Evaluation of sorghum hybrids for biomass production in central Italy

Two field experiments were carried out in 2005 and 2006 in central Italy in order to evaluate the biomass production and quality in eight sorghum hybrids, to define their biomass partitioning among leaves, panicles and stems and to identify which were the most adapted at early harvest. Sorghum showed a high potential in terms of biomass production in central Italy, with biomass dry yield of 25 t ha⁻¹ in average, adopting low input in terms of irrigation and fertilization. The most productive hybrids were H133 (26.3 t ha⁻¹) and H952 (25.9 t ha⁻¹) among the biomass hybrids and SS506 (27.3 t ha⁻¹) among the forage hybrids. The trends of dry weight and moisture content of biomass during the different hybrids growth cycles allowed to estimate the biomass production of each hybrids, hypothesizing an early harvest at 20 August with in-field drying of biomass. Early harvest reduced dry weight of biomass from 4.6% to 21.7%, depending of hybrids; SS506 and H128 showed to be the most adapted at early harvest. HHV and LHV of biomass showed average values higher in biomass hybrids (18.4 and 17.5 MJ kg⁻¹ d.m.) than in forage hybrids (17.7 and 16.8 MJ kg⁻¹ d.m.); while, ash content average values were lower in biomass hybrids (6.8% d.m.) than in forage hybrids (7.7% d.m.). The highest values of leaves + panicles partitioning in the forage hybrids increased ash content, reducing the quality of their biomass for thermal utilization; the biomass hybrids should be therefore preferable.     

Switchgrass (Panicum virgatum L.) nutrients use efficiency and uptake characteristics,and biomass yield for solid biofuel production under Mediterranean conditions

Switchgrass produces high amounts of biomass that can be used for solid biofuel production. In this study, the dry biomass yield vs. N–P–K nutrient uptake relations as well as the N-mineralization and the N-fertilization recovery fraction for switchgrass (cv. Alamo) were determined under field conditions for three N-fertilization (0, 80 and 160 kg ha⁻¹) and for two irrigation (0 and 250 mm) levels, in two soils in central Greece with rather different moisture status over the period 2009–2012. It was found that dry biomass yield on the aquic soil may reach 27–30 t ha⁻¹ using supplemental irrigation, and remain at high levels (19–24 t ha⁻¹) without irrigation. In the xeric soil, however, lower biomass yields of 14–15 t ha⁻¹ may be produced with supplemental irrigation. The average N-concentration varies between 0.23% in stems and 1.10% in leaves, showing the very low needs in N. P-content varies between 0.16% in leaves and 0.03% in stems, whereas K-content fluctuates between 0.67% and 0.78%. Linear biomass yield-nutrient uptake relationships were found with high R², pointing to nutrient use efficiencies of 240 and 160 kg kg⁻¹, for N and K respectively. The base N-uptake ranged 70–84 kg ha⁻¹ in the aquic to 60 kg ha⁻¹ or less in the xeric soil. N-recovery fraction was about 30% in the aquic soil and lower in the xeric. Therefore, switchgrass is very promising for biomass production and its introduction in land use systems (especially in aquic soils of similar environments) should be seriously taken into consideration.     

Biomass production and soil nutrients in organic and inorganic fertilized willow biomass production systems

The use of organic waste materials as nutrient sources for willow biomass production is an attractive means to decrease fertilization costs, increase biomass production and reduce greenhouse gas emissions associated with the system. In this study, changes in soil nutrients and biomass production of two willow varieties (Salix miyabeana–SX64 and Salix purpurea–9882-34) in organic and synthetic fertilized systems were compared at three locations in Northeastern U.S.A: Middlebury VT (MID), Delhi NY (DEL) and Fredonia NY (FRE). A 150 and 200 kg available N ha⁻¹ of urea as commercial fertilizer (CF), biosolid compost (BC) and digested dairy manure (DM) and a control (CT0) treatments were applied in June 2008 to the willow which was re-sprouting after coppice. There was no significant difference (p > 0.05) in biomass production among the fertilization treatments at any of the three sites and for either of the varieties. First rotation biomass production of 9882-34 ranged from 9.0 to 11.6 Mg ha⁻¹ yr⁻¹ at DEL, 3.4–8.8 Mg ha⁻¹ yr⁻¹ at MID and 3.5–7.7 Mg ha⁻¹ yr⁻¹ at FRE. For SX64, biomass production ranged from 13.2 to 19.0 Mg ha⁻¹ yr⁻¹ at DEL, 9.0–15.0 Mg ha⁻¹ yr⁻¹ at Mid and 5.5–9.3 Mg ha⁻¹ yr⁻¹ at FRE. SX64 deployed small numbers of large stems and produced more biomass than 9882-34 which deployed large numbers of small stems. Application of BC significantly increased soil N and P levels at MID in both 2008 and 2009 (p < 0.05). At DEL, BC and DM treatments increased soil N, Ca, Mg and OM levels in both 2008 and 2009 (p < 0.05). The fertilization treatments had no significant effect on any soil nutrients at FRE. This study indicates that willow biomass can be produced without fertilizer additions in the first rotation across this range of sites due to the nutrient status of these sites and high internal nutrient cycling in these systems.     

Yield potential and stand establishment for 20 candidate bioenergy feedstocks

Here we assess 20 bioenergy crop accessions across 10 species, and examine the influence of weed management and annual harvest treatments over three growing seasons in Virginia and one season in Kentucky. Species in this study include: Andropogon gerardii, Arundo donax, Miscanthus × giganteus (sterile triploid and seeded tetraploid), Miscanthus sinensis (ornamental and naturalized), Miscanthus sacchariflorus, Panicum virgatum, Phalaris arundinacea, Saccharum sp., Sorghum bicolor and the unconventional choice of Sorghum halepense. There was a large difference in yield between locations at the end of the planting year, with all accessions producing equivalent or greater biomass in Kentucky. Weed management did not impact yield in the establishment year, as biomass was predictably low. After the third growing season, only A. gerardii and two accessions of naturalized M. sinensis had noticeable reductions in yield due to competition from weeds. After three growing seasons, we obtained the highest yields from M. × giganteus (63, 51 and 39 Mg ha⁻¹ for ‘Illinois’, ‘PowerCane’ and ‘Nagara’ varieties, respectively), naturalized accessions of M. sinensis (54 Mg ha⁻¹), and A. donax (39 Mg ha⁻¹), using traditional cropping practices. Few accessions had low establishment rates limiting overall yields (<10 Mg ha⁻¹); however, when aboveground biomass was calculated on an individual plant basis, yields were comparable to high yielding species, encouraging further examination at higher population densities. Our results indicate that site characteristics such as soil parameters and water availability may be more important for yield than weed competition, especially over time.     

Determination of biomass accumulation in mixed belts of Salix,Corylus and Alnus species in combined food and energy production system

Given the energetic, demographic and the climatic challenges faced today, we designed a combined food and energy (CFE) production system integrating food, fodder and mixed belts of Salix, Alnus and Corylus sp. as bioenergy belts. The objective was to assess the shoot dry weight-stem diameter allometric relationship based on stem diameter at 10 (SD₁₀) and 55 cm (SD₅₅) from the shoot base in the mixed bioenergy belts. Allometric relations based on SD₁₀ and SD₅₅ explained 90–96% and 90–98% of the variation in shoot dry weights respectively with no differences between the destructive and the non-destructive methods. The individual stool yields varied widely among the species and within willow species with biomass yield range of 37.60–92.00 oven dry tons (ODT) ha⁻¹ in 4-year growth cycle. The biomass yield of the bioenergy belt, predicted by allometric relations was 48.84 ODT ha⁻¹ in 4-year growth cycle corresponding to 12.21 ODT ha⁻¹ year⁻¹. The relatively high biomass yield is attributed to the border effects and the ‘fertilizing effect’ of alder due to nitrogen fixation, benefitting other SWRC components. On termination of 4-year growth cycle, the bioenergy belts were harvested and the biomass yield recorded was 12.54 ODT ha⁻¹ year⁻¹, in close proximity to the biomass yield predicted by the allometric equations, lending confidence and robustness of the model for biomass yield determination in such integrated agro-ecosystem.     

Reed canarygrass (Phalaris arundinacea) outperforms Miscanthus or willow on marginal soils,brownfield and non-agricultural sites for local,sustainable energy crop production

Growing biomass on non-agricultural land could potentially deliver renewable energy services without displacing land from food production, avoiding the social and environmental conflicts associated with bioenergy. A variety of derelict underutilized and neglected land types are possible candidates, sharing a number of challenges for agronomy, including contaminants in soils, potential uptake and dispersion through energy use. Most previous field trials have grown woody biomass species during phytoremediation. Five one-hectare brownfield sites in NE England, were each amended with c.500 t ha⁻¹ of green-waste compost, planted with short-rotation coppice willow, Miscanthus, reed canarygrass and switchgrass,¹ and then harvested for 3–5 years.Critical issues for the economic and environmental viability of energy production on brownfield land were investigated: The yields achieved on non-agricultural land; the potential for fuel contamination; the suitability for use and potential markets for any biomass produced. RCG appears best suited to the challenging soil conditions found on non-agricultural land, outperforming other species in ease of establishment, cost, time to maturity, yield and contamination levels. Invasive spreading and low melting ash compositions were not observed. Annual yields of 4–7 odt ha⁻¹ from the second growth season were found consistently across a range of previously-developed, capped or former landfill sites, with a gross annual energy yield of 97 GJ ha⁻¹ at contamination levels acceptable for domestic pellets. The analogy with marginal agricultural land suggests that this species and approach could help boost biomass production while avoiding the natural capital “nexus” related to global food-fuel-land-water limits.     

Sweet sorghum as a bioenergy crop: Literature review

Sweet sorghum (Sorghum bicolor L. Moench) is a widely adapted sugar crop with high potential for bioenergy and ethanol production. Sweet sorghum can yield more ethanol per unit area of land than many other crops especially under minimum input production. Sweet sorghum is well-adapted to marginal growing conditions such as water deficits, water logging, salinity, alkalinity, and other constraints. Sweet sorghum potential exists for ethanol yield of 6000 L ha⁻¹ with more than three units of energy attained per unit invested. Traditionally, sweet sorghum has served as a syrup crop and its culture and production are well understood. Sweet sorghum is genetically diverse and variations exits for characteristics such as Brix % (13–24), juice sucrose concentration (7.2–15.5%), total stalk sugar yield (as high as 12 Mg ha⁻¹), fresh stalk yield (24–120 Mg ha⁻¹), biomass yield (36–140 t ha⁻¹) and others indicating potential for improvement. Transitioning sweet sorghum to a bioenergy crop is hampered by inadequate technology for large-scale harvest, transport and storage of the large quantities of biomass and juice produced, especially where the harvest window is short. Conversion of sweet sorghum to ethanol can be achieved by fermenting juice expressed from stems or directly fermenting chopped stalks. Integration of the fermentation and distillation of sweet sorghum juice in corn ethanol plants has not yet been achieved.     

Will energy crop yields meet expectations?

Expectations are high for energy crops. Government policies in the United States and Europe are increasingly supporting biofuel and heat and power from cellulose, and biomass is touted as a partial solution to energy security and greenhouse gas mitigation. Here, we review the literature for yields of 5 major potential energy crops: Miscanthus spp., Panicum virgatum (switchgrass), Populus spp. (poplar), Salix spp. (willow), and Eucalyptus spp. Very high yields have been achieved for each of these types of energy crops, up to 40 t ha⁻¹ y⁻¹ in small, intensively managed trials. But yields are significantly lower in semi-commercial scale trials, due to biomass losses with drying, harvesting inefficiency under real world conditions, and edge effects in small plots. To avoid competition with food, energy crops should be grown on non-agricultural land, which also lowers yields. While there is potential for yield improvement for each of these crops through further research and breeding programs, for several reasons the rate of yield increase is likely to be slower than historically has been achieved for cereals; these include relatively low investment, long breeding periods, low yield response of perennial grasses to fertilizer, and inapplicability of manipulating the harvest index. Miscanthus × giganteus faces particular challenges as it is a sterile hybrid. Moderate and realistic expectations for the current and future performance of energy crops are vital to understanding the likely cost and the potential of large-scale production.     

Long-term biomass productivity of willow bioenergy plantations maintained in southern Quebec,Canada

Maintaining the long-term productivity of short-rotation coppice plantations is very important to ensure the large-scale deployment of biomass as a renewable energy source. In Quebec (Canada), willow short rotation coppice has been studied since the early ‘90s, thereby allowing long-term analysis of the dynamic performance of several species and hybrids as well as management practices. In this study, we report on the long-term productivity of two trials maintained in southern Quebec and carried out to compare a) growth and biomass yield of willow Salix viminalis (cultivar 5027) grown for 15 years under fertilized and unfertilized conditions and b) growth of different willow cultivars over three successive rotations (10 years). The first trial showed that after four rotations, sludge-fertilized S. viminalis 5027 produced significantly more biomass, 19.2 odt ha⁻¹ yr⁻¹, whereas unfertilized plots yielded 13.8 odt ha⁻¹ yr⁻¹. The second trial showed that among the wide variety of commercial willow cultivars available, SX64 and SX61 along with some indigenous species (i.e. S25, S365, S546) were the most suitable for short-rotation forestry in southern Quebec.     

A novel approach to simulate growth of multi-stem willow in bioenergy production systems with a simple process-based model (3PG)

An important requirement for commercialization of willow biomass production in short-rotation crop (SRC) plantations is the reliable and cost-efficient estimation of biomass yield. Predictions and simulations of willow stand biomass have been problematic due to issues with modeling the multi-stem growth form of willow. The aim of this paper was to develop a new approach for managing allometric measurements from multi-stemmed willow for stand growth simulations. The 3PG model (Physiological Principles in Predicting Growth) was parameterized for willow and was used for biomass yield simulation for an entire 22-yr cycle (seven 3-yr rotations) of willow in SRC plantations. The multi-stemmed growth form was transformed into a single-stem modeling form by deriving whole plant willow allometric relationships using detailed stem-level measurements of basal area, stem biomass and volume. 3PG model predictions for plant diameter, height, biomass, and stand biomass and volume were within the 95% confidence range of mean plot values. Model simulations showed that after seven 3-yr rotations only 20% of planted cuttings would survive (a decrease from 15,152 to 3022 plants ha⁻¹), but stand volume would increase continuously with each subsequent rotation. 3PG predictions for cumulative (for 22 yr) aboveground biomass was 272 Mg ha⁻¹ and mean annual yield was 12 Mg ha⁻¹ yr⁻¹, comparing favorably with other findings. To our knowledge, this work is the first where the 3PG model was calibrated and used for willow species. Once parameterized for a specific willow clone, 3PG can predict biomass accumulation for any agricultural land in North America using only available soil and climate data.     

Effects of delayed winter harvest on biomass yield and quality of napiergrass and energycane

Napiergrass (Cenchrus purpureus (Schumach.) Morrone) and energycane (Saccharum hyb.) are perennial grasses that are well-suited for biomass production in the southeastern USA. The purpose of this study was to determine the effects of delayed winter harvest on biomass yield and quality of these grasses. The study was conducted on two adjacent sites near Midville, GA. Each site used a split-plot design with four replications, with species as the main plot, and harvest times (December, January, or February) as sub-plots. Dry matter (DM) yields were measured by mechanical harvesting, and a sample of biomass was taken from each harvest for determination of ethanol production by simultaneous saccharification and fermentation (SSF). Biomass moisture, N, P, K, and ash mass fractions were also measured. Energycane DM yields were stable from December (46.8 Mg ha⁻¹) to January (42.9 Mg ha⁻¹), but then declined (36.8 Mg ha⁻¹), while napiergrass yields declined sharply from December (47.0 Mg ha⁻¹) to January (35.0 Mg ha⁻¹). Napiergrass moisture mass fraction was reduced by an average of 18% in February harvests compared to December. Mass fractions of N, K, and ash tended to decrease with later harvesting, but sometimes increased due to changes in biomass composition. Delaying harvest of napiergrass from December to January reduced N removal by an average of 144 kg ha⁻¹, while delaying harvest of energycane to February reduced N removal by an average of 54 kg ha⁻¹. In SSF, later-harvested energycane produced less ethanol per unit of DM while napiergrass was less affected by harvest date.     

Nutrient sources and harvesting frequency on quality biomass production of switchgrass (Panicum virgatum L.) for biofuel

Improper management of cattle manure and poultry litter from confined animal farming are usually source of water pollution. However, appropriate application of these products on switchgrass (Panicum virgatum L.) field can enhance biomass yield and promote nutrient recycling. We evaluated the effects of harvest frequency and nutrient sources on yield and quality of switchgrass for biofuel feedstock. The experiment was carried out at Perkins and Lake Carl Blackwell, Oklahoma, from 2009 to 2011 using split plot design with four replications. The main plot treatments were two harvest frequencies single (June), and twice (June and November). The subplot treatments were nutrient sources: 1) cattle manure (CM), 2) poultry litter (PL), 3) urea (nitrogen at 150 kg ha⁻¹), 4) combined chemical fertilizer (nitrogen-P₂O₅–K₂O) with nitrogen at 150 kg ha⁻¹, P₂O₅ at 40 kg ha⁻¹, and K₂O at 20 kg ha⁻¹, 5) inter-seeded Crimson clover (Trifolium incarnatum L.), and 6) control. Mean biomass yield was higher (12.4 Mg ha⁻¹) in 2010 than other years possibly due to optimum moisture and temperature in 2010. At Perkins in 2010, application of CM and PL increased biomass yield significantly by 30 and 23% compared with combined chemical fertilizer (12.9 Mg ha⁻¹). The effect of nutrient sources on cellulose, hemicellulose and lignin content was not significant at both locations. Cumulative biomass from twice harvest was similar to single harvest except in 2011 due to dry weather after the first cut. The cellulose and lignin content were significantly higher for single harvest compared with twice harvest at both locations.     

Effects of a 20-year old Miscanthus × giganteus stand and its removal on soil characteristics and greenhouse gas emissions

Miscanthus is a perennial rhizomatous C4 grass with high yield potentials and low nutrient needs, thus a promising candidate for the production of cellulosic biomass. While optimal management options and yields attainable on a commercial scale are still debated, no study has yet addressed its removal and potential effects on following crops. Here, we present results from a trial involving a 20-year old Miscanthus stand on i) soil C, N, P and K stocks, compared with an adjacent field cultivated with a rotation of annual arable food crops, ii) the greenhouse gases (GHG) emissions following the removal of Miscanthus and iii) the immediate short-term effects on the following land use (re-cultivation to wheat or set-aside).Compared to the adjacent field under annual crops, the Miscanthus plot had a larger soil organic C stock (by 13 t C ha⁻¹) but a similar N stock, and lower P and K stocks (with differences of 100 kg P ha⁻¹ and 1170 kg K ha⁻¹, respectively). These losses imply that some degree of fertilization may be necessary as compensation. The effects of Miscanthus removal for the following wheat were significant on crop N content but negligible on grain yield.1.5 t CO₂ ha⁻¹ of CO₂ were released after the Miscanthus removal and the N₂O emissions increased from 150 g N₂O-N ha⁻¹ to 493 g N₂O-N ha⁻¹ during the following year. These results highlight the importance of investigation of the end-of-life stage of perennial crops for an accurate assessment of their environmental impacts.     

Long-term biomass production and nutrient uptake of birch, alder and willow plantations on cut-away peatland

The leafless above-ground biomass production of planted silver birch (Betula pendula), downy birch (Betula pubescens), grey alder (Alnus incana), indigenous willows (Salix triandra and Salix phylicifolia) and an alder-willow mixture growing on a cut-away peatland area in Central Finland was investigated during a period of 18 (willows) or 19 (birches and alders) years. Biannual fertilization of the birches (0, NPK) and alders (0, PK) and annual fertilization of the willows (NPK1, NPK2) were continued for 10 years. S. phylicifolia had the highest yield (123 t ha⁻¹). The yield of the fertilized downy and silver birch was 112 t ha⁻¹ and 108 t ha⁻¹ respectively, and that of fertilized grey alder 85 t ha⁻¹, and alder S. triandra mixture 93 t ha⁻¹. The mean annual increment of willow was highest at the age of 10 years (S. phylicifolia 7.9 t ha⁻¹ a⁻¹; S. triandra 5.6 t ha⁻¹ a⁻¹). NPK-fertilization increased the 19-year biomass production of downy and silver birch by 14 and 29 t ha⁻¹ respectively and PK fertilization that of alders by 25 t ha⁻¹. The alder plantations bound more N, P, K, Ca and Mg per unit leafless biomass produced after 10–11 growing seasons than the silver birch and downy birch plantations. The silver birch used more N, K and Ca, but similar amounts of P and Mg per unit leafless biomass produced than the downy birch. S. triandra used more N, P, K and Mg per unit biomass produced than S. phylicifolia and both birch species.     

Biomass equations for hybrid larch growing on farmland

Johansson, T. 2011. Biomass equations for hybrid larch growing on farmland.Data were collected from 20 stands of hybrid larch (Larix x eurolepis) growing on abandoned farmland in southern and central Sweden (Lat. 55–60° N.). The mean stand age was 19 years (range 18–23). The mean number of stems per hectare was 1150 (range 364–2374) and the mean breast height diameter (over bark) was 15.6 cm (6.8–24.2). Soil types in the stands were light and medium clay and tills (sandy-silty and light clay).Mean dry weight above stump level (20 cm) for a hybrid larch tree in this study was 117 kg (range 36–245) and the standing dry weight for hybrid larch stands was 120 t ha⁻¹ (42–350). Mean annual increment (MAI) for the tree was 6.09 kg y⁻¹ (1.89–13.61) corresponding to production of 90–120 t ha⁻¹ after 15–20 years growth and a stem number of 1000–1500, if the stand is mainly used for biomass. Alternatively, for pulp wood and timber production a rotation period of 30–40 years can be used, with thinnings being exploited for biomass.     

Simulated biomass,environmental impacts and best management practices for long-term switchgrass systems in a semi-arid region

Long-term information on switchgrass (Panicum virgatum L.) as a biomass energy crop grown on marginally saline soil and the associated impacts on soil carbon (C) and nitrogen (N) dynamics, greenhouse gas (GHG) emissions, and best management practices (BMPs) are limited. In this study, we employed the DAYCENT model, based on a 4-year switchgrass field experiment, to evaluate the long-term biomass yield potential and environmental impacts, and further to develop BMPs for switchgrass in a semi-arid region.The model showed that long-term (14-year) annual mean biomass yields were 9.6 and 5.2 Mg ha⁻¹ for irrigated and rainfed switchgrass systems, respectively. The simulated biomass yields correlated well with field-measured biomass with r² values of 0.99 and 0.89 for irrigated and rainfed systems, respectively. Soil organic carbon (SOC) and soil total nitrogen (STN) accumulated rapidly after switchgrass establishment, with mean accrual rates of 0.99–1.13 Mg C ha⁻¹ yr⁻¹ and 0.04–0.08 Mg N ha⁻¹ yr⁻¹, respectively. Based on the outputs of numerous long-term model simulations with variable irrigation water supplies and N rates, the irrigation regime and N rate with the highest yield to input ratio were chosen as BMPs. The DAYCENT model predicted-BMP was irrigating every 14 days at 70% potential evapotranspiration combined with an N rate of 67 kg ha⁻¹ yr⁻¹. Switchgrass established and produced biomass reasonably well in this semi-arid region; however, appropriate irrigation and N fertilization were needed for optimal biomass yield. Switchgrass had a great potential to sequester C into soils with low N₂O emissions while supplying significant quantities of biomass for biofuel synthesis.     

Biomass yield,nitrogen response,and nutrient uptake of perennial bioenergy grasses in North Carolina

Although perennial grasses show considerable potential as candidates for lignocellulosic bioenergy production, these crops exhibit considerable variation in regional adaptability and yield. Giant miscanthus (Miscanthus × giganteus Greef & Deuter), Miscanthus sinensis Anderss. ‘Gracillimus’ and MH2006, plume grass (Saccharum arundinaceum Retz.), ravenna grass (Saccharum ravennae (L.) L.), switchgrass (Panicum virgatum L. ‘Alamo’), and giant reed (Arundo donax L.) field plots were established in 2008, treated with four nitrogen (N) fertilizer rates (0, 34, 67, 134 kg ha⁻¹ y⁻¹), and harvested annually in winter from 2008 to 2011. Giant reed, ‘Gracillimus’, switchgrass, MH2006, giant miscanthus and ravenna grass at the Mountain site produced mean dry matter yields of 22.8, 21.3, 20.9, 19.3, 18.4, and 10.0 Mg ha⁻¹ y−¹, respectively (averaged over the last two years). Dry matter yields at the Coastal site for giant reed, giant miscanthus, switchgrass, ravenna grass, and ‘Gracillimus’ were 27.4, 20.8, 20.1, 14.3, and 9.4 Mg ha⁻¹ y⁻¹, respectively (averaged over the last two years). Increasing N rates up to 134 kg N ha⁻¹ did not have a consistent significant effect on biomass production. High yields coupled with high mortality for plume grass at both sites indicates its potential as a bioenergy crop and need for continued improvement. Overall, the perennial grasses in this study had low nutrient removal, although giant reed and plume grass often removed significantly more N, P, K and S compared with Miscanthus spp. and switchgrass. Our results indicate that giant reed, giant miscanthus, and switchgrass are productive bioenergy crops across geographic regions of North Carolina.     

Effect of fertilisation on biomass yield,ash and element uptake in SRC willow

Optimal fertilization of short rotation coppice (SRC) willow is important both in terms of economic yield and environmental effect. We measured biomass yield and nutrient uptake in two willow clones, Inger and Tordis, grown on a coarse sandy soil and within six different fertilization regimes. Fertilization treatments were carried out during two two-year harvest rotations, beginning in the 2nd growth year of the plantation. Willow was fertilized as follows with names referring to type of fertilizer and total quantities of nitrogen (kg ha⁻¹) in first and second year within both rotations: 1) Control₀₊₀, 2) NPK₁₂₀₊₀, 3) Slurry₁₈₀₊₀, 4) NPK_120+120, 5) NPK₂₄₀₊₀, 6) Slurry₃₆₀₊₀. Fertilization affected biomass yield significantly but interacted with rotation and clone. In first rotation, fertilization increased dry matter (DM) yield across clones significantly from 3.7 Mg ha⁻¹ y⁻¹ for Control₀₊₀ to 6.5, 6.4 and 5.6 for Slurry₃₆₀₊₀, NPK_120+120 and NPK₂₄₀₊₀, respectively. In second rotation, yield increased from 6.2 Mg ha⁻¹ y⁻¹ to 8.8, 8.2, 7.8 and 7.4 for Slurry₃₆₀₊₀, NPK₂₄₀₊₀, Slurry₁₈₀₊₀ and NPK_120+120, respectively. Biomass dry matter yield per ha increased linearly at 15 kg kg⁻¹ of applied total-N in both rotations. The yield increase in response to fertilization was generally larger in Inger than in Tordis. In general, element concentration in the harvested biomass was either unaffected or slightly reduced by fertilization. In conclusion, yield response to fertilization appears to be primarily related to the quantity of N applied but the effect depended on fertilizer type, harvest rotation and willow clone.     

Yield of perennial herbaceous and woody biomass crops over time across three locations

The use of perennial biomass crops is expected to increase and will likely be part of a diversified approach to cropping system design that focuses on multiple economic, ecological, and environmental benefits. Field experiments were conducted from 2006 to 2011 at three locations in Minnesota to quantify biomass production across a diverse set of perennial herbaceous and woody crops. Herbaceous crops were harvested annually in the fall while the woody crops were harvested once following five years of growth. Willow produced more total biomass than all other woody and herbaceous biomass crops across all locations. However, miscanthus biomass yield was similar to ‘SX67’ willow at St. Paul and Waseca, but was dependent on the cultivar of miscanthus. Prairie cordgrass cultivars were among the highest and most consistent yielding herbaceous biomass crops across locations. Miscanthus cultivars produced the highest annual dry matter yield of 35 Mg ha⁻¹ yr⁻¹ biomass, but only during the final year of the study. Other herbaceous crops such as switchgrass performed well in certain locations and may offer flexibility in cropping choice. This unique information on comparative biomass yield across a diversity of perennial crops will inform the overall decision-making process in a way that reduces risk and optimizes productivity in specific environments. This study shows that several biomass crop species can be successfully grown as part of a diversified biomass cropping enterprise.     

Impact of different establishment methods in terms of tillage and weed management systems on biomass production of willow grown as short rotation coppice

To date little information is available on methods including soil preparation and weed control in SRC. For this purpose, in 2010, a field trial with willow cv. ‘Tordis’ was established in southwest Germany. Three different tillage systems (mouldboard plough, chisel plough + ley crop, no-till) were implemented in the establishment year in combination with eight chemical and mechanical weed management systems. Over a period of three years, plant and weed specific parameters were collected to determine the effect of tillage systems and weed treatments on final biomass production of willow. The highest biomass yields were obtained by mouldboard plough with chemical weed control (14.0 Mg ha⁻¹ dry matter) as well as by mouldboard plough with rotivation and band spraying of herbicides (14.2 Mg ha⁻¹ dry matter), followed by 13.7 Mg ha⁻¹ dry matter in no-till with broadcast application of herbicides. Chisel ploughing with ley crop led to lower willow yields in most weed treatments. It was assumed that chisel ploughing + ley crop would lead to a high competition for light, water and nutrients especially in the first year. Consequently, it is not recommended as an establishment method for willow. Additionally, mulching with wood chips and no weed management generally resulted in low biomass yields. Overall, the results suggest that the tillage system in combination with effective chemical or mechanical weed control is of major importance for the success of willow establishment.