2017, Vol. 15, No. 4

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/5358

Sirvi

Nüüd näidatakse 1 - 20 34

Experimental analysis of hydrotreated vegetable oil (HVO) and commercial diesel fuel blend characteristics using modified CFR engine
(2017) Gailis, M.; Rudzitis, J.; Kreicbergs, J.; Zalcmanis, G.
Performance parameters of different commercial diesel fuels is a subject of interest for fuel consumers. Fuel retailer Neste recently introduced a new brand of WWFC 5th grade diesel fuel in Baltic market, consisting of diesel fuel and hydrotreated vegetable oil (HVO) blend. Fuel samples have been recently tested on chassis dynamometer, measuring wheel power and torque and in road conditions, measuring fuel consumption. Evaluation of fuel consumption and performance parameters in road or laboratory conditions may yield uncertain results due to complexity of modern automobile engine management and emission reduction systems. To better evaluate the combustion, fuel samples have been tested in modified CFR engine at various intake air pressure, temperature and compression ratio settings. Engine indicated performance parameters and combustion phasing of regular diesel fuel and diesel fuel-HVO blend are presented. Comparing to regular diesel fuel, fuel blend with HVO showed reduced apparent heat release rate (AHRR) during premixed combustion phase at low inlet air temperature and low compression ratio conditions, comparing to regular diesel fuel. Premixed combustion phase AHRR of diesel-HVO blend increased above AHRR of regular diesel fuel at higher inlet air temperature and higher compression ratio conditions. Diffusion controlled combustion phase AHRR of diesel-HVO blend increased above AHRR of regular diesel fuel at higher inlet air temperature, higher compression ratio conditions and supercharged air supply.
Occupational diseases among agricultural workers in the Russian Federation: review of statistical data
(2017) Mazitova, N.; Simonova, N.; Adeninskaya, E.; Trofimova, M.
The aim of the study is to analyze the epidemiological situation of occupational diseases among agricultural workers in Russia. To address this task, the analysis of occupational diseases incidence was carried out. Conclusions.For the last decades the proportion of rural working population in Russia is gradually decreasing, but remains noticeably higher than in other industrialized countries. There is a huge difference between entities of the Russian Federation in occupational illnesses incidence rates among agriculture workers, which can be explained by: (a) the distinction of health care availability; (b) lack of occupational physicians in rural areas; (c) the high level of the incidence of non-communicable diseases, which can disguise occupational illnesses among agricultural workers. The improvement of the health care regulatory legal framework, development of evidence-based clinical practice guidelines, quality improvement in postgraduate education of medical doctors in rural areas, increasing in the number of occupational health physicians in rural areas, and implementation of long-term health promotion programs are necessary in order to maintain the heath of agricultural workers in the Russian Federation. This list of priority measures is not sufficient, as it highlights only the main issues in the field of occupational health.
Fodder galega (Galega orientalis Lam) grass potential as a forage and bioenergy crop
(2017) Meripõld, Heli; Tamm, Uno; Tamm, Sirje; Võsa, Taavi; Edesi, Liina
Fodder galega (Galega orientalis Lam.) is a forage legume that has been grown in Estonia for almost forty five years. Pure galega is known to be persistent, high-yielding crop and rich in nutrients, in particular crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF). Galega is usually grown in a mixture with grass in order to optimize its nutrient concentration, increase dry matter (DM) yield and improve fermentation properties. The trial plots were established on a typical soddy-calcareous soil. There are certain grass species suitable for the mixture. In this study galega mixtures with reed canary grass cv. ‘Marathon’, timothy cv. ‘Tika’, red fescue cv. ‘Kauni’ and festulolium cv. ‘Hykor’ were under investigation in three successive years (2013–2015). In order to increase competitiveness of grasses and the yield of the first cut, two N fertilization levels were used: N0 and N50 kg ha-1 . Two cuts were carried out during the growing season in all three years. The total dry matter yield varied from 9.1 to 12.8 t ha-1 . The NDF concentration in the DM varied from 495−559 g kg-1 . Both DM-yield and NDF were dependent on the year, mixture, cutting time and fertilization. Nitrogen fertilization (N50 kg ha-1 ) favoured grass growth and reduced the role of galega in the sward.
Theoretical research into the stability of motion of the ploughing tractor-implement unit operating on the ‘push-pull’ principle
(2017) Bulgakov, V.; Adamchuk, V.; Nadykto, V.; Kistechok, O.; Olt, Jüri; Estonian University of Life Sciences. Institute of Technology
The reduction of power consumption in the ploughing operations can be achieved by way of improving the grip properties of the implement-carrying tractors, which is facilitated by setting up ploughing units for operation on the ‘push-pull’ principle. The aim of the current research is to substantiate the set-up and parameters of the ploughing unit with a front-mounted plough basing on the theoretical investigation of the stability of its motion in the horizontal plane. The methods of research include obtaining the amplitude- and phase-frequency response characteristics of the dynamic system in order to analyse the stability of its motion under the action of external statistically random perturbations. Also, the methods of software development and PC-based numerical computation are applied. The results of the study prove that the increase of the ploughing unit’s travel speed results in the considerable rise of the gain of the amplitude of the tractor’s heading angle oscillation in response to the oscillation of the angular displacement of the front-mounted plough in the horizontal plane. The phase-frequency response displays the same behaviour, changing substantially together with the unit’s travel speed. Raising the coefficient of resistance to tyre slip of the tractor’s rear wheels from 100 to 130 kPa and the front wheels from 140 to 175 kPa results in a minor decrease of the amplitude of oscillation of the tractor’s heading angle φ. The ploughing unit has the best response to the input effect, i.e. the oscillation of the front-mounted plough’s angular displacement βp, when it operates using the 1+5 combination. The increase of the number of front-mounted plough bodies from 1 to 3 results in the substantial growth of the tractor’s heading angle oscillation amplitude. Taking into account the way, in which the ploughing unit as a dynamic system responds to the input perturbance, the increase of its travel speed can be restricted not by the condition of its motion stability, but solely by the agrotechnical requirements applied to such a process operation as ploughing. The ploughing unit’s motion stability substantially improves in case of higher air pressure in the tyres on the tractor’s front and rear wheels. This effect is especially pronounced in the perturbance oscillation frequency range (0...1.5 s –1 ) that covers the main part of its dispersion.
Critical velocity of solid mineral fertilizers in a vertical upward airstream and repose angle
(2017) Hůla, J.; Kroulík, M.; Honzík, I.
Critical velocity of mineral fertilizers in airstream is important not only at the application of fertilizers by spreaders but also at combine of fertilizing and sowing. The knowledge of angles of repose is important to design hoppers on spreaders for solid mineral fertilizers. Critical velocities for six solid mineral fertilizers were measured in the vertical aspiration duct of a laboratory sorting machine. Variation curves were constructed for particular fertilizers and the mean critical velocity of fertilizers (velocity of uplift) was computed. The mean critical velocity of fertilizers was between 8.53 and 12.43 m s -1 . The lowest critical velocity was found out in the fertilizer UREA 46%, the highest in the fertilizer LAV. Statistical significance of differences in the critical velocity of fertilizers was assessed. Angles of repose of eight solid mineral fertilizers were also measured and statistical significance of differences was evaluated. The highest values of repose angle were determined for potassium salt and ammonium sulfate (35.9° respectively 34.9°), the lowest values for UREA and LAV (28.7° respectively 29.6°). The obtained results extend information applicable to an assessment of parameters of the operation quality of spreaders during mineral fertilizer application.
Livestock manure management practices in rural households in Tapanuli Utara regency of North Sumatra
(2017) Roubík, H.; Mazancová, J.; Situmeang, R.C.; Brunerová, A.; Simatupang, T.M.
Livestock manure management is a big challenge for low income economies including the region of North Sumatra, Indonesia. Currently, low percentages of manure managed cause illegal disposals, and negative impacts on public health and environment. Therefore, the objective of this study was to assess the current trends among livestock manure management practices in rural households and to recognize potential problems with it. The questionnaire survey using randomly selected households (n = 196) was administered in the province of North Sumatra, Tapanuli Utara regency, from July to August 2014; then followed by several field visits from August to September 2016. Data obtained in the survey were analysed with descriptive statistics and cross tabulation. Majority (81%) of rural households handle manure in the process of either composting (75%) or sun-drying (6%). Remaining 6% of the respondents does not handle manure at all. Manure could represent valuable energy and plant nutrition resource, if used appropriately. However, if not handled at all or handled inappropriately, it can lead to the environmental problems. Our results revealed that current ways of stabling of livestock are inappropriate from the environmental perspective. The stabling has got only dusty earthen floor, which makes difficult for farmers wash out the excrements and pollution. Hence, there is a need to improve manure management practice to eliminate potential threats as current practices do not protect either humans, animals or environment against the risk of contamination with potential zoonotic pathogens.
Some factors affecting the efficiency of potato production, under Al–Ghab plain conditions, Syrian Arab Republic
(2017) Prochazka, P.; Murjan, A.; Hönig, V.; Pernica, K.
Data were collected by a field survey of 300 farmers from Al–Ghab region (Syria) during 2014–2015. The non–parametric Data Envelopment was used in analyzing the Technical efficiency. The relationship between farm size and production efficiency was considered. Technical efficiency amounted about 53% and most of farms are operating at low level of technical efficiency. The relationship between farm size and productivity efficiency is Non– linear, it decreases from small to medium farm size and then increases as the size increase. Large farms have the higher net farm income per thousand square metersand are the most efficient technically followed by small and medium farm size. To disclose that factors causing the technical efficiency, Two–limit Tobit Regression Model was used. The calculated results showed that, Household Size, Occupation, Farm Size, Experience in Farming, Seed Type and Membership are factors that cause the technical inefficiency potato farming at Al–Ghab region. Therefore, the Syrian Planning Board and Decision Makers should take this results into account when they draw their plans to improve farmer's skills by allocating more investment in farm research and extension programmers.
Fair Trade and social responsibility – whose duty? Estonian consumers’ attitudes and beliefs
(2017) Riivits-Arkonsuo, Iivi; Ojasoo, Merle; Leppiman, Anu; Mänd, Kristina
This article investigates how the Estonian consumers endorse the idea of Fair Trade (FT) and understand the principles of social responsibility. The article is based on a study on Fair Trade and social responsibility conducted in 2014. The study examined the consumers’ attitudes and beliefs associated with FT and local Estonian agricultural production. The article aims to compare if there are any difference in the beliefs and attitudes among the Estonian consumers towards supporting local farmers and producers versus supporting the FT ideas which benefit the farmers and producers from the Global South. The authors fully recognise that there is no competition among these two groups per se, but the perception exists in the minds of the consumers. The respondents of the nation-wide representative sample (n = 1,007) evaluated the responsibility of different economic agents such as public sector, retailers, suppliers, producers, and consumers. Most of the respondents regarded the principle of social responsibility as giving the priority to local Estonian agricultural production. The Estonian consumers tend to be sceptical about the benefits of FT or the workers and farmers from the developing countries. The awareness and knowledge about FT ideas is not high.
The assessment of hazelnut mechanical harvesting productivity
(2017) Bernardi, B.; Tous, J.; Benalia, S.; Abenavoli, L.M.; Zimbalatti, G.; Stillitano, T.; De Luca, A.I.
Hazelnut cultivation represents a new opportunity for Calabrian mountainous and sloping areas (Southern Italy), where no alternative fruit crops, except forestry, could be settled. In this Region, hazelnut production doubled during the last fifty years, inciting the farmers to introduce mechanization in cropping practices such as harvesting in order to increase productivity and decrease production costs. Indeed, harvesting is currently one of the most expensive processes of the productive cycle, moreover to be time consuming if carried out manually. Mechanization degree depends significantly on the terrain topography: in sloping areas, rakes are often associated to aspirating machines to harvest the fallen fruit, while the employment of harvesting machines from the ground prevails in flat areas. In this context, the present paper aims to assess technical and economic aspects of harvesting operation, using a harvester from the ground model ‘Jolly 2800’ (GF s.r.l., Italy). Particularly, for technical purposes data about operational working time as well as working productivity were collected according to CIOSTA requirements, in two harvesting sites, whereas, for mechanical harvesting economic evaluation, an estimation model was applied to calculate machinery cost per hour. Moreover, the cost per kg of hazelnut in shell and the average cost per hectare were estimated also. The obtained results show a working productivity of 0.065 ha h-1 op-1 in the first harvesting site, while it was equal to 0.022 ha h -1 op-1 in the second one. Concerning the average cost per hectare, the second harvesting site showed the worst economic performances, with 550.76 € ha-1 against 182.54 € ha-1 obtained in the first one.
Comparison of tillage systems in terms of water infiltration into the soil during the autumn season
(2017) Kovář, S.; Mašek, J.; Novák, P.
The soil belongs to the most valuable parts of the planet Earth. It is, endangered by water erosion, which causes huge destruction every year, or damage to farmland. More than half of the agricultural land in the Czech Republic is threatened by water erosion. The measurement was performed in the location Nesperská Lhota. The trial has been established on loamy sand Cambisol. In the field experiment, there were created 6 different variants which wad differed by soil tillage and crop. In the individual variants maize and oats were located. The field trial has been existing for a long time, as it was founded in 2009. Two measuring methods of water infiltration were used for the measurements: a mini disk infiltrometer and a single ring. The measurement was performed in the period of September 2016 before the harvest of maize. The soil aggregates were already stabilized at that time after all tillage operations. The measurement result showed the difference between the methods of soil tillage. The greatest ability of infiltration had a variant of maize with inter-row oats. Surprisingly, it was followed by maize, which was processed by ploughing technology. The lowest infiltration capacity was showed by oats reduced by soil tillage. A variant without vegetation had the second lowest infiltration. Our results obtained at rate of water infiltration into the soil affirm the need to control measures in the late vegetative stages. It is important for most of the rainfall to be quickly infiltrated so that it prevents the formation of massive surface runoff.
Theoretical research into the motion of combined fertilising and sowing tractor-implement unit
(2017) Bulgakov, V.; Adamchuk, V.; Arak, Margus; Petrychenko, I.; Olt, Jüri; Estonian University of Life Sciences. Institute of Technology
A mathematical model has been developed representing the motion of a seed drill combination simultaneously performing the preceding banded placement of mineral fertilisers. Such a combined unit comprises the gang-up wheeled tractor, the fertiliser distribution module behind the tractor attached to it with the use of a hitch and intended for the banded placement of mineral fertilisers and the grain drill behind the fertiliser distribution module attached to it also with the use of a hitch. For the components of this dynamic system the coordinates of their centres, their masses as well as the external forces and the reactions of the soil surface applied to them have been determined. In order to use the original dynamic equations in the form of the Lagrange equations of the second kind, the generalised coordinates and kinetic energy relations have been determined. Following the necessary transformations, a system of six differential equations of motion has been generated, which characterises the behaviour of the combined machine unit during its plane-parallel motion. In this system, two line coordinates and one angular coordinate characterise the behaviour of the propulsion and power unit (wheeled tractor), while three angular coordinates characterise the rotations of the draft gear and the centres of the machines integrated with its use.
Effectiveness of simulation models on technical skills among surgeons. A critical review
(2017) Raimla, Riin; Merisalu, Eda; Estonian University of Life Sciences. Institute of Technology. Husbandry Engineering and Ergonomics
Based on simulation models the surgeons can train technical skills and improve their functional status of musculoskeletal state. Work in good ergonomic position could reduce and prevent musculoskeletal disorders. The aim of this review is to carry out critical analysis of research on simulation techniques analysing the effectiveness of simulators on technical skills among the surgeons. The search of the articles based on the databases EBSCO, Science Direct and Web of Science. The articles published in 2011–2016 years and not the literature reviews of simulator models in surgery were the selection criteria. Most often the simulator models have used for training of laparoscopic operations, choosing new instruments or introducing new methodologies. Some articles have paid more attention to ergonomic equipment layout in practice to prevent musculoskeletal disorders. It is important to use simulators in the university hospitals, where the young surgeons and medical students are practicing.
Performance analysis of biodegradable municipal solid waste collection in the Czech Republic
(2017) Chotovinský, O.; Altmann, V.
The article deals with the issues of biodegradable municipal solid waste management system, focusing on its separate collection. The two basic locations are compared – rural area and urban area. The emphasis is put on evaluation of individual biodegradable municipal solid waste collections development from 2012 to 2015. Individual technological performances of collection are also observed and evaluated (e.g. biodegradable municipal solid waste production, development of container quantity and collection frequency). The observed data also verify the efficiency of biodegradable municipal solid waste management compared to relative representation of this waste in rest municipal solid waste, which is produced in both locations. Also referential locations without separate biodegradable municipal solid waste collection are observed for evaluation. There are one locality of an urban area and one rural area too. The decrease of biodegradable municipal solid waste in rest of municipal solid waste at the basic rural researched area indicates that the directive on landfills could be followed with well-chosen technological parameters of separate biodegradable municipal solid waste collection at a given site. A statistically significant impact of separate biodegradable municipal solid waste production on relative amount of the biodegradable part in rest municipal solid waste has been demonstrated at the side of this basic rural area.
Skeletal muscle tone and motor performance characteristics in dentists as compared to controls
(2017) Ereline, Jaan; Pärenson, Kaira; Vahtrik, Doris; Pääsuke, Mati; Gapeyeva, Helena
The daily work tasks of dentists are associated with repeated movements and static load during the treatment of patients. Dentists’ profession includes manual dexterity and maintaining the occupational posture for a long time. Previously it has been noted that dentists have increased muscle stress in neck, shoulder and lower back regions. The aim of the present study was to compare the muscle tone and motor performance characteristics of neck and shoulder region in dentists and representatives of other professions who do not have similar static load of long-time duration (as controls). Twenty women aged 34–55 years participated in the study: ten dentists with the age (mean and SE) of 40.2 ± 3.9 years and ten controls (bookkeepers, security guards, office workers, printing house workers, laundry and dry cleaning workers) with the age of 40.9 ± 2.4 years; working period was on the average 14 years in both groups. The tone characteristics of m. trapezius and m. extensor carpi radialis were investigated by device Myoton- 2 (Müomeetria Ltd, Estonia) at rest and at maximal voluntary contraction (MVC) in sitting position at the workplace of participants. The cervical range of motion (CROM) and the handgrip strength were measured. Significantly higher (P < 0.05) tone and elasticity characteristics of m. extensor carpi radialis and lower (P < 0.05) tone and elasticity characteristics of m. trapezius at rest were noted in dentists compared to controls. At MVC, no significant differences were found in the studied characteristics between body sides in the measured groups. Dentists had lower (P < 0.05) CROM of flexion and rotation than controls. In dentists emerged significant difference in muscle elasticity characteristics for the right body side, this is related with stretching for dentistry instruments.
Comparison of mechanical and electric drive of mulcher
(2017) Pexa, M.; Čedík, J.; Kumhála, F.; Pražan, R.
The contribution is focused on comparison of mechanical and electric drive of mulcher with vertical axis of rotation by means of mathematical model. The mulcher has working width of 6 m and it is usually aggregated with tractor of minimal power of 150 kW. On the test plot the torque and power transferred trough the tractor PTO, fuel consumption and the production of gaseous emissions components were monitored. This field measurement served as a basis for modelling as well as measured complete characteristics of the combustion engine of the tractor John Deere 7930. As a main base for the modelling the record of real operation of the tractor with mulcher was used. Then, in the software product MathCad the operation of the tractor with mechanical and electrical drive of the mulcher was modelled. In the case of the electrical drive of the mulcher the tractor with internal combustion engine, connected to generator was taken into consideration. Due to overall lower efficiency of the electrical drive with generator, worse values of the fuel consumption and emissions production in comparison with mechanical drive were reached in case of electric drive. At hypothetical use of batteries (100% electro-powered tractor) and when the energy mix at Czech Republic is taken into consideration, it is possible to reach the quarter values of emissions production in comparison with combustion engine.
Effect of rake angle and cutting speed on energy demands of mulcher with vertical axis of rotation
(2017) Čedík, J.; Pexa, M.; Pražan, R.
The contribution deals with the reduction of agriculture energy demands. For maintenance and treatment of permanent grassland areas, areas left fallow and put to rest the mulching in combination with other workflows (mowing, grazing) is advantageous procedure. As conventional impact grass cutting and chopping is energy demanding procedure, it is proper to reduce the energy demands of such device. In the paper the effect of shape of cutting tool, particularly the rake angle, on energy demands of mulcher with vertical axis of rotation is studied. The effect of cutting speed on energy demands is also verified. The measurement was performed using mulcher MZ 6000 made by Bednar FMT Ltd. with working width of 6 m and three rotors. During the measurement the test rides using the cutting tools with different rake angle and cutting speeds of 105m s-1 , 89 m s-1 and 79 m s-1 were performed. The rake angle of cutting tools were chosen 0°, 15° and 25°. The test area was pasture with permanent grassland. During the measurement the torque and power, transferred through PTO to the machine, fuel consumption and GPS coordinates were measured. From each test ride the samples of grass matter were taken in order to determine the yield and moisture content. It was found that increase of the rake angle up to 25° and decrease of the cutting speed resulted in decrease of the power requirement of the mulcher.
Comparison of tractor slip at three different driving wheels on grass
(2017) Abrahám, R.; Majdan, R.; Drlička, R.
The paper deals with a possibility of tractor slip reduction on a grass and evaluates an use of two versions of special wheels. Both prototypes were developed at the Department of Transport and Handling of the Slovak University of Agriculture in Nitra. The first system was designed in 2010 year as blades wheels. The second system (spikes device) consists of spikes which are mounted onto standard tractor tyres with special cuts, was designed in 2014 year. The spikes are settled in these cuts while moving on road surface. The second one is placed near the drive wheels and uses the blades. The spikes and blades are ejected to reduce wheels slip when tractor operates on grass or soil. The base position allows tractor transport on road with standard tyres. The goal of experiments realized on grass surface was to compare mutually slip behaviour achieved. The measurements were realized with standard tyres without any modification, too. A tractor with three types of drive wheels were loaded by heavier tractor. Drawbar pull and wheel rotation speed for slip calculation were measured in tests. The results show a fact that a loss of energy due to the wheels slip increases, while a penetrometric resistance in the surface layers of a soil decreases, at soil humidity 33.2%. An application of both prototypes is very advantageous because they reduce the wheels slip, increase tractor operation efficiency and so protect the soil.
Investigation of coaxial laser cladding process parameters influence onto single pass clad geometry of tool steel
(2017) Locs, S.; Boiko, I.; Drozdovs, P.; Dovoreckis, J.; Devoyno, O.
This paper is devoted to the investigation of the influence of technological parameters on the single pass clad geometry and quality as well as elemental composition in the clad after coaxial laser cladding (CLC). The objects of the investigation are components of expensive machines and tools for presswork needed to be repaired, i.e. refurbished for the future application with the goal of effective using of material resources in production. Nowadays such repair of worn tools is an actual task due to tendency for thrifty management of resources at affordable cost. Experimental work was carried out using CLC system, which consists of industrial robot and a ytterbium fiber laser with a core diameter of 100 μm, integrated to the coaxial powder supplying cladding head. During research separate cladding tracks of metal powder AISI М2 (particle size 53–150 μm) were deposited on the top surface of steel plates, which were grinded before treatment. This work’s highlighted parameters for variation were laser scanning speed and laser beam focus plane distance. The clad geometry was examined on cross-sections with SEM. Elemental composition was determined by the X-ray spectroscopy analysis. Gladding beads with good surface quality were achieved. Cross-sectional observation presented that clads has a good fusion with the base material without exfoliation. Keyhole shape of molten substrate area was achieved, which leads to increase of the dilution value. The future research is needed to achieve stable quality of cladding, which is extremely necessary for industry.
Improving job satisfaction with different intervention methods among the school personnel in Estonia and Latvia
(2017) Hrenov, G.; Vilcane, I.; Urbane, V.; Tint, Piia
This investigation was carried out in two high schools: one in Estonia (EST1) and one in Latvia (LAT1). The offices EST2 and LAT2 were chosen from the countryside of the both countries. Office EST1 is situated in an atrium-type building for educational and research needs. The second building is mainly for education (auditoriums) and the offices LAT1 are situated on the ground floor. The third and the fourth offices were taken for comparison. Office EST2 is situated in a countryside in an old wooden building; the fourth office LAT2 is located in a new building in Latvian countryside. All together 181 office-workers were involved. At first, the work environment conditions were measured. The ergonomics of workplaces was assessed with ARTtool and Kiva-questionnaire was used to study psychosocial conditions and job satisfaction at computer-equipped workplaces. Occupational hazards were measured to clarify, do the work environment influence on the behaviour and the job motivation and satisfaction of the worker at workplace? After the first questioning of workers using Kiva-questionnaire, the Metal Age programme was implemented and after the intervention, the Kiva-questionnaire was carried out again. The results showed that if the preventive measures for solving the problems at workplace are implemented, and the employers and the employees are trained and consulted using the appropriate programmes, the stress situations could be avoided. The workers in all offices were confident that the discussion about the problems is very important as the work with computers is intensive and there is a very short time to communicate with each other. The educational work is also stressful.
Weed community trajectories in cereal and willow cultivations after termination of a willow short rotation coppice
(2017) Welc, M.; Lundkvist, A.; Nordh, N-E.; Verwijst, T.
According to guidelines for willow short rotation coppice (SRC), weeding is needed during establishment, while weed populations which develop later under a well-established willow canopy do not require control. However, farmers are concerned that weeds which develop in SRC may result in long-lasting weed infestations in succeeding crops after SRC termination. We assessed the effects of two SRC-termination methods (with shallow and deep soil cultivation) on the development of the weed flora in a cereal system (CS) and in SRC during six seasons. Richness, ground cover, life-cycle strategy and composition of the weed species, and their environmental requirements (inferred from Ellenberg index) were evaluated. SRC-termination method had no effect on the weed community trajectories in the succeeding SRC and CS. However, cropping system and growing season had significant impacts on species richness, ground cover and composition of the weed flora. Differences in weed communities over time and between cropping systems were related to the impact of cropping systems on factors such as light, soil moisture, nitrogen level, and soil reaction, as inferred from the Ellenberg index. After termination of the old willow cultivation, the weed flora of the SRC and CS rapidly diverged and approached the weed flora characteristic for old willow stands and non-weeded old cereal plot, respectively. We conclude that willow stands can be converted, regardless of termination method, either into willow or cereal cultivations without additional risk of weed infestations other than those specific for their respective cropping systems. Furthermore, willow cultivations in agriculture contribute to floristic diversity at the landscape scale. Key words: life cycle, Salix spp., short rotation forestry,

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