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.

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.

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 objective of this study was to examine the range of variation and correlation relationships of some grain physical traits of different barley types. Field experiments were carried out at the State Stende Cereal Breeding Institute from 2004 to 2006. Grain samples of 52 spring barley (Hordeum vulgare L.) genotypes were analysed for 1000 grain weight, test weight, relative hardness index and hull content. The mean value of 1000 grain weight and test weight for two-row barley was significantly higher than for six-row barley. Test weight for hull-less barley was significantly higher than for covered ones (mean values - 774.6 g lE-1 and 669.8 g lE-1 respectively). The hull content was higher for six-row barley type (10.4%) than for two-row (8.6%) barley. There was no significant difference in relative hardness index between different types of barley. The coefficient of variation for grain hardness ranged from 13.7% for six-row barley to 18.7% for hull-less barley. Among varieties bred in Latvia relative hardness index ranged from 47.1 for two-row variety ‘Sencis’ to 80.4 for only six-row variety ‘Druvis’. Significant (p is less than 0.05) positive correlation was detected between grain hardness index and β-glucans for covered two-row head types of barley (r2-row, covered =0.418 is greater than r25; 0.05=0.396).

The investigation was carried out from 2006 to 2008 with the aim of observing the stability of morphological traits in Latgale's melon (Cucumis melo L.) lines in the Tukums region of Latvia. Four lines of Latgale's melons ('8', '14', '5(2)', and '4(3)') were grown in high plastic tunnels: five plants from each line. The following parameters were measured to determine stability of morphological traits in melons: fruit petiole and flower scar diameters (cm), length and wide of melon fruit (cm), and thickness of flesh (cm). Results showed that there was a significant difference in fruit petiole scar diameter between the years 2006 and 2007 for all lines. The melon line '14' was stable in all parameters from 2006 till 2008 except fruit flower scar diameter. The melon line '4(3)' was less stable in all parameters between all melon lines in all years of investigation.

The investigation was done at the Latvia State Institute of Fruit-Growing in Dobele in 2009, on the basis of an established field experiment planted in 1997 with apple (Malus domestica Borh.) cultivar 'Melba' (rootstock B9) trees spaced at 1.5 × 4 m distances. Three different treatments of soil moisture management were compared: control, sawdust mulch and fertigation. Soil of the experimental plot was Haplic Luvisol (Hypereutric), sandy loam, interspaced with Cutanic Luvisol, sandy loam. Organic matter – 25 g kgE-1, soil reaction pH – 6.5. Plant available P was 130.9, K – 157.7, and Mg – 102.2 mg kgE-1. The aim of the investigation was to determine nitrogen removal with fruit yield taking into consideration the used soil moisture regulation method – sawdust mulch or fertigation. The applied soil moisture regulation methods (mulch and fertigation) had significant influence on the content of dry matter in apple fruits (p is less than 0.05). The highest content of dry matter was found in the control treatment. A significantly higher nitrogen concentration (47 g kgE-1) in apple dry matter was in the control treatment, whereas in mulch and fertigation treatments nitrogen concentrations were lower (36 and 42 g kgE-1). The highest nitrogen concentration in dry matter was found in fruits with the biggest mass (r=0.61). A negative significant (p is less than 0.05) correlation was found between nitrogen concentration and trunk diameter (r=–0.85), and between nitrogen concentration and yield (r=–0.84). Removal of N was 24.4 kg haE-1 in the control, 22.3 kg haE-1 in the mulch, and 25.0 kg haE-1 in the fertigation treatment.

Assortment improvement is a natural process of updating varieties and improving the quality of variety assortment. The article presents the results of studying the introduced grape (Vitis vinifera) varieties in the conditions of the southeast of Kazakhstan, in particular in the bottom-mountain area of Almaty region. The beginning and the end of the main phenological phases passing for the vegetative period in a grape plant directly depended on climatic and weather conditions of this district. It is established that varieties ‘Kuibyshevsk early-maturing’, ‘Iyulsky’ and ‘Priusadebny’ have a good degree of eyes wintering buds and are able to give a yield of high quality in this area in comparison with recognized variety ‘Almaty early-maturing’.

The characteristics of the new potato cyst nematode (Globodera rostochiensis, pathotype RO1) resistant, medium ripening potato variety ‘Teele’ (‘Cinja’ ´ ‘Paola’) developed at the Estonian Crop Research Institute (ECRI) is discussed in this paper. The variety ‘Teele’ was included in Estonian and European Variety List in 2013.The variety ‘Teele’ passed the preliminary, dynamic and final trials in 2008 - 2012 at the ECRI, where it was compared with standard varieties ‘Maret’ (early), ‘Piret’ (medium) and ‘Anti’ (late). The official trials in Estonia and the technical examination (DUS test) in Czech Republic were carried out in 2011 – 2012. Potato cyst nematode (Ro1) and wart (Synchytrium endobioticum (Schilbersky) pathotype 1 (D 1)) resistance of the new variety were determined in Poland in the Plant Breeding and Acclimatization Institute. Tuber yield and tuber weight of the variety ‘Teele’ were equal to ‘Maret’ and ‘Anti’ but higher than ‘Piret’. The number of tubers per plant was equal in all standard varieties. Tuber yield and yield of marketable tubers of dynamic trials present the medium ripening of the variety ‘Teele’. The potato variety ‘Teele’ had good quality characteristics (shallow eyes, regular shape) and good culinary traits of table potato variety. It had a relatively good resistance to late blight (Phytophthora infestans) (field resistance), overcoming standard varieties ‘Maret’ and ‘Piret’.

In Latvia, Picea abies and Pinus sylvestris as the commercially most valuable species make more than half of all woodlands. It has been found that about 23% of spruce stands are infected by root rot, caused predominantly by fungal pathogen Heterobasidion annosum s.l. To restrict the spread of root rot in coniferous forests of Latvia, the Joint Stock Company ''Latvijas valsts meži'' collaborated with Latvian State Forest Research Institute ''Silava'' in 2006 and launched a project for testing the Rotstop biological preparation, containing a suspension of Phlebiopsis gigantea spores. This project had a general task to accomplish Rotstop using technology approbation in Latvia and develop control system. Starting with the year 2008, preparation was used for stump treatment during thinning operations. When analysing the field data, a conclusion made in other studies was confirmed - P. gigantea colonizes pinewood more intensively even in case of improper stump treatment. It implies that the quality of stump treatment is decisive when using Rotstop for rot control in spruce stands.