Miscanthus is a genus of high‐yielding perennial rhizomatous grasses with C4 photosynthesis. Extensive field trials of Miscanthus spp. biomass production in Europe during the past decade have shown several limitations of the most widely planted clone, M. × giganteus Greef et Deu. A 3‐yr study was conducted at five sites in Europe (Sweden, Denmark, England, Germany, and Portugal) to evaluate adaptation and biomass production potential of four acquisitions of M. × giganteus (No. 1–4) and 11 other genotypes, including M. sacchariflorus (Maxim.) Benth. (No. 5), M. sinensis Andersson (No. 11–15), and hybrids (No. 6–10). At each site, three randomized blocks containing a 5‐ by 5‐m plot of each genotype were established (except in Portugal where there were two blocks) with micropropagated plants at 2 plants m−2. In Sweden and Denmark, only M. sinensis and its hybrids satisfactorily survived the first winter following planting. Mean annual yields across all sites for all surviving genotypes increased each year from 2 t ha−1 dry matter following the first year of growth to 9 and 18 t ha−1 following the second and third year, respectively. Highest autumn yields at sites in Sweden, Denmark, England, and Germany were 24.7 (M. sinensis hybrid no. 8), 18.2 (M. sinensis hybrid no. 10), 18.7 (M. × giganteus no. 3), and 29.1 t ha−1 (M. × giganteus no. 4), respectively. In Portugal, where irrigation was used, the top‐yielding genotype produced 40.9 t ha−1 dry matter (M. sinensis hybrid no. 7). Highest‐yielding genotypes in Sweden and Denmark were among the lowest yielding in Portugal and Germany, demonstrating strong genotype × environment interactions.

Abstract:There is a growing need to increase global crop yields, whilst minimising use of resources such as land, fertilisers and water. Agricultural researchers use ground-based observations to identify, select and develop crops with favourable genotypes and phenotypes; however, the ability to collect rapid, high quality and high volume phenotypic data in open fields is restricting this. This study develops and assesses a method for deriving crop height and growth rate rapidly from multi-temporal, very high spatial resolution (1 cm/pixel), 3D digital surface models of crop field trials produced via Structure from Motion (SfM) photogrammetry using aerial imagery collected through repeated campaigns flying an Unmanned Aerial Vehicle (UAV) with a mounted Red Green Blue (RGB) camera. We compare UAV SfM modelled crop heights to those derived from terrestrial laser scanner (TLS) and to the standard field measurement of crop height conducted using a 2 m rule. The most accurate UAV-derived surface model and the TLS both achieve a Root Mean Squared Error (RMSE) of 0.03 m compared to the existing manual 2 m rule method. The optimised UAV method was then applied to the growing season of a winter wheat field phenotyping experiment containing 25 different varieties grown in 27 m 2 plots and subject to four different nitrogen fertiliser treatments. Accuracy assessments at different stages of crop growth produced consistently low RMSE values (0.07, 0.02 and 0.03 m for May, June and July, respectively), enabling crop growth rate to be derived from differencing of the multi-temporal surface models. We find growth rates range from −13 mm/day to 17 mm/day. Our results clearly display the impact of variable nitrogen fertiliser rates on crop growth. Digital surface models produced provide a novel spatial mapping of crop height variation both at the field scale and also within individual plots. This study proves UAV based SfM has the potential to become a new standard for high-throughput phenotyping of in-field crop heights.

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The reasons for these requirements can be summarized as follows. Biomass with moisture contents below Miscanthus spp. are high-yielding perennial C 4 grasses, native to 200 to 250 g kg Ϫ1 fresh matter can be stored safely Asia, that are being investigated in Europe as potential biofuels. Production of economically viable solid biofuel must combine high without the danger of self ignition (Clausen, 1994) and biomass yields with good combustion qualities. Good biomass com-burns more efficiently while ash lowers the heating value bustion quality depends on minimizing moisture, ash, K, chloride, N, of the biomass and causes slagging of the boiler heat and S. To this end, field trials at five sites in Europe from Sweden exchangers (Hartmann et al., 1999). High levels of K to Portugal were planted with 15 different genotypes including M. ϫ are undesirable because it decreases the ash melting giganteus, M. sacchariflorus, M. sinensis, and newly bred M. sinensis point, but critical levels will depend on combustion techhybrids. Yield and combustion quality at an autumn and a late winter/ nique. Chloride can lead to corrosion through reaction early spring harvest were determined in the third year after planting with water to form HCl or with K to form gaseous when the stands had reached maturity. As expected, delaying the KCl, both of which are corrosive and reduce boiler life harvest by three to four months improved the combustion quality of (Baumbach et al., 1997). Furthermore, high chloride all genotypes by reducing ash (from 40 to 25 g kg Ϫ1 dry matter), K (from 9 to 4 g kg Ϫ1 dry matter), chloride (from 4 to 1 g kg Ϫ1 dry concentrations can lead to emissions of dioxine and matter), N (from 5 to 4 g kg Ϫ1 dry matter), and moisture (from furane (Siegle and Spliethoff, 1999). Nitrogen concen-564 to 291 g kg Ϫ1 fresh matter). However, the delayed harvest also trations in biofuels need to be as low as possible to decreased mean biomass yields from 17 to 14 t ha Ϫ1 . There is a strong minimize fertilizer off-takes and to reduce emissions interaction among yield, quality, and site growing conditions. Results of NO x during combustion. To avoid SO 2 emissions, show that in northern regions of Europe, M. sinensis hybrids can be biomass S concentrations also need to be as low as recommended for high yields (yielding up to 25 t ha Ϫ1 ), but M. sinensis possible. (nonhybrid) genotypes have higher combustion qualities. In mid-and To date, most research on Miscanthus sp. as an energy south Europe, M. ϫ giganteus (yielding up to 38 t ha Ϫ1 ) or specific crop has concentrated on maximizing the yield of a high-yielding M. sinensis hybrids (yielding up to 41 t ha Ϫ1 ) are more genotypes selected, there were four acquisitions of M. ϫ gigan-

Accurate estimation of the greenhouse gas (GHG) mitigation potential of bioenergy crops requires the integration of a significant component of spatially varying information. In particular, crop yield and soil carbon (C) stocks are variables which are generally soil type and climate dependent. Since gaseous emissions from soil C depend on current C stocks, which in turn are related to previous land management it is important to consider both previous and proposed future land use in any C accounting assessment. We have conducted a spatially explicit study for England and Wales, coupling empirical yield maps with the RothC soil C turnover model to simulate soil C dynamics. We estimate soil C changes under proposed planting of four bioenergy crops, Miscanthus (Miscanthus  giganteus), short rotation coppice (SRC) poplar (Populus trichocarpa Torr. & Gray  P. trichocarpa, var. Trichobel), winter wheat, and oilseed rape. This is then related to the former land use -arable, pasture, or forest/seminatural, and the outputs are then assessed in the context of a life cycle analysis (LCA) for each crop. By offsetting emissions from management under the previous land use, and considering fossil fuel C displaced, the GHG balance is estimated for each of the 12 land use change transitions associated with replacing arable, grassland, or forest/seminatural land, with each of the four bioenergy crops. Miscanthus and SRC are likely to have a mostly beneficial impact in reducing GHG emissions, while oilseed rape and winter wheat have either a net GHG cost, or only a marginal benefit. Previous land use is important and can make the difference between the bioenergy crop being beneficial or worse than the existing land use in terms of GHG balance.

1. Concern about climate change and energy security is stimulating land-use change, which in turn precipitates social, economic and environmental responses. It is predicted that within 20 years in the UK, bioenergy crops could occupy significant areas of rural land. Among these, dedicated biomass crops, such as Miscanthus ( Miscanthus spp.) grass and short rotation willow ( Salix spp.) coppice, differ significantly from arable crops in their growth characteristics and management. It is important that the potential impacts of these differences are assessed before large-scale, long-term planting occurs. 2. We used a Sustainability Appraisal Framework (SAF) approach to landscape planning in the UK to identify stakeholder aspirations (objectives) and associated criteria (indicators) for the planting of dedicated biomass crops. 3. The use of environmental and physical constraints mapping allowed the SAF to focus only on environmentally-acceptable locations, thereby avoiding unsustainable trade-offs. The mapping identified 3·1 million ha of land in England as suitable for planting, suggesting the UK government target of 1·1 million ha by 2020 is feasible. 4. Evaluation of the SAF identified that while biodiversity was of concern to stakeholders, some current indicators of biodiversity are not appropriate. Butterfly abundance proved the most appropriate indicator, and it was found that total abundance was greater in field margins of both willow and Miscanthus biomass crops than in arable field margins. 5. Synthesis and applications. The potential conflicts of assuring food security, water availability, energy security and biodiversity conservation are recognized as a key challenge by governments worldwide. Methods with which decision-makers can compare the performance of different land-use scenarios against sustainability objectives will be crucial for achieving optimized and sustainable use of land-based resources to meet all four challenges. Using biomass crops planting as an example, this work illustrates the potential of a Sustainability Appraisal Framework, subject to identification and agreement of appropriate indicators, in securing a holistic understanding of the wide-ranging implications of large-scale, long-term changes to rural land-use in the wider context of sustainable land-use planning per se .

The need for climate change mitigation and to meet increasing energy demands has led to a rise in the land area under bioenergy crops in many countries. There are concerns that such large-scale land conversion will conflict with food production and impact on the environment. Perennial biomass crops could be grown on more marginal agricultural land. However, for sustainable solutions, biomass yields will need to be sufficient and the wider implications of land-use changes considered. Here, focusing on Miscanthus in England as an example, we combined an empirical model with GIS to produce a yield map and estimated regional energy generation potentials after masking out areas covered by environmental and socio-economic factors which could preclude the planting of energy crops. Agricultural land quality and the distributions of currently grown food crops were then taken into account. Results showed that: (i) regional contrasts occur in the importance of different factors affecting biomass planting; (ii) areas with the highest biomass yields co-locate with food producing areas on high grade land, and; (iii) when such high grade land and unsuitable areas are excluded, a policy-related scenario for increased planting on 350,000 ha utilised 4-28% (depending on the region) of lower grade land and would not necessarily greatly impact on UK food security. We conclude that the GIS-based yield and suitability mapping described here can help identify important issues in bioenergy generation potentials and land use implications at regional or finer spatial scales that would be missed in analyses at the national level.