Received: February 8th, 2021 ; Accepted: April 24th, 2021 ; Published: April 30th, 2021 ; Correspondence: grigory.slesarev@urfu.ru

Blackberries (Rubus caesius), elderberries (Sambucus nigra L), highbush blueberries (Vaccinium corymbosum L) and black currants (Ribes nigrum) were selected for research on their content of phenolic compounds, including anthocyanins and comparing their content in these berries. Samples were also assayed for ascorbic acid and soluble solid content. The unifying mark of these fruits is purple-black color, which indicates high content of anthocyanins. Analyses of these fruits showed that they contain high biological activity components that justify the uses of these fruits. The research was done at the Department of Chemistry, Latvia University of Life Sciences and Technologies, year 2019. Berry samples were bought at the supermarket (highbush blueberries) or collected from garden in Jelgava, Latvia (blackberries, elderberries and black currants). All berries were at full maturity. The content of ascorbic acid, total phenols, anthocyanins, flavonoids as well as soluble solids was determined. Descending order of ascorbic acid content in berries is: black currants > blackberries > elderberries > highbush blueberries. Elderberries had the highest content of anthocyanins, total phenols and flavonoids on average 161.5, 537.9 and 112.6 mg 100 g -1 FW, respectively. The content of soluble solids changes from 5.83 Brix (elderberries) to 13.67 Brix (black currants).

The influence of bio humus on chemical indicators of the arable layer of soil, productivity and ecological safety indicators of spring wheat of ‘Chelyaba - 75’ variety during the period of 2017–2019 were studied. The object of research was samples of the soil arable layer from the control and experimental field, the structure of wheat yield from control and experimental plots. Bio humus aqueous extract was introduced in the soil of the experimental field before wheat sowing and in the phase of spring tillering at the rate of 10 L/200 L /1 hm2 using the trailer sprayer ‘Zarya’ (Russia) during the dark hours of day. In the study of soil and grain samples, generally accepted methods and techniques were used. It is established that regular chernozems under the conditions of technogenic impact of emissions of thermal power plants are characterized by low humus content (4.58–4.60%) and weak acid reaction of medium (pH = 6.1–6.5); imbalance between biochemically active (copper, zinc, cobalt) and toxic (lead, nickel, cadmium) elements, as confirmed by soil contamination coefficients: for copper (C0 = 1.50–1.58), zinc (C0 = 0.79–0.85). The introduction of bio humus in the tilth top soil before sowing and during tillering of spring wheat contributed to the increase in humus composition by 1.88 times, the change in acidity to pH = 6.9–7.0, reduction of lead and cadmium concentrations in 1.63 and 1.20 times against the background of increased zinc and cobalt levels by 15.62% and 7.98%; increase of field germination of spring wheat from 75.0 ± 0.4 to 82.0 ± 0.9%; quantity of developed stems to be harvested per 1 m2 by 10.15%, productive tilling capacity by 8.33%, average quantity of spikes per ear by 20.00%, average quantity of grain per ear by 7.69%, mass of 1,000 grains by 16.12%, and wheat yield increase by 10.2 hwt ha-1 and decrease in spring wheat grain concentration of lead and cadmium at 14.00 and 16.00%.

Currently chia seeds (Salvia hispanica L.) are considered as a filler of functional food. However, ground chia seeds have a low viscosity and cohesion properties that are limited its applications. Based on previous data oat-chia seeds composites in different proportions as filler for yogurt have been tested. The investigation of water holding capacity of samples allowed to select the yogurt with filler in the ratio of 1:1 (oat bran:chia seed) in the amount of 3% and 5% as the most close to the control sample without any filler. The rheological characteristics of yogurt samples were investigated and their thixotropic and viscoelastic properties were identified depending on the amount of filler in the product. The yogurt without any filler had the less thixotropic properties in compare with yogurt with oat-chia seeds composites. The structure recovery of yogurt with 3% and 5% filler was close to 100% and greater than 100% respectively. Based on the data of G' and G" moduli was possible to ascertain the yogurt with filler has more viscoelastic properties compared with yogurt without filler. Yogurt with 5% filler exceeds yogurt without filler in biological value according to the content of essential amino acids and polyunsaturated fatty acids.

Large-scale cultivation of contamination free plants requires a good standardization protocol and production methods. Basil is widely used for cosmetics, food and pharmaceutical industries as it is rich in many bioactive compounds. This present study aimed to evaluate the growth and in vitro anatomical aspects of apical buds of basil grown under different concentrations rowth regulators like: NAA (Naphthalenoacetic Acid), BAP (6-benzylaminopurine), and KIN (Kinetin). The in vitro establishment was evaluated every 20 days to calculate the, the percentage of plants with calluses, appearance of the roots, any abnormal seedlings, any oxidized seedlings, and the number of sprouts per plant. Growth, physiological, and morpho-anatomical evaluations were performed at 80 days. Basal callogenesis was observed when cytokinin’s and auxins are used in combination. Auxin treatments caused hyperhydricity in the stems and leaves. Medium A2 (0.05 mg L -1 of NAA and 0.1 mg L -1 of BAP), and A3 (0.05 mg L -1 of NAA and 0.1 mg L -1 of KIN) resulted in the best development of basil plants, cultivar ‘Alfavaca Green’. The A2 produced plants with greater numbers of leaves, an average bud length of 59.81 mm, and the best root properties. A2 and A1 have a higher percentage of hyperhydricity (83 and 67%). The A3 resulted in an acceptable number of leaves (range: 21–39), and this treatment produced the best shoot properties as well as fewer plants with hyperhydricity. In addition, the A3 treatment produced plants with a shoot length, high shoot fresh and dry mass (2.82 and 0.23 g), high chlorophyll index and leaf anatomy that was similar to the control. Excluding the control, the other treatments presented more than 90% of the explants with calluses in their bases.

The practice of separating grain mixtures with the use of the difference in the aerodynamic properties of their components has proved that the process of separating mixtures in the aspiration separator is the most promising one with regard to the improvement of quality and intensification of production. The authors have developed a new improved design of aspiration seed separators, in which the work process of separating seed material is performed with the use of vibration processes. In this seed material separator, the constant force air flow that acts on the sail members on the central pipe of the separator, when seeds are fed for processing, generates self-excited oscillations in the pipe, which produces centrifugal forces of inertia in the seed feeding system. As a result of the mentioned effect, the propelling force in the process under study substantially increases, accelerating the seeds of different fractions, which differ in their masses, to different velocities. The motion paths of the seed particles change accordingly, heavier particles moving closer to the vertical axis of the aspiration channel, which provides for increasing the efficiency of separation of the seeds of different fractions from each other. In this paper, a new mathematical model is developed for the motion of a seed mixture material particle in the operating space of the separator’s aspiration channel. The mathematical modelling of the process of vibration and aspiration separation has indicated that the separation of the motion paths of the medium and heavy fractions takes place within the range of 20–40 mm; the flying speed of the particles is equal to 3.2–8.0 m s–1, respectively; and their acceleration is equal to 1.8– 3.3 m s–2, which provides the necessary conditions for the accurate and high quality separation into the required fractions. In view of the found differences between the kinematic characteristics of the separated fractions of the grain mixture, the diameter of the pipeline for the medium fraction is to be within the range of 90–100 mm, for the heavy fraction – 50–70 mm.

Results of the research were based on a field experiment carried out in 2007–2009 at the Experimental Plant of the IHAR-PIB in Jadwisin, on podzolic soil with a granulometric composition of loamy sand. The experiment was established by means of a random sub-block method in a dependent split-plot pattern, in triplicate. The first order factor were the potato cultivars: ‘Irga’ and ‘Fianna’, the second order factor were the methods of weeds regulation: 1) control − without chemical protection; 2) extensive mechanical treatments (every 2 weeks) from planting to closing the rows; 3) Sencor 70 WG – 1 kg ha-1 before potato emergence; 4) Sencor 70 WG – 1 kg ha-1 + Titus 25 WG – 40 g ha-1 + Trend 90 EC – 0.1% before potato emergence; 5) Sencor 70 WG – 0.5 kg ha-1 after potato emergence; 6) Sencor 70 WG – 0.3 kg ha-1 + Titus 25 WG – 30 g ha-1 + Trend 90 EC – 0.1% after potato emergence; 7) Sencor 70 WG – 0.3 kg ha-1 + Fusilade Forte 150 EC – 2 dm3 ha-1 after potato emergence; 8) Sencor 70 WG – 0.3 kg ha-1 + Apyros 75 WG 26.5 g ha-1 + Atpolan 80 SC – 1 dm3 ha-1 after potato emergence. The number, floristic compositions, fresh weight and dry matter of weeds were determined. A high, yield-protective effect of herbicides was obtained as a result of limited competition of weeds. Mechanical care contributed to the increase in the total potato yield by 36.2%, and the marketable yield by 45.7%, as compared to the control object.

In the retrofitting of older buildings with central heating into nearly zero-energy buildings more and more air to water heat pumps are used. These heat pumps are normally connected to heating systems, producing heat only on demand. The greatest demand for heat occurs when the outside temperature and therefore the COP of the pump is lowest. Outside temperature varies during the day, meaning it is possible to save energy by producing and storing heat in a situation where the COP is higher. To determine the periods with higher COP values weather forecast data and COP curves are used. The data enables to rank and select time periods for heat production. This in conjunction with the heat demand curve of the building enables to create an operation schedule for the heat pump. The aim of the study is to develop heat pump control methods for renovated buildings to comply with nearly zero energy building codes. Dependant on the heat pump and weather conditions, up to 10 % of the electricity demand for heating can be decreased.

We evaluated the efficiency (the netto agronomic efficiency – NAE, the physiological efficiency – PE, and the apparent recovery efficiency – ARE) of farmyard manure (FYM) applied alone, and together with mineral N (FYM+N), and NPK (FYM+NPK), on the biomass production of silage maize at three localities (Caslav, Ivanovice, Lukavec) in the Czech Republic, characterised by different soil-climate conditions. The effect of fertilizer treatment on soil chemical properties was also analyzed. After four years of evaluation, the application of FYM resulted in comparable biomass production as in the FYM+N, and FYM+NPK treatments, showing the good ability of the mineralized FYM to provide enough nutrients during the growing season. Increasing doses of applied nutrients were connected with higher biomass production. However, no significant differences were recorded between fertilizer treatments. The efficiency of applied nutrients was higher on soils of worst quality (sandy loamy Cambisol – Lukavec), while lower on naturally fertile loamy degraded Chernozem (Ivanovice). But again, no significant differences between the selected parameters were recorded. Although the application of mineral fertilizers has not increased maize biomass yield significantly, they positively affected soil chemical properties, mainly the soil concentration of P, K, Mg, and soil organic carbon content. This shows the beneficial effect of the application of mineral fertilizers, especially in the Czech Republic, where the application of mineral P and K decreased drastically during the last thirty years.

Increased cost-effectiveness in crop production can be achieved by automating technological operations. This is also the case for berry cultivation in plantations. Starting any berry cultivation automation process should, quite naturally, begin with fertilisation, since this is the first technological operation to be carried out during the vegetation period and is a relatively simple one. The main task here is to apply the correct amount of fertiliser under the canopy of plants. Blueberry plantations that have been established on milled peat fields have plants that have been planted in parallel rows at a pre-designated interval. The fertilisation of plants must take place individually in the first years of their growth, so that each plant is fertilised separately. This form of fertilisation can be referred to as precision fertilisation. The aim of this paper was to provide an overview of the levels of technology now available when it comes to precision fertiliser equipment and to introduce the concept of a new precision-automated fertiliser unit, while also justifying the efficiency of using automated equipment. The automated fertiliser unit that is to be designed will be autonomous, will move unmanned through the plantation, and will include the necessary sub-systems for the precision fertilisation of individual plants, such as a plant detection system, a fertilising nozzle, a motion system and, additionally, a service station. On the basis of the results obtained, it can be argued that the use of an automated precision fertilisation unit increases productivity levels by approximately 2.25 times and decreases the specific fertiliser costs by approximately 8.4 times when compared with the use of a portable spot fertiliser.