• Energy Research

Agricultural land abandonment due to biophysical and socioeconomic constraints is increasing across Europe. Meanwhile there is also an increase in bioenergy demand. This study assessed woody crop performance on several relevant types of marginal agricultural land in Europe, based on field experiments in Latvia, Spain and Ukraine. In Latvia, hybrid aspen was more productive than birch and alder species, and after eight years produced 4.8 Mg ha−1 y−1 on stony soil with sandy loam texture, when best clone and treatment combination was selected. In Spain, Siberian elm produced up to 7.1 Mg ha−1 y−1 on stony, sandy soil with low organic carbon content after three triennial rotations. In Ukraine, willow plantations produced a maximum of 10.8 Mg ha−1 y−1 on a soil with low soil organic carbon after second triennial rotation. The productivity was higher when management practices were optimized specifically to address the limiting factors of a site. Longer rotations and lower biomass yields compared to high-value land can be expected when woody crops are grown on similar marginal agricultural land shown in this study. Future studies should start here and investigate to what extent woody crops can contribute to rural development under these conditions.

AbstractIn Ukraine, 6.5 million hectares of agricultural land characterized by heavy clay soil could be available for sustainable bioenergy crop cultivation because they are considered marginal for food crop cultivation. This study investigated the biomass dry matter yield (DMY) of willow (Salix triandra L. and Salix viminalis L.) and Miscanthus (Miscanthus × giganteus Greef et Deuter) at two experimental sites with heavy clay in Ukraine. To promote plant rooting and adaptation in the first year of cultivation under low‐input conditions, tillage, moisture‐retaining agents, foliar fertilization, planting density and row spacing were varied. Willow obtained notable DMY on hard clay soils (clay >50%). The variety ‘Tora’ revealed the best DMY performance, indicated by the highest increment (4.1–4.6 m) in the first year of the second cycle. The highest biomass DMY (28.8 Mg ha−1) was obtained at a planting density of 15 000 plants ha−1 and a row spacing of 0.75 × 1.50 m. However, neither willow nor Miscanthus allow for a feasible biomass production at clay contents above 64%, because the young roots are damaged and deprived of nutrients as the soil dries out. For Miscanthus, plowing provided better soil loosening and easier sprouting of rhizomes compared with mini‐till. The application of moisture‐retaining agent Aquasorb (200 kg ha−1) supported Miscanthus plants with moisture in the first year of vegetation, but it did not maintain soil moisture in the long term. Therefore, growing willow and Miscanthus on soils with clay contents above 64% is not feasible because the soil texture and tendency to crack significantly reduce the DMY. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

This study deals with approaches for a social-ecological friendly European bioeconomy based on biomass from industrial crops cultivated on marginal agricultural land. The selected crops to be investigated are: Biomass sorghum, camelina, cardoon, castor, crambe, Ethiopian mustard, giant reed, hemp, lupin, miscanthus, pennycress, poplar, reed canary grass, safflower, Siberian elm, switchgrass, tall wheatgrass, wild sugarcane, and willow. The research question focused on the overall crop growth suitability under low-input management. The study assessed: (i) How the growth suitability of industrial crops can be defined under the given natural constraints of European marginal agricultural lands; and (ii) which agricultural practices are required for marginal agricultural land low-input systems (MALLIS). For the growth-suitability analysis, available thresholds and growth requirements of the selected industrial crops were defined. The marginal agricultural land was categorized according to the agro-ecological zone (AEZ) concept in combination with the marginality constraints, so-called ‘marginal agro-ecological zones’ (M-AEZ). It was found that both large marginal agricultural areas and numerous agricultural practices are available for industrial crop cultivation on European marginal agricultural lands. These results help to further describe the suitability of industrial crops for the development of social-ecologically friendly MALLIS in Europe.

Abstract This study provides a country level estimate of geographically available agricultural land area which has been out of production for more than two years and has not been converted into forest or urban area, and is suitable for short rotation woody crop (SRWC) production to meet EU 2020 renewable energy targets in Latvia. Geographic information system (GIS) was used to estimate the total amount and location of agricultural land suitable for SRWC. Several criteria of restrictions were applied in the assessment process, such as agricultural land use status, soil and slope restrictions, designated territories of protection, minimum size of agricultural land within each tax parcel and minimum tax parcel distance from the roads. A total estimated amount of agricultural land that meets the minimum criteria is 261,710 ha. Most (42%) of the suitable agricultural land for SRWC is in the range from 10 to 50 ha. The greatest proportion (29%) of that land is located in the Latgale region. If only 5% (13,085 ha) of the estimated agricultural land were used for SRWC with yields of 7–10 Mg dry ha −1 yr −1 , it could produce 485,475–693,532 MWh of biomass energy annually, which is roughly 412,653–589,502 MWh of delivered energy if the heating systems are 85% energy efficient. It would result in 13–18% of the total heat energy produced by heating plants in Latvia in 2012.

Cutaway peatland is a marginal land, which without further management is an unfavourable environment for plant growth due to low bearing capacity, high acidity and unbalanced nutrient composition of the soil. After wood-ash application, the soil becomes enriched with P and K, creating better conditions for tree growth. In addition to being economically viable, tree plantations ensure long-term carbon storage and promote habitat restoration. In a three-year term, we studied how distance from a drainage ditch and three different doses of wood-ash—5, 10, and 15 tons per hectare—affect the diversity of vascular plants in a tree plantation on a cutaway peatland. Plant species richness, vegetation cover and composition were positively affected by the distance from the drainage ditch and application with fertiliser, but in most cases, fertiliser dose had no significant effect. Both cover and species diversity were not affected by the planted tree species. In a tree plantation, herbaceous plants provide soil fertility by decay and recycling, and reduce mineral leaching in the long term. Since vascular plants play an important role in both the development of habitats and tree growth, it is important to know how multiple factors influence the development of vegetation in tree plantations.

Short-rotation forest plantations on former agricultural land capture CO2, provide bioeconomic materials, and mitigate climate change. This study aimed to enhance our understanding of the long-term effects of wood ash and wastewater sludge fertilization on various tree species (birch, hybrid aspen, grey alder, black alder, and hybrid alder) in short-rotation forestry plantations on abandoned agricultural land where tree growth measurements were taken over an 11-year period. After 11 years, the highest aboveground biomass (AGB) was observed for hybrid aspen clone No. 4 under wastewater sludge treatment (109.0 t ha−1), birch under wood ash treatment (34.3 t ha−1), black alder under wastewater sludge treatment (33.6 t ha−1), grey alder under wastewater sludge treatment (40.9 t ha−1), hybrid alder under control conditions (36.2 t ha−1), and hybrid aspen clone No. 28 under wood ash treatment (37.2 t ha−1). The average survival rate was 73% in control plots, 81% under wastewater sludge treatment, and 78% under wood ash treatment. Short-term positive impacts on tree growth were observed, effects that were not consistent over the long term. The impact of these treatments on tree growth varied between species, and the effects tended to diminish over time, which must be considered before fertilization.

The main goal of this review was to provide an assessment of the potential of fast-growing tree species for the suitable transformation of agroforestry areas for biomass production in the Baltic Sea region. Our interest was to highlight the research on the management process of agroforestry zones by establishing short rotation plantations with the tree species Salix spp., Populus spp. and Alnus spp. to explore the prospects of planning these zones as biomass producers. Short rotation forestry (SRF) with trees whose rotation period is 15 to 30 years, depending on the species, is the most suitable approach for management of these agroforestry zones. Willows (Salix spp.) and poplars (Populus spp.) are suitable for short rotation coppice (SRC), as these tree species can be harvested at much shorter intervals, respectively, 1–5 and 4–10 years, facilitating their use in agricultural systems. The rotation period of Alnus spp. in short rotation plantations for energy wood production is generally assessed to be 15–30 years. The black alder plantations in agroforestry zones are used for sawnwood and firewood production, with a rotation period of 20–40 years. The calculated repayment period of the economic agroforestry zone is about 10–15 years, if 2021 costs and prices are used.