Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services

Abstract

Marginal lands are candidates for growing dedicated energy crops such as perennial warm-season grasses (WSGs) and short-rotation woody crops (SrWCs), but actual field data on ecosystem services have not been widely discussed. This review (i) discusses potential marginal lands studied for energy crop production, (ii) considers the impacts of energy crops on ecosystem services, and (iii) underlines research needs. Some marginal or degraded lands studied for energy crops include highly erodible, flood-prone, compacted, saline, acid, contaminated, or sandy soils, reclaimed minesoils, urban marginal sites, and abandoned or degraded croplands. Field data are few but indicate that ecosystem services vary with the type of marginal land, management (i.e., fertilizer or amendment rates), and perennial species. M arginal lands are candidates for growing dedicated bioenergy crops, such as perennial WSGs and SRWCs, to reduce competition for land between energy and food production. Marginal lands can be defined as soils that have physical and chemical problems or are uncultivated or adversely affected by climatic conditions. The potential of marginal lands for growing WSGs and SRWCs as biofuel has received increased attention in recent years. Several questions remain, however, about which and how to grow dedicated energy crops on marginal lands, how dedicated energy crops will perform on different types of marginal lands, and whether these sites can produce abundant biomass while maintaining or improving ecosystem services.Many have used models to address the above questions and estimate the global and regional potential of marginal lands for cellulosic biomass production. These modeling studies have suggested that marginal lands offer a large potential for producing dedicated bioenergy crops while sequestering soil C, reducing net greenhouse gas emissions, and improving water quality (Davis et al., 2010;Gelfand et Humberto Blanco-Canqui* Core Ideas• Dedicated bioenergy crops can enhance ecosystem services in marginal lands.• Ecosystem services vary with the type of marginal land.• More field data are needed about the performance of energy crops on marginal lands.

Species and Genotype Effects of Bioenergy Crops on Root Production, Carbon and Nitrogen in Temperate Agricultural Soil

“…In addition to production of biomass, perennial bioenergy crops may have a secondary benefit if they increase stocks of soil organic C (SOC), and total N (TN) by association, through capture of atmospheric C and allocation to belowground plant biomass [8]. Realising the potential for C sequestration over the lifetime of the stand, which is typically more than 15 years and up to 30 years for willow [9,10], is likely as perennial bioenergy crops require no cultivation during their lifetime, aside from at planting, and hence disturbance to the soil and the root system is minimised.…”

“…Realising the potential for C sequestration over the lifetime of the stand, which is typically more than 15 years and up to 30 years for willow [9,10], is likely as perennial bioenergy crops require no cultivation during their lifetime, aside from at planting, and hence disturbance to the soil and the root system is minimised. The roots may persist longer than under annual crops, which is important knowing that SOC is primarily derived from roots [8,11]. The roots do need to turn over, however, to be incorporated into SOC, operationally defined as the < 2 mm soil size fraction, in order to contribute to sequestration.…”

“…The roots do need to turn over, however, to be incorporated into SOC, operationally defined as the < 2 mm soil size fraction, in order to contribute to sequestration. Perennial bioenergy crops allocate nutrients and C below ground to the root system during senescence in readiness for the following growing season [1,12], and some crops extend their root systems deep into the subsoil, especially Miscanthus [8,13,14]. In their comprehensive review, Agostini et al [15] found that root C stocks as an input were greater for willow (1.0 Mg ha −1 year −1 ) than Miscanthus (0.5 Mg ha −1 year −1 ), but that the latter had a greater mean residence time (1.3 years) than the former (1.8 years), based on the finer nature of willow roots and their fast turnover.…”

“…The potential for C sequestration is site-specific in part, being dependent on local environmental and management factors, including previous land use which largely controls initial SOC and TN contents [2,8,[16][17][18]. Whilst it may be desirable that bioenergy crops are concentrated on less-productive 'marginal' land [8,16], land used for food production has also been planted with bioenergy crops, causing a conflict between food and bioenergy production on higher-quality soils [2].…”

“…Whilst it may be desirable that bioenergy crops are concentrated on less-productive 'marginal' land [8,16], land used for food production has also been planted with bioenergy crops, causing a conflict between food and bioenergy production on higher-quality soils [2]. This is important because whether such crops are established on degraded or fertile soils may control the potential for C sequestration [8].…”