The cultivation of perennial energy crops is a new agricultural system and so there is limited information available on its effects on biodiversity. The aim of this study was to assess the impact of the cultivation of energy crops on the diversity of weed flora and to compare this diversity with that found in crop production systems on arable land. The best habitats for weed flora were created by willow (Salix viminalis), poplar (Populus sp.), false acacia (Robinia pseudoacacia), and perennial grasses (25–30 species), with the exception of reed canary grass (Phalaris arundinacea) (20 species). The lowest diversity and abundance of weed flora were observed on plantations of Virginia mallow (Sida hermaphrodita) and Jerusalem artichoke (Helianthus tuberosus). Weed communities in energy crops included more perennial species (by 11%), ruderal species (by 10%), and those typical for grassland (by 7%) and forests (by 4%), in comparison to arable land. The plantations of energy plants promoted an increase in the density of the invasive species Solidago gigantea (from 1.9 to 6.3 plants m−2 over six years). The introduction of perennial energy crops into an agricultural landscape causes quantitative and qualitative changes in weed flora communities and, therefore, control of the spread of some non-native and invasive species is needed.

The chemical composition and efficiency of biogas production in the methane fermentation process of silages of wild and cultivated varieties of reed canary grass were compared. An attempt was made to answer the question on how the habitat and the way of utilization of plants affect chemical composition and biogas yield. Physicochemical properties such as dry matter, organic dry matter, protein, fat, crude fiber fraction, macro- and microelements content were considered. The anaerobic digestion process and FTIR analysis were also carried out. The results showed that the two varieties differ essentially in their physical and chemical properties. The cultivated variety was characterized by higher biogas yield (406Ndm(3)kg(-1) VS) than the wild one (120Ndm(3)kg(-1) VS). This was probably related to the chemical composition of plants, especially the high content of indigestible crude fiber fractions and ash. These components could reduce biogas quantity and quality.

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The purpose of the study was to compare earthworm communities under winter wheat in different crop production systems on arable land-organic (ORG), integrated (INT), conventional (CON), monoculture (MON)-and under perennial crops cultivated for energy purposes-willow (WIL), Virginia mallow (VIR), and miscanthus (MIS). Earthworm abundance, biomass, and species composition were assessed each spring and autumn in the years 2014-2016 using the method of soil blocks. The mean species number of earthworms was ordered in the following way: ORG > VIR > WIL > CON > INT > MIS > MON. Mean abundance of earthworms decreased in the following order: ORG > WIL > CON > VIR > INT > MIS > MON. There were significantly more species under winter wheat cultivated organically than under the integrated system (p = 0.045), miscanthus (p = 0.039), and wheat monoculture (p = 0.002). Earthworm abundance was significantly higher in the organic system compared to wheat monoculture (p = 0.001) and to miscanthus (p = 0.008). Among the tested energy crops, Virginia mallow created the best habitat for species richness and biomass due to the high amount of crop residues suitable for earthworms and was similar to the organic system. Differences in the composition of earthworm species in the soil under the compared agricultural systems were proven. Energy crops, except miscanthus, have been found to increase earthworm diversity, as they are good crops for landscape diversification.

In recent years renewable energy sources (RES) have played a key role in current strategies to mitigate the impacts of global warming and independence on foreign energy sources. Miscanthus (Miscanthus x giganteus) is one of perennial grass which was identified as among best choices for low input bioenergy production. Our paper presents the relationship between the quality of soil and yielding as well as the biometrics features of miscanthus (Miscanthus x giganteus). Following this study Miscanthus x giganteus has best yields on soils of average quality, not too heavy. Obtained results can also conclude that achieving Miscanthus x giganteus yield at 2-4 kg DM (m 2 ) -1 is possible in the case of plants which grow from 30 to 60shoots for stump with a diameter of 7-9 mm and a height exceeding 2.5 m.

The influence of the fertilization level and soil type on the energy efficiency of the biogas production from maize, sorghum and reed canary grass silages were studied in this work. The plant material used to prepare silages was obtained from the experimental field with light, medium and good soil. High yields of biogas were obtained from maize silage with the lowest fertilization level of 80 kg N ha −1 from 194.5 up to 315.33 m 3 t −1 green mass (g.m.) depending on soil quality. The highest biogas yields of sorghum and reed canary grass were lower (about 120 m 3 t −1 g.m.) than that for maize. Depending on the soil type, the Energy Return on Energy Investment index (ERoEI) and the Net Energy Value (NEV) values for maize ranged from 5.05 and 189 000 MJ ha −1 (light soil), obtained at the level of 120 kg N ha −1 to 9.76 obtained at the level of 80 kg N ha −1 and 433 000 MJ ha −1 at the level of 120 kg N ha −1 (good soil). For sorghum (light soil) values of about 5.2 and 200 000 MJ ha −1 were appropriately obtained at the level of 160 kg N ha −1. In the case of reed canary grass the highest ERoEI and NEV values obtained at the level of 80 kg N ha −1 amounted to 3.8 and 74 000 MJ ha −1 (light soil), respectively. The investigations indicate that in general, the production technologies of crops where the low levels of nitrogen fertilization were applied proved to have the highest energy efficiency.

The paper assesses regional differences in the interactions between the natural and organisational factors in Polish agriculture. The analysis carried out in the dynamic approach covers the 2002-2013 period, and the indicators for individual voivodeships are compared to the average for Poland as a reference system. The research, in addition to descriptive statistics, uses also grouping of voivodeships with the use of cluster analysis with method of k-means. Conducted research indicates that the direction and strength of the interaction of selected environmental and organisational factors is differentiated between Polish regions. The observed nationwide trends and interdependencies of analysed natural and organisational factors do not reflect properly the scale and effects of changes in different regions of the country. Because of the multifactor determinants of agricultural production, consequences of their impact on the regions are highly different. This is manifested by realization, in various parts of Poland, of different models of agricultural production, which are characterised by different levels of organisation and intensity. The analysis indicates the need for regionalisation of national agricultural policy, including the Rural Development Programme. This approach should contribute to more effective spending of funds addressed to agriculture and rural areas by optimising the process of their development.