Contamination of soil by toxic elements is a global issue of growing importance due to the increased anthropogenic impact on the natural environment. Conventional methods of soil decontamination possess disadvantages in forms of environmental and financial burdens. This fact leads to the search for alternative approaches of remediation of contaminated sites. One such approach includes phytoremediation. Phytoremediation advantages consist of low costs and small environmental impact. Several fast-growing energy plant species are suitable for phytoremediation purposes. Our article focuses on the phytoremediation potential of energy woody crops of Salix and Populus, and energy grasses Miscanthus and Arundo, which are grown primarily for biomass production. This approach links the environmentally friendly and economically less demanding remediation approach with the production of the local sustainable form of energy that decreases dependency on external energy supplies. Energy plants are able to provide high biomass yields in a short period of time, they are resistant against abiotic stress conditions and have the ability to accumulate toxic substances, thus helping to restore the desirable soil properties. The phytoremediation research is very interdisciplinary in its nature. In order to implement phytoremediation practices together with bioenergy successfully, it is crucial to involve site owners, local people, farmers, technology providers and consultants, remediation experts, sustainability assessors, regulatory agencies and certification bodies, biorefineries, financial sponsors, NGOs and other voluntary organizations. Some disadvantages and challenges of phytoremediation are also indicated.

Recent studies show that biochar improves physical properties of soils and contributes to the carbon sequestration. In contrast to most other studies on biochar, the present study comprise a long-term field experiment with a special focus on the simultaneous impact of N-fertilizer to soil structure parameters and content of soil organic carbon (SOC) since SOC has been linked to improved aggregate stability. However, the question remains: how does the content of water-stable aggregates change with the content of organic matter? In this paper we investigate the effects of biochar alone and in a combination with N-fertilizer (i) on the content of water-stable macro- (WSAma) and micro-aggregates (WSAmi) as well as soil structure parameters; and (ii) on the contents of SOC and labile carbon (CL) in water-stable aggregates (WSA). A field experiment was conducted with different biochar application rates: B0 control (0 t ha−1), B10 (10 t ha−1) and B20 (20 t ha−1) and 0 (no N), 1st and 2nd level of nitrogen fertilization. The doses of level 1 were calculated on required average crop production using the balance method. The level 2 included an application of additional 100% of N in 2014 and additional 50% of N in the years 2015–2016 on silty loam Haplic Luvisol at the study site located at Dolná Malanta (Slovakia). The effects were investigated after the growing season of spring barley, maize and spring wheat in 2014, 2015 and 2016, respectively. The results indicate that the B10N0 treatment significantly decreased the structure vulnerability by 25% compared to B0N0. Overall, the lower level of N combined with lower doses of biochar and the higher level of N showed positive effects on the average contents of higher classes of WSAma and other soil structure parameters. The content of SOC in WSA in all size classes and the content of CL in WSAma 3–1 mm significantly increased after applying 20 t ha–1 of biochar compared to B0N0. In the case of the B20N1 treatment, the content of SOC in WSAma within the size classes >5 mm (8%), 5–3 mm (19%), 3–2 mm (12%), 2–1 mm (16%), 1–0.5 mm (14%), 0.5–0.25 mm (9%) and WSAmi (12%) was higher than in B0N1. We also observed a considerably higher content of SOC in WSAma 5–0.5 mm and WSAmi with the B10N1 treatment as compared to B0N1. Doses of 20 t biochar ha−1 combined with second level of N fertilization had significant effect on the increase of WSAma and WSAmi compared to the B0N2 treatment. A significant increase of CL in WSA was determined for size classes of 2–0.25 mm and WSAmi in the B20N2 treatment. Our findings showed that biochar might have beneficial effects on soil structure parameters, SOC, CL in WSA and carbon sequestration, depending on the applied amounts of biochar and nitrogen.

This paper evaluates the selected population-biological characteristics and size structure of invasive neophyte Asclepias syriaca in three habitat types (abandoned vineyards, grassland and road side) in the district of Veľký Krtíš in Central Slovakia. Three permanent research plots (1 m × 1 m) were established and monitored during the growing season in 2012. The density of the population at the end of the growing season ranged from 15 to 29 stems per m2. The greatest average plant height was recorded in the roadside plot (129 cm) and the lowest in the abandoned vineyard (92 cm). Main stem thickness reached 1.5-2.0 cm at the base. The highest number of main stem leaves was recorded at the end of June and July (from 24 to 27). The number of inflorescences varied from 1.6 to 3.4 and the number of fruits ranged from 1.2 to 3.8 per generative stem. Statistically significant differences were found in the plant height, thickness of the main stem and the number of fruits at the three different locations.

Pauková Ž.: invasive plant species in the three microregions of nitra region, south-west Slovakia. Ekológia (Bratislava), vol. 32, no. 2, p. 262-266, 2013. alien plant species were recorded by field survey in three selected microregions (submontane in district Zlaté Moravce, hilly in district nitra and lowland in districts nové Zámky) in nitra region, SW Slovakia in 2011. in the microregions totally 19 invasive neophytes were recorded. The most frequent and abundant species were the following: Ailanthus altissima, Ambrosia artemisiifolia, Conyza canadensis, Fallopia x bohemica, Helianthus tuberosus, Iva xanthiifolia, Negundo aceroides, Robinia pseudoacacia, Solidago canadensis and Stenactis annua. On the basis of the data we can preliminary conclude that the number of species and the number of localities in the southern lowland microregion were almost twice higher than those in the northern hilly region.

In this paper, we compare the current spread of invasive populations of neophytes, the genus Fallopia (Polygonaceae) in town Hlohovec (SW Slovakia) in intensively farmed agricultural landscape after ten years. F. × bohemica has been the most successfully spreading hybrid. In 2001, it had colonized the area of 1 520 m 2 on 54 localities and in 2011 by 120 % more (3 338 m 2 , 63 localities). The total surface area occupied by F. japonica was small.