The aim of the research was to study the effect of resource-saving technologies in the cultivation of spring wheat and barley in several regions of Western Siberia on the distribution and taxonomic composition of root rot pathogens, as well as the evaluation of protective measures efficiency. In the context of the resource-saving technologies of crop cultivation in Western Siberia, root rot became of particular relevance; the development of root rot exceeds the thresholds by up to 5-7 times, especially in the first half of the growing season. We identified substantial changes in the taxonomic composition of the pathogen complex of root rot towards expansion of the plant pathogens range by fungi of the Pythium genus and strengthening of the Fusarium genus fungi domination. There is a tendency of the ecological niches of plant pathogens spreading in organs of plants: B.sorokiniana better adapted to topsoil organs and the Fusarium genus fungi-to the underground ones. We identified environmental factors with the greatest impact on strengthening and spreading of the root rot pathogenesis: high number of intra-stem pests, which exceeds the threshold by 2-3 times, contamination of crops with cereal weeds-reserves of root rot pathogens, as well as low microbiological activity and soil suppressive qualities caused by a short growing season and lack of plant residues. We studied the efficiency of improvement methods for the phytosanitary condition of soil and underground plant organs of spring wheat and barley through the introduction of phytosanitary crop rotation and preceding crops, seed treatment and technologies to improve plant resistance in the initial phases of development.
The soil resources of the Altai dry steppe (and their fertility in particular) degrade in their evolutionary anthropogenic development. Transformation of fertility is occurring due to a combination of phenomena, such as natural conditions, intensive use, farming system practiced in the absence of science-based regimes. It is established that the humus content and humus horizon thickness are statistically significantly reduced due to the activation of deflation and dehumification processes. More than that, areas of alkaline soils are increasing. The authors also point out to the degrading granulometric composition. Also, the amount of physical clay, silt fractions, cation exchange capacity, exchangeable calcium, potassium, and mobile phosphorus decreases. Statistical processing of fertility parameters of allowed us to develop a scale of process dynamism and establish the degree of dynamism in the considered soil properties, as well as to assess the rate of increasing adverse changes or their absence. Intensity of degradation processes and indicators determining it contributed to the development of levels of agro-ecological state, such as “Norma”, “Risk”, “Krizis” and “Bedstviye” (based on GIS).
The purpose of the study was to assess the number and state of populations of B. sorokiniana conidia in the soil of agrocenoses and virgin areas. Studies were carried out in 2017-2021 in dry steppe regions of the Altai Territory (Russia) and Pavlodar Region (Kazakhstan) by conventional methods. For the experimental data analysis variance and correlation analytical methods were used. A comparative analysis of Bipolaris sorokiniana conidia populations in agrocenoses and virgin soils of arid areas was carried out. A significant phytopathogen conidia population in agrocenosis soils has been established, reaching 10.8 regional economic harmfulness thresholds in Altai and 16.6 thresholds in Kazakhstan. A lower population number in virgin soils was revealed in comparison with agrocenoses’ ones, which is associated with more active resting structures degradation. A clear tendency towards a decrease in the number of conidia with increasing depth was revealed, which manifests itself to different degrees in the regions and tillage systems, but has the same orientation: the upper layer (0-5 cm) is populated several times stronger than the lower (10-15 cm) one. The phytosanitary precursors in both regions (fallow, sunflower, pees, oat with vetch, sweet clover) reduced the conidia number in the soil on average 59%; they significantly increased the conidia proportion with the degradation signs-average by 27.1%. Soil suppressive activity against B. sorokiniana increased significantly (on 19.8-38.3%) after cultivation of phytosanitary predecessors, especially rape.
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