In this article, the topic under discussion is the development of deformations in semi-rigid knee joints made of dowel type fasteners and consequences expected regarding overall deformations of timber portal frame structure. The use of semi-rigid connection resolves the problem of transportation, but development of small rotation in connection reduces the stiffness of the connection that becomes significant during service life. It is assumed that the rotational stiffness modulus Kφ (kNm∙radE−1) is the relevant characteristic of semi-rigid connection. Timber portal frame structure (span 30 m) designed with dowel type fasteners located around two circles has been subjected to different loading trials by using Dlubal software (RFEM). Results of a numerical study of portal frame model demonstrate the importance of characteristics of semi-rigid knee joints for design. It is found that developing deformations in the semi-rigid knee connection produce up to 90% bigger vertical displacement at an apex point and 96% bigger horizontal displacement comparing with the rigid knee joint model.

Global scale environmental problems and economic issues are the main aspects what point out exigency to do research in the construction of renewable building materials. Renewable building materials are those materials that can be regenerated quickly enough and in theory, their production could be carbon-neutral. In order to evaluate the thermal efficiency of renewable materials in the framework systems of building envelope structures, test samples were made with the filling of renewable materials. The aim of the work is to find out the thermal conductivity coefficient of these natural composites and to compare them. Different size test samples were created for determination of thermal conductivity coefficient: 1.type as reference value: (width x height x depth) 290 x 290 x 30 mm; 2.type as experimental construction value (imitation of real wall construction): (width x height x depth) 980 x 980 x (165; 250; 345) mm. In this research as renewable insulating materials were used: maple leaves, legume (Galega orientalis), the composition of hemp shives (Bialobrzeskie) and sapropel with lime. A renewable insulating materials (also known as eco-thermal insulating) as alternative building materials discussed in this research work meets the requirements of the normative documents of the Republic of Latvia on sustainable construction principles. The analysis of results indicates significant difference among investigated materials – 0.040 W mE−1KE−1 lowest obtained value of thermal conductivity coefficient.

Nowadays, with the rapid development of robotics and automation, there is a need for more powerful, more compact data processing equipment that also emits more heat. Various electronics cooling solutions are already in use, others are in development. Each cooling solution has its advantages and disadvantages. Active cooling usually dissipates heat more efficiently, but passive cooling is more reliable, especially when the electrical system is exposed to aggressive environmental influences. The possibility of using graphene in the manufacture of electrical equipment components is widely studied. Graphene could significantly improve the efficiency of passive cooling because its thermal conductivity is much better than copper.

The feature of the microorganisms of rumen microbiocenosis is the ability to form a number of digestive enzymes, including cellulases, which allows ruminants use the energy of feeds rich in fiber. Microorganisms that are promising as a source of cellulases, biodestructors of toxins having antagonistic properties against pathogens for creating probiotic feed additives, both for reindeer and for other livestock, were isolated from the reindeer rumen. The aim of the study was to create a collection of microorganisms that are promising for creating a biopreparation. As a result, collections of 63 associations of microorganisms decomposing cellulose and carboxymethylcellulose were created; their morphology and cultural properties were described. It was found that the amount of cellulose degradation was 44 – 62% in the 4 most active isolates (No 14, 15, 21 and 26). The obtained data allowed to make a conclusion about the ability of bacterial strains isolated from the rumen to synthesize cellulolytic enzymes carrying out cellulose biodegradation, which allows them to gain a competitive advantage in the rumen of the reindeer diets with an abundance of cellulose. Isolates No 14 and 15 showed high antagonistic activity to Fusarium sporotrichioides, and isolate No 15 and 16 showed high antagonistic activity to Fusarium oxysporum. Isolate No 15 showed a wider antifungal activity compared to other isolates. Among all isolated strains, this bacterial isolate is represented as having a large spectrum of activities, including both high cellulolytic and high antifingal activity.

The main direction of using wheat grains is grinding them into low-extraction flours. The flours collected from individual passages differ in terms of chemical composition and physical properties, which in turn differentiates their baking value. The aim of the study was to evaluate the baking value of passage flours obtained from the milling of spring and winter wheat grain. Wheat grain was milled in a 6-pass laboratory mill MLU-202 by Bühler. The baking value of the obtained passage flours was evaluated by an indirect method (protein content, gluten content and quality, falling number, farinograph analysis) and by a direct method (by baking and performing quality evaluation of the obtained bread). The research showed that the efficiency of flours from individual milling passages varied. The passages flours differed significantly in terms of chemical composition and baking value. The highest flour yields were obtained from the first and second grinding stages, while the smallest from the third grinding stage. Ash and total protein content, flour water absorption, and amylolytic enzymes activity increased together with the subsequent milling stage in both reduction-passage and grinding-passage. The gluten content increased with the next reduction stage, while it decreased with the subsequent grinding passage. The bread from the laboratory baking test was diversified in terms of sensory characteristics, loaf volume, and crumb porosity. The best quality bread was obtained from flour from the first two reduction passages. The lowest quality bread was obtained from flour from the final grinding passage.

Winter oilseed rape is the main oilseed crop in Latvia. High yield production depends on applied plant nutrients, especially nitrogen. Nitrogen is one of the most mobile plant nutrients in the soil and, therefore, nitrogen fertilizer management is an important part of agriculture. The objective of this paper is to evaluate the effect of nitrogen fertilizer rate on nitrogen use efficiency (NUE) in winter oilseed rape. The field experiment was conducted during four growing seasons (2014/2015, 2015/2016, 2016/2017 and 2017/2018) at the Research and Study farm ‘Pēterlauki’ of Latvia University of Life Sciences and Technologies (56° 30.658´ N and 23° 41.580´ E). In total, eight nitrogen rates were used in this experiment (kg ha-1 of N pure matter): N0 or control, N60, N90, N120 (80+40), N150 (100+50), N180 (120+60), N210 (120+60+30) and N240 (140+60+40). All NUE parameters were calculated only for five nitrogen rates (N0; N60, N120, N180 and N 240). Results indicated that the nitrogen fertilizer rate had a significant (p is less than 0.001) effect on winter oilseed rape seed yield. The yield increased until the rate N120 – N180. Nitrogen fertilizer rate also significantly (p is less than 0.001) affected N, P2 O5 and K2 O removal with oilseed rape biomass. N and K2 O removal with seed yield significantly increased until the nitrogen rate N120 – N180, but P2 O5 until N60 – N180. Results showed that the nitrogen fertilizer significantly (p is less than 0.001) affected NUE, nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency (NUtE), but it did not have a significant (p=0.840) effect on nitrogen harvesting index (NHI). By increasing the nitrogen fertilizer rate, NUE, NUpE and NUtE decreased.

New types of polymer fertilizer series ‘Vitanoll’ are used in adaptive-varietal agro technology in the cultivation of seed potatoes. The experiments were conducted on sod-podzolic soils, typical of the North-West region of the Russian Federation. The aim of the research was to study the effect of new polymer fertilizers on potato yield. Research tasks included assessing the effect of various polymer fertilizers (Polymer-N, Polymer-P, Polymer-K.), as well as the effect of Polymer-N on different potato varieties. Based on the studies conducted, the most responsive potato varieties to polymeric fertilizers with nitrogen were identified. They turned out to be Salin (increase of 7.1 t haE−1) and Mocart (increase of 4.1 t haE−1). Evaluation of the influence of different types of polymer fertilizers revealed that the most effective are polymer fertilizers with potassium.

Winter wheat (Triticum aestivum L.) leaf diseases are an important risk factor that influences the productivity and quality of wheat production. The aim of the present study was to review published scientific literature about the possibilities for integrated control of winter wheat leaf diseases. The most common and economically important wheat leaf diseases are Septoria leaf blotch (caused by Zymoseptoria tritici), tan spot (caused by Pyrenophora triticirepentis), yellow rust (caused by Puccinia striiformis), and powdery mildew (caused by Blumeria graminis). The severity of winter wheat diseases has varied significantly over the years and depended on meteorological conditions, variety resistance to pathogen, and tillage system. The crop rotation and an efficient residue management significantly decrease the development of tan spot. The development of Septoria leaf blotch mainly depends on meteorological conditions, but agronomic practice is less important. The use of disease-resistant varieties is the most economical, safe, and effective way to prevent and control wheat leaf diseases. Many European countries have a number of decision support systems for optimizing and minimizing the use of fungicides. Decision support systems are based on control thresholds and meteorological observations. Most used parameters are: air temperature, relative air humidity, and precipitation. These systems have been developed in the countries with a milder climate and a longer vegetation period than Latvia, and systems need to be adapted to Latvian conditions. The main groups of fungicides for disease control in winter wheat are azoles, strobilurin, and carboxamides. The results of many studies about the effectiveness of fungicide groups show that the obtained results differ and further research is needed.

The aim of the work was to study accessions of Dactylis glomerata L. of different origin for breeding in the Leningrad region. The work was carried out at the Leningrad Agricultural Research Institute. The study involved 15 accessions. The nursery was founded in 2016 and included two replications for green yield and two – for seed production. Cutting and sampling for biochemical studies were conducted in May-June 2018, seeds were collected in July. The amount of ascorbic acid, carotenoids and chlorophylls and crude protein were determined. Statistical analysis included the calculation of the parameters of variation, ANOVA and correlation analysis. Three groups were identified by the degree of ripeness: a small group of early maturing – 31 days, a group of late maturing (single accession from Karelia) – 51 days, a large group of middle maturing – 34–37 days. For the late maturing accession the mechanism of regulation of the beginning of heading is due to the sensitivity to photoperiod. The adaptive potential of widely zoned varieties is wider than for localized. Their productivity is higher. The content of pigments in the green mass is closely correlated. The system of pigments in the complex of characters is separate, but is positively associated with the seed productivity and negatively – with the content of ascorbic acid. The seed productivity of the accessions is related to the total pigment content and power of the generative shoots (length and mass).

Studies were conducted at the experimental station of the Stavropol State Agrarian University on leached chernozem, powerful, low-humus heavy loam on loess-like loam in 2017. The goal was to study the effect of the introduction of rocks rich in chemical composition (limestone-shell rock, apatite and phosphogypsum), both separately and jointly, on the microbial phase of the soil. The determination of the number of microorganisms was produced on dense nutrient medium by direct counting of colonies. It was found that the amount of ammonifiers under the control was 37 ml CFU gE−1 (colony-forming units), increasing 1.3–1.5 times with separate use and 2.5–3 times with the joint use of rocks. Similar changes were observed with respect to the number of nitrifiers and aerobic nitrogen fixers of the type Azotobacter. The number of cellulose-depleting microorganisms in the remineralization variants reached 220,00–230,00 CFU gE−1 compared to 115,00 CFU gE−1 under the control. With the introduction of separate rocks, there was a decrease in the occurrence of pathogens, while with a joint introduction they were not detected. The frequency of occurrence of toxin formers, such as Aspergillus and Penicillium, reached 100% at the control and decreased by 20–40% at the experimental variants. It was revealed that the introduction of shell limestone, apatite and phosphogypsum had an effect on the increase in the number of soil microbiota of various physiological groups. Among the fungal microflora, the number of pathogens and toxin formers decreases and the number of pathogen antagonists increases.