Maize is increasingly used for energy production in agricultural biogas plants. The first biogas production project in agriculture is realized in the Research and Study Farm (RSF) Vecauce of the Latvia University of Agriculture in 2008 and animal manure together with plant biomass are planned to be used as substrate. The paper aimed to evaluate ten maize hybrids possibly suitable for biomass production at three different harvesting times. Field trial was carried out in Research and Study farm Vecauce of the Latvia University of Agriculture in 2008. Ten maize hybrids with different maturity rating according FAO numbers (FAO 180 - 270) were harvested at three different times beginning on 5 September at fourteen days intervals. Results showed that harvest time effect on maize yield was substantial (p is less than 0.05), but hybrid influence on the average yield per all harvest dates was not substantial (p is greater than 0.05). The highest organic dry matter yield was obtained harvesting maize on October 3. The Total N, crude ash, protein, fibre, cellulose, lignin, neutral detergent fibre (NDF) and acid detergent fibre (ADF) concentration decreased, but crude fat concentration increased during plant development. Relevance was not noticed between harvest dates and total carbon and hemi - cellulose content. The C : N ration rose from 34.76 at first, early harvest on 5 September to 37.97 at the last harvest on 3 October.

Formation of yield in crop cultivation is affected by influence of many factors. Simple summation of individual factors is quite rare occasion. Interaction among factors is a dynamic value. The effect of interactions varies depending on the crop development stages as well as by graduation of factors. The study aimed to evaluate the soil penetration resistance effect on winter wheat grain yield and development. It allows specifying recommendations for soil treatment difference criteria for use in site-specific soil tillage. Field trials were carried out at the Research and Study farm Vecauce of Latvia University of Agriculture during the years 2005-2007 to investigate factors influencing formation of winter wheat grain yield. Forty seven points (distributed as grid 50x50 m) were selected in the winter wheat Triticum aestivum L. field. All points were attached to their geographic coordinates. Data shows significant effect of soil resistance to grain yield - increase of soil penetration resistance by 100 kPa cmE-2 reduced yield of winter wheat by 0.37 to 0.48 t haE-1. By contrast in 2007 a significant linear regression relationship between soil penetration resistance and the yield was not detected. Differences of fresh weight of winter wheat plants in tillering stage and the beginning of stem elongation were insignificant compared to different groups of soil penetration resistance at soil layers 0.10-0.30 m in both experimental years. Higher impact of soil penetration resistance on flag leaf area difference had soil resistance at the layer of 0.20 - 0.30 m and differences were significant in both trial years.

The objective of the research was to study the removal of nitrogen, phosphorus and potassium with summer-pruned branches of apple-trees grown on dwarfing rootstocks under the influence of applied moisture regulation methods. The investigation was done at the Latvia State Institute of Fruit-Growing in Dobele, on the basis of an existing field experiment planted in 1997 with cultivar 'Melba' (rootstock B9) at 1.5 - 4 m trees spacing distances. Three different treatments of soil moisture management were compared: control (without moisture regime regulation), sawdust mulch and fertigation. Inter-row strips were covered by grass vegetation (Lolium perenne L. and Poa pratensis L., in proportion 1:3). Pruning of apple-trees was done in mid-July. The results of the research showed that the applied soil water regulation treatments (mulch and fertigation) had significant influence (p is less than 0.05) on the apple-tree biomass (leaves, one-year and older wood) removed by summer pruning, as well as on the content of dry matter in biomass. The contents of N and K were influenced both by the treatment and age of tree vegetative parts, but the content of P did not differ significantly among treatments or tree parts (p is greater than 0.05). Removal of N with summer-pruned leaves and branches was 30 kg haE-1 N in the mulch treatment and 16 - 17 kg haE-1 in control and fertigation treatments (p is less than 0.05). Removal of K in the control treatment was 19 kg haE-1, in the mulch treatment 40 kg haE-1, but in the fertigation treatment 27 kg haE-1 (p is less than 0.05). Removal of P varied from 5.04 to 9.84 kg haE-1, no significant differences were found among treatments (p is greater than 0.05).

Sour cherries become more popular due to their food value. Therefore sour cherries could be a profitable crop for fruit growers in Latvia. Information about sour cherry response to soil moisture adjustment is needed, because based on previous studies it is not possible to predict the influence of irrigation and mulch on sour cherry growing. The trial was carried out at the Latvia State Institute of Fruit Growing in 2007 to determine the effect of soil moisture adjustment on the growth of different sour cherry cultivars. Woodchip mulch and drip irrigation were used as main factors, cultivars 'Bulatnikovskaya', 'Desertnaya Morozovoi', 'Latvijas Zemais', 'Orlica', 'Shokoladnica', 'Tamaris', 'Zentenes' were used as a secondary factor. Vegetative growth, branching angles of lateral shoots, proportions of pruned shoots, spurs and twigs were determined to characterize the response of cultivars to mulching and irrigation. In general use of drip irrigation increased vegetative growth of sour cherries, but the use of woodchip mulch decreased this growth. Branching angles were wider in variant with woodchip mulch. Cultivar 'Zentenes' most positively responded to use of woodchip mulch and drip irrigation.

Winter hardiness is very important for introducing and commercial cultivation of blueberries in North Europe. Winter survival in the field is influenced by multiple factors that are influenced by uncontrollable environmental parameters. In the years 2006-2008, in eight farms were surveyed in different fruit-growing areas of Latvia, which produce highbush blueberries. We were interested in the plants physiological conditions (winter hardiness) after the winter, yields and the growth conditions. All study sites were evaluated by 6-year-old plant of highbush blueberry cultivars 'Polaris', 'Chippewa', 'Patriot', 'Northblue' and 'Duke'. After the year 2006/2007, the highest winter hardiness was observed for 'Polaris', 'Chippewa', 'Northblue' and 'Patriot'. The lowest winter hardiness was observed in 'Duke'. December 2007, January and February 2008 changing weather conditions did not do significant damage in plantations. 'Patriot' and 'Chippewa' had the highest average yield (kg per bush) throughout the production period, cultivar 'Northblue' had the lowest yield. On the other hand, 'Northblue' had the highest 100 berry weight. Cultivar 'Patriot' had the largest berry size - most of the berries had a diameter of 15 - 16 mm.

Under open environmental conditions, Trihodermin and BioMikss were used for trial purposes to study lettuce (Lactuca sativa L.) and strawberry (Fragaria x ananassa Duch) yields in 2008. Experiments were carried out in the Region of Riga at the farm 'Pukulejas'. The lettuce cultivar 'May King' and the strawberry cultivar 'Senga Sengana' were both used in the trial. The purpose of the trial was to evaluate the use of biological products when applied on the above mentioned trial plants. In the field trial, both Trihodermin and BioMikss in dry powder form in peat mixture were applied for soil treatment 10 kg haE-1. Trihodermin contains cells of microscopic fungus Trichoderma harzianum 8-21 and Trichoderma viride 1-5. BioMikss is a mixture of microorganisms, containing cells of seven various bacteria (Azotobacter chroococcum 23, Polyangium cellulosum 5-t, Polyangium 56, Pseudomonas putida 48-t, Rhizobium meliloti 15, Streptomyces griseoviridis P-t and Streptomyces cellulosae D) and cells of two various fungus (Trichoderma harzianum 7-t and Trichoderma viride A-L). Three times during the growing period Trichodermin and BioMikss water solution 100 g kgE-1 was applied on the trial plants. When compared to non-treated plants, significantly increased yield was observed on BioMikss-treated lettuce. A significantly increased yield was also observed on BioMikss-treated strawberries. The results of the experiments showed that in open environment, both strawberry and lettuce plants treated with BioMikss showed resistance to the grey mould, caused by a parasitic fungus Botrytis cinerea. The results prove that biological products, by environmentally friendly means, revitalize soils, protect plants, and enhance growth, immunity and productive potential.

The production of rainbow trout (Oncorhynchus mykiss) is developing and it is most cultured finfish species in Turkey. It was first introduced in Turkey in the mid 1970s from Italy. In the following years, culture studies of native trout strains, mainly Black Sea trout; Salmo trutta labrax and Abant Lake trout, Salmo trutta abanticus started in late 1990. Market size trout production was performed in two main categories, inland areas (mainly concrete ponds by flow through fresh water and cages) and in sea (offshore cages). Total trout production was 61.173 tons in 2007.

The aim was to study changes of chemical composition (fat content, protein content), pH and colour of poultry meat during chilled storage. Various criteria are used for evaluation of bird and carcass quality, while the combination of several indices determines the quality of poultry meat, which has an important role in the following meat processing and quality of end product. Chilled poultry meat is offered in retail and it is used in processing plants for various meat products production. Chemical composition (fat content, protein content), pH and colour are important quality determinants. Hens' meat is cheaper compared to broiler meat; therefore its use in processing is profitable. Parents stock hens of the cross Ross 308 were used for the study. Parent stock hens were fed compound feed. After chilling a hen fillet [musculus pectoralis], hen thighs [musculus biceps] and hen drumsticks [musculus gastrocnemius; musculus fibularis longus] were separated from carcasses. The obtained products were refrigerated at temperature +1+-0.5 deg C. The analyses were performed 1 day after slaughter and on the 5th day of storage. The following parameters were analysed: pH value (3510pH Meter - JENWAY); total protein content (LVS ISO 937:1978); fat content (LVS ISO 1443:1973); colour changes (Color Tec-PCM; software ColorSoft QCW for colour data analysis). The analysed parameters significantly differ in 'white' and 'red' poultry meat, and in various cuts of 'red' meat.

Potato is an important source of nutrients and bioactive compounds with profitable effect for health, such as antioxidants, vitamins and essential amino acids. The knowledge about metabolite composition of various potato cultivars is necessary to facilitate development of new cultivars with desirable properties. In the present study, the hydrophilic metabolite composition of six potato cultivars with different resistance against potato late blight disease was analyzed. For this, an HPLC-based method was developed and used for the analysis of water-ethanol extracts of freeze-dried potato tubers. Significant differences in concentrations of adenosine, chlorogenic acid, and rutin were revealed. Some other metabolites were found to be cultivar-specific.

In the study the growth and stem quality characters of geographically different Latvian Scots pine (Pinus sylvestris L.) populations were evaluated. In various regions of Latvia proportionally to the distribution of Scots pine 21 sample plot was established in 85 to 95 years old pure stands in forest type Myrtillosa growing conditions. In every sample plot 100 trees were evaluated estimating height of the tree, diameter at breast height, stem volume, length and quality of the branch-free stem section, relative branch thickness, branch angle and stem straightness. Pine populations were compared in different seed zones (Western and Eastern), as well as in various regions (Western, Central, South-eastern, North-eastern). In order to describe the geographical differences of populations with help of growth features, tree height was chosen because the relation between height and stem quality features is positive. The populations of the Eastern seed zone substantially overcome the populations of the Western seed zone both in terms of growth features, as well as in stem quality. Substantial are also differences between populations growing in various regions in terms of average height, length and quality of branch-free stem section, relative branch thickness and branch angle, but not stem straightness. Western populations present the lowest growth feature values and stem quality. The height and stem quality features of the North-eastern populations considerably exceeded the features of other regions' populations.