Laura D’Andrea*
Consiglio per la Ricerca in Agricoltura e l’analisi dell’economia agraria (CRA) - Unità di Ricerca per i Sistemi Colturali degli Ambiente Caldo-Aridi (SCA), via Celso Ulpiani, 5, Bari
*laura.dandrea@entecra.it
Abstract
Perennial rhizomatous grasses (PRG) have high biomass yields and good bioenergy characteristics. Among PRG crops, giant reed and switchgrass were chosen for this research to study their biomass yield potential. The study was carried out on marginal land in order to one possible strategy for reducing competition for land with food production and for improving soil quality. The experimental field was carried out by in a hilly area, located in Alberobello (BA), where the soil was a “Typical Palexeralf clayey-skeletal” and the climate was an “accentuated thermo Mediterranean”. The results were lower compared to data obtained in other trial carried out in Europe. In conclusion, these energy crops can not be grown in this area because of the pedo-climatic conditions from the point of view of sustainable agriculture. Whereas, they can increase ecological advantages e.g. reduced risk of soil erosion and increase in soil carbon content, because of their rhizome systems.
Keywords: energy crops, biomass yield, marginal land, giant reed, switchgrass
Parole chiave: colture energetiche, resa di biomassa, terreno marginale, canna comune, panico
Introduction
The European Union Directive 2009/28/EC defined the so- called “20-20-20 targets”: a reduction in EU greenhouse gas emissions of at least 20% below 1990 levels; 20% of EU energy consumption to come from renewable resources; a 20% reduction in primary energy use compared with projected levels, to be achieved by improving energy efficiency.
Energy from green plants has much to offer, being renewable and largely carbon neutral in comparison to fossil fuel combustion (Rowe et al., 2009).
Many energy crops were tested in Europe and among those the perennial rhizomatous grasses (PRG) showed high biomass yields and good bioenergy characteristics (Lewandowski et al., 2003).
Among PRG crops, giant reed (Arundo donax L.) and switchgrass (Panicum virgatum L.) were chosen for this research in order to study their biomass yield potential on marginal land.
Giant reed was chosen because of its widespread distibution and its multiple uses (musical instruments, rayon, paper and pulp, particle boards, hand-woven baskets, fishing roars, fencing, shading or as ornamental) (Lewandowski et al., 2003).
Switchgrass was chosen because the US experience showed that it is a promising bioenergy crop and has many varieties divided into upland and lowland ecotypes (Sanderson et al., 1996).
The study was carried out on marginal land in order to one possible strategy for reducing competition for land with food production (sustainable agriculture) and for improving soil quality (environmental impact).
Materials and Methods
The research was carried out by CRA-SCA of Bari in a hilly area, located in Alberobello (BA) (latitude 40°45'35" N, longitude 17°12'21" E, 428 m above mean sea level). The soil was a Typical Palexeralf clayey-skeletal (Soil Taxonomy), characterised by 35% rock fragment (>2 mm) and 20% slope. Soil samples were collected within 0 to 40 cm of the surface on September 2010 and analyzed .
The climate in the area of Alberobello is generally “accentuated thermo Mediterranean” (UNESCO-FAO), with temperatures below 0 °C in the winter and above 30 °C in the summer. Annual rainfall is concentrated during the winter months. Air temperature and rainfall data during the experimental period were collected from a weather station that was installed in the field.
In both crops, minimum tillage was conducted in the autumn of 2010 on a soil previously for a set aside, then one harrowing (at 10 cm) was conducted immediately before planting to seedbed preparation.
Three treatments were carried out: zero nitrogen supply (N0), one fertilisation level with 50 kg N ha-1 (N50) and intercropping with subterranean clover Trifolium
brachycalycinum Katzn. and Morley) (NT). Nitrogen
fertiliser (ammonium sulfate) was applied at the beginning of the growing season in April. The seeds of subterranean clover were sown manually in late March using 30 kg ha-1 of seed.
The experimental design was a randomized block with three replications (plot size 5 m x 15 m each).
The rhizomes of giant reed (Arundo donax L.), “local” ecotype, from the Salento (Southern Italy), were planted manually on 22th December 2010, at 10-20 cm of soil depth, at 0.50 m x 1.0 m spacing (20.000 plants ha-1).
The seeds of switchgrass (Panicum virgatum L.), "wild" ecotype, from arid areas of Wisconsin (USA), were sown manually on 5th April 2011, in rows spaced 0.80 m, using 4.5 kg ha-1 of seed.
In the second year of the trial, the total dry above-ground biomas yield was harvested on 20th December 2012 per giant reed and on 23th October 2012 per switchgrass.
Fig.1 - Meteorological data during 2012 in field of Alberobello (BA), compared to long-term (30 years) data of weather station of Gioia del Colle (BA).
Fig.1 – Dati metereologici durante il 2012 nel campo di Alberobello (BA), confrontati con i dati di lungo periodo (30 years) della stazione meteorologica di Gioia del Colle (BA).
Fig.2 - Total dry above-ground biomas yield of giant reed (Arundo donax L.) and switchgrass (Panicum virgatum L.), in the second year of the experimental trial.
Fig.2 - Resa areica in biomassa secca totale della canna comune (Arundo donax L.) e del panico (Panicum virgatum L.), nel secondo anno di prova sperimentale.
Results and Discussion
The soil was clayey-silty (sand=5.5%, silt=42.0%, clay=52.5%) and was characterised by: pH=8.2, organic matter content=33.1%, total nitrogen=1.5 g Kg-1, available phosphorus=8.5 mg Kg-1, exchangeable potassium=315.0
mg kg-1, field capacity water content=31.0 wt % and the permanent wilting point water content=10.0 wt %.
The meteorological data were presented in Fig. 1. Minimum temperatures were higher compared to long-term data. Winter months (December, January and February) were coldest. Minimum values were determined in the half of January (-1.02°C) and in the half of February (-1.16°C). Maximum temperatures were higher in July and August and in general were lower compared to long-term data. The hottest day was on 6th August (37.1°C) and the hottest period was in mid-July (35.8°C). Rainfall was higher (790.9mm) compared to the annual average of long-term (519.0 mm). The wettest months were February (210.9mm) and November (165.6mm). The driest months were June, July and August with 63 mm in total.
The results (Fig. 2) of total dry above-ground biomass yield were 420 g m-2 and 72 g m-2 in average, respectively per giant reed and switchgrass. They were lower compared to data obtained in other trial carried out in Europe (Alexopoulou et al., 2000; Angelini et al., 2005; Christou et
al., 2005; Mantineo et al., 2009; Sanderson et al., 1996).
The yield was not influenced by fertilization in both energy crops. In fact treatment not fertilized (N0) had a higher yield than the treatment fertilized (N50). Moreover, the subterranean clover has shown a very strong competition with the both crops.
Conclusion
In conclusion, these two energy crops can not be grown in this marginal land because of the pedo-climatic conditions from the point of view of sustainable agriculture. Whereas, they have a low demand for nutrient inputs and a long periods without tilling, so they can increase ecological advantages e.g. reduced risk of soil erosion and increase in soil carbon content, because of their rhizome systems.
Aknowledgements
This work has been supported by Italian Ministry of Agriculture, Food and Forestry Policies (MiPAAF) under SOBIMA project (D.M. 26278/7303/09, 12th November 2009) (Sostenibilità di filiere bioenergetiche per valorizzare le aree semi-marginali e marginali del comprensorio meridionale).
References
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Angelini L.G., et al., 2005. Biomass yield and energy balance of giant reed (Arundo donax L.) cropped in central Italy as related to different management practices. European Journal of Agronomy 22, 375–389. Christou M., et al., 2005. Biomass production from perennial crops in
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Lewandowski I., et al., 2003. The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe. Biomass Bioenergy 25, 335–361.
Mantineo M., et al., 2009. Biomass yield and energy balance of three perennial crops for energy use in the semi arid Mediterranean environment. Field Crop Research 114, 204-213.
Rowe R.L., et al., 2009. Identifying potential environmental impacts of largescale deployment of dedicated bioenergy crops in the UK. Renewable and Sustainable Energy Reviews 13, 271–290.
Sanderson M.A., et al., 1996. Switchgrass as a sustainable bioenergy crop. Bioresource Technology, 56, 83–93. 0 100 200 300 400 Ja n u a ry Fe b ru a ry Ma rc h Ap ri l Ma y Ju n e Ju ly Au g u st Se p te m b e r Oc to b e r No v e m b e r D ecem b e r (m m ) -15 -10 -5 0 5 10 15 20 25 30 35 (°C )
Rainfall - field Rainfall - long-term Min Temp - field Min Temp - long-term Max Temp - field Max Temp - long-term
Giant reed (Arundo donax L.)
a a b 0 200 400 600 N0 N50 NT Average Treatments (g m -2)
Switchgrass (Panicum virgatum L.)
b b a 0 40 80 120 N0 N50 NT Average Treatments (g m -2)