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Recently, the greenhouse gas (GHG) emissions from agriculture have received much attention because of the worldwide GHG reduction policy and predicted growing food demand in following years, caused by an increase in population to 9.8 billion in 2050 [UN 2017]. Agriculture contributes 24% to the global GHG emissions [IPCC 2014] and this sector is the largest contributor to the global emissions of non-CO 2 greenhouse gases. Globally increasing food demand may result in ca. 77% rise of GHG related to agriculture, as a consequence not only of the growing livestock population which is expected to induce an increase of emissions from enteric fermentation by 22% in the period from 2005 to 2030 [EPA 2012], or fertilizers usage but also as a result of deforestation and further mechanization [Bajzelj et al. 2014]. Agriculture is responsible for more than 81% of total global anthropogenic nitrous oxide (N 2 O) emissions [Isermann 1994] and 43% of the total anthropogenic methane (CH 4) emissions [Turner et al. 2015]. Enteric fermentation

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Abstract. Along with the development of anaerobic digestion processes, digestate, a by-product of biogas production has emerged as a new organic soil amendment. One of the substrates in anaerobic digestion is biomass of plants mown in wetlands as a part of extensive conservation measures. However, this biomass can be used also as fodder in animal production. Feed value of wetland plants varies and the system of numerical values (Lwu) can be used to compare the nutritional values of individual plant species. The aim of the research was to evaluate suitability of studied wetland plants for energy production and further for fertilization and feeding purposes. The examined digestates were obtained in the laboratory experiment on the bio-methane potential of five plant species. The degree of transformation of fermented organic matter was determined based on the results of the earlier experiment concerning CO 2 emissions from soils enriched with the studied digestates. Among tested plants, reed canary grass (R-C) with Lwu = 7 had the highest feed value, while one of the worst was for common reed (C-R) with Lwu = 1. This classification looks interesting, when we compare it with the results of the CO 2 emissions and degree of mineralization of OM supplied to soils with individual plant digestates. Among the studied wetland plants, the highest emission and the largest amount of potentially mineralized carbon had reed canary grass, while the lowest emission and lowest amount of mineralized carbon in the case of common reed was observed. As a result, C-R turned out to be the plant that used for biogas production was enriching soil with the largest amount of carbon delivered with the material remaining after anaerobic digestion. At the same time, C-R is one of the worst fodder plants, while R-C is the best one. Therefore, despite the fact that reed canary grass is characterized by high yield potential and belongs to plants with very good energy properties, it should be first of all used for animals feeding.

Anaerobic digestion of energy crops and wastes of different origin are widely recognized as a climateneutral source of energy, while digestate became valuable fertilizer substituting animal manure. To compare the effect of soil fertilization with digestates and cattle slurry on nitrogen dynamics we ran an incubation experiment. The loamy sand soil was amended with: (1) anaerobically digested maize silage with chicken droppings and potato pulp (MSD); (2) anaerobically digested common reed silage (CRD) and (3) raw cattle slurry (CS). All fertilizers supplied NH 4-N to the soil. However, the addition of CS resulted in the highest NH 4-N content in the soil. The NH 4-N dynamics showed a similar overall pattern with some differences in the first week of incubation. Soils fertilized with CR and MSD showed a rapid transformation of NH 4-N resulting in its decline in the first two weeks after digestate application with the further slower decrease, while in soil fertilized with CS this process was more gradual. However, in all cases after 42 days, the NH 4-N content decreased to values close to zero, which remained until the end of incubation on day 56. Contrasting to NH 4-N, the content of NO 3-N was initially low and similar in all treated soils and control. The NO 3-N concentration in the samples treated with CR and CS rose rapidly from day 2 to day 28. In the soil fertilized with MSD, the NO 3-N content increased gradually and reached its maximum on the 42 nd day of the experiment. Addition of different organic fertilizers to the soil triggered a range of processes including nitrification, immobilization, and emission, however, the most pronounced process was nitrification of the applied NH 4-N. The pattern of inorganic-N transformation suggests that digestate can be used successfully as organic fertilizer but fast nitrification may lead to enhanced loss of NO 3-N by leaching. Therefore, application of digestate should follow the same rules as traditional liquid organic fertilizers.

Streszczenie. Celem pracy jest klasyfikacja obszarów wiejskich na poziomie gmin w województwie podlaskim pod względem dominujących funkcji na tle uwarunkowań przyrodniczych i społeczno-ekonomicznych. W badaniach wykorzystano wybrane cechy diagnostyczne, które oparto na ogólnie dostępnych danych statystycznych, głównie z roku 2010, uzupełnionych informacjami z roku 2002 i 2005. Zastosowanie metody Warda pozwoliło na wyodrębnienie wśród badanych gmin sześciu w miarę jednorodnych klas funkcjonalnych. W wyniku analizy stwierdzono, że obszary wiejskie województwa podlaskiego charakteryzują się znacznym udziałem funkcji rolniczej, która zdecydowanie dominuje na ponad 50% jego powierzchni. Są to w większości obszary problemowe rolnictwa, o niskiej jakości przestrzeni rolniczej i negatywnych tendencjach demograficznych. Mimo wspierania wielofunkcyjnego rozwoju na obszarach wiejskich udział funkcji pozarolniczych jest tu wciąż znacznie niższy niż w innych rejonach kraju. Funkcje te wyraźnie zaznaczają się zaledwie na 29% powierzchni województwa.

Abstract. Although the biomass from nature conservation management is gaining particular attention as a supplement or even substitute to energy crops, there is still little research on the production of biogas from wetland biomass and the quality of digestate obtained in anaerobic digestion. This study aimed to analyse selected physical and chemical properties of residues from anaerobically digested biomass harvested in a fluviogenous mire in a context of suitability as an agricultural fertilizer. We conducted a biomethane potential assay of five wetland plants: reed canary grass (Phalaris arundinacea), common reed (Phragmites australis), reed sweet-grass (Glyceria maxima), tufted sedge (Carex elata) and woollyfruit sedge (Carex lasiocarpa), cut in three different seasons of the year. Obtained digestates characterized a higher content of organic matter (75.1-82.4 % TS) and electrical conductivity (12.9-18.8 mS·cm -1 ) compared to the residues from a conventional agricultural biogas plant, treating mainly maize silage. They had, however, lower pH (7.4-7.8) and content of total phosphorus (0.7-1.2 % TS), while total nitrogen and potassium contents were similar (2.8-6.2 % TS and 4.3-6.1 % TS, respectively). Significant differences were found between digestates from different species of wetland plants. Although the term of biomass harvest had the impact on the physical and chemical properties of the digestates, each of the analysed AD products was found to be valuable sources of nutrients and organic matter and possessed a high potential as agricultural fertilizers.