Winter rape (Brassica napus L.) significance among field crops is unchangeable for last decade in Latvia. Rape plant development in autumn, plant wintering and plant yielding is partly influenced by plant density. The aim of our research, started in autumn 2007 in the Research and Study farm ''Vecauce'', was to investigate the influence of agro-ecological factors (sowing date, sowing rate and fungicide (as growth regulator in autumn) application) on two type (line and F1) winter rape varieties' plant density in autumn, in spring and at harvesting. Plant density in autumn, in spring and during harvesting was determined also by meteorological parameters as air temperature and precipitation. Oilseed rape field germination was observed from 84% sown on 1st of August in 2007 till 67% sown on 1st of August in 2008. A significant impact (p is less than 0.05) of the sowing rate was noted for plant winter hardiness (in points) for variety 'Californium' in both years: 2008 and 2009. Fungicide application effect on plant survival during winter was observed for treatments with greater plants density. A very little average plant number decrease per square m during summer growth period was noted for all treatments in both years - within 1 to 4% in some cases. The tendency was observed that final plant density at harvest if greater sowing rates had been used, was never high on average for 'Californium' from 75 plants per 1 square m (120 germinable seeds per square m) to 60 plants per 1 square m (100 germinable seeds per square m) in 2009. Correlations between plant density at harvest time and seed yield were found.

Fast-growing hybrid aspen clones are recommended for establishment of plantation on abandoned agriculture land in Northern Europe. In this study we assessed the productivity, quality and assortment structure of hybrid aspen clones at final felling. Data were collected during the hybrid aspen clonal experiment conducted in the central part of Latvia. Large variation in the productivity level between different clones was affected by growth and survival. From the compared 5 most and least productive clones, based on the yield m**3 haE-1, the faster growing clones have about 17% better survival rate at age 10. Also, the mean annual increment (MAI) differed notably and significantly (p is less than 0.05, α = 0.05) between hybrid aspen clones at the age of 18 years ranging from 7 to 34 m**3 haE-1 yearE-1. Theoretical assortment structure of hybrid aspen at the age of 18 years was the following: 43 ± 4.86% of small dimension saw logs (SDS logs), 21 ± 4.86% high quality saw logs (HQS logs), 18 ± 4.33% pulpwood, 4 ± 0.77% firewood and 13 ± 0.08% of logging residues (tops). The outcome of HQS logs on average is more than 30% from the 5 best clones and further increase can be predicted with age. Stem volume (H2 = 0.32), height (H2 = 0.47) and quality parameters (stem straightness - H2 = 0.73, branch angle - H2 = 0.60) had a high heritability and large differences between clones, indicating notable possibilities to improve the productivity of plantations via selection of the best-growing genetic material.

Bioethanol can be used for food production and to partially replace fossil fuel. Bioethanol is mainly produced from renewable biomass that contains sugars, starch or lignocellulose. The main raw materials for production of bioethanol are cereals, maize (Zea mays), sugarbeets (Beta vulgaris sacccharifera) and other plant species. During the trial that took place in State Stende Cereals Breeding Institute during a three year period (from 2009/2010 to 2011/2012) we examined the suitability of grain from winter wheat (Triticum aestivum L.), triticale (×Triticosecale Wittm) and rye (Secale cereale L.) for the production of bioethanol. Three varieties of each species were used in the trial. During the trial period the grain yield, the ethanol outcome (L tE-1) and the ethanol yield (L haE-1) were determined. It was established that during three years wheat and triticale provided the highest starch content (more than 700 g kgE-1) of the grain as well as the highest ethanol outcome (L tE-1). These species provided both high grain yield (more than 9 t haE-1 on average) and the highest ethanol yield (3300 – 4665 L haE-1). The choice of variety was also important as both the grain starch content and the grain yield depend on the genotype of the variety.

Advances in milk production and the expansion of dairy herds have increased the need for improved manure management and whole farm nutrient balance. It is well known in dairy management that the balanced feeding and holding technology is an important level by which milk production and milk composition can be modified. The objective of this study was to evaluate urea content and urea yield in different farms with different holding technologies. Four farms represent three cow breeds (Holstein Black and White, Latvian Brown, and cross breed XP). Individual cow milk samples (n=2740) were collected monthly from September 2009 to November 2010. Milk samples were analyzed for total protein, casein, fat, lactose, and urea content with instrumental infrared spectroscopy method. The average milk yield per cows in farms was significantly different (from 27.9 to 17.0 kg per control day). The urea content in cow milk was between 20.3 to 46.6 mg dLE-1. The average urea content in farms A, B and D was up to standard (from 15.0 to 30.0 mg dLE-1). In the farm C, average urea content ranged between 17.4 and 79.9 mg dLE-1, which indicated problems in feeding or management in the farm. It was established that milk urea content and yield significantly (p is less than 0.05) varied in farms with different dairy cow holding and feeding technologies. Urea content can be used to evaluate feed protein utilization in farms and predict environmental pollution.

Short rotation forests (SRF) can be used for biomass production for energy applications in Latvia. Establishment of plantations could be one of possibilities how to reach targets of renewable energy resource (RES) consumption of 40% in 2020. In Latvia’s conditions, one of most suitable species that could be used for SRF is willow (Salix sp.). Abandoned agricultural lands are suitable for establishment of plantations. Productivity of 8 oven- dried tons (ODT) ha-1 year -1 can lead to Rate of Return (IRR) of 17.1% and Net Present Value (NPV) 1099 Latvian Lats (LVL) if the biomass price is 33 LVL ODT-1. Establishment, harvesting and transporting costs account for 88% of the total cost of production. Price of wood chip and fuel plays the most important role in economics of plantation.

Bioenergy production growth rates in the recent years are leading to waste – digestate and wood ash amount increases, which are essential to be managed in the most efficient and safe way. In the formation of plant nutrient recycling these waste products are useful to be included in the energy crop fertilisation plan. In order to study the waste products application options for energy crops – reed canary grass (Phalaris arundinacea L.) and festulolium (×Festulolium pabulare) fertilisation trials were arranged in 2012 at the Skriveri Latvian University of Agriculture (LLU) Research Institute of Agriculture. In all fertiliser treatments: wood ash; digestate one time per season; digestate two times per season and mineral fertilisers the same doses of the main plant nutrients (N, P, K) were provided, the missing quantities of elements compensating with mineral fertilisers. To obtain the grass biomass, two cutting regimes were used – two-cut and one-cut harvest system. This article summarizes the findings on the productivity of the 1st year of use grassland swards and sward structure data. The productivity of perennial grass biomass was dependent on the type of applied fertilisers, grass species and cutting regime. In the first production year the highest average dry matter yield (7.30 t haE-1) was produced by reed canary grass. The highest DM yields in average for both grass species were obtained by mowing once per season – in autumn at crop senescence (7.01 t haE-1) and in fertilisation treatments of wood ash (WA) – 8.06 t haE-1 and mineral fertilisers (MF) – 7.24 t haE-1.

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.

Biogas can be produced from industrial by-products, household waste and raw materials of agricultural origin. Agricultural resources can be agricultural by-products, for example, manure as well as biomass of energy crops. The objective of the trial was to evaluate the methane outcome from the winter wheat (Triticum aestivum L.) silage depending on the variety and the growth stage during the harvest. The trial was carried out in State Stende Cereals Breeding Institute in the autumn of 2009. The biomass of three varieties of winter wheat, harvested at three stages of maturity - at the beginning of flowering (GS 60-62), early milk ripeness (GS 70-72), and early yellow ripeness (GS 80-82) - was ensiled in laboratory conditions. The silage was analysed 180 days after it had been ensiled. The biogas and methane outcome in laboratory conditions (in Germany) was determined for samples of silage made from winter wheat variety ‘Skalmeje’ at all harvesting times according to VDI 4630 method. The theoretically obtainable methane outcome was calculated for silage samples of all varieties by using the results of chemical composition analysis (crude protein, crude fibre, crude fat, N-free-extracts). The highest methane outcome from one ton of winter wheat silage was acquired by harvesting and ensiling the biomass during the flowering stage. However, evaluating the methane yield from one hectare, the best results were obtained by harvesting and ensiling the biomass at the early milk stage of ripeness and at the stage of early yellow ripeness.

Renewable energy resources play an important role in energy production both in Latvia and in the world. Bio-ethanol is used as a substitute for oil products in various countries of the world. It is produced from the plants containing starch: cereals, potatoes, beet, maize. The task of the research was to evaluate the suitability of different varieties of winter wheat, triticale and rye for extraction of bio-ethanol in Latvia. The research was carried out at the State Stende Cereals Breeding Institute in 2009, and the following varieties and lines of cereals were examined: winter wheat varieties 'Mulan', 'Skalmeje', and the line '99-115', developed at the State Stende Cereals Breeding Institute; winter triticale varieties 'SW Valentino', 'Dinaro', and the line '0002-26', developed at the State Priekuli Plant Breeding Institute; winter rye varieties 'Matador', 'Placido' Fp and 'Dankowskie Nowe'. The content of crude protein and starch of grains, the grain yield, and the bio-ethanol yield were determined. The highest bio-ethanol yield was acquired from the winter wheat and triticale varieties that had the highest starch content and the lowest crude protein content of grains. The best results were obtained from winter wheat line '99-115' and variety 'Mulan' (409.4 and 406.8 L tE-1), triticale variety 'Dinaro' (423.3 L tE-1), and winter rye variety 'Matador' (370.1 L tE-1.).

Renewable energy resources have been developing very fast due to negative effects and finite reserves of the fossil fuels. Biomass is ranked among the most promising renewable energy resources within the Central Europe. Corn (Zea mays L.) is currently the most widely grown crop in the Czech Republic; nevertheless, the cultivation of corn provokes soil erosion by water. Perennial energy grass called tall wheatgrass (Elymus elongatus subsp. Ponticus cv. Szarvasi-1) is supposed to be a good and environment-friendly alternative to corn. Field trials including these two crops were established in the experimental locality of South Bohemia. Their yield potential was monitored during spring harvest periods (use for combustion). Dry phytomass was fundamentally analysed (N, C, H, S) and higher heating value was determined too. Universal Soil Loss Equation was calculated for both crop species. Corn provided much higher average yield in a three-year interval; corn phytomass reached higher heating value as well. The area of Elymus elongatus should enlarge considerably, if we wanted to get the identical amount of energy from corn and Elymus elongatus. However, we found that, compared to Zea mays L., water erosion theoretical land losses would be several times less serious for Elymus elongatus.