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.

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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-

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Abstract. Nitrate leaching under newly planted Miscanthus grass was measured for three years. The crop received either no fertilizer‐N or an annual spring application of 60 kg or 120 kg N ha‐1. During three winters soil water was collected from porous cup probes installed 90 cm deep. Nitrate leaching was calculated from the mean drain flow recorded in two drain gauges multiplied by the mean nitrate‐N concentration in the soil water solutions collected. In the first year soil water nitrate concentrations were high on all treatments and N losses were 154, 187 and 228 kg ha‐1 respectively on the unfertilized treatment and those that received 60 or 120 kg N ha‐1. Leaching losses in the second and third years were, in turn, 8, 24 and 87 kg ha‐1 and 3, 11 and 30 kg ha‐1 for the unfertilized treatment and for the 60 and 120 kg N ha‐1 treatments respectively. Leaching losses were closer to those recorded under extensively managed grassland than arable land. The large losses in the first year were probably due to the previous agricultural management at the site and excessive inputs of N on the fertilized plots. In the second and third year, lower drainage volumes may also have influenced losses. The results show that Miscanthus, once established, can lead to low levels of nitrate leaching and improved groundwater quality compared with growing arable crops.

SUMMARY The leaching of nitrate‐N under autumn‐sown arable crops was measured using hydro‐logically isolated plots, about 0.24 ha in area, from 1984–1988. Fluxes of water and nitrate moving over the soil surface (surface runoff), at the interface between topsoil and subsoil (interflow), and in the subsoil (drainflow) were monitored in plots with mole‐and‐pipe drain systems (drained plots); surface runoff and interflow only were monitored in ‘undrained’ plots. Half the drained and undrained plots were direct‐drilled, and on the other half seedbeds were prepared by tillage to 200 mm. Tillage increased the total leaching loss of nitrate by 21 % compared with direct drilling in drained plots. About 95% or the nitrate moving from the soil was present in the water intercepted by the subsoil drains in these plots. In undrained plots less water and nitrate were collected in total; more of the nitrate was present in interflow on ploughed plots and in surface runoff in direct‐drilled land. Losses of nitrate for the whole experiment from 1978‐1988 were analysed. This showed that, between the harvest of one crop and the spring application of fertilizer to the next, loss of nitrate‐N from ploughed land (Lp) was approximated by Lp=22+Fkg N ha−1, where F was the autumn fertilizer‐N applied. After fertilizer was applied in spring, loss of nitrate‐N depended on rainfall such that for 100 mm rainfall about 30% of the fertilizer‐N was lost by leaching. About 18% more nitrate‐N was lost from direct‐drilled land than from ploughed land in spring, but the total loss was generally small compared to that over winter. The apparent net mineralization of organic‐N was measured in 1988. In autumn and winter there was little effect of tillage treatment (26 and 31 kg N ha−1 on direct drilled and tilled plots respectively). However, over the year 83 kg N ha−1 were mineralized in tilled plots, and 67 kg N ha−1 in direct‐drilled plots. Five factors governing the leaching of nitrate are assessed and this identified that fertilizer nitrogen application to the seedbed of winter sown crops and the mineralization of nitrogen from the residues of the previous crop are the most significant factors for nitrogen leaching in the UK.

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The effect of harvest date on dry matter production per hectare and moisture content of 13 genotypes of Phalaris arundinacea (reed canary grass) was studied between 1995 and 1998 and N, P and K concentration in biomass was measured in 1998. There were two winter harvests, the first at crop senescence and the second after a subsequent delay of several weeks which varied each year. Average dry matter production was higher at the first (conventional) harvest than at the delayed harvest except in 1996. Each year there were differences in yield between genotypes and some differences were significant. Delayed harvest reduced yield by an average of 24% in 1997 and 23% in 1998 when losses resulted from 48% loss of leaf and 16% of stem matter. Delayed harvest decreased moisture content by 50% in 1997 and 52% in 1998 but it was 49% higher in 1996. In 1998, delayed harvest did not reduce N concentration in all genotypes and the reduction of P was variable, but K concentration was reduced by an average of 54%. Results indicate the suitability of reed canary grass as a biofuel, and variability between genotypes offers potential for crop improvement through selection and breeding.