The paper presents the results of investigations on wastewater formation and its treatment in constructed wetlands (CW) with horizontal flow. The investigations were carried out on a dairy farm in the period of 1995-2004. On farmsteads containing cattle sheds, the pollution of wastewater is 2-3 times higher compared with domestic wastewater. The largest amount of slowly decomposing organic pollutants is retained during wastewater filtration via a septic tank (62.7% according to CODCr). During wastewater filtration through a horizontal CW, the amount of retained organic pollutants biochemical oxygen demand (BOD5) and chemical oxygen demand (CODCr) is 93.6%. During wastewater filtration through CW, nutrients (Ntotal and Ptotal) treatment efficiency on the dairy farms, where Ntotal concentration is 101.0 mg lE-1, is one the average 61.4% of nutrient load, and 41.4% of P where Ptotal concentration is 21.5 mg lE-1. The analyzed wastewater treatment facilities (septic tank + CW) are distinct for their buffering capabilities. They are affective enough, however due to limited P removal processes in sustainable natural environment, additional P-removal means are to be used in wastewater treatment facilities arranged on dairy farms.

Theoretical and experimental investigations are carried out to estimating the impact of the plough body working width on its specific draft resistance, as well as the ploughing efficiency. By using analytical correlations derived as a result of theoretical research, a computer algorithm has been worked out for simulating the functions of the plough body and the forces exerted by soil upon the operating parts, as well as its draft resistance. Specific draft resistance of the plough body, energy consumption, as well as labour efficiency and ploughing costs depend considerably on the working width of the body. By increasing it, the energy capacity, specific fuel consumption and expenditure decrease, but labour efficiency increases.

Biodiesel is renewable and environmentally friendly fuel, which can be used as a substitute for diesel in compression ignition (CI) engines. Nowadays it is also successfully used not only in transport sector, but also in commercial construction equipment and space heating. As the production of biodiesel (rapeseed methyl ester RME) is started now and is planned to grow rapidly, it is necessary to investigate biodiesel impact on engine performance and exhaust gas composition. This paper describes results of the investigation the aim of which was to find out the impact of biodiesel and its blends on an engine's dynamical, economical and ecological parameters in laboratory conditions on an engine test bench. The experimental work was done with an XD2P diesel engine in the Motor testing and biofuels laboratory of the Motor Vehicle Institute of Latvia University of Agriculture. The engine was fuelled on fossil diesel, rapeseed methyl ester (RME) and on blends of 5 (5RME) and 35 (35RME) percent RME/diesel fuel. The results indicated that power for biodiesel and blends was lower than with ordinary petrol diesel on average. 7.9% on 100RME and 3.6% on 35RME. The reduction in torque and increase in fuel consumption was observed. Experimental results showed that the addition of RME to diesel can significantly reduce oxides of nitrogen (NOx), carbon monoxide (CO), and absorption coefficient.

The processing of milk in dairy companies produces a certain amount of wastewater and liquid wastes. During the treatment process of such wastes sludge is accumulated in treatment facilities. The sludge is a rather valuable soil fertilizer; however, apart from plant available nutrients, it also contains large amounts of pollutants. The paper analyzes the quality of wastewater treatment process performed in treatment facilities of dairy companies, and specifies the amounts of plant available nutrients contained in sludge accumulated during the treatment process of wastewater and liquid wastes. The amounts of heavy metals contained in sludge are compared with their maximum allowable concentrations determined in the environmental requirements for soil fertilization (Aplinkosaugos reikalavimai..., 2001). On the basis of the study results and normative documents of environment protection, the article presents optimal rates and regime for sludge fertilization as well as analyzes the agro-technical and qualitative characteristics of sludge spreaders made at the Water management Institute of Lithuanian University of Agriculture and used during the technological process of fertilization.

Same public goods can only be produced jointly with private goods. This paper focuses on the biological diversity that could be produced on semi-natural pastures through the assistance of grazing animals. The question that is being investigated is what shapes the total and marginal cost functions for biological diversity production on semi-natural pastures have if private goods are already being produced using livestock at farms near the pastures. The empirical analysis shows that a quadratic function describes the costs well and that the production is characterized by increasing marginal costs.