Science》2010,43(5):541-549

The flux rates of carbon dioxide, methane, and nitrous oxide in the soils on autonomous, transitional, transitional-accumulative, and accumulative positions of a catena on the Oka River’s right bank (Moscow oblast) were assessed using the chamber method. The lowest rate of C-CO₂ emission (18.8–29.8 mg/m² per hour) was found for the gray forest soil in the autonomous position, and the highest rate (52.4–66.1 mg/m² per hour) was found for the alluvial meadow soil of the accumulative landscape. In the summer, the uptake of methane from the atmosphere exceeded its release from the soil at all the points of the catena (9–38 μg/m² per hour). The highest rate of the C-CH₄ uptake was observed for the soil in the transitional position. In the fall, the soils in the autonomous, transitional, and transitional-accumulative positions served as a sink of C-CH₄, and the soil of the accumulative position was a source of methane emission. The rate of the N-N₂O emission from the catena soils increased when going from the autonomous position to the accumulative one (0.41–11.2 μg/m² per hour). The spatial variation of the C-CO₂, C-CH₄, and N-N₂O fluxes within the catena was 33, 172, and 138%, respectively. The upper (0- to 10-cm) soil layer made the major contribution to the emission of carbon dioxide. This soil layer was characterized by its C-CH₄ uptake, and the emission of methane was typical for the deeper (0- to 20-cm) layer. The layers deeper than 10 and 20 cm emitted more N-N₂O than the surface layer.  相似文献