Research PaperRoot system characterization and water requirements of ten perennial herbaceous species for biomass production managed with high nitrogen and water inputs
Introduction
Global energy demand is growing rapidly. Currently, more than 84% is satisfied by non-renewable energy fossil resources (Sawatdeenarunat et al., 2015), leading to obvious sustainability concerns. In this context renewable energy resources can largely substitute fossil fuels with important positive effects on the environment. New energy technologies have to contribute to reduce greenhouse gases emission in the atmosphere as required by European Union in its policy objectives (Popp et al., 2014). For this purpose, the agricultural sector contributes by producing several types of biomass that can be transformed into energy outputs by different processes (McKendry, 2002, Barbanti et al., 2014, Molari et al., 2014, Marchetti et al., 2016). In general, biomass as a renewable energy resource includes various substrates such as forest matrices, agricultural residues, post-processed biomass wastes and energy crops (Bentsen and Felby, 2012). These last are usually cultivated in intensive systems, adopting high plant density, mechanization and energy inputs, with short rotations (from 1 to 4 years) and plant cycles (less than 20 years) (Fiorese and Guariso, 2010). Currently, several food crops (e.g. corn, sorghum, sugar beet) are used for bioenergy purposes (Brauer-Siebrecht et al., 2016) leading to strong competition for arable land between energy and food production (Harvey and Pilgrim, 2011, Miyake et al., 2012). In this scenario, non-food biomasses derived from wetland perennial herbaceous species, harvested in marginal and set-aside lands, could offer an interesting integration to traditional energy crops (Pappalardo et al., 2015). Among these, particular attention is being paid to Arundo donax L. (Cosentino et al., 2006; Barbagallo et al., 2014, Corno et al., 2015) and Miscanthus x giganteus Greef et Deu. (Clifton-Brown et al., 2004, Dohleman and Long, 2009, Chung and Kim, 2012, McCalmont et al., 2015), due to their high potential productivity and stable yield over time (Angelini et al., 2005, Angelini et al., 2009). These species can be sustainably cultivated minimizing the yearly costs of soil tillage (Lewandowski et al., 2003, Somerville et al., 2010) normally used for annual crops. In fact, the majority of agronomic operations (e.g. soil tillage, rhizomes transplant, fertilization, weed control) are concentrated in the first season during crop establishment (Angelini et al., 2009, Corno et al., 2014) even though the highest biomass productions are obtained by suppling water and nutrients over the years (Cosentino et al., 2007, Cosentino et al., 2014, Borin et al., 2013, Florio, 2014). Thanks to high pollutant load tolerance and nutrient uptake (Zhao et al., 2014), perennial herbaceous species could be used to exploit non-conventional waste and water resources, also in open field conditions. Wastes could include animal slurry or bioenergy byproducts (e.g. digestate) that are rich in organic matter and nutritive elements, thus reducing the dependency on inorganic fertilizers and their associated economic and environmental costs (Walsh et al., 2012, Maucieri et al., 2016a, Maucieri et al., 2017). Different types of wastewater can be used to irrigate perennial herbaceous species, such as urban wastewater (Zema et al., 2012), constructed wetland effluents (Barbagallo et al., 2014), or marginal waters (Molari et al., 2014).
In this context, wastewaters can only be rationally managed if perennial herbaceous species water requirements and water absorbing root systems are understood. Although a lot of information on water requirements is available in the scientific literature for open field herbaceous (Allen et al., 1998, Abdelhadi et al., 2000, Piccinni et al., 2009, Ko et al., 2009) and woody crops (Allen et al., 1998, Guidi et al., 2008) as well as shrubs (Rajaona et al., 2012), perennial herbaceous species have not been well-investigated from this point of view. A few papers have reported the water requirements of the most promising perennial herbaceous species for biomass production, such as A. donax, M. x giganteus (Triana et al., 2015) and Phragmites australis (Cav.) Trin. ex Steud. (Zhou and Zhou, 2009, Salvato and Borin, 2010, Borin et al., 2011, Headley et al., 2012). Other studies have characterized the root systems of A. donax (Monti and Zatta, 2009, Nassi o Di Nasso et al., 2013, Maucieri et al., 2014, Toscano et al., 2015) and M. x giganteus (Himken et al., 1997, Neukirchen et al., 1999, Kahle et al., 2001, Hansen et al., 2004, Monti and Zatta, 2009, Amougou et al., 2011, Toscano et al., 2015) cultivated in soil or substrates, while the root systems of Carex spp. (Aerts and De Caluwe, 1994, Pappalardo et al., 2017) and Iris pseudacorus L. (Pavan et al., 2015, Pappalardo et al., 2017) have been studied in hydroponic conditions. To our knowledge, no research has so far contemporarily characterized the water consumption and root systems of perennial herbaceous species. This paper presents the results of a four-year experiment on ten species, usually transplanted in constructed wetland systems and already investigated as a promising source of biomass for bioenergy production (Mantineo et al., 2009, Marchetti et al., 2016), but as yet little investigated when cultivated in agricultural soil with high water and organic fertilizers supply. The main objectives were to provide: 1) a characterization of their root systems in the top 50 cm soil depth; 2) their water requirements 3) individuation of the crop coefficients.
Section snippets
Site description and trial setup
The experiment was conducted at the University of Padua “L. Toniolo” Experimental Farm in Veneto Region, North-East Italy (Lat. 45°21′N, 11°58′E, 6 m a.s.l.) from 2010 to 2014, over four growing seasons. The climate of this area is sub-humid with a long-term (1995–2010) mean annual temperature of 13.3 °C and mean cumulative annual rainfall (1995–2010) of 867.4 mm, uniformly distributed throughout the year (Fig. 1). The experimental site was composed of 48 growth boxes (4 m2 surface area), arranged
Meteorological data
During the whole experimental period, global radiation followed the typical seasonal bell-shaped trend, with the highest values recorded during summer (July) and the lowest during winter (December and January) (Fig. 1). The average global radiation values measured in 2011 and 2012 (15.1 and 14.8 MJ m−2, respectively) were higher than the long-term average (13.6 MJ m−2), which was instead in line with values detected in the first (13.5 MJ m−2) and fourth (13.7 MJ m−2) years of the study.
Average air
Conclusions
This paper provides a water balance calculation and a quantitative and qualitative characterization of root systems of ten plant species suitable for biomass production and wastewater treatment in constructed wetland systems in a four-year study with high organic fertilizer and water supplies.
Monthly ETc and Kc followed the same seasonal trend for all studied species, although a high variability was detected. The cumulated ETc values ranged from 1406.0 mm for G. maxima to 1675.1 mm for A. donax,
Acknowledgements
The research was supported by the Italian Ministry of Agriculture, Food and Forestry, within FITOPROBIO project “Production of macrophyte wetland biomass irrigated with wastewater to obtain second-generation ethanol”. Meteorological data were provided by ARPAV (Agenzia Regionale per la Prevenzione e la Protezione Ambientale del Veneto).
References (82)
- et al.
Estimation of crop water requirements in arid region using Penman–Monteith equation with derived crop coefficients: a case study on Acala cotton in Sudan Gezira irrigated scheme
Agric. Water Manage.
(2000) - et al.
Biomass yield and energy balance of giant reed (Arundo donax L.) cropped in central Italy as related to different management practices
Eur. J. Agron.
(2005) - et al.
Comparison of Arundo donax L. and Miscanthus x giganteus in a long term field experiment in Central Italy: analysis of productive characteristics and energy balance
Biomass Bioenergy
(2009) - et al.
Anaerobic digestion of annual and multi-annual biomass crops
Ind. Crop. Prod.
(2014) - et al.
Effects of five macrophytes on nitrogen remediation and mass balance in wetland mesocosms
Ecol. Eng.
(2012) - et al.
Evaluation of Phragmites australis (Cav.) Trin. evapotranspiration in Northern and Southern Italy
Ecol. Eng.
(2011) - et al.
Biomass production and N balance of giant reed (Arundo donax L.) under high water and N input in Mediterranean environments
Eur. J. Agron.
(2013) - et al.
Nutrient requirements of Miscanthus x giganteus: Conclusions from a review of published studies
Biomass Bioenergy
(2012) - et al.
Water use efficiency and biomass partitioning of three different Miscanthus genotypes with limited and unlimited water supply
Ann. Bot. London
(2000) - et al.
Arundo donax Arundo donax L.: a non-food crop for bioenergy and bio-compound production
Biotechnol. Adv.
(2014)