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 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.

The article analyses the seasonal nitrogen variation in drainage water, when the plants in the field crop rotation are fertilized with slurry during different seasons. The investigations were carried out in 2001-2003 in Juodkiškis experimental site of the Lithuanian Water Management Institute. The investigations established that the largest amounts of nitrogen are leached out in spring and in winter. In the autumn fertilized variant 38.8% more of this element was leached out in winter and spring compared with the variant fertilized in spring. During autumn nitrogen leaching was also 21% higher from the variant fertilized in autumn. It was established that the fertilization rate and dissolved inorganic nitrogen (DIN) supply in soil have influence on the concentrations of this element. During the cold season nitrogen concentrations in drainage water, when plants had been fertilized with slurry in spring, were more affected by the supply of dissolved inorganic nitrogen in soil more compared with the rate of fertilization; and if fertilization had been performed in autumn - the concentrations were more affected by the fertilization rate. In warm season both the fertilization rate and the supply of dissolved inorganic nitrogen in soil had similar influence on the concentrations of nitrogen in the drainage water in both treatments. Meteorological conditions affect nitrogen leaching a lot. During the cold season a greater amount of nitrogen is leached out when the air temperature is higher and during the warm season - when more precipitation falls.

The traditional way of dealing with manure - storage, transportation, spreading in the fields - is currently applied very successfully, but is economically very expensive. People complain about very unpleasant smells, which are caused by gasses (indole, merkaptanas, hydrogen sulphide, ammonia) being released from the manure. Scientists are searching for other ways of handling manure which try to convert it to less harmful substances, reduce its odour and at the same time make it thicker by extracting its water content. The aim of our work was to evaluate the composition of slurry after processing it mechanically, and to test the effectiveness of the application of new coagulants and flocculants on its clarification. Fresh liquid manure from 'Sajas' pig complex(Kelme district) and the liquid manure treated in biogas reactors from Lekėčiai pig complex (Šakiai district) was used for research (2006-2008). Anionic coagulants such as aluminium chloride (Al2Cl), ferrous chloride (Fe2Cl) and pollycrilamide cationic flocculant 'Magnofloc 1011' were applied to clarify manure. 40-44% of organic pollutants can be removed from the aerated sewage under constant processing by coagulants and flocculants. The best result in pollutant removal from sewage is achieved when it is processed with 1.5 kg mE-3 norm of aluminium saline (AlCl) and 3.0 g mE-3 norm of flocculant 'Magnofloc 1011'.

The paper deals with monitoring results of nitrate nitrogen (NO3 --N) run-off in three small agricultural catchments in Latvia (Berze, Mellupite, and Vienziemite) during the period of 1995 - 2007. Continuous flow measurements and water sampling were carried out in two scales - catchment and drainage field. Water quality data was analyzed statistically to identify outliers at various intensity agricultural production systems. The results indicated that with increase of agriculture intensity outlying values are higher and scattered from the rest of the data set thereby the risk of NO3 --N leaching is higher. It can be explained by application of different rates of organic and inorganic fertilization. To analyze water discharge data, cumulative distribution was used. The results show that main part of the water discharge is observed from late autumn to spring, whereas in summer period it is low and stable. The dependence of NO3 --N concentrations on the discharge is expressed by Spearman's correlation coefficient - at catchment scale it is 0.37 in Vienziemite site, 0.39 - in Berze, and 0.44 in Mellupite. Calculated correlation coefficients are statistically reliable.

The data on chemical composition of groundwater in the boreholes installed in the fields of a swine-breeding complex JSC Kontvainiai irrigated by liquid manure and in the production territory are presented in the article. This complex is situated on the Lithuanian coast, southeast of Klaipeda district. The data covers the period 2001-2005. It was established that the chemical composition of groundwater depends mainly on the soil. Ion sum was 2 times higher in the water of the well which was installed in the soil having a peat layer. The chemical composition of groundwater depended as well on its movement direction. As groundwater moves to the southeast, south and southwest from the fertilized area, the mineralization of water in wells 1 and 4 was the highest – 699 and 728 mg lE-1, respectively.

Maize (Zea mays L.) is one of the agricultural plants that is suitable substrate for biogas production. Fresh as well as ensiled maize can be used as biogas substrate. Practically, mainly maize silage is used because fresh maize is available only for short term during the vegetative period. The paper is aimed to determine the impact of ensiling on substrate composition of maize hybrids. A field trial was carried out in the Research and Study farm ''Vecauce'' of the Latvia University of Agriculture (LLU) in 2008 and 2009. Ten (in 2008) to eleven (2009) maize hybrids with different maturity rating according to FAO numbers (FAO 180 – 340) were harvested at three different times beginning on 5 September at fourteen-day intervals. Chopped maize samples of 1-3 kg were ensiled in plastic silos. Samples of fresh and ensiled (for at least 90 days) maize were analyzed detecting 14 parameters in the Scientific Laboratory of Agronomy Research of LLU using standard methods. Our results showed that ensilaging influence on organic dry matter and hemi-cellulose content was not substantial. High (p is less than 0.05) correlation between organic dry matter content of fresh and ensiled samples was noted. The crude protein, crude fibre, ash and cellulose concentration was greater in the ensiled samples if compared with fresh maize samples in 2008 and 2009. After ensilaging process neutral detergent fibre (NDF) concentration was higher compared with fresh samples in 2009 but lower in 2008.

The objective of the present studies is to estimate a distribution of nitrogen and phosphorus compounds in filter media of horizontal filters. The studies were carried out in 2009 within two wastewater treatment facilities of horizontal flow in Lithuania. From both treatment facilities sand samples of different depth and separate profiles in the direction of water flow were taken. These samples were used to determine sandmoisture and concentration of N-NO3, N-NH4 and total P. The measurements of sand moisture showed that the filtration of wastewater through the sand is in process only in the lower layer of sand filter and near the distribution pipe. Moisture regime in the sand influences the composition of nitrogenous compounds in it. In the part of the filter, where sand's moisture is lowest, nitrate concentration is highest. Ammonia concentrations are completely opposite. In the lower part of the filter anaerobic conditions are dominant and nitrification processes stop. Analysis of phosphorus concentrations in filter's sand showed similar tendencies as nitrogen analysis. In the upper part of the sand phosphorus concentration turns out to be 2-3 times lower than in the lower part of the sand. In the filters of horizontal flow, part of the sand contributes little or does not contribute to the wastewater treatment process at all; therefore, it is advisable to use wastewater recirculation for the improvement of nitrogen and phosphorus removal. For that purpose in the part of the filter not included in the treatment process the filter of vertical flow could be arranged.

Wood based ash can be used as a liming material and fertilizer in forest, thus providing a solution for utilization of wood ash and formation of additional increment of trees, especially on organic soils, where lack of potassium and phosphorus is a well-known factor limiting the growth of trees. Yet, many studies have been made with adverse results mostly because of different soil types and species investigated. However, by now the best results on fertilization with wood ash have been found on drained peatlands, where some nutrient deficiencies have emerged. The aim of this study was to find out the growth response of Norway spruce on drained organic soils after spreading of potassium sulphate (K2SO4) and wood ash (WA). The experiment was carried out in three middle aged Norway spruce (Picea abies) stands on drained mineral and peat soil. Experiment consisted of three replications of each treatment in each stand including WA, K2SO4 and the control on 400 square meter sub-sample plots each. The diameter and height of trees were measured. The samples of increment cores were collected 4 years after fertilization to determine the additional volume increment, which varied from 8.5 m**3 haE-1 in WA plots and from 9.7 m**3 ha-1 to 17.2 m**3 haE-1 on K2SO4 plots. Both - the wood ash and potassium application - significantly increased the increment of Norway spruce on drained mineral and peat soil, although no significant differences were found between the treatments (p = 0.82, α = 0.05).

The paper presents data on the water quality in drainage from manure-fertilized areas in a large livestock company (629 conditional livestock) from 2008 to 2012. The scheme of investigation consists of two field variants: manure fertilized and non-fertilized. Researches are carried out in drained areas, where the drainage water is drained away through outlets. The nitrogen rate 170 kg haE-1 is used annually to fertilize fields in spring. The aim of the research was to ascertain the impact of large livestock company fields fertilized annually with manure on the water quality in drainage. For the purpose of chemical investigations, water samples from drainage were taken once per month. Water analyses were carried out by the accredited Chemical Analytical Laboratory of the Water Management Engineering Institute of Aleksandras Stulginskis University according to specified methods. Investigation results have demonstrated that fields fertilized annually with manure raised the contents of Nmin and P2O5 in the soil by 1.5 and 2.2 times respectively in comparison to the non-fertilized ones. The increase in these contents was conditioned by the higher air temperature and the lower rainfall. The seasonality of Ntotal concentrations in drainage water was discovered: higher concentrations were identified in autumn and winter, lower concentrations – in spring and summer. Due to low dissolubility in the soil, low Ptotal concentrations were identified in drainage water. The highest concentrations were identified with the start of drainage operation.