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.     

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.     

Soil carbon accrual in particle-size fractions under Miscanthus x. giganteus cultivation

The energy crop Miscanthus x. giganteus is a deep rooting perennial rhizomatous C4 grass with great biomass production, even under temperate German climate conditions. Accordingly we hypothesized that this crop may accumulate great amounts of carbon in soil, particularly in deeper soil layers. We sampled several former C3-derived arable fields that had been cropped with Miscanthus for 0–19 years. We were able to trace the origin and turnover of soil organic C (SOC) on the basis of natural ¹³C/¹²C abundance measurements. The analysis was performed on bulk soil samples and on particle-size fractions that are known to comprise SOC of different availability for decay. Miscanthus-derived C accumulated at a rate of 1800 kg ha⁻¹ y⁻¹ down to a soil depth of 100 cm. Only about 50% of this C accrual occurred in the surface soil (0–10 cm). The C accumulation differed among size fractions. Miscanthus-derived C in the coarse-POM fraction increased rapidly during the first years of Miscanthus cultivation until a steady state was reached after approximately seven years. The stocks of Miscanthus-derived C associated with the clay fraction increased at a rate of 230 kg ha⁻¹ y⁻¹ in 0–5 cm, 45 kg ha⁻¹ y⁻¹ in 20–30 cm and 38 kg ha⁻¹ y⁻¹ in 50–75 cm. The C accumulation rate decreased with increasing soil depth. In particular, Miscanthus-derived C associated with the clay fraction led to increasing SOC stocks, even below the former Ap; that is, below a depth that would respond sensitively to a future land use change.     

Tree species composition,biomass and carbon stocks in two tropical forest of Assam

Tropical forests store higher above ground biomass (AGB) and AGB carbon (AGBC) than any other forest ecosystems. In the present study the tree composition, diversity, dominance and carbon stocks in the AGB and soil of tropical forests viz., the Gibbon wildlife sanctuary (GWS) and the Kholahat reserve forest (KRF) of Assam, India were assessed. Soil sampling, tree survey, girth above 1.3 m height of plants >10 cm girth of plants were assessed in 1000 m² quadrate. Allometric model for moist forest stands was used to determine AGB and AGBC. A total of 71 and 108 different tree species belong to 32 and 42 families were found in the GWS and KRF, respectively. In the GWF, the Shannon diversity index (1.22) and the Simpson index (0.085) were significant, while for the KRF these indices were insignificant. The basal area, AGB and AGBC in the GWS and KRF were 62.49–90.29 m² ha⁻¹, 135.30–146.42 Mg ha⁻¹, and 67.64–73.21 Mg ha⁻¹, respectively. The average soil carbon stock (SOC) in the upper, middle and lower layers was 57.74–78.44 kg m⁻², 39.22–64.93 kg m⁻² and 30.32–42.86 kg m⁻², respectively, in the GWS and KRF. However, compared to GWS, a higher AGB and AGBC were found in KRF. This finding reveals that the higher AGB, AGBC and SOC in the KRF were due to old growth matured forest with big and diverse tree species.     

Effects of accession,spacing and pruning management on in-situ leaf litter decomposition of Jatropha curcas L. in Zambia

Jatropha curcas L. leaf litter decomposition and subsequent nutrient release was monitored in three experimental J. curcas plantations in Zambia, comparing accessions from six countries, pruned versus non-pruned and different plant spacings. Leaf litter production was low (267–536 kg ha⁻¹ at the end of the growing season) and contained, on average, 1.23% N, 0.14% P and 2.61% K. Litter decomposed rapidly, losing 80% of total mass between 70 and 105 days after incubation in the field and followed a negative exponential pattern with an average decomposition constant, k, of 0.08 week⁻¹. No significant effects of plant accession, plant spacing or pruning on the decomposition rate were detected. K, P, Mg and Na had nutrient release rates exceeding mass loss, explained by their high mobility and solubility, together with high soil temperature and rainfall conditions. Others, such as Ca and Mn, were initially retained in the decaying leaf litter before later release. The rate of N release closely approached that of mass loss. J. curcas litter can be a supplemental source of nutrients in areas known for nutrient deficiency and low organic matter, which represents an additional input in intercropping systems above biofuel production. Considering that the total primary nutrient input through J. curcas litterfall to the soil is limited (for example, for nitrogen between 9.7 and 14.2 g kg⁻¹ and for phosphorus between 0.8 and 1.9 g kg⁻¹), organic or mineral fertilizer application remains crucial to satisfy fully the nutrient requirements of surrounding crops.     

Nutrients and energy in proleptic branches and leaves of poplar under a short-rotation coppice

Renewable energy is often generated from biomass, produced in short-rotation coppice (SRC) cultures. These cultures are frequently established on former agricultural land with ample availability of plant nutrients as nitrogen, phosphorous, potassium, calcium and magnesium. Nevertheless, little is known about the annual recycling of these nutrients through the leaves, as well as about the amounts that are removed at harvest. We therefore quantified soil nutrient concentrations, as well as nutrient concentrations and the gross calorific value of the proleptic branches and of the leaves of 12 poplar (Populus) genotypes in the second rotation of an operational SRC (with two-year rotations). For the produced leaf biomass, we also quantified the standing energy stock and the nutrient stock of each genotype. After four years the P, K, Ca and Mg soil concentrations had not significantly changed, while the N concentration at 30–60 cm of soil depth had significantly increased. On average, the standing aboveground woody biomass of the 12 genotypes in 2013 was 13.75 Mg ha⁻¹ and the total leaf biomass was 3.54 Mg ha⁻¹. This resulted in an average standing energy stock in the leaves of 64.8 GJ ha⁻¹. Nutrient concentrations were lower in the proleptic branches as compared to the leaves, but the proleptic branches and leaf nutrient concentrations significantly varied among the genotypes.     

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.     

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.     

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.     

Harvest frequency effects on white clover forage biomass,quality, and theoretical ethanol yield

Understanding the growth of white clover (Trifolium repens L.) under varying management regimes and weather conditions will aid producers in making sound decisions on the utilization of this crop. The objectives of this study were to determine the effect of harvest frequencies on white clover forage biomass potential, theoretical ethanol yield, crude protein (CP) concentration, and in vitro digestible organic matter (IVDOM). Frequency of forage removal (treatment), year, and treatment × year interactions significantly affected forage quantity and quality. This 4-year study indicated that forage dry matter (DM) yield, theoretical ethanol yield, CP concentration, and IVDOM with four harvests (15 May, 1 and 15 June, and 1 July) or two harvests (15 May, and 15 June) were consistently better than the other one, two, or three harvest systems. Four harvests yielded on average 2380 ± 80 kg ha⁻¹ (a theoretical ethanol yield of 570 ± 20 L ha⁻¹) with 540 kg ha⁻¹ of CP and 1780 kg ha⁻¹ of digestible DM. Forage removed with two harvests (15 May and 15 June) yielded on average 2200 ± 80 kg ha⁻¹ (a theoretical ethanol yield of 530 ± 20 L ha⁻¹) with 490 kg ha⁻¹ of CP and 1640 kg ha⁻¹ of digestible DM. A two harvest system would reduce harvest costs over that of a four harvest system and would allow for two haying or grazing rotations (each with 28–30 day rest) before a decline of white clover DM production in mid-summer.     

Some metals in aboveground biomass of Scots pine in Lithuania

The stocks of iron (Fe), manganese (Mn), zinc (Zn) and aluminium (Al) in different compartments of the aboveground tree biomass were estimated in Scots pine (Pinus sylvestris L.) stands in Lithuania. Simulated removals of metals due to the forest biomass extraction in a model Scots pine stands during a 100-year-long rotation period were compared with metals pools in sandy soil and the fluxes through atmospheric deposition. Applying whole tree harvesting, total removal comprised about 20 kg ha⁻¹ of each Al and Mn, and 5 times lower amount of each Zn and Fe. The metals were mainly removed with stemwood and living branches. However, metal export with aboveground biomass represented relatively small proportion of metals in mineral sandy soil. The annual inputs of Fe and Zn with atmospheric deposition were over 10 times higher than the mean annual removals with total aboveground biomass. The content of metals in forest biomass fuel ash was relatively small to compare with their total removals. The findings of this study have an important implications for future practice, i.e. the recommended maximum forest biomass fuel ash dose for the compensating fertilising could be increased with respect to balanced output – input in Lithuania.     

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 equations for determining fractions of common and grey alders growing on abandoned farmland and some practical implications

A study was conducted in order to construct functions for above-ground biomass of fractions of young common alders (Alnus glutinosa (L.) Gaertn.) and grey alders (Alnus incana (L.) Moench.). The constructed functions were designed to be used to predict the amount of biofuel produced from small areas. Biomass production was estimated in 10 stands of common alder and 15 stands of grey alder, growing on abandoned farmland. The common alder stands were located in Sweden at latitudes ranging from 58° to 60° N, and their total age varied from 4 to 36 years. Grey alder stands were located at latitudes ranging from 60° to 66° N, and their total age varied from 5 to 35 years. A modified ‘mean tree technique’ was used to estimate biomass production, i.e. the tallest tree was chosen for sampling. The mean total dry weight above the stump level for common alder stands was 39 tonnes ha⁻¹ with a range of 5 to 140 d.w. ha⁻¹ and 61 tonnes ha⁻¹ with a range of 3 to 140 tonnes d.w. ha⁻¹ for grey alder stands. The mean annual increment for common alder stands was 3.11 tonnes ha⁻¹ y⁻¹ (0.50–7.71) and 4.38 tonnes ha⁻¹ y⁻¹ (0.66–9.32) for grey alder stands. In addition to estimating conventional dry weights of trees and tree components, specific leaf area, total surface area and leaf area index (LAI), among other measures, were estimated. The mean LAI for common alder stands was 3.16 and 2.03 for grey alder stands. The specific leaf area per tree for common alder was 16.1 m² kg⁻¹ and 14.4 m² kg⁻¹ for grey alder. Practical implications of the findings are discussed.     

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.     

Wood ash and nitrogen influence on ground vegetation cover and chemical composition

An experiment was set up in a 38-year-old Scots pine stand (forest type Pinetum vacciniosum) on a sandy soil (Haplic Arenosol). Raw wood ash (WA) and nitrogen (N) fertilizers were applied. There were 6 treatments: (1) 1.25 t WA ha⁻¹; (2) 2.5 t WA ha⁻¹; (3) 5.0 t WA ha⁻¹; (4) 180 kg N ha⁻¹; (5) 2.5 WA t ha⁻¹ together with 180 kg N ha⁻¹; and (6) control (without ash or N). The effects on ground vegetation cover, biomass and chemistry of Pleurozium schreberi (Brid.) Mitt. were studied.The ground vegetation cover measurements were performed from the initial phase of the experiment and continued annually in all treatments. The ground vegetation biomass and the concentrations of the main plant nutrients (N, P, K, Ca and Mg) and some heavy metals (Cr, Cd, Pb, Ni, Cu and Zn) were determined in the 5.0 t WA ha⁻¹ and 180 kg N ha⁻¹ plots 2 years after the application.The study results showed a significant reduction of the moss cover after the application of wood ash, and the higher ash dose gave a higher decrease. N and wood ash applied together with N also decreased the cover of the moss. Small changes in the mean cover of the vascular plants occurred after the N application. The biomass of the moss remained unaffected. Significant increases of the P, Ca and Mg concentrations in P. schreberi were found after the application of 5.0 t WA ha⁻¹, and also higher N concentrations were obtained after N application. No wood ash influence on the heavy metal (Cd, Pb, Cr, Ni, Cu and Zn) concentrations in P. schreberi was found.     

Biochar and plant growth promoting rhizobacteria effects on switchgrass (Panicum virgatum cv. Cave-in-Rock) for biomass production in southern Québec depend on soil type and location

Switchgrass (Panicum virgatum L.) is a fast growing native C₄ perennial and a lignocellulosic biomass crop for North America. In combination with biochar, an active plant growth promoting rhizobacterial (PGPR) community can contribute to the long-term sequestration of carbon in soil, fix nitrogen, and enhance the availability of other nutrients to plants. Biochar and PGPR have the potential to improve grass biomass production, but they have not been tested together under high-latitude temperate zone field conditions. Therefore, the objective of this three-year field study was to determine whether there were effects on biomass yield and yield components of switchgrass (cv. Cave-in-Rock) due to a rhizobacterium that was able to mobilize soil phosphorus (Pseudomonas rhodesiae), a bacterial consortium that was able to supply nitrogen (Paenibacillus polymyxa, Rahnella sp., and Serrati sp.), and pine wood chip biochar applied as a soil amendment at 20 Mg ha⁻¹. The incorporation of biochar, or inoculation with the N-fixing consortium, and the combined inoculation of the experimental bacteria had positive effects on switchgrass height. At a loam soil site in Sainte-Anne-de-Bellevue, Québec, when nitrogen fertilizer was not applied, the addition of biochar had a positive effect on stand count (tillers m⁻¹ row). On the sandy soil in Sainte-Anne-de-Bellevue, when biochar was applied with 100 kg N ha⁻¹, biomass yield increased over the control but did not provide additional benefits over plots receiving only 50 kg N ha⁻¹. It remains unclear whether or not the increased C sequestration of this management system justifies increased N fertilizer usage.     

Energy and CO2 analysis of poplar and maize crops for biomass production in north Italy

The rising price of fossil fuel and the increasing environmental concern encourage the use of biomasses as energy sources. Aim of this study was to compare two poplar SRC and vSRC (6 and 3 years rotation cycle) with an annual crop (maize), used for biomass production in north Italy.The average of the biomass production was 13.9 Mg DM ha⁻¹ per year for the SRC and vSRC poplar and 19.2 Mg DM ha⁻¹ for the maize.The energy consumption for the poplar cultivations was about 15 GJ ha⁻¹ per year, which represented only the 6% of the energy biomass product (about 257 GJ ha⁻¹ per year).The input value of the maize was higher (26.8 GJ ha⁻¹ per year). In this case, the input value was about the 7% of the energy content in the biomass product (about 370 GJ ha⁻¹ per year).During the vSRC cultivation an amount of 8090 kg CO₂ eq ha⁻¹ was emitted, 6420 kg CO₂ eq ha⁻¹ for the SRC and 26,370 kg CO₂ eq ha⁻¹ for the maize.Compared to the maize, the poplar SRC (or vSRC) crops are interesting from an energetic point of view, while maize requires less manpower, but it has major problems related to the landscape biodiversity.     

Relationships among Jatropha curcas seed yield and vegetative plant components under different management and cropping systems in Indonesia

An understanding of how Jatropha curcas seed yield relates to vegetative plant components under different management regimes is lacking. Such information is necessary to predict yields and design management strategies. This study investigated yield and vegetative plant component interactions, and the effects of management practices in monoculture, intercropping, and hedge cropping systems in Indonesia. Monoculture and intercropping experiments in Gunungkidul Regency used jatropha IP-1M material; hedge experiments in Sumbawa Regency used the Sumbawa provenance. In two-year-old monoculture, pruning significantly decreased yield from 109 kg ha⁻¹ to 28 kg ha⁻¹ due to a 40% decrease in canopy volume and LAI. In four-year-old jatropha intercropping, root barriers reduced yields 80% by limiting jatropha root access to soil moisture and nutrients in the maize plantings. Intercropping without root barrier and with leaf mulch produced the largest yields of 25 kg ha⁻¹. In hedge plantings, plant height influenced yield. Single rows of one-year-old monoculture produced 0.97 g m⁻¹ at 10 cm spacing, 1.69 g m⁻¹ at 30 cm, and 0.14 g m⁻¹ for 20 cm of mixed jatropha–gliricidia. Pruning significantly decreased LAI with 20 cm spacing indicating a higher proportion of above-ground biomass allocated for wood growth. Results indicate that seed yield across the three cropping systems can be determined by plant height and numbers of productive twig/branch, although number of inflorescences cluster per productive twig may be more important. Future research should focus on the transition of branches to reproductive phases, and on increasing numbers of productive twigs/branches and inflorescence clusters.     

Above-ground biomass production and nutrient accumulation in young stands of silver birch on abandoned agricultural land

During the last decade, more than 400 000 ha of agricultural land was abandoned in Estonia. Such areas are often characterized by rapid natural afforestation with silver birch, which has led to an increase both in the woodland area and in the area of silver birch stands. However, many bioenergetic aspects related to birch stands growing on arable land are still poorly understood. The main aim of the present study was to investigate the above-ground biomass production, nutrient (NPK) accumulation, and foliar characteristics of young silver birch stands on abandoned agricultural land. Five 8-year-old stands of silver birch growing on different soil types were included in the study.The density of the studied stands varied from 3060 to 36 200 trees per ha and their above-ground biomass varied from 6.0 to 22.9 t DM ha⁻¹. The largest share in the above-ground biomass of the birches (59–80%) was from the stems. The mean stem mass of the birches ranged from 0.29 to 1.79 kg, and the mean total above-ground biomass ranged from 0.36 to 3.03 kg. The leaf area index for the studied stands varied from 1.21 to 4.64 m² m⁻², being the highest for the stand of medium density. Mean single leaf area varied from 9.4±0.2 to 15.4±0.3 cm², leaf weight per area varied from 61.1±0.4 to 77.5±0.5 g m², and specific leaf area varied from 13.2±0.1 to 16.8±0.1 m² kg⁻¹. However, no significant differences were found between stand density and the foliar characteristics. There was a strong positive correlation between soil nitrogen concentration and leaf nitrogen concentration (R=0.92); regarding phosphorus concentration, the corresponding correlation was weak (R=0.52) and regarding potassium concentration, no significant correlation was found. The amount of nitrogen accumulated in the above-ground part of the silver birch stands varied between 42.4 and 145.8 kg ha⁻¹, the amount of phosphorus, between 5.9 and 27.9 kg ha⁻¹, and the amount of potassium, between 7.2 and 78.6 kg ha⁻¹. The N:P:K ratios for the foliage were comparable. It is evident that the proportion of nitrogen and phosphorus are close to optimum, while the N:K ratio was lower than optimum value in all cases.     

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.