Pollution of atmosphere and decrease of fossil fuels stimulates people to search for an alternative energy sources for production of energy, both electrical and heat. In Latvia it is possible to use almost all alternative energy sources for production of energy, including solar energy that becomes more relevant year by year. Solar radiation in direct way makes no hazardous, but, as the intensity of solar radiation in geographical location of Latvia is comparatively low, the utilization of it demands relatively expensive equipment. Production of energy from other sources of energy also demands certain investments as well as the purchase of fuel, maintenance of equipment and presence of different manipulators. In practice several types of solar collector constructions with efficiency from 30 up to 75% exist and expenses vary in the wide range. The average number of sunshine hours in Latvia is about 1800 hours yearly. Nevertheless solar collectors for water heating in Latvia are used. Mostly flat-plate collectors are used whose efficiency often is not sufficient and water has to be additionally warmed-up. The aim of our investigation is to study operation of evacuated tube collector in conditions characteristic to Latvia. It is stated that it is feasible to use evacuated tube collector for water heating in Latvia, especially from March till October. During winter period solar collector can be used as additional energy source for water heating.

This paper presents results of pressure oscillation investigation in hydraulic hitch-system of a tractor Claas Ares ATX 557 during the motion during artificial roughness road test. During experiments oscillation at different driving speed, tyre pressure and hitch-system oscillation damping (turned on/off) were investigated. Tractor hydraulic hitch-system was equipped with a pressure sensor Wika Transmitter ECO-1 and data processing software PicoLog. Results of experiments present maximum pressure peak of 210 bar in the tractor hydraulic system when hydraulic hitch-system oscillation damping system at driving speed 8 km·hE-1 is not used and system pressure peak reduces to value of 180 bar if the hydraulic hitch-system oscillation damping is used.

Barley is a key ingredient in beer production. The aim of the current research was to study the dynamics of vitamin C and vitamin E in flaky and hull-less barley grains during steeping, germinating, and kilning. The research was accomplished on hull-less barley (two lines – '3528' and '3537') and flaky barley selected in Latvia in 2009 with a germination capacity above 95%. The grains were steeped, germinated and kilned using traditional malt production technology. During research the vitamin content was analysed using standard methods: vitamin C by EN 14130:2003, and vitamin E by AOAC 971.30. The content of vitamin C increased during steeping in flaky barley grains till 0.23 mg 100 gE-1, but in hull-less barley grains: line '3537' till 0.47 mg 100 gE-1, and line '3528' till 0.30 mg 100 gE-1. During germination vitamin C content in flaky barley increased by 68%, in hull-less barley: line '3528' – by 82%, and line '3537' – by 57%. The content of vitamin C in the analysed malt samples was 0.35-0.38 mg 100 gE-1. The content of vitamin E in all barley samples was similar after grain steeping. The content of vitamin E was 3.9 times higher in flaky barley, but in hull-less barley lines: '3528' – 4.1, and '3537' – 4.5 times higher compared with its initial content after germination. After grain kilning, the content of vitamin E decreased in all barley grain samples. The results show that using some cultivars of hull-less barley for malt production, it is possible to obtain a higher content of vitamins C and E in the end-product.

Jerusalem artichoke powder (JAP) from Jerusalem artichoke (Helianthus tuberous L.) roots is a nutritive valuable product that can be used for a healthy product development. The influence of JAP on the quality and degree of liking of cakes was investigated. Sensory evaluation of cakes was realized in two stages: the first - to define the quality attributes of the cakes with JAP from the point of view of the experts, the second – to find out the consumers' views on the cakes, whose quality has been improved in accordance with the recommendations of the experts. As a control sample, the classic home cake was evaluated. Control sample was compared with the cakes, where the amount of wheat flour prescribed by recipe was partly substituted with JAP at different concentrations. Experts evaluated cakes and defined the highest acceptable concentrations of JAP in cakes. For the consumers it was offered to assess the cakes with JAP at concentration 30% and with different taste and aroma enhancers. Cakes with 30% of JAP additive were the most favoured by the sensory properties: aroma, texture, softness elasticity, porosity and softness, surface crust, appearance, colour, shape, and size. Results of analysis of variance showed that there no significant differences in the degree of liking between the cakes with JAP and the cakes with taste and aroma enhancer additives (p is greater than 0.05). There had been performed hardness analysis and colour measurement for cakes with JAP. The observed results declare high influence of aroma and taste enhancer on cakes structure and colour.

The pears (Pyrus communis) are one of most popular fruits that consumers willingly use as fresh produce. On the market place, consumer mainly pays attention to per's externals, size, colour, as well as to fruit taste, substantially influenced by degree of readiness, which in its turn has affect on the chemical composition of pears. The physical, chemical and sensory indices are significant when fruits have been used for fresh-cut fruit salad preparation. All tests have been carried out at Latvia State Institute of Fruit Growing, Dobele in year 2009-2010. The objective of this study was to evaluate the physical, chemical and organoleptical properties of winter cultivars of pears grown in Latvia. The object of the research was 13 cultivars of pears: 'Delta', 'Latgale', 'Tayushchaya', 'Talgarskaya', 'BP 8965', 'Elektra', 'Janvarskaya', 'Beta', 'Bere Kiyevskaya', 'Eckehard', 'Belorusskaya Pozdnaya', 'Erika', and 'Conference' and as a control commercial cultivar. The pears were analysed and their parameters were measured: average mass and diameter of fruits, flesh firmness, colour of flesh, titratable acid (TA) and soluble solids content (SSC) were determined. Sensory analyses were carried out by 9-point hedonic line scale method. Soluble solids content (degree Brix) of pear fruits grown in Latvia is within 9.6 - 14.5 degree Brix. The titratable acidity (TA) is insignificant (0.05-0.26%). The average mean mass of one fruit depending on a cultivar, is 174 g, the flesh firmness at the maturity stage is on average 10.7 to 26.5N. The fruits of cultivars 'Tayushchaya', 'Elktra', and 'Bere kiyevskaya' by their sensory indices were evaluated as the best.

Appropriate discount rate for forestry is still an issue for the forest economy. Therefore, it is significant to understand the importance of discounting, and how costs of forestry production process are valued. Forest regeneration and new stands tending costs are considered as investments; they are related to each particular stand. For that reason, the goal of this study was to compare how the value of this investment is growing at the bank deposit or 1 ha forest stand. The study examined the growth rate of two different tree species value with young forest stand establishment and tending investments depositing in the bank or the growth rate of compound interests. As discounting formula derived from a compounding formula, it would allow to find an appropriate discount rate for each timber species. High rates of compound interest cause a very rapid and unrealistic future value increase, while low rates cause slow value increase for a very long period represented by a common forest rotation; for that reason high discount rates used in forestry are not rational. Taking into account an income from intermediate cuttings, the value of timber species in comparison with the deposit significantly improves. Suitable discount rate determination in forest assessment is mainly determined by the species of wood productivity and cutting age. As it is hard to find two identical forest properties, each situation should be considered individually, taking into account and understanding the relationship between a growth rate of timber and compound interests, thus choosing an appropriate discount rate.

The forests and woods are the main resources in Latvia. It is vital to understand the amount of wood resources that is being extracted from private forests now and in future in order to be able to predict the forest sector development and growth. The study objective was to identify the key factors in the wood resource availability and assess their role in private forests. In October 2009, the study was conducted to appraise the private forest owners the operational results and find out the future plans in connection to wood resource extraction. In the study a random sampling method was applied, where in the respondent selection the State Forest Service database information was used. In the study the respondent interviewing method CATI with computerized telephone interviews was used. In the selection of affecting factors the expert's method was applied. The study showed that only 25.40% of all private forest owners claimed that there was wood resources extraction in forests, but 29.50% of all private forest owners claimed that they were planning to perform the wood resource extraction in 2010. If the timber selling prices increased by more than 10 LVL per m3 in 2010, then 38% of all respondents claimed that they would increase the wood resource extraction in forests. The study data show that 30% of all private forest owners admit that there are growing stands in the forests, but they can’t be harvested, because road infrastructure is poorly developed or there are no roads in the forests.

This paper discusses the use of medium resolution Landsat TM satellite images to support conventional approaches of Lithuanian forest inventory practices. Estimation accuracies achieved using just field measured sample plots, Landsat TM satellite images and two non-parametric k-nearest neighbour and most similar neighbour estimators were studied at a level of compartments. 19 mature forest areas, prepared for final felling with GPS measured borders and all trees callipered, were used for validation. Notably higher estimation accuracies were achieved using field sample plots distributed through the whole forest area studied than just ones located on mature forest stands. The root mean square deviations in estimating compartment-wise volume of growing stock per 1 ha was around 27-28% if the best variant of estimation approach was used. Possible influence of the accuracy in locating the borders of validation areas on the estimations is discussed in the paper, too.

This paper introduces the first test results to use laser scanning and high resolution digital colour infrared aerial image data to estimate average tree crown density at a sample plot level. General methodological framework based on two-phase sampling schemes, non-parametric estimators and satellite images as the auxiliary data sets was adopted for the use with airborne data sources. More than 400 circular sample plots were established and measured in a special research forest area near Kaunas, the central part of Lithuania. The tree crown density was visually estimated for every coniferous tree belonging to the 500 square m plot together with other conventional forest parameters. Two variants of digital colour infrared aerial images (ground sampling density 15 and 40 cm), LiDAR point clouds, based on 1 point/square m scanning density and two phase sampling approach with non-parametric k-nearest neighbour and most similar neighbour estimators were used to test the accuracies of tree crown density estimation at a sample plot level. Reliable estimates were found to be possible on pure coniferous stands only. Average tree crown density was estimated with the root mean square error around 17.5-18% at a sample plot level, bearing in mind average crown density around 64% for the whole study area. The estimates were unbiased. Integration of laser scanning based variables with the ones available from digital aerial images resulted in lowest estimation root mean square errors. Laser scanning based variables used as the auxiliary data set independently resulted in better estimation errors than the variables available from digital colour infrared images.

Researching new remote sensing and data processing methods is very important subject in forestry. The objectives of research are to explore methods to determine single tree characteristics using LIDAR and adapt them for Latvian forest conditions. Different algorithms and mathematical relations for automatic calculation of tree species, coordinates, height and diameter at breast height are described. Within the project four different clustering methods for tree identification were evaluated. The first method's construction is based on reflection point count in certain height range. The second and third methods are searching for global and local maximums on height axis of LIDAR data collection. In the fourth method segmentation of aerial photography is done by using the user selected sample data. Tree tops were s discovered by searching similarly coloured regions. Field measurements were used for the calibration of LIDAR data and analysis. Sample plots were fitted in the study area with different species composition, age and density. The total number of measured trees in sample plots is 1844. Results show that height can be found mainly for I, II, III craft class trees with average error 2.5%. Stem diameter estimation error of pine is 28%, spruce 17%, birch 4.2% and second storey trees 5.4% using linear equations D = 0.6616*H + 4.6969 (for coniferous trees) and D = 0.7756*H + 3.7132 (for deciduous trees). Dividing trees in classes of coniferous and deciduous can be done by using near infra red photography. The total number of first storey trees identified by LIDAR is 91%, by aerial photographic method 94%.