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Shrub willow (Salix spp.) is a potential source of biomass feedstock for bioenergy, biofuels, and other bioproducts, but, to be considered sustainable, production systems must not result in long-term degradation of soil resources. Shrub willows are expected to reduce soil loss and improve soil health over time, but data are lacking to model soil erosion from shrub willow cropping systems. Our objectives were to characterize shrub willow across a chronosequence of age classes and to use these data to parameterize the Revised Universal Soil Loss Equation (RUSLE2) and model estimated soil loss from a range of soil types, slopes, management practices, and willow cultivars. Predicted average annual soil loss from shrub willow over seven 3-year rotations ranged from 1.68 to 1.97 Mg ha−1 yr−1, below the estimated soil loss tolerance value (T = 6.7 Mg ha−1 yr−1). Steeper slopes and silty soils were more susceptible to soil loss, but soil loss estimates across the production cycle were consistently below T. However, in all cases, the first year of production resulted in predicted soil loss above T (11–17 Mg ha−1 yr−1 under typical growing conditions). Soil disturbance during site preparation and planting and the lack of cover until canopy closure in the second year of production leave the soil susceptible to erosion in the first growing season. Cover crops, if they do not interfere with the growth of the willow crop, may reduce risk to the soil and provide additional benefits. [ABSTRACT FROM AUTHOR]

The elemental composition of woody biomass has important consequences for both energy conversion processes and agronomic management of nutrient budgets. In this study, the largest shrub willow yield trial dataset in North America has been leveraged to evaluate the effects of cultivar, growing environment and their interaction on elemental concentrations and content in shrub willow. Stem samples from six commercial cultivars in four trial locations in the Northeastern USA were separated into bark and wood and analyzed for C, N, and H by combustion and for elemental composition by ICP-OES. A second set of samples in the form of whole biomass from the same six cultivars and from six additional trial locations were also analyzed, totaling to 252 total independent observations. A Salix purpurea cultivar had greater N, Mg, and Fe concentrations in bark, whereas S. miyabeana cultivars had high Ca concentrations in both bark and wood. Hybrids between these two species displayed intermediate values. Multivariate analyses of the broader suite of biomass samples showed strong environmental effects on elemental composition, but there were a number of significant cultivar × location interactions. Nutrient export rates at harvest were largely a function of yield. These results showed potential cultivar-specific differences in nutrient uptake, but more broadly the results provide a robust method for nutrient management planning. These findings suggest a capacity to exploit existing genetic resources for improving phytoremediation and excess nutrient management projects. [ABSTRACT FROM AUTHOR]

Fifteen varieties of willow (Salix) hybrids were observed in a replicated study on five diverse sites in Michigan during the establishment year and over two subsequent 3-year rotations. Sixty-one percent of the total variation in yield observed was due to environmental factors, 11% was due to genetic factors, and the remainder was unexplained. Biomass yield over 6 years ranged from 50.5 oven-dry Mg ha−1 at one site to 22.9 oven-dry Mg ha−1 at another. Warmer and wetter sites tended to produce more biomass than colder drier sites, but correlations between yield and other edaphic and climatic factors were less clear. High-yielding varieties tended to be taller, but survival and number of stems per stool were uncorrelated with yield. A cohort of elite varieties selected based on test-wide performance produced up to 26% more biomass than randomly chosen varieties. Cohorts of elite varieties selected based on performance in local tests did better, producing up to 31% more biomass than randomly chosen varieties. Because of ranking changes, selections made after two rotations outperformed those made after only one rotation by as much as 9%. Adequately tested planting stock has the potential to increase the financial return to a willow energy farmer by nearly $100 ha−1 year−1. This will multiply rapidly as willow is planted on some of the 700 million hectares of retired cropland in the USA. The nominal cost of breeding and field testing willow energy crops can be easily justified as we proceed to the envisioned billion-ton bioeconomy. [ABSTRACT FROM AUTHOR]

To assess the effects of propagule phenology and planting system on growth performance of three willow clones grown under different weeding regimes, a field experiment was performed in central Sweden 2014-2016. Freshly harvested (non-dormant) and cold-stored (dormant) cuttings (planted vertically) and billets (planted horizontally) from willow clones Tordis, Tora, and Jorr were planted in weeded and in unweeded plots. Sprouting was significantly higher for willows grown from non-dormant (74%) than dormant (58%) propagules and for cuttings (84%) compared with billets (42%). Survival was higher for willows from non-dormant propagules in weeded (71%) compared with unweeded (63%) plots, willows from dormant propagules in weeded (72%) compared with unweeded (60%) plots, and for willows from cuttings (93%) compared with billets (39%). During 2014-2016, aboveground biomass production was significantly higher for willows from cuttings (11.71 t DW ha−1) than from billets (6.13 t DW ha−1), grown in weeded (15.29 t DW ha−1) than in unweeded (2.55 t DW ha−1) plots, and differed significantly among willow clones (11.48, 9.27, and 6.01 t DW ha−1 for Tordis, Tora, and Jorr, respectively). In this study, (i) planting with cold-stored and freshly harvested willow propagules was equally successful and therefore cold storage could be potentially avoided and replaced with planting of freshly harvested propagules in early spring; however, (ii) in terms of measured growth performance parameters, willows grown from cuttings performed better than grown from billets; and (iii) weed competition significantly reduced survival and aboveground biomass production, confirming that weed control during establishment of willow is crucial. [ABSTRACT FROM AUTHOR]

Bioenergy crops have a secondary benefit if they increase soil organic C (SOC) stocks through capture and allocation below-ground. The effects of four genotypes of short-rotation coppice willow (Salix spp., ‘Terra Nova’ and ‘Tora’) and Miscanthus (M. × giganteus (‘Giganteus’) and M. sinensis (‘Sinensis’)) on roots, SOC and total nitrogen (TN) were quantified to test whether below-ground biomass controls SOC and TN dynamics. Soil cores were collected under (‘plant’) and between plants (‘gap’) in a field experiment on a temperate agricultural silty clay loam after 4 and 6 years’ management. Root density was greater under Miscanthus for plant (up to 15.5 kg m−3) compared with gap (up to 2.7 kg m−3), whereas willow had lower densities (up to 3.7 kg m−3). Over 2 years, SOC increased below 0.2 m depth from 7.1 to 8.5 kg m−3 and was greatest under Sinensis at 0-0.1 m depth (24.8 kg m−3). Miscanthus-derived SOC, based on stable isotope analysis, was greater under plant (11.6 kg m−3) than gap (3.1 kg m−3) for Sinensis. Estimated SOC stock change rates over the 2-year period to 1-m depth were 6.4 for Terra Nova, 7.4 for Tora, 3.1 for Giganteus and 8.8 Mg ha−1 year−1 for Sinensis. Rates of change of TN were much less. That SOC matched root mass down the profile, particularly under Miscanthus, indicated that perennial root systems are an important contributor. Willow and Miscanthus offer both biomass production and C sequestration when planted in arable soil. [ABSTRACT FROM AUTHOR]

An increasing interest to convert lignocellulosic biomass into biofuels has highlighted the potential of using willows for this purpose, due to its fast growth in short rotation coppice systems. Here, we use a mapping population of 463 individuals of a cross between Salix viminalis and S. viminalis × S. schwerinii to investigate the genetic background of different wood chemical traits, information of importance for breeding towards different uses of wood. Furthermore, using a subset of the mapping population, the correlation between biogas production and chemical traits was investigated. The phenotyping of wood was carried by Furrier-transformed-Infrared spectrometry (FT-IR) and water content analysis. Quantitative trait loci (QTLs) analysis was used to identify regions in the genome of importance for the phenotypic variation of these chemical traits. We found 27 QTLs for various traits. On linkage group (LG) VI-1, QTLs for signals assigned to G-lignin, lignin, and the S/G ratio were collocated and on LG XIV we found a cluster of QTLs representing signals assigned to lignin, cellulose, hemicellulose, and water. The QTLs explained from 3.4 to 6.9% of the phenotypic variation indicating a quantitative genetic background where many genes influence the traits. For the biogas production, a positive and negative correlation was seen with the signals assigned to acetyl and lignin, respectively. This study represents a first step in the understanding of the genetic background of wood chemical traits for willows, information needed for complementary studies, mapping of important genes, and for breeding of varieties for biofuel production purposes. [ABSTRACT FROM AUTHOR]

In this study, an integrated system of harvesting, collecting, and transporting willow biomass crop to a storage site was modeled and evaluated using the IBSAL simulation model. A scenario analysis was used to quantify the impacts of five major input parameters on the performance of the integrated system. These parameters include parcel size, field shape, willow yield, distance to the storage site, and type of the collection equipment. Multiple performance indicators were identified to quantify the impacts on the system such as size of the equipment fleet, effective material and field capacity of the harvester, operating costs, and waiting times. The input data were collected from 36 commercial, short-rotation, shrub willow fields in northern New York State. The simulation results indicated that crop yield and type of collection equipment have the highest impact on operating costs and the equipment fleet size. As the size of equipment fleet increases in the system, variability in the system performance tends to increase. Field shape has the least impact on the overall system performance compared to the other four input parameters. The simulation results suggest that a combination of performance indicators need to be considered to evaluate the overall performance of the dynamic and complex system of harvesting, collection and transportation in commercial willow fields. The developed IBSAL model and scenario analysis approach can assist in planning this system based on the characteristics of field, crop, and logistical equipment to reach a high system performance. [ABSTRACT FROM AUTHOR]

Shrub willow has potential for being a viable dedicated bioenergy crop in temperate northern latitudes of the USA. Selection of high-producing willow cultivars is critical for economic viability and long-term sustainability of willow production systems. Long-term trials are needed in different geographic areas to better understand genetic by environment interactions on biomass yield for greater profitability and to enhance future breeding efforts. Field trials were conducted in two contrasting environments, northern New York and southern Minnesota, to explore changes in shrub willow yield ranking over three harvest cycles across a range of cultivars and diversity groups. Overall, the MN site produced higher, more stable biomass yields than the NY site due primarily to more productive soils, warmer climate, and less weed pressure. However, between-site differences in willow biomass yield were nominal after the second harvest cycle. Yield variability among the top five willow cultivars at each harvest was significantly less than variability among all cultivars regardless of site. Shrub willow cultivars identified in the top-ranking groups were different between sites. Results show that willow can be a viable long-term crop for sustained biomass feedstock production across a wide range of soils and climates but proper cultivar selection is critical for biological and economic success. [ABSTRACT FROM AUTHOR]

To assess the effects of cutting phenology on early growth performance of three willow clones grown under different weed treatments and planting dates, freshly harvested (non-dormant) and cold-stored (dormant) cuttings from willow clone Tora, Jorr, and Olof were planted in bucket experiment outdoors in central Sweden on five planting dates (May-June 2013) with or without a model weed (spring barley). Non-dormant cuttings sprouted faster than dormant cuttings when planted early in the season. For cuttings planted later in the season, bud sprouting was affected only by willow clone. Aboveground biomass production was affected by cutting phenology, planting date, clone, and weed treatment. When planted on May 3 and May 10, biomass produced from non-dormant and dormant cuttings did not differ, while willows grown from dormant cuttings produced 59% more aboveground biomass than willows grown from non-dormant cuttings when planted on May 24-June 16. Tora produced on average 12% more biomass than Jorr and Olof, and weed competition reduced aboveground biomass production on average with 36%. The ability of willow to suppress weeds (WSA) was 26 (non-dormant cuttings) and 12% (dormant cuttings) higher for willows planted on May 3 compared with WSA of willows grown from cuttings planted later in the season. The ability to tolerate competition from weeds (WT) was 51 and 52% lower for willows grown from non-dormant and dormant cuttings planted late in the season compared with WT of willows planted earlier in the season. We conclude that planting with long-term cold storage of willow cuttings can be replaced with planting freshly harvested cuttings when planting is performed in early season, and that weed competition strongly reduces biomass production. Weed control during the establishment phase is crucial in order to maximize willow biomass production. [ABSTRACT FROM AUTHOR]

The establishment of short-rotation willow coppice plantations for bioenergy production is proposed as a land management practice to reduce the use of fossil fuels. However, there is little information on the performance of different willow ( Salix spp.) cultivars on various types of soils and over climate gradients. This study aimed to determine which set of soil, climatic conditions, and cultivars are conducive to greater growth in eastern Canada. The performance of five willow cultivars was followed over three growing seasons on eight sites representing a large hydroclimatic gradient. Both geographic location and cultivar had a significant effect on annual yields. Annual yields were on average greater in the southern part of the climatic gradient. Across all cultivars, annual yields were positively correlated to average annual temperature ( r = 0.23), total annual precipitation ( r = 0.77), average growing season temperature ( r = 0.21), average growing season precipitation ( r = 0.47), and degree days ( r = 0.18), as well as soil pH ( r = 0.37) and soil extractible P ( r = 0.38), and negatively correlated to soil clay content ( r = 0.33). Cultivars of the SX group (i.e., Salix miyabeana SX61, SX64, and SX67) showed greater yield than did cultivars of the SV group (i.e., Salix × dasyclados SV1 and Salix viminalis SV5027). These results indicate that at the landscape level, climate variables, especially climate-related variables, largely explain the yield of the selected willow cultivars. Nonetheless, soil pH, extractable P, and clay content likely play an important role in plantation yield. [ABSTRACT FROM AUTHOR]

Aboveground biomass yields of short rotation cultures (SRC) of willow can vary substantially depending on site quality. Among others, aboveground biomass yields depend on climatic conditions, soil properties, age of the SRC, and number of harvesting cycles. In this study, we investigated the effects of coppicing on growth variables (i.e., largest basal stem, height, and aboveground biomass) at ten SRC of Salix miyabeana SX67 established on various soils in southern Quebec. More than 1100 shrubs with stool ages varying between 1 and 15 years were measured. Strain analysis was carried out to calculate past annual aboveground productivities, and maximum annual yield potential was quantified at each site. Annual growth rates were highly variable and depended on site and coppicing history. To achieve optimal stool development and aboveground yields, two to three growing seasons following coppicing were necessary for sandy and clayey sites, respectively. The delays for reaching maximum yields were shortened when soil cation exchange capacity was dramatically low and were prolonged when soil was physically restricting stool development. This lag influenced the total yield of the first rotation and also modulated the magnitude of the increase of aboveground biomass that is generally observed in the second rotation. To increase yields in southern Quebec, our results suggest that it is preferable to extend the length of the first rotation instead of coppicing at the end of the first growing season after establishment. [ABSTRACT FROM AUTHOR]

Eight willow ( Salix) clones (Inger, Klara, Linnea, Resolution, Stina, Terra Nova, Tora, Tordis) were planted on two soil types in Denmark. The biomass quality was evaluated after 3 years of growth by measuring differences in concentrations of 14 elements associated with ash behavior during combustion, and total ash content. Three-year-old shoots of Tordis and Tora performed in general the best with relatively lower mean concentrations of K, Ca, Na, S, and total ash content than other clones across the two experimental sites. Terra Nova was the least suited for combustion as it contained up to 22, 27, 35, and 23 % higher concentrations of K, S, Ca, and total ash than the other clones. In addition to clone and site, appropriate management could further improve the fuel quality of willow biomass. When shoots of Inger were harvested annually (1-year shoots) high concentrations of K and Cl were found in all three consecutive harvests, but concentrations decreased significantly when rotation length was extended beyond 1 year of growth. Significant decreases of Mg, Na, P, S, and Zn were also registered from 2- to 3-year-old shoots. No difference in quality of biomass was found between two plant densities (8000 and 12,000 trees ha) of the clones Inger and Tora after the first 3-year rotation when grown at the site with a coarse sandy soil. The study indicates considerable diversity in concentration of elements within commercially available willow cultivars and suggests breeders and growers to select clones not only according to biomass yield potential but also according to biomass quality. [ABSTRACT FROM AUTHOR]

The increasing demand for bioenergy and the combination of agricultural production with conservation has made short-rotation agroforestry systems (SRAFS) a sustainable land-management option. Aboveground woody biomass is a decisive factor in economic and ecological assessment of those systems. To study the yields of organic and conventional SRAFS, the tree species black alder, black locust, poplar clone Max 3, poplar clone Androscoggin, willow clone Inger, and a mixture of different native species were established in an alley-cropping configuration in 2009 and coppiced in 2012. Biomass was determined by harvesting the inner rows of the tree strips and, to investigate row differences within a strip, by an allometric model which estimates tree biomass from stem diameter. Significant variation was observed between species. For inner rows and at the conventional system, highest harvested average annual yield was observed for poplar Androscoggin (10.5 t ha year), followed by black locust (9.7 t ha year), poplar Max 3 (8.6 t ha year), black alder (7.6 t ha year), the native mix (4.9 t ha year), and willow (3.9 t ha year). At the organic system, highest yields were observed for poplar Max 3 (Androscoggin not planted) (10.9 t ha year), followed by black locust (8.1 t ha year), black alder (7.4 t ha year), willow (6.4 t ha year), and the native mix (4.7 t ha year). Farming system differences were only significant for willow and poplar Max 3; however, the higher yields of the organic system seemed to be a result of varying small-scale site properties rather than a management effect. Border rows showed 18-111 % more yield than inner rows because of greater tree diameters or heights and higher number of stems. This edge effect was emphasized in the conventional systems, possibly indicating that trees benefit from fertilizers applied at adjacent crop fields. [ABSTRACT FROM AUTHOR]

To evaluate the effects of weed competition and nitrogen fertilization on the early growth performance of willow, cuttings of the clone Tora ( Salix schwerinii x S. viminalis) were planted in buckets together with model weeds (spring barley or white mustard) sown 15, 26, and 30 days after willow planting. The buckets were fertilized with 30 or 90 kg N ha. Willow with weeds sown after 15 days produced less biomass and smaller leaf area and had a lower maximum shoot height compared to willow planted without weeds and willow with weeds sown after 26 or 30 days. Fertilization with 90 kg N ha gave higher willow biomass production in willow with weeds sown after 26 or 30 days. Type of model weed had no effect on willow performance. Weed biomass and maximum shoot height were higher in weeds planted without willows compared to the willow-weed mixtures. A high nitrogen level gave more weed biomass when planted without willows and in the willow-weed mixture with weeds sown after 15 days. We conclude that for the given high density of willow, competition from weeds emerging soon after willow planting had strong effect on early production. Furthermore, if there is a risk of weed infestation, fertilization should be delayed. [ABSTRACT FROM AUTHOR]

Short-rotation woody crops are an integral component of regional and national energy portfolios, as well as providing essential ecosystem services such as biomass supplies, carbon sinks, clean water, and healthy soils. We review recent USDA Forest Service Research and Development efforts from the USDA Biomass Research Centers on the provisioning of these ecosystem services from woody crop production systems. For biomass, we highlight productivity and yield potential, pest susceptibility, and bioenergy siting applications. We describe carbon storage in aboveground woody biomass and studies assessing the provision of clean and plentiful water. Soil protection and wildlife habitat are also mentioned, in the context of converting lands from traditional row-crop agriculture to woody production systems. [ABSTRACT FROM AUTHOR]

Soil erosion, loss of productivity potential, biodiversity loss, water shortage, and soil and water pollution are ongoing processes that decrease or degrade provisioning (e.g., biomass, freshwater) and regulating (e.g., carbon sequestration, soil quality) ecosystem services. Therefore, developing environmental technologies that maximize these services is essential for the continued support of rural and urban populations. Genotype selection is a key component of these technologies, and characteristics of the species used in short rotation woody biomass systems, as well as the silvicultural techniques developed for short rotation woody crops are readily adapted to environmental applications. Here, we describe the development of such woody crop production systems for the advancement of environmental technologies including phytoremediation, urban afforestation, forest restoration, and mine reclamation. The primary goal of these collective efforts is to develop systems and tools that can help to mitigate ecological degradation and thereby sustain healthy ecosystems across the rural to urban continuum. [ABSTRACT FROM AUTHOR]

Understanding the characteristics of short rotation woody crops (SRWC), like shrub willow, that affect feedstock quality and its variability is a priority as this source of biomass is expanded. Because of its relationship to ash content, the allotment of bark and wood within the stem is often highlighted as a factor impacting feedstock quality. Bark-to-wood ratios are frequently determined in willow by measuring this ratio for the centroid and assuming it represents the entire stem. The objectives of this study were to determine how site and genetic factors influenced the allometry of whole stem bark (WSB%) content on a dry weight basis and if the centroid bark percentage (CB%) on a dry weight basis adequately represents WSB%. A multiple linear regression approach was used to model WSB% and centroid bark content (CB%) using diameter, cultivar, and site factors. Five candidate models were evaluated ranging from parsimonious to complex. The simplest models estimated WSB% from CB% ( R = 0.76) and stem diameter ( R = 0.44). The most complex model included all factors and had an R of 0.90. Two key relationships demonstrated by several models are that (1) CB% adequately predicts but underestimates WSB%, particularly for larger stems, and (2) WSB% increases as diameter decreases. However, empirical models can be enhanced with the inclusion of diameter, site, and cultivar information. The overall approaches can be useful for making relative comparisons between cultivars and sites. In a 3-year-old stand of willow stems less than 20 mm had high WSB%, the maximum being 23.8 %, but accounted for only 5 to 15 % of the total biomass. Large diameter stems accounted for the majority of the total and bark biomass, but the WSB% in large diameter stems is as low as 11.5 %. WSB% ranged from 12.9 to 14 % across the two cultivars at the stand level. [ABSTRACT FROM AUTHOR]

How representative are yields from experimental plots compared to large-scale commercial implementation? This study analyses the yields of fast-growing willow plantations for energy reported in experimental trials in Sweden during the period 1980-2012 compared with those from commercial willow plantations for the period 1986-2006. The study reviews 16 academic publications, which include 466 records from experimental plots, and records from 2073 commercial plantations across the country. The average yield recorded from experiments was 7.7 odt ha year, compared to commercial plantations' yields 2.6 and 4.2 odt ha year for the first and second rotations, respectively. The measured area of the experimental plots seems to have an effect in the overestimation of the average yields, which can be attributed to extrapolation errors. In addition, to explain the broad differences between yield estimates, we identify the following as potential factors: near-optimal management practices and choice of land age differences and rotation lengths, edge effects, measurement methods, harvesting losses, increased mortality, and increased probability of hazard. The results can help to rationalize the expectations derived from experiments and to a more realistic planning of future plantation schemes. [ABSTRACT FROM AUTHOR]

Yield estimates from single stands in short-rotation willow ( Salix spp.) have been reported to differ substantially, depending on the estimation methods used. The magnitude of differences in estimates resulting from different methods may vary among clones on the same site. This indicates that some assumptions, implicitly made by using a certain method, cannot be generalised for all clones. To assess why estimates of different methods may differ and why the magnitude of the differences may be clone-specific for a given site, a number of assumptions underlying destructive and non-destructive protocols for the estimation of aboveground willow biomass were tested. Apart from general problems in satisfying the demands of representative sampling and meeting the assumptions that underlie the proper use of statistical models, it was found that basic assumptions with regard to the physical structure and phenology of willow may lead to the observed differences. For a given clone, the moisture content of willow shoots may vary over time and may be dependent on shoot size. For a given shoot, the moisture content of basal, apical and central stem parts may differ, with the magnitude of differences being dependent on the clone. Stem taper and curvature may be clone-specific and can also underlie differences in biomass estimates obtained by different methods. To improve estimates of aboveground biomass in short-rotation willow, it is important to state explicitly the assumptions underlying the methods used and, wherever possible, to test the assumptions and evaluate the effects of their violation on the resulting estimates. [ABSTRACT FROM AUTHOR]

To date, most of the data on the characteristics of many short rotation woody crops has come from biomass that was hand harvested from small-scale yield trials. Concerns have been raised that there is insufficient information regarding the variability in biomass characteristics when material is harvested at commercial scales, which can impact the efficiency of biorefineries and other end users. The objectives of this study are to (1) characterize the biomass (i.e., ash, moisture, energy and elemental content, and particle size distribution) generated from commercial-scale shrub willow harvests at two sites, (2) evaluate compliance the published International Organization for Standardization (ISO) standards, and (3) contrast with 'pristine' biomass from yield trials. Commercially generated chips were generally compliant with ISO standards for B1 chips. The mean ash content was 2.1 % (SD 0.59) dry basis and ranged from 0.8 to 3.5 % for samples collected from 224 truckloads of chips. There was a site effect for ash: 100 % compliance at one site and 82 % compliance at the second; loads exceeded the 3 % standard by less than 0.5 percentage points. The ash content of the Fish Creek cultivar was almost 1 % less than other cultivars and it is significantly lower ( P < 0.0001). The mean moisture content was 44 % (SD 2.2) and ranged from 37 to 51 %. The harvested biomass was similar to pristine biomass with the exception of ash content, and the variability was similar across all characteristics measured. The low variability of willow biomass characteristics suggests that material with a consistent set of characteristics can be generated from willow crops with a cut-and-chip harvesting system. [ABSTRACT FROM AUTHOR]

Determining the appropriate wastewater dose to supply nutrients while avoiding overirrigation is essential for achieving more balanced above- and belowground development of the plants, thereby ensuring high filtering functionality of a willow vegetation filter system. Aboveground biomass and root development of a 3-year-old willow vegetation filter in response to three increasing doses of secondary-treated urban wastewater under both fertilized and unfertilized conditions were evaluated. Fine, coarse and total root biomass, fine root length density (FRLD), specific fine root length (SFRL) and specific root area (SRA) were assessed in soil core samples collected at four different depths (0-20, 20-40, 40-60 and 60-80 cm) in all treatments. While aboveground biomass increased as wastewater amounts and fertilization increased (from 23.89 Mg ha in non-irrigated condition to 47.07 Mg ha in the highest wastewater dose, from 31.5 Mg ha in unfertilized plots to 40.1 Mg ha in the fertilized), total and fine root biomass decreased when willow was irrigated with the highest wastewater dose (i.e. total root biomass is 2.54 Mg ha in non-irrigated condition-1.36 Mg ha in the highest wastewater dose). The root biomass did not follow the same development pattern, and a significant decrease in fine root biomass was observed when the highest irrigation dose was applied. In these circumstances, we believe that the supply in water and nutrient is sufficient to the development of the willows which react by diminishing the amount of roots proportionally to the aboveground parts. This may lead to a higher transpiration rate and allow willows to avoid a surplus of water in the soil. [ABSTRACT FROM AUTHOR]

To assess the effects of different planting systems on early performance (survival, shoot emergence time, number of shoots, maximum shoot height and biomass shoot production) of willow, cuttings of varying lengths were planted horizontally at different depths and compared with vertically planted cuttings. Cutting lengths of (i) 25-200 cm and (ii) 7-21 cm were studied in a field experiment and in a box experiment, respectively. Shorter cuttings planted deeper had a lower survival rate and emerged a few days later compared to longer cuttings planted shallower. The performance was considerably higher at the apical part of the cuttings, regardless of cutting length. Longer cuttings planted shallow had a higher performance. Vertically planted cuttings produced more biomass and shoots per length unit than horizontally planted cuttings. We conclude that planting systems based on the use of longer horizontally planted cuttings would probably lead to an uneven establishment and gaps in the stand caused by apical dominance. Also, to achieve the same performance, the need of planting material would be considerably higher compared to systems with vertically planted cuttings. To obtain a fast and more even early establishment of willows, we recommend the use of vertically planted cuttings with a length of at least 20 cm. If cuttings are planted horizontally, they should not be planted deeper than 5 cm. [ABSTRACT FROM AUTHOR]

The objectives of this study were to estimate biomass production in commercially grown short rotation coppice willow in Denmark and to investigate effects of site and management factors on willow yield. Biomass production assessed by non-destructive sampling on 296 plots from 25 plantations was analyzed using a mixed model approach. Average production in the stands varied between 2.4 and 15.1 odt ha year, and average second rotation growth (8.2 odt ha year) was significantly higher than first rotation growth (6.5 odt ha year). Annual production was significantly correlated with clone, soil texture, soil drainage, fertilization, weeds, rotation number, and shoot age. Further, interactions between clone and soil drainage as well as between clone and soil texture were significant, indicating the importance of a site-specific choice of clones. [ABSTRACT FROM AUTHOR]

The Government of Saskatchewan is evaluating whether biomass crops can be successfully used as an affordable, reliable, and environmentally sustainable bioenergy source. The objective of this study was to determine the first 3-year-rotation biomass yields of 30 willow cultivars planted in central Saskatchewan. Annual willow morphological data were collected throughout the first rotation, and stem biomass equations were developed. A willow yield map was produced for the SV1 cultivar across climates and soils of Saskatchewan. The majority of willow biomass equations were with high R values (>0.90), and there was a strong agreement between equation-derived yield and harvested biomass (RMSE = 13.6 %; bias = -3.3 %). The average diameter, height, and stem count of 3-year-old stems were 14.1 (standard deviation (SD) =1.7) mm, 304.7 (SD = 45.4) cm, and 8.7 (SD = 1.8), respectively. The average first-rotation harvested yield was 10.5 (SD = 3.3) Mg ha, and the average survival rate was 81 %. Simulated SV1 productivity was 13.6 and 11.8 Mg ha across marginal agricultural lands of the Prairies (1.7 million ha) and Boreal Plains (0.4 million ha) ecozones, respectively. Low growing degree days, heavy clay soils, low nitrogen availability, and winter stem dieback at these northern latitudes were the main factors to influence willow production at relatively lower yields observed in this study. Based on first-rotation results, the Tully Champion cultivar had the highest potential to be utilized as biomass feedstock in Saskatchewan, producing 17.4 Mg ha, which was 70 % greater biomass than the average yield of the other 29 cultivars. The use of willow as a bioenergy source appears promising, but further research is needed. [ABSTRACT FROM AUTHOR]

Polyploidy is a common observation in the genus Salix, including some of the shrub willow species currently being bred as a potential bioenergy feedstock. Breeding of shrub willow has produced new species hybrids, among which a disproportionate number of high-yielding genotypes are triploid, produced from crosses between diploid and tetraploid parents. These novel hybrids display significant variation in biomass compositional quality, including differences according to ploidy. The triploid and tetraploid genotypes possess lower lignin content than diploid genotypes. Biomass composition was also significantly different across the 3-year growth cycle typical of bioenergy plantings. There were differences in syringyl/guaiacyl (S:G) lignin ratios among the 75 genotypes examined, in addition to significant correlations with willow growth traits, yield, and composition. These differences suggest that a long-term strategy of breeding for triploid progeny will generate cultivars with improved growth traits and wood composition for conversion to biofuels. [ABSTRACT FROM AUTHOR]

Although numerous studies have quantified different social, economic, energetic, and environmental benefits associated with short-rotation coppice (SRC) willow plantations, comprehensive assessments of nutrient cycling are rare. The objective of this study was to examine the biomass production and attendant biogeochemical cycling of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg) during the initial 4-year rotation of six willow varieties grown at four locations along a 500 km north-south pedoclimatic gradient within Saskatchewan, Canada. Nutrient budgets consisted of quantifying various nutrient inputs (e.g., atmospheric deposition and soil mineral weathering), outputs (e.g., fine and coarse root biomass, leaf biomass, harvested biomass, leaching, and denitrification), and transfers (e.g., soil organic matter mineralization, canopy exchange, leaf litter decomposition, and fine root turnover) associated with the plant available soil nutrient pool. Total above- and below-ground production during the rotation was approximately 40 Mg ha, with calculated soil nutrient budget deficits (i.e., nutrient outputs > inputs + transfers) of 17, 39, 112, 271, and 74 kg ha for N, P, K, Ca, and Mg, respectively, averaged across the varieties and sites, but a soil S surplus of 60 kg ha. While soil nutrient budget deficits varied among sites, there were no significant differences ( P > 0.05) among willow varieties. Despite the relatively low nutrient-demanding nature of willow and negligible leaching or denitrification losses, nutrient export in harvested biomass over multiple rotations will require soil nutrient amendments to maintain SRC willow productivity, particularly N and P, albeit a fraction of the amount required for annual agronomic crops. [ABSTRACT FROM AUTHOR]

Use of high-yielding genotypes is one of the means to achieve high yield and profitability in willow ( Salix spp.) short rotation coppice. This study investigated the performance of eight willow clones (Inger, Klara, Linnea, Resolution, Stina, Terra Nova, Tora, Tordis) on five Danish sites, differing considerably in soil type, climatic conditions and management. Compared to the best clone, the yield was up to 36 % lower for other clones across sites and up to 51 % lower within sites. Tordis was superior to other clones with dry matter yields between 5.2 and 10.2 Mg ha year during the first 3-year harvest rotation, and it consistently ranked as the highest yielding clone on four of the five sites and not significantly lower than the highest yielding clone on the fifth site. The ranking of the other clones was more dependent on site with significant interaction between clone and site. For instance, Tora obtained the same yield level as Tordis on two locations but significantly lower yield on the other sites. Dry matter content at harvest differed significantly among clones, ranging from 44.5 to 46.8 % across sites with highest level in Inger, Linnea, Resolution, and Tordis. Compared to the best site, yield level was up to 51 % lower on other sites across all clones, probably due to combined effects of differences in soil type, climate and management. Thus, willow yield depends both on the use of high-yielding clones and on the combined site effects of soil, climate, and management. [ABSTRACT FROM AUTHOR]

Harvesting is the single largest cost in the production of short-rotation woody crops (SRWC) like shrub willow, and previous systems tested in North America have not been effective for the size of material grown. The objective of this study was to evaluate the performance of a single-pass, cut and chip harvester in conjunction with two locally sourced chip collection systems on 54 ha of coppiced willow harvests in New York State. Harvesting and collection equipment was tracked for 153 loads over 10 days of harvesting using GPS data loggers. Effective material capacities ( C) increased linearly with standing biomass up to 40 to 45 Mg ha because ground speed was limited by ground conditions. This relationship changed dramatically with standing biomass in the 40-90 Mg ha range, where C plateaued between 70 and 90 Mg h and was limited by crop conditions and harvester capacity. The relationship between standing biomass and the harvester's C will probably change under different crop and ground conditions. The size of the harvester and the experience of the operator are other factors. This nonlinear relationship will impact cost and optimization modeling SRWC systems. Improperly sized headland and long haul distances impeded the performance of locally sourced collection systems resulting in a 33 % decrease in C from the field to the headlands, and 66 % from the field to short-term storage as biomass moves through the system. [ABSTRACT FROM AUTHOR]

Short-rotation coppice willow (SRCW) is a fast-growing and potentially high-yielding energy crop. Transition to bioenergy has been identified in Sweden as one strategy to mitigate climate change and decrease the current dependency on fossil fuel. In this study, life cycle assessment was used to evaluate and compare the climate impacts of SRCW systems, for the purpose of evaluating key factors influencing the climate change mitigation potential of SRCW grown on agricultural land in Sweden. Seven different scenarios were defined and analysed to identify the factors with the most influence on the climate. A carbon balance model was used to model carbon fluxes between soil, biomass and atmosphere under Swedish growing conditions. The results indicated that SRCW can act as a temporary carbon sink and therefore has a mitigating effect on climate change. The most important factor in obtaining a high climate change-mitigating effect was shown to be high yield. Low yield gave the worst mitigating effect of the seven scenarios, but it was still better than the effect of the reference systems, district heating produced from coal or natural gas. [ABSTRACT FROM AUTHOR]

Quantifying short-rotation coppice (SRC) willow leaf litter dynamics will improve our understanding of carbon (C) sequestration and nutrient cycling potentials within these biomass energy plantations and provide valuable data for model validation. The objective of this study was to quantify the decomposition rate constants ( k) and decomposition limit values (LV), along with associated release rates ( k) and release limits (LV) of nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca), and magnesium (Mg) of leaf litter from several native and exotic willow varieties during an initial 4-year rotation at four sites within Saskatchewan, Canada. The k, LV, k, and LV values varied among the willow varieties, sites, and nutrients, with average values of 1.7 year, 79 %, 0.9 year, and 83 %, respectively. Tissue N had the smallest k and LV values, whereas tissue K and Mg had the largest k and LV values, respectively. The leaf litter production varied among willow varieties and sites with an average biomass accumulation of 7.4 Mg ha after the 4-year rotation and associated C sequestration rate of 0.2 Mg C ha year. The average contribution of nutrients released from leaf litter decomposition during the 4-year rotation to the plant available soil nutrient pool across varieties and sites was 22, 4, 47, 10, 112, and 18 kg ha of N, P, K, S, Ca, and Mg, respectively. Principal component analysis identified numerous key relationships between the measured soil, plant tissue, climate, and microclimate variables and observed willow leaf litter decomposition and nutrient-release characteristics. Our findings support the contention that SRC willow leaf litter is capable of enhancing both soil organic C levels and supplementing soil nutrient availability over time. [ABSTRACT FROM AUTHOR]

To estimate fossil fuel demand and greenhouse gas emissions associated with short-rotation willow ( Salix spp.) crops in New York State, we constructed a life cycle assessment model capable of estimating point values and measures of variability for a number of key processes across eight management scenarios. The system used 445.0 to 1,052.4 MJ of fossil energy per oven-dry tonne (odt) of delivered willow biomass, resulting in a net energy balance of 18.3:1 to 43.4:1. The largest fraction of the energy demand across all scenarios was driven by the use of diesel fuels. The largest proportion of diesel fuel was associated with harvesting and delivery of willow chips seven times on 3-year rotations over the life of the crop. Similar patterns were found for greenhouse gas emissions across all scenarios, as fossil fuel use served as the biggest source of emissions in the system. Carbon sequestration in the belowground portion of the willow system provided a large carbon sink that more than compensated for carbon emissions across all scenarios, resulting in final greenhouse gas balances of −138.4 to −52.9 kg CO eq. per odt biomass. The subsequent uncertainty analyses revealed that variability associated with data on willow yield, litterfall, and belowground biomass eliminated some of the differences between the tested scenarios. Even with the inclusion of uncertainty analysis, the willow system was still a carbon sequestration system after a single crop cycle (seven 3-year rotations) in all eight scenarios. A better understanding and quantification of factors that drive the variability in the biological portions of the system is necessary to produce more precise estimates of the emissions and energy performance of short-rotation woody crops. [ABSTRACT FROM AUTHOR]

A correction to the article "Fertilization of SRC Willow, II: Leaching and Element Balances" that was published in the November 7, 2013 issue is presented.

Short rotation coppice (SRC) willow is an emerging cropping system in focus for production of biomass for energy. To increase production, the willow is commonly fertilized, but studies have shown differing effects of fertilization on biomass production, ranging from almost no response to considerable positive effects. Focus has also been on replacing mineral fertilizer with organic waste products, such as manure and sludge. However, the effect on biomass production and environmental impact of various dosage and types of fertilizer is not well described. Therefore we studied the environmental impacts of different doses of mineral fertilizer, manure and sewage sludge in a commercially grown SRC willow stand. We examined macro nutrient and heavy metal leaching rates and calculated element balances to evaluate the environmental impact. Growth responses were reported in a former paper (Sevel et al. 'Fertilization of SRC Willow, I: Biomass Production Response' Bioenergy Research, 2013). Nitrogen leaching was generally low, between 1 and 7 kg N ha year when doses of up to 120 kg N ha year were applied. Higher doses of 240 and 360 kg N ha as single applications caused leaching of 66 and 99 kg N ha year, respectively, indicating N saturation of the system. Previous intensive farming including high doses of fertilizer may be responsible for a high soil N status and the high N leaching rates. However, moderate fertilization input could not compensate P and K exports with the biomass harvest. No elevated leaching of heavy metals was observed for any fertilization treatments and more cadmium than applied with the fertilizer was removed with the biomass from the system. [ABSTRACT FROM AUTHOR]

Willow, a leading bioenergy feedstock, may be planted for bioremediation and has been used, more recently, as the biomass feedstock in the manufacture of biochar for agricultural applications. Here, we present a detailed study of the physical and chemical factors affecting willow char properties, where the feedstock is a by-product of bioremediation, potentially transferring pollutants such as heavy metals to the wood feed. Biochar samples were produced via pyrolysis of short-rotation coppice willow, grown on contaminated land, using several treatment times at heat treatment temperatures (HTTs) in the range 350-650 °C, under a constant flow of argon, set at either 100 or 500 mL min. The samples were analysed for yield, elemental analysis and structural characteristics, including surface area and pore size distribution, surface functionality and metal content. All chars obtained have high fixed carbon contents but vary in surface characteristics with a marked increase in basic character with increasing HTT, ascribed to the removal of surface oxygen moieties. Results indicate a minimum pyrolysis temperature of 450 °C is required to produce a defined mesoporous structure, as required to facilitate oxygen transport, HTT ≥ 550 °C produces total surface area of >170 m g and, more importantly, an appreciable external surface area suitable for microbial colonisation. The data show that selection and optimisation of char properties is possible; however, the interplay of factors may mean some compromise is required. [ABSTRACT FROM AUTHOR]

Short rotation coppice (SRC) willow is often regarded as one of the most promising crops to increase biomass production and thereby meet the growing demand for renewable energy. This study is based on the hypotheses that biomass production of SRC willow responds positively to increasing doses of nitrogen, and that similar biomass production response can be achieved by use of mineral fertilizer, sewage sludge and animal manure. A 2-year experiment was established with the clone Tordis grown on a sandy soil in northern Jutland, Denmark. The experiment included mineral fertilizer, sludge and manure, and treatments of different doses up to 360 kg nitrogen ha. The fertilization led to a modest but significant increase in biomass production. The largest production of 11.9 oven dried tons/ha/year was obtained for the application of 60 kg nitrogen ha annually. Higher doses did not lead to increased biomass production; in fact, production seemed to decline with increasing fertilization application (not significant). We found no difference in production between different types of fertilizers. The limited response of the fertilization may be caused by a high fertility of the soil due to former agricultural fertilization. The number of sagging shoots increased significantly with increasing nitrogen dose. [ABSTRACT FROM AUTHOR]

Shrub willow has great potential as a dedicated bioenergy crop, but commercialization and adoption by growers and end-users will depend upon the identification and selection of high-yielding cultivars with biomass chemistry and quality amenable to conversion to biofuels and bioenergy. In this study, critical traits for biomass production were evaluated among new genotypes of shrub willow produced through hybrid breeding. This study assessed the variation in yield, pest and disease resistance, biomass composition, and wood density in shrub willow, as well as the impact of genotypic and environmental factors on these particular phenotypes. Analysis of clonal genotypes established on two contrasting sites in New York State, Tully and Belleville, showed statistical differences by site for all of the traits. The greatest yield was observed at Belleville, NY, for two cultivars, 'Fish Creek' (41 Mg ha) and 'Onondaga' (40 Mg ha). Yields of Salix eriocephala genotypes were lowest, and they displayed susceptibility to rust and beetle damage. Variation in cellulose content in the stem biomass was controlled by environmental factors, with the majority of the genotypes displaying greater cellulose content at Belleville compared with Tully. In contrast, wood density was significantly greater at Tully than Belleville, and cellulose content was correlated with wood density. There were no significant correlations between biomass yield and density or any of the composition traits. These trials demonstrate that new genotypes produce improved yield and pest and disease resistance, with diverse compositional traits that can be matched with conversion technologies. [ABSTRACT FROM AUTHOR]

Routine monitoring of above ground biomass within purpose-grown willow biomass energy production systems is important for timing harvest and other operations to maximize profit and increase plantation productivity. The objective of this study was to assess the efficacy of an elegant nondestructive mensurative technique for providing reliable estimates of harvestable biomass for six willow varieties during a 3-year rotation. The LAI-2000 Plant Canopy Analyser was used to measure the stem area index of growing willow and relate it to harvestable biomass at four locations within Saskatchewan, Canada over a 3-year period. Given the highly significant relationship ( R = 0.95; P < 0.0001) between measured stem area index and harvestable willow biomass, independent of variety, age, or location, this simple mensurative technique is a promising alternative for estimating above ground biomass in short-rotation willow plantations. [ABSTRACT FROM AUTHOR]

The economics of willow biomass crops are strongly influenced by yield, production, and harvesting costs and the delivered price for biomass. Under current management practices, willow biomass crops with yields of 12 oven-dried metric tons (odt) ha year and a delivered price of $60 odt have an internal rate of return (IRR) of about 5.5 %. Yields below 9 odt ha year have an IRR <0 %. We examined the impact of different incentive programs on the returns from willow biomass crops and the hectares or tons of willow biomass supported across a range of yields. Incentive programs examined included establishment grants (EG), annual payments (AIP), low cost startup loans, and matching payments offered by two existing programs, the Conservation Resource Program (CRP) and more recently the Biomass Crop Assistance Program (BCAP). EGs covering 75 % of the establishment costs provide high returns for growers on medium to high-productivity sites. Stand-alone AIPs with payments of $124 ha year paid over 5-15 years had little impact on profitability for growers but were costly for a funding agency. Low-cost loans with an interest rate of 2-4 % are one of the least expensive approaches ($1.3-6.6 odt) and improve profitability for medium- and high-yielding (8-16 odt ha year) sites. A matching payment incentive providing $50 per odt delivered was the only individual incentive approach that made low-yielding sites (6 odt ha year) profitable but was costly per odt compared to other incentives. Current CRP incentives made willow profitable across all productivity scenarios. The BCAP program generates higher profits for all productivity scenarios but comes at a higher cost. Effective financial incentives need to be well designed and monitored so that the target audience is reached and the intended policy goals are attained. [ABSTRACT FROM AUTHOR]

Willows ( Salix spp.) grown as short rotation coppice are recognised as an important bioenergy crop, and breeding programmes are underway in several countries, including the Czech Republic. The basket willow Salix viminalis is one of the few willow species that is widespread in the Czech Republic and thus a potential source of diversity, but the most extensive germplasm collection available shows evidence of redundancy. To investigate levels of variation in natural populations of this species for use in crop improvement programmes, a set of 38 microsatellite markers was used to assess genetic diversity and population structure among 84 S. viminalis individuals collected from seven Czech rivers (the Odra, Bečva, Morava, Dyje, Jihlava, Sázava and Vltava), covering a wide geographic distribution. The markers detected 6.95 alleles per locus on average with 92 % of the sampled individuals having a unique multilocus genotype giving a high clonal richness measure among all samples ( R = 0.952). Three sets of putative clones (with identical genotypes as determined by the markers used here) were also identified. Significant levels of genetic diversity were revealed within all sampling sites. With the exception of sites on the Odra and Morava, pairwise F (0.02-0.1) values indicated moderate differentiation between sites. Principal coordinates analysis revealed some separation of the Dyje individuals from all others. This was in agreement with the population structure results derived from Bayesian analyses using STRUCTURE software. These results provide the first evidence that potentially useful levels of genotypic variation are present within natural S. viminalis populations in the Czech Republic. [ABSTRACT FROM AUTHOR]

Short rotation coppice (SRC) willow is currently emerging as an important dedicated lignocellulosic energy crop in the UK. However, investigation into the variation between species and genotypes in their suitability for liquid transport biofuel processing has been limited. To address this, four traits relevant to biofuel processing (composition, enzymatic saccharification, response to pretreatment and projected ethanol yields) were studied in 35 genotypes of willow including Europe's leading SRC willow cultivars. Large, genotype-specific variation was observed for all four traits. Significant positive correlations were identified between the accessibility of glucan to enzymatic saccharification before and after pretreatment as well as glucose release and xylose release via acid hydrolysis during pretreatment. Of particular interest is that the lignin content of the biomass did not correlate with accessibility of glucan to enzymatic saccharification. The genotype-specific variations identified have implications for SRC willow breeding and for potential reductions in both the net energy expenditure and environmental impact of the lignocellulosic biofuel process chain. The large range of projected ethanol yields demonstrate the importance of feedstock selection based on an ideotype encompassing the performance of both field biomass growth and ease of conversion. [ABSTRACT FROM AUTHOR]

Willow shows great promise as a biomass crop and is now used worldwide. However, willow is a nutrient and water demanding plant that often requires the use of nitrogen (N) fertilizer to maximize growth on poor soils. The intercropping of Salix miyabeana with the atmospheric N-fixing Caragana arborescens on poor soils of the Canadian Prairies could provide a portion of the N demand of the willow. The main objectives were to: (1) determine the yield potential, N nutrition and water use efficiency (WUE) of willow and Caragana grown in pure and mixed plantations across a range of soil productivity and (2) assess the extent of atmospheric N-fixation by the Caragana within the first rotation in central Saskatchewan. We found large differences in willow yields, foliar N and WUE across the sites. The willow yields (1.24 to 15.6 t dry matter ha over 4 years) were low compared to northeastern North American values and reflect the short and dry summers of the region. The yields were positively correlated to foliar N (ranging between 14.3 and 32.4 mg g), whereas higher WUE (expressed as δC) were not positively correlated to water availability but to higher yields. Caragana N-fixation (measured using N isotope dilution) was not active at the most productive site but up to 60% of the foliar N was of atmospheric origin at the two other sites. Willow growth increased with Caragana proportions at the least productive site, which is typical of the benefits of N-fixing plants on the growth of other plants on poor soils. At the most productive site, Caragana decreased the growth of willow early on due to competition for resources, but willow eventually shaded Caragana to a point of significant canopy decline and dieback. It is therefore more appropriate to intercrop the two species on less productive soils as Caragana is more likely to add N to the system via N-fixation and is less likely to be shaded out by willow. [ABSTRACT FROM AUTHOR]

Short rotation coppice (SRC) with willow has been grown in Sweden from the late 1980s to produce biomass for energy on agricultural land. This study evaluated the effects of SRC on water quality by determining differences in leaching of nitrogen and phosphorus to groundwater of a number of commercial 'old' SRC willow stands in Sweden compared to adjacent arable fields grown with 'ordinary' crops. The study was conducted in 16 locations under three vegetation seasons. NO-N leaching from willow SRC fields was significantly lower than that from reference fields with cereals. The opposite was observed for PO-P; concentrations in the groundwater of SRC were higher compared to reference fields. Sewage sludge applications were not responsible for the elevated PO-P leaching under SRC compared to reference crops. [ABSTRACT FROM AUTHOR]

Short rotation coppice (SRC) is a biomass production system for energy usually grown on former agricultural land with fast-growing tree species. In Sweden, willow SRC has been grown since the late 1980s. SRC on arable soils may induce changes in some soil quality parameters due to differences in crop characteristics and management practices. In this study, pH, organic carbon (C), and trace element concentrations in the soil of 14 long-term (10-20 years) commercial willow SRC fields in Sweden were compared with those in adjacent, conventionally managed arable soils. The results showed that organic C concentrations in the topsoil and subsoil of SRC fields were, on average, significantly higher (9 % in topsoil, 27 % in subsoil) than in the reference fields. When comparisons were made only for the ten sites where the reference field had a crop rotation dominated by cereal crops, the corresponding figures were 10 % and 22 %. The average concentration of cadmium (Cd), which is considered the most hazardous trace element for human health in the food chain, was 12 % lower in the topsoil of SRC fields than in the reference fields. In the corresponding comparison of subsoils, no such difference was found. For chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), there were no significant differences in concentrations between SRC fields and the reference fields in either topsoil or subsoil. Negligible differences in pH in the same comparisons were found. [ABSTRACT FROM AUTHOR]

In a lowland drinking water catchment area, nitrate leaching as well as groundwater recharge (GWR) was investigated in willow and poplar short rotation coppice (SRC) plantations of different ages, soil preparation measures prior to planting and harvesting intervals. Significantly increased nitrate concentrations of 16.6 ± 1.6 mg NO-N L were measured in winter/spring 2010 on a poplar site, established in 2009 after deep plowing (90 cm) but then, subsequently decreased strongly to below 2 mg NO-N L in spring 2011. The fallow ground reference plot showed nitrate concentrations consistently below 1 mg L and estimated annual seepage output loss was only 1.36 ± 1.1 kg ha a. Leaching loss from a neighboring willow plot from 2005 was 14.3 ± 6.6 kg NO-N ha during spring 2010 but decreased to 2.0 ± 1.5 kg NO-N ha during the subsequent drainage period. A second willow plot, not harvested since its establishment in 1994, showed continuously higher nitrate concentrations (10.2 ± 1.7 NO-N L), while a neighboring poplar plot, twice harvested since 1994 showed significantly reduced nitrate concentrations. Water balance simulations, referenced by soil water tension and throughfall measurements, showed that at 655 mm annual rainfall, GWR from the reference plot (300 mm a) was reduced by 40 % (to 180 mm a) on the 2005 willow stand, mainly due to doubled rainfall interception losses. However, transpiration was limited by low soil water storage capacities, which in turn led to a moderate impact on GWR. We conclude that well-managed SRC on sensitive areas can prevent nitrate leaching, while impacts on GWR may be mitigated by management options. [ABSTRACT FROM AUTHOR]

A correction to the article "Incorporating Uncertainty into a Life Cycle Assessment (LCA) Model of Short-Rotation Willow Biomass (Salix spp.) Crops" that was published in the July 6, 2013 issue is presented.