Recently we have been noticing words as 'sustainable development', 'environment protection', 'environmentally friendly' etc more and more often. We understand meaning of those concepts, but there are no unambiguous definitions of these words in literature. Each of these notions includes particular characterizing elements which understanding and characterizing of which make possible to detect correctness of application or context. Sustainability like entrepreneurship is a process which takes place within definite environment around it. Mutual interaction of the processes produces consequences which have to satisfy all the interested parties. Therefore, it is necessary to integrate several science branches to solve this problem- i. e. economics and ecology. Nowadays, environment issues become part of each person, institution, policy and law. Environmental questions are integrated in different fields of economics and entrepreneurship, as well. It is hard to define environmentally friendly entrepreneurship. But there is a flexible definition that could be used in different economical spheres with great variability of economical circumstances, and it is- characterised circumstances would not be secured for a long time, yet. It is complicated to define the concept since this is a value involving process. Values which are sources for idea of sustainable development are based on need to form society satisfying human interests and unthreatening future generations, necessity to secure economical growth including moral, social and ecological aspects.

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.

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.

The paper presents study results on nutrient leaching in crop rotation fields where slurry was applied. The studies were carried out within the period of 2001-2003. As the study results have shown, phosphorus (P) concentrations much depend on drainage runoff. Increasing drainage runoff resulted in decreased P concentrations (r=0.7). P leaching also depends on the precipitation amount (r=0.83). Higher precipitation rates resulted in more intensive P leaching. P leaching more depended on the drainage runoff and the type of cultivated crops rather than on fertilization rates. P leaching also depends on the precipitation amount (r=0.83). Higher precipitation rates resulted in more intensive P leaching. P leaching more depended on the drainage runoff and the type of cultivated crops rather than on fertilization rates. P leaching decreased when higher amounts of phosphorus were accumulated in crop yield; the mineralization process of vegetative residuals that were left in the test field enhanced more intensive P leaching. When slurry was applied on crops of the test field, P concentrations never exceeded maximum allowable rates determined in normative documents of the environment of Lithuania. From the point of view of the environment protection, it is more expedient to apply slurry in spring because in this season of the year the leached amount of total P input into the soil is 37.5% less compared to its leached amount when slurry is applied in autumn.

The efficiency of solving of the state environmental protection policy and implementation of the environmental problems are closely related to identification of the existing problems of the environmental protection in a definite territory. In the rural territories this process depends on the process of agricultural production. In the society, alongside with the opinion about necessity of sustainable development there is also an opinion that the primary goal is to attain total economic increase even if it can damage the environment itself. Analyzing definite indices of the effect of agriculture on the environment, it is possible to evaluate changes in the development of the branch and the environmental condition as well as their mutual interrelation.

With this issue of 2009, we bring 52 proceedings of the 98, which started life as presentations at the Annual 15th International Scientific Conference Research for Rural Development 2009 held at the Latvia University of Agriculture, in Jelgava, on 20 to 22 May 2009. In the retrospect of four months later, we can count the Conference as a great success. The theme - Research for Rural Development - attracted participation of 321 researchers with very different backgrounds. There were 4 presentations from Ukraine, 3 from Sweden, 2 from Belarus, 3 from Estonia, 1 from Belgium, 1 from India, 1 from Turkey, 10 from Lithuania and 64 from Latvia. Four independent reviewers estimated each report. The proceedings of the Annual 15th International Scientific Conference Research for Rural Development 2009 is intended for academics, students and professionals researching in the area of crop production, animal breeding, agricultural engineering, agrarian and regional economics, food sciences, veterinary medicine, forestry, wood processing, water management. The proceedings will also be useful for researchers in educational sciences.