The properties of the transverse section surface of the wood are crucial when using it as an adhesive in finger joints. Contact angles of three test liquids sessile drops - water, diiodomethane and ethylene glycol - with known characteristics of surface free energy were measured on wood surface with the grain orientation 45 ° against the plane. Acid–base approach was used to calculate surface free energy and its characteristics of Scots pine (Pinus sylvestris L.) with moisture content of 21% and Norway spruce (Picea abies L. Karst) with moisture content of 10% wood samples from values of the contact angle. The wetting behavior of the wood samples was examined with the contact angle method (goniometer technique) in the Laboratory of the Department of Chemistry of Latvia University of Agriculture at the beginning of 2013. The aim of this study was to verify possibility of determining the contact angle values of the wood and calculate the surface free energy and its components of wood from the obtained contact angle values using acid-base theory. At the end of this study it was concluded that the acid–base approach is a suitable method to calculate surface free energy and its characteristics of wood from the values of the contact angle. Nevertheless, indirect methods of liquid drop contact angle value estimation must be used because direct determination is not feasible on wood surfaces with open capillaries.

The paper overviews the research material related to occurrence of sinkholes and change of their water quality in the conditions of increasingly natural environment and minimal anthropogenic impact. Sinkholes create favourable conditions for interaction of surface and groundwater. Identification of possible sources of sinkholes pollution is very important in solution of groundwater safety problems. Water quality investigations are carried out in 4 sinkholes, which are of different age and have differently overgrown slopes. Sinkhole water quality may worsen due to accumulation of organic materials (increasing peat content) or natural changes of environment (abrasion of slopes, overgrowth, etc.), while anthropogenic impact is minimal. Water quality in peat-filled sinkholes and young sinkholes with mineral slopes is different. Water of peat-filled sinkholes has bigger amounts of N-NO3, PTotal, SO4 and BOD7 than water in young sinkholes. The highest N-NO3 and SO4 concentration is observed in the sinkhole that is overgrown with trees and shrubs.

The concept of polycentric development at multinational, national and regional level is broadly used in academic research of regional development and spatial planning. It is also reflected in the normative agenda by the European Union. However, polycentricity has been considered a fuzzy concept, and it still lacks commonly accepted definition or measurement methods. Albeit a plethora of researchers and policy makers favours polycentric development as a tool for reduction of regional disparities, these statements are not based on empirical foundations. The research objectives are twofold and consecutive. The first objective is to define the morphological measures of polycentricity and apply these measures at country level. The second objective is to empirically test the following hypotheses: regional disparities in countries with polycentric urban system are less pronounced than in countries with monocentric urban system; income distribution in countries with polycentric urban system is more equal than in countries with monocentric urban system. The hypotheses stated by the objective of the study can be rejected: regional disparities in countries with polycentric urban system are not less pronounced than in countries with monocentric urban system; income distribution in countries with polycentric urban system is not more equal than in countries with monocentric urban system. The research results clearly suggest the polycentric development cannot be considered a tool for diminishing regional disparities and providing more cohesion between regions.

The first independent career related decisions are made during the ninth grade of the elementary school when the further educational institution is selected. The concept of possible selves can be used in career education to help students increase self-awareness, explore and generate options, and formulate plans to achieve future goals. The aim of the article is to examine rural adolescents’ ability to generate career-related possible selves and plausible strategies to attain these possible selves. On the basis of the Possible Selves Theory, the open-ended measure was developed by the author. The pilot research was carried out in Latvia in January 2013. Forty six nine-graders from two rural elementary schools and two rural secondary schools participated in the research. Next year and adult possible selves generated by rural adolescents include such domains as education, employment, leisure activities, physical and personal development, as well as interpersonal relationships and lifestyle. The most important ones are domains of education and employment. Statistically significant differences of the results among the gender subgroups are not found in the research, statistically significant differences exist between the possible selves and their attaining strategies generated by rural secondary school students and rural elementary school students.

Several fungicide applications are used to control a pear scab (Venturia pirina Aderh.) on pear (Pyrus communis L.) trees. Minimal chemicals use in fruit-growing constantly has been important condition in the integrated fruit production; therefore, sanitation is recommended to reduce a primary inoculum in orchards. The study was carried out in an integrated pear orchard located in Sigulda district, in the central part of Latvia to estimate if a fall treatment of a pear orchard with urea reduces an amount of pseudothecia and pear scab incidence level the following season. Six treatments trial was arranged in the autumn 2011 on a moderately susceptible pear cultivar ‘Belorusskaya Pozdnaya’. An amount of leaf litter, pseudothecia and incidence level of a disease on leaves and fruits were determined. The results showed that urea application reduced both an amount of leaf litter and a number of pseudothecia. An average amount of leaf litter was 127 leaves per 0.25 square m in a control and 89 leaves in a treatment with urea application. The number of pseudothecia reached 250 pseudothecia per one leaf disc in a control and 160 pseudothecia in a treatment with the urea application, the difference was not significant (p is greater than 0.05). The reduction of disease incidence level on leaves was significant (p is less than 0.05) only in the first assessment of five in total.

Oat breeders have improved yielding ability potential of oat (Avena sativa L.) cultivars, but set lower standards for biochemical composition of grain. Nowadays the quality of grain for consumers has become important especially in terms of lipids and β-glucan content. Experiments were carried out at State Stende Cereal Breading Institute in the year 2012 to evaluate the oats yield and grain quality. 15 different cultivars of Stende collection were compared by yield and parameters of productivity (test weight and 1000 kernel weight) as well as biochemical parameters (protein, starch, lipid, β-glucan, content). Biochemical parameters were tested by Infratec Analyser 1241. To obtain an equal research background all cultivars were grown in a plant breeding crop rotation field, with similar growing conditions (sowing-time, fertilizer, plant protection activities), which agree with generally accepted technology of oat cultivation in Latvia. Experiments were done in four replications. Plots were laid randomized. ANOVA procedures were used for data analysis. Yield of experimental cultivars varied between 4.28 ± 0.19 - 5.93 ± 0.22 t haE-1, test weight 46.85 ± 0.99 - 52.75 ± 0.44 kg hLE-1, 1000 kernel weight 33.70 ± 0.24 - 46.34 ± 0.80 g. Significant differences of tested yield parameters among oat cultivars were observed. The highest protein content was observed for local breed cultivars ‘Arta’ and ‘Mara’ 119.5 ± 02.6 and 110.5 ± 1.9 g kgE-1 accordingly. Low starch content, but high β-glucan content is characteristic for all Latvian cultivars.

Agricultural farms in modern production system are specialized; therefore, animal-origin organic fertilizers are not available for many of them. Researches on the use of organic products in agriculture to restrict the use of pesticides and mineral fertilizers have been performed for a long time. Nowadays different organic preparations that are acquired as a result of complex processes are produced, ensuring ready-to-use biologically active substances in them and also activating their properties. One of the purposes of the research was to evaluate the impact of extracts from organic products on the potato (Solanum tuberosum) yield and tuber quality in the conventional cultivation system. A field experiment using cultivars ‘Borodyansky Rozovij’ (early maturity) and ‘Lenora’ (mid-early maturity) was arranged in the State Stende Cereals Breeding Institute in 2011 and 2012. Peat elixir and vermicompost extract obtained at different temperatures: + 45 °C and + 95 °C, as well as a mixture of these extracts were used for treatment of tubers and plants. The research included 24 treatments in total, including control (without treatment) and a standard potato cultivation technology. Tubers were treated immediately before planting, but plants were treated three times during the vegetation period. Average two-year research results showed that the use of organic product extracts significantly (p is less than 0.05) affected the tuber yield in different treatments for both cultivars ‘Borodyansky Rozovij’ and ‘Lenora’. The content of nitrates in tubers, using extracts, did not exceed the allowable level (160 mg kgE-1) in any of treatments.

In the last years total area of buckwheat (Fagopyrum esculentum) has increased notably in Latvia, including the Eastern part of the country but there is a lack of actual information about buckwheat growing, best terms of sowing and seeding rates. This study presents the influence of different sowing times, methods and rates on the seed quality of buckwheat yield – (TGW) thousand grain (nutlet) weight and (HLV) bulk density. A field experiment was conducted on the farm “Arāji”, Krāslava region in 2010 and 2012. Buckwheat was sown on six different dates - 15.05, 25.05, 30.05, 05.06, 10.06 and 15. 06. Two types of sowing were used – drill sowing, where 4 seed rates were used - 200, 300, 400, 500 fertile nutlets per m2 , and the column sowing with the three seed rates - 150, 250, 300 fertile nutlets per square m. It was found out that crop sowing time and type significantly affected buckwheat yield quality. Compensation mechanisms of yield in early terms of sowing when lower seeding rates were used were expressed less than that in later sowing terms. It could be concluded, that in early terms different seeding rates could be used with equal success. In later terms of sowing, smaller seeding rates are more appropriate. After two year investigation the most suitable sowing terms were around 4th and 9th June, where TGW and HLW was the highest. The most inappropriate terms were around 25th and 30th May, because meteorological conditions after sowing in both years were unfavorable that resulted in 0.5 to 1.0 t haE-1 lower yields.

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.

The traditional consumption of citrus juices as a breakfast beverage has historical ties to obtaining one’s daily requirement of vitamin C. Vitamin C is one of the most important vitamins found in citrus juices, including orange juice. The aim of the study was to determine the effect of processing and storage on the content of vitamin C in orange juice varieties of ‘Valencia’ and ‘Navel’ of orange juice. The content of vitamin C (mg 100 gE-1) was determined with the iodine method in freshly squeezed orange juices and in pasteurized and packaged in aseptic bags orange juices of ‘Valencia ‘and ‘Navel’ variety, after processing and during 24 weeks of storage at 20 ± 1 °C and 5 ± 1 °C. The study results showed that the average content of vitamin C in freshly squeezed orange juice ‘Valencia’ was found at 33.56 mg 100gE-1 but in freshly squeezed orange juice ‘Navel’ the content of vitamin C was higher than in ‘Valencia’ variety orange juice average at 46.18 mg 100gE-1. The loss of vitamin C for both orange juices on average about 7% during processing The storage study showed that after 24 weeks of storage at 5 ± 1 °C and at 20 ± 1 °C, in pasteurized orange juice ‘Valencia’ the content of vitamin C decreased by 9.83% and 19.73 respectively. In the pasteurized orange juice ‘Navel’ the content of vitamin C decreased by 8.53% and 15.24% respectively.