TThe aim of this study was to evaluate an impact of nitrogen fertilizer rates on industrial hemp’s (Cannabis sativa L.) growth and development in Latvia. The trial was carried out during 2012 on the Research and Study farm Peterlauki of the Latvia University of Agriculture in the sod calcareous soil. There were three industrial hemp cultivars ‘Futura 75’, ‘Tygra’ and ‘Felina 32’ tested under different fertilizer rates: N0P0K0 – control, N0P80K112 – background fertilizer (in text marked as F), F+N30, F+N60, F+N90, F+N120, F+N150, F+N180 kg haE-1. Weather conditions were proper for good hemp biomass production. Depending on the selected cultivars, the optimal fertilizer rate was in the range of 90 – 150 kg ha-1. Industrial hemp stalk length was significantly (p is less than 0.05) influenced by the applied nitrogen fertilizer rate and cultivars. The highest stalk length was observed in the cultivar ‘Futura 75’ under all nitrogen fertilizer rates. The highest stalk length (3.18 m) had reached under the nitrogen fertilizer rate 150 kg haE-1 at 138 growing day from sowing. At the beginning of growing season (June - July) the growth intensity of hemp stalk length is high. Within one month the stalk length grew up for 1.23 meters of cultivar ‘Futura 75’. The intensive growth of hemp stalk declines when the flowering stage is reached. Flowering stage occurred in early August, and it was dependent on nitrogen fertilizer rate. Under higher nitrogen fertilizer rate the flowering stage reached later.

Ground beetles (Coleoptera: Carabidae) and rove beetles (Coleoptera: Staphylinidae) as predators of many pests and weeds in every crop are significant elements of integrated pest management. Worldwide studies show that ground beetles reflect different soil tillage methods, crop rotation, chemical and genetic pollution, usage of fertilizers and landscape fragmentation. All these factors are the parameters based on which it is possible to assess agriculture whether it is sustainable or not. Ground beetles also can indicate different farming systems and potentially serve as keystone indicators of pest abundance. Thus ground beetles can be good indicators of sustainable agriculture, but rove beetles have a good potential to do it. Researches on crop dwelling ground beetles and rove beetles have been done infrequently in Latvia. Mainly these are faunistic studies not paying attention to agricultural environmental factor effect to ground beetles and rove beetles. For using ground beetles and rove beetles as indicators of sustainable agriculture in Latvia, studies on these beetles reaction to different farming activities should be done. These studies must occur in different crops and different places of country, because ground beetle and rove beetle reflection to changes of agricultural environmental factors may be crop- and site - or even field-specific. Overview of literature on ground and rove beetles’ ecology in agroecosystems recorded in Latvia, other European countries and Northern America has been used for this study.

The aim of the present study was to estimate variance and covariance components and genetic parameters for birth, weaning and yearling weights. The data were collected from lambs who born in period from 2007 to 2010 years and located in 58 pure-bred sheep herds in Latvia. Records of 11310 lambs from 160 rams and 4180 ewes for birth and weaning weight and on 3194 lambs from 134 rams and 2058 ewes for yearling weight were used in this study. The total number of individual pedigree was 18932. The fixed effects in the model were sex and type of birth, birth year and month and age of dam, because all growth traits were significantly affected by these fixed effects (p is less than 0.01, p is less than 0.05). Genetic parameters for growth weights were estimated by Restricted Maximum Likelihood (REML) procedure fitting three animal models including various combinations of maternal and herd effects. Based on the most appropriate fitted model which included additive genetic, maternal additive genetic and herd effect, direct heritability’s were estimated to be 0.26 ± 0.01, 0.29 ± 0.63, 0.29 ± 2.63, but maternal heritability’s 0.14 ± 0.00, 0.04 ± 0.19, 0.04 ± 0.94, respectively for birth, weaning and yearling weights. The results showed maternal and strong herd influence in this study, therefore inclusion of maternal and herd effects into the model for growth traits is necessary.

The experiment was carried out in the Latvia University of Agriculture. The objectives of this research were to study changes of bean (Phaseolus) protein fractions occurring under the thermal treatment conditions and determine the critical temperature for Maillard reactions in beans. In these reactions lignified protein is made from amino acids and sugars, and it decreases the nutrition value of the food. If lignified protein exceeds 50% of crude protein content in food, then food is considered unsuitable for daily diet. In this experiment beans were milled and then heated at 50 ± 3 °C, 75 ± 3 °C, 100 ± 3 °C, 125 ± 3 °C and 150 ± 3 °C temperature in the drying oven for 20 h. As a control sample non heated beans were used, and they all were kept in a plastic jar at room temperature (20 ± 1 °C). Dry matter, crude protein, starch, sugar and lignified protein content were determined in heated beans and control samples. No significant changes of crude protein content were observed due to thermal treatment. It was from 24.3 ± 0.3 g 100 g-1 of dry matter. Similarly, no significant changes were observed in starch content, as it stayed averagely 47.1 ± 0.2 g 100 g-1 of dry matter. Medium high correlation was observed (0.64) between lignified protein content and sugar content for in different temperature treated beans. Lignified protein showed exponential growth if the samples were heated at a temperature of 100 ± 3 °C and higher, giving exponential change.

Fruits and vegetables are a major source of antioxidants. The aim of current research was to study and compare the antiradical activity, the total polyphenol content (TPC) and the total flavonoid content (TFC) in dried carrots (Daucus carota), pumpkins (Cucurbita maxima), leeks (Allium ampeloprasum var. porrum) and black radish (Raphamussativus) using a traditional convective drier and a microwave-vacuum drier. For each vegetable steaming as pre-treatment was used. Vegetables were harvested in Latvia in 2012, gathered when ripe and then dried. Analyses were made in Latvia University of Agriculture, Faculty of Food Technology laboratories. The total polyphenol content was determined by the Folin- Ciocalteu method and the total flavonoid content - using spectrophotometric method. The antiradical activity was analyzed by the 2,2-diphenyl-1-picrilhydrazyl (DPPH) assay. The results of experiments demonstrate that the total amount of polyphenols ranged from 98.97 to 623.70 mg gallic acid equivalent (GAE) 100 gE-1 in dry weight and the total amount of flavonoids ranged from 40.32 to 100.23 mg catechin equivalent (CE) 100 gE-1 in dry weight. The value of DPPH antiradical activity for vegetable samples ranged from 6.10 to 45.14 percents.

Malt is a natural food product produced by germinating cereal grains. Safety of cereal grains and cereal products is a very important area. Experiments were carried out at the Faculty of Food Technology of the Latvia University of Agriculture. The research object was rye malt. The purpose of the research was to investigate and compare the influence of copper and selenium on microbiological indicators of rye malt. Rye grains of 96% viability were soaked and germinated at temperature +6 ± 2 °C for 4 days, using copper(II) sulphate pentahydrate CuS04*5H2 O solutions (Cu concentration 10 mg LE-1, 50 mg LE-1, 100 mg LE-1) and for 3 days using sodium selenate Na2 SeO4 solutions (Se concentration 3 mg LE-1, 5 mg LE-1, 10 mg LE-1) then the soaked grains dried in the oven for 24 hours. The total plate count and yeast colony forming units were determined in rye malt samples. The obtained results showed that the increasing of copper and selenium concentration in solution significantly changes microflora of rye malt comparing with the control sample.

The main purpose of the research was to investigate the physically-chemical parameters of organic and conventional hull-less barley (Hordeum vulgare) harvested in Latvia. In the experiment the following hull-less barley harvested in 2012 from the State Priekuli Plant Breeding Institute (Latvia) was used: ‘Irbe’, PR4651, PR3808.21 and PR5099. The following quality parameters of grain – protein, starch, the bulk density and β-glucan content – were measured by standard methods – Infratec™ 1241 Grain Analyser (Denmark) corresponding to ISO 12099; thousand-grain weight (TGW) (ISO 520:2010); the falling number (ISO 3093:2009); moisture content (LVS 272:2000) were also determined. In the present experiments no significant differences in protein, moisture, starch, β-glucan content and TGW were detected, however, significant differences in the bulk density of all analyzed hull-less barley samples were established. The lower analyzed parameter value of 780 ± 1 g LE-1 was obtained for the conventional and organic hull-less barley PR 5099. However, the higher bulk density value of 821 ± 1 g LE-1 was obtained in the conventional hull-less barley variety ‘Irbe’. No significant differences in the bulk density of conventional and organic hull-less barley ‘Irbe’, PR4651 and PR3808.21 were found. Significant differences in the falling number were detected in the analyzed hull-less barley samples harvested in the conventional and organic farming. The lower falling number value was obtained in the organic hull-less barley line PR 5009 – 81 ± 4 s, the higher in the conventional and organic hull-less barley line PR 3808.21 as 362 ± 5 s and 373 ± 2 s, respectively.

The research paper discusses simulation of the loading process of the vertical axis wind turbine with the permanent magnet synchronous generator. Experimental and analytical studies were done in the year 2013. The research results show that electrical load on the wind turbine generator is important for the wind turbine performance. If the load is above or below the power gained from the wind energy, the turbine operation cannot be considered efficient and its dynamic parameters fail to achieve the efficiency level at the proper operation load when the load is built up strictly in accordance with the wind energy input. In the research, 3 separate virtual electrical loading models with static, discrete, dynamic electrical load were established. MATLAB SIMULINK simulated virtual model shows the importance of usage of the right amount of electrical load in the vertical axis wind turbine with the permanent magnet synchronous generator. Final research results showed that the most effective loading process of wind turbine generator is a dynamic load.

The aim of current study was to investigate the spectral separability trends of different tree species due to varying foliage spectral reflectance properties during the growing season. Five tree species prevailing in Lithuania were chosen for the study: aspen (Populus Tremula L.), black alder (Alnus Glutinosa (L.) Gaertn.), Norway spruce (Picea Abies L.), Scots pine (Pinus Sylvestris L.) and silver birch (Betula Pendula Roth). The hyperspectral reflectance data was collected under laboratory conditions scanning the foliage samples from two healthy middle aged stands. Hyperspectral scanning was implemented using Themis Vision Systems LLC VNIR 400H hyperspectral imaging camera in 400-1000 nm range. Principal component analysis and the Jeffries-Matusita distance measure were applied for the analysis of hyperspectral data. The wavelengths providing the best separability between tree species were determined. They were discovered to vary during the growing season: in late spring – early summer the most informative wavelengths were concentrated in blue and near infrared spectral zones, in summer they shifted towards green and red zones, and in autumn they moved further to longer waves - the red and near infrared - spectral zones. The investigated tree species were determined to be spectrally separable during the whole growing season, but the particular periods were revealed to contribute for improved spectral separability between certain tree species. The separability between coniferous species was best in September, while deciduous species were best separable when the samples were collected in August.

Tree species identification is important for a variety of natural resource management and monitoring activities especially in forest inventory. The objective of research is to identify tree species using digital aerial photography and LIDAR data in Latvian forest conditions. The study outlines a number of tree species identification possibilities: the ability to identify conifers and deciduous trees; the ability to identify pine and spruce; the ability to identify birch, aspen and black alder. The study site is a forest in the middle part of Latvia at Jelgava district (56º39’ N, 23º47’ E). Aerial photography camera (ADS 40) and laser scanner (ALS 50 II) were used to capture the data. LIDAR resolution is 9 points m-2 (500 m altitude). The image data is RGB, NIR and PAN spectrum with 20 cm pixel resolution. During the study a modified region growing algorithm was developed to determine tree canopy and tree species identification using threshold segmentation, Fourier transform, frequency filtering and reverse Fourier transform. Tree species classification of coniferous and deciduous trees is possible in 82% of the cases; the first storey of the trees can be classified correctly in 96% of the cases, but the second storey of the trees only in 49% of the cases. Spruce identification is possible in 81.1% of the cases, for first storey trees in 89.6% of the cases and for the second storey trees in 72.9% of cases. Deciduous tree correct classification is possible in 63% of the cases, birch 75%, black alder 60% and aspen only in 41% of the cases.