Perennial Biomass Crops Research Articles

Targeted subfield switchgrass integration could improve the farm economy, water quality, and bioenergy feedstock production

AbstractProgress on reducing nutrient loss from annual croplands has been hampered by perceived conflicts between short‐term profitability and long‐term stewardship, but these may be overcome through strategic integration of perennial crops. Perennial biomass crops like switchgrass can mitigate nitrate‐nitrogen (NO3‐N) leaching, address bioenergy feedstock targets, and – as a lower‐cost management alternative to annual crops (i.e., corn, soybeans) – may also improve farm profitability. We analyzed publicly available environmental, agronomic, and economic data with two integrated models: a subfield agroecosystem management model, Landscape Environmental Assessment Framework (LEAF), and a process‐based biogeochemical model, DeNitrification‐DeComposition (DNDC). We constructed a factorial combination of profitability and NO3‐N leaching thresholds and simulated targeted switchgrass integration into corn/soybean cropland in the agricultural state of Iowa, USA. For each combination, we modeled (i) area converted to switchgrass, (ii) switchgrass biomass production, and (iii) NO3‐N leaching reduction. We spatially analyzed two scenarios: converting to switchgrass corn/soybean cropland losing >US$ 100 ha−1 and leaching >50 kg ha−1 (‘conservative’ scenario) or losing >US$ 0 ha−1 and leaching >20 kg ha−1 (‘nutrient reduction’ scenario). Compared to baseline, the ‘conservative’ scenario resulted in 12% of cropland converted to switchgrass, which produced 11 million Mg of biomass and reduced leached NO3‐N 18% statewide. The ‘nutrient reduction’ scenario converted 37% of cropland to switchgrass, producing 34 million Mg biomass and reducing leached NO3‐N 38% statewide. The opportunity to meet joint goals was greatest within watersheds with undulating topography and lower corn/soybean productivity. Our approach bridges the scales at which NO3‐N loss and profitability are usually considered, and is informed by both mechanistic and empirical understanding. Though approximated, our analysis supports development of farm‐level tools that can identify locations where both farm profitability and water quality improvement can be achieved through the strategic integration of perennial vegetation.

Lack of Impacts during Early Establishment Highlights a Short-Term Management Window for Minimizing Invasions from Perennial Biomass Crops.

Managing intentional species introductions requires evaluating potential ecological risks. However, it is difficult to weigh costs and benefits when data about interactions between novel species and the communities they are introduced to are scarce. In anticipation of expanded cultivation of perennial biomass crops, we experimentally introduced Miscanthus sinensis and Miscanthus × giganteus (two non-native candidate biomass crops) into two different non-crop habitats (old field and flood-plain forest) to evaluate their establishment success and impact on ambient local communities. We followed these controlled introductions and the composition dynamics of the receiving communities over a 5-year period. Habitats differed widely in adult Miscanthus survival and reproduction potential between species, although seed persistence and seedling emergence were similar in the two biomass crops in both habitats. Few introductions survived in the floodplain forest habitat, and this mortality precluded analyses of their potential impacts there. In old field habitats, proportional survival ranged from 0.3 to 0.4, and plant survival and growth increased with age. However, there was no evidence of biomass crop species effects on community richness or evenness or strong impacts on the resident old field constituents across 5 years. These results suggest that Miscanthus species could establish outside of cultivated fields, but there will likely be a lag in any impacts on the receiving communities. Local North American invasions by M. sinensis and M. sacchariflorus display the potential for Miscanthus species to develop aggressively expanding populations. However, the weak short-term community-level impacts demonstrated in the current study indicate a clear management window in which eradicating species footholds is easily achieved, if they can be detected early enough. Diligent long-term monitoring, detection, and eradication plans are needed to successfully minimize harmful invasions from these biomass crops.

Provenance variation, genetic parameters and potential gains from breeding for biomass and cineole production in three-year-old Eucalyptus loxophleba subsp. lissophloia progeny trials

ABSTRACTMallee eucalypts are being domesticated for use as a perennial biomass crop for dryland agriculture in southern Australia. Nine provenances of Eucalyptus loxophleba subsp. lissophloia were tested in trials at Brookton, Western Australia, Monarto, South Australia, and Condobolin, New South Wales. Provenance rankings for biomass production were more similar between Brookton and Condobolin than between Monarto and the other sites. Provenances Mt Walker and Yellowdine ranked amongst the top three performers on all three sites. Type B genetic correlations between pairs of sites ranged from r = 0.13 to r = 0.67, suggesting significant genotype x environment interaction amongst sites. Heritability (ĥ2) for biomass productivity on the three sites was 0.19 ± 0.05, 0.13 ± 0.04 and 0.25 ± 0.05 for Monarto, Condobolin and Brookton respectively. Heritability of leaf cineole concentration at Brookton was 0.53 ± 0.07. Gains from selection scenarios treating the three trials as separate regions gave the highest gain in biomass productivity, whilst treating all three sites as one region resulted in about 6% lower gain. Leaf cineole concentration is a useful selection criterion in the absence of data for total mass of cineole produced per tree.

Issue Information

GCB BioenergyVolume 9, Issue 1 p. 1-3 Issue InformationOpen Access Issue Information First published: 16 December 2016 https://doi.org/10.1111/gcbb.12412AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume9, Issue1Special Issue: Perennial biomass crops for a resource constrained worldJanuary 2017Pages 1-3 RelatedInformation

Perennial biomass crops for a resource‐constrained world

Perennial biomass crops for a resource‐constrained world

Miscanthus as biogas substrate – cutting tolerance and potential for anaerobic digestion

AbstractIn the anaerobic digestion and biogas industry in Germany, the step of energy crop production accounts for a high proportion of the greenhouse gas emissions and environmental impacts. Replacing annual energy crops, for example maize, by perennial biomass crops such as miscanthus offers the potential to increase the sustainability of biogas crop production. However, the cutting tolerance of miscanthus and the mechanisms influencing it need to be investigated to assess its potential as a biogas crop. For this purpose, a field trial with different harvest regimes was conducted to identify the potential methane yield and cutting tolerance of Miscanthus x giganteus. Several fertilization regimes were tested under nitrogen‐limited conditions in a pot trial to investigate the mechanisms behind the cutting tolerance. The refilling of carbohydrate (starch) stores in the rhizome was identified as a very important factor influencing the cutting tolerance of miscanthus, whereas the nutrient relocation appeared to be of less importance. The field trial revealed that Miscanthus x giganteus offers a very high methane yield potential of approx. 6000 m3 ha−1 when harvested in October, which is within the range of the methane hectare yield of energy maize. The substrate‐specific methane yield of Miscanthus x giganteus biomass decreased with later harvest dates and reached 247 ml (g oDM)−1 in October. This harvest date delivered very high, stable yields of on average 26 t DM ha−1 over two years and enabled a good cutting tolerance. Green harvest in October was identified to be suitable for Miscanthus x giganteus and is recommended for biogas utilization. In conclusion, the perennial biomass crop Miscanthus x giganteus is a very promising biogas crop and offers the potential to increase the sustainability of the anaerobic digestion sector in Germany by replacing a substantial area of biogas maize cultivation.

Xylem morphology determines the drought response of two Arundo donax ecotypes from contrasting habitats

AbstractArundo donax exhibits rapid growth and requires little nutrient input, making it an ideal perennial biomass crop species. However, this growth is accompanied by high rates of water use, potentially restricting the use of A. donax in rain‐fed marginal lands. Here, we investigated the physiological and morphological responses to drought in two ecotypes of A. donax from contrasting habitats: one from an arid environment in Morocco, and the second from a warm humid sub‐Mediterranean climate in central Italy. Prolonged drought resulted in identical reductions in leaf‐level photosynthesis (PN) and stomatal conductance (Gs) in the two ecotypes. However, water deficit induced an increase in xylem vessel diameter in the Moroccan plants, improving the movement of water along the stem, but also likely reducing the resistance to embolism. In contrast, the Italian ecotype reduced xylem vessel area, thus increasing resistance to water transport and xylem embolism. The increased xylem vessel size and associated vulnerability to embolism in the Moroccan plants may have contributed to an increase in the loss of leaf numbers, but also to higher relative water content (RWC) in the remaining leaves in comparison to the Italian ecotype, where a greater number of leaves persisted. Despite the Moroccan plants possessing stems with a lower basal area than their Italian counterparts, both ecotypes exhibited identical leaf to supporting stem area ratios under both control and water deficit conditions. This may account for the similarities observed in leaf area measures of PN and Gs in this and previous studies of different A. donax ecotypes. Selection of A. donax ecotypes on the basis of xylem responses to drought may facilitate the development of varieties suited to arid environments prone to severe drought and wetter habitats where prolonged droughts occur less frequently.

Does Plant Biomass Manipulation in Static Chambers Affect Nitrous Oxide Emissions from Soils?

One of the most widespread approaches for measurement of greenhouse gas emissions from soils involves the use of static chambers. This method is relatively inexpensive, is easily replicated, and is ideally suited to plot-based experimental systems. Among its limitations is the loss of detection sensitivity with increasing chamber height, which creates challenges for deployment in systems including tall vegetation. It is not always possible to avoid inclusion of plants within chambers or to extend chamber height to fully accommodate plant growth. Thus, in many systems, such as perennial forages and biomass crops, plants growing within static chambers must either be trimmed or folded during lid closure. Currently, data on how different types of biomass manipulation affect measured results is limited. Here, we compare the effects of cutting vs. folding of biomass on nitrous oxide measurements in switchgrass ( L.) and alfalfa ( L.) systems. We report only limited evidence of treatment effects during discrete sampling events and little basis for concern that effects may intensify over time as biomass manipulation is repeatedly imposed. However, nonsignificant treatment effects that were consistently present amounted to significant overall trends in three out of the four systems studied. Such minor disparities in flux could amount to considerable quantities over time, suggesting that caution should be exercised when comparing cumulative emission values from studies using different biomass manipulation strategies.

Biomass production and energy balance of herbaceous and woody crops on marginal soils in the Po Valley

AbstractA wealth of data and information on the cultivation of perennial biomass crops has been collected, but direct comparisons between herbaceous and woody crops are rare. The main objective of this research was to compare the biomass yield, the energy balance and the biomass quality of six perennial bioenergy crops: Populus spp., Robinia pseudoacacia, Salix spp., Arundo donax, Miscanthus × giganteus, and Panicum virgatum, grown in two marginal environments. For giant reed and switchgrass, two levels of nitrogen fertilization were applied annually (0–100 kg ha−1). Nitrogen fertilization did not affect biomass or energy production of giant reed; thus, it significantly reduced the energy return on investment (EROI) (from 73 to 27). In switchgrass, nitrogen fertilization significantly increased biomass production and the capacity of this crop to respond to water availability, making it a favorable option when only biomass production is a target. Net energy gain (NEG) was higher for herbaceous crops than for woody crops. In Casale, EROI calculated for poplar and willow (7, on average) was significantly lower than that of the other crops (14, on average). In Gariga, the highest EROI was calculated for miscanthus (98), followed by nonfertilized giant reed and switchgrass (82 and 73, respectively). Growing degree days10 during the cropping season had no effect on biomass production in any of the studied species, although water availability from May to August was a major factor affecting biomass yield in herbaceous crops. Overall, herbaceous crops had the highest ranking for bioenergy production due to their high biomass yield, high net energy gain (NEG), and biomass quality that renders them suitable to both biochemical and thermochemical conversion. Miscanthus in particular had the highest EROI in both locations (16 and 98, in Casale and Gariga), while giant reed had the highest NEG on the silty‐loam soil of Gariga.

Environmental costs and benefits of growing Miscanthus for bioenergy in the UK.

Planting the perennial biomass crop Miscanthus in the UK could offset 2–13 Mt oil eq. yr−1, contributing up to 10% of current energy use. Policymakers need assurance that upscaling Miscanthus production can be performed sustainably without negatively impacting essential food production or the wider environment. This study reviews a large body of Miscanthus relevant literature into concise summary statements. Perennial Miscanthus has energy output/input ratios 10 times higher (47.3 ± 2.2) than annual crops used for energy (4.7 ± 0.2 to 5.5 ± 0.2), and the total carbon cost of energy production (1.12 g CO2‐C eq. MJ−1) is 20–30 times lower than fossil fuels. Planting on former arable land generally increases soil organic carbon (SOC) with Miscanthus sequestering 0.7–2.2 Mg C4‐C ha−1 yr−1. Cultivation on grassland can cause a disturbance loss of SOC which is likely to be recovered during the lifetime of the crop and is potentially mitigated by fossil fuel offset. N2O emissions can be five times lower under unfertilized Miscanthus than annual crops and up to 100 times lower than intensive pasture. Nitrogen fertilizer is generally unnecessary except in low fertility soils. Herbicide is essential during the establishment years after which natural weed suppression by shading is sufficient. Pesticides are unnecessary. Water‐use efficiency is high (e.g. 5.5–9.2 g aerial DM (kg H2O)−1, but high biomass productivity means increased water demand compared to cereal crops. The perennial nature and belowground biomass improves soil structure, increases water‐holding capacity (up by 100–150 mm), and reduces run‐off and erosion. Overwinter ripening increases landscape structural resources for wildlife. Reduced management intensity promotes earthworm diversity and abundance although poor litter palatability may reduce individual biomass. Chemical leaching into field boundaries is lower than comparable agriculture, improving soil and water habitat quality.

Comparative water use by maize, perennial crops, restored prairie, and poplar trees in the US Midwest

Water use by plant communities across years of varying water availability indicates how terrestrial water balances will respond to climate change and variability as well as to land cover change. Perennial biofuel crops, likely grown mainly on marginal lands of limited water availability, provide an example of a potentially extensive future land cover conversion. We measured growing-season evapotranspiration (ET) based on daily changes in soil profile water contents in five perennial systems—switchgrass, miscanthus, native grasses, restored prairie, and hybrid poplar—and in annual maize (corn) in a temperate humid climate (Michigan, USA). Three study years (2010, 2011 and 2013) had normal growing-season rainfall (480–610 mm) whereas 2012 was a drought year (210 mm). Over all four years, mean (±SEM) growing-season ET for perennial systems did not greatly differ from corn (496 ± 21 mm), averaging 559 (±14), 458 (±31), 573 (±37), 519 (±30), and 492 (±58) mm for switchgrass, miscanthus, native grasses, prairie, and poplar, respectively. Differences in biomass production largely determined variation in water use efficiency (WUE). Miscanthus had the highest WUE in both normal and drought years (52–67 and 43 kg dry biomass ha−1 mm−1, respectively), followed by maize (40–59 and 29 kg ha−1 mm−1); the native grasses and prairie were lower and poplar was intermediate. That measured water use by perennial systems was similar to maize across normal and drought years contrasts with earlier modeling studies and suggests that rain-fed perennial biomass crops in this climate have little impact on landscape water balances, whether replacing rain-fed maize on arable lands or successional vegetation on marginal lands. Results also suggest that crop ET rates, and thus groundwater recharge, streamflow, and lake levels, may be less sensitive to climate change than has been assumed.

Bioenergy Supply and Environmental Impacts on Cropland: Insights from Multi‐market Forecasts in a Great Lakes Subregional Bioeconomic Model

AbstractUsing subregional models of crop production choices in central Wisconsin and southwest Michigan, we predict biomass production, land use, and environmental impacts with details that are unavailable from national scale models. When biomass prices are raised exogenously, we find that the subregional models overestimate the supply, the land use, and the beneficial environmental aspects of perennial biomass crops. Multi‐market price feedbacks tied to realistic policy parameters predict high threshold absolute prices for biomass to enter production, resulting in intensified production of biomass from annual grain crops with damaging environmental impacts. Multi‐market feedbacks also predict regional specialization in energy biomass production in areas with lower yields of food crops. Policies promoting biofuels will not necessarily generate environmental benefits in the absence of environmental regulations.

13C abundance shows effective soil carbon sequestration in Miscanthus and giant reed compared to arable crops under Mediterranean climate

Many studies on soil organic carbon (SOC) sequestration in perennial biomass crops are available for Atlantic and continental environments of North Central Europe, while there is insufficient information for Southern Europe. Therefore, we assessed SOC turnover under Mediterranean climate, after a 9-year-old conversion from two annual crop systems, continuous wheat and maize/wheat rotation, to Miscanthus (Miscanthus sinensis × giganteus) and giant reed (Arundo donax), respectively. The naturally occurring 13C signature down to 0.60 m was used to evaluate the total amount of SOC in annual vs perennial species and to determine the portion of SOC derived from perennial species. Soil organic C was significantly higher under perennial (average, 91 Mg C ha−1) than annual species (average, 56 Mg C ha−1), with a stronger accumulation in the topsoil (0–0.15 m). This difference was consistent with reduced soil disturbance associated with perennial crop management. After 9 years of Miscanthus plantation, the amount of C4-derived C was 18.7 Mg ha−1, mostly stored at 0–0.15 m, whereas the amount of C3-derived C under giant reed was 34.7 Mg ha−1 and was more evenly distributed through soil depths, probably due to its deeper root apparatus. It is suggested that both Miscanthus and giant reed have a remarkable potential for SOC sequestration also under Mediterranean conditions, while supporting the growing bioenergy sector with biomass supply.

Site‐related set‐back by weeds on the establishment of 12 biomass willow clones

SummaryTen commercial clones of willow and two breeding clones were studied for their ability to compete with weeds during the establishment year at three different sites in southern Sweden. Cuttings were planted according to commercial practice in April, and the two treatments, ‘Weeded’ and ‘Unweeded’, were laid out in a strip‐plot design. Weeds in the ‘Weeded’ treatment were removed mechanically and by hand hoeing. Willow plant shoot weight and plant mortality were measured after the first growing season to evaluate the initial effect of weeds. In addition, weed flora, weed aboveground biomass, soil properties, shoot damage and soil moisture were assessed during the growing season. Plant mortality was <1% in the ‘Weeded’ treatment at the three study sites, while in ‘Unweeded’ it was significantly higher, 2.7%, 24.6% and 37.4%. Weeds reduced willow plant shoot weight by 93.4%, 94.0% and 96.1% at the three sites. Only one site showed clonal differences in shoot growth reduction, as well as in plant mortality. These results show the importance of weed control in willow plantations, as growth of all clones tested were dramatically hampered by weeds during the first growing season, regardless of trial site conditions. Moreover, conditions at certain sites, such as soil properties in combination with weed cover, may cause high plant mortality during the establishment year in this perennial biomass crop.

Establishment of bioenergy crops on metal contaminated soils stimulates belowground fauna

Soils of contaminated agrosystems represent potential arable land surfaces for the production of non-alimentary crops. The aim of this study is to monitor changes in belowground biodiversity (Collembola), potentially occurring following establishment of perennial biomass crop systems on contaminated agricultural land. We selected, within an agricultural trial, two different biomass crops, miscanthus (Miscanthus x giganteus) and switchgrass (Panicum virgatum) and an annual wheat crop (Triticum sp.) used as a control. About 20-fold more individuals were found under miscanthus and switchgrass than under wheat. The highest mean number of species was found under miscanthus being 30% greater than in switchgrass and 424% than in annual wheat. Furthermore, abundance and species richness of the three collembolan life-forms (epedaphic, hemiedaphic, and euedaphic) differed between the crops leading to distinctly different assemblages.On metal contaminated soils, perennial bioenergy crops have the potential to increase belowground faunal diversity and abundance with the identity of crops as a critical factor driving soil animal assemblages.

Yield of perennial herbaceous and woody biomass crops over time across three locations

The use of perennial biomass crops is expected to increase and will likely be part of a diversified approach to cropping system design that focuses on multiple economic, ecological, and environmental benefits. Field experiments were conducted from 2006 to 2011 at three locations in Minnesota to quantify biomass production across a diverse set of perennial herbaceous and woody crops. Herbaceous crops were harvested annually in the fall while the woody crops were harvested once following five years of growth. Willow produced more total biomass than all other woody and herbaceous biomass crops across all locations. However, miscanthus biomass yield was similar to ‘SX67’ willow at St. Paul and Waseca, but was dependent on the cultivar of miscanthus. Prairie cordgrass cultivars were among the highest and most consistent yielding herbaceous biomass crops across locations. Miscanthus cultivars produced the highest annual dry matter yield of 35 Mg ha−1 yr−1 biomass, but only during the final year of the study. Other herbaceous crops such as switchgrass performed well in certain locations and may offer flexibility in cropping choice. This unique information on comparative biomass yield across a diversity of perennial crops will inform the overall decision-making process in a way that reduces risk and optimizes productivity in specific environments. This study shows that several biomass crop species can be successfully grown as part of a diversified biomass cropping enterprise.

A web-based tool for biomass production systems

A web-based tool is presented for the estimation of biomass production and transportation costs with regard to input requirements, internal processes, and output. The tool relates to the production, harvest and out-of-field transport of biomass in multiple-crop production systems of bioenergy crops, including perennial biomass crops and short-rotation coppice, and focuses on details of the individual production units such as distance from associated facilities, soil conditions, machinery system, and labour types. By testing various alternatives, the tool can support decisions for biomass production systems on a strategic level (e.g., number and dimensioning of machines, machine capacity, crop selection, and labour requirements), tactical level (e.g., fertiliser/chemical application plans and labour budgets), and operational level (operation specifications). This work was part of the collaborative Intelligent Energy Europe Programme project, BioEnergy Farm and the web tool can be accessed on-line at www.bioresource4energy.eu or through www.bioenergyfarm.eu . • A DSS for biomass production management. • Detailed consideration of biomass production and transportation characteristics. • Estimation of the total production and transport cost in multiple-crop systems.

Long‐term biomass yields of giant reed, mimosa and switchgrass in Alabama

AbstractThe US Department of Energy conducted two studies to estimate the potential of cellulosic biomass crops for production of biofuels on a national scale. However, limited long‐term experimental information is available to support the resultant yield projections. The objectives of this research were: (i) to determine long‐term (>10 years) biomass yields and soil impacts of switchgrass (Panicum virgatum L.), giant reed (Arundo donax L.) and mimosa (Albizia julibrissin Durazz.) in Alabama; and (ii) to establish relationships between precipitation and yields of these perennial biomass crops, and yields of cotton, maize, and soybean. Mimosa and giant reed received no fertilizer and were harvested once each year while switchgrass received 84 kg ha–1 of N fertilizer annually, and was harvested twice each year. Cotton, maize, and soybean were managed according to traditional practices for these crops in this region. Average annual biomass yields of mimosa, giant reed, and switchgrass were 40.1, 35.5 and 23.5 kg ha–1 over 16‐, 11‐ and 22‐year periods, respectively, with corresponding estimated annual N accumulation in aboveground biomass of 388, 372 and 163 kg ha–1. Yields of maize, cotton and soybean decreased sharply with decreasing precipitation, but there was no corresponding decrease in yield of the three perennial biomass crops. Changes in the yields of the biomass crops with age were also relatively small. Analysis of topsoil samples suggested considerably less removal of P, K, Ca, and Mg than was estimated from yield and concentrations of these elements in the biomass that was actually removed. © 2013 Society of Chemical Industry and John Wiley & Sons, Ltd

Perennial biomass crop cultivation and its territorial patterns

The cultivation of miscanthus, a new agricultural crop used in the production of energy and biomaterial, is a potential competitor for agricultural land use. Modelling approaches are therefore needed to predict the spatial patterns of changing land use throughout a territory. Given the lack of information about how crop location is determined within the territory, a detailed understanding of farmers' choices is a prerequisite for the construction of such models. This paper presents the results of a study involving ten farmers; it shows the complexity of their decision-making processes and the diversity of practices in crop location.

Production of Napiergrass as a Bioenergy Feedstock Under Organic Versus Inorganic Fertilization in the Southeast USA

Napiergrass (Pennisetum purpureum Schum.) is a high-yielding perennial biomass crop that is well adapted to the Southeast USA where poultry litter is readily available. This research was conducted to compare biomass production and nutrient utilization of napiergrass fertilized with either poultry litter or inorganic fertilizer. Each spring, approximately 100 kg ha−1 of N, 40 kg ha−1 P, and 90 kg ha−1 K were applied as poultry litter or equivalent inorganic fertilizer. Biomass was harvested each winter after senescence. For the first 2 years, dry matter yield did not differ among treatments, but in the third and fourth years, yields declined in all treatments and were lowest in the unfertilized treatment. Biomass N concentration and N removal were greatest in the inorganic treatment. In general, N removal exceeded the amount applied, suggesting that higher application rates may be necessary to maintain yields. Biomass P concentration and total P uptake were greatest in the litter fertilized treatment, demonstrating that napiergrass can remove some of the excess P from applied litter. Soil cores were taken periodically to assess changes in soil properties. After 2 years of production, soil pH in the surface layer (0–15 cm) was lower in the inorganic treatment than in the other treatments. After 4 years, total soil C had increased by an average of 3,180 kg ha−1 though fertilizer treatments did not differ. Yield declined in all treatments after 4 years and N supplementation is recommended for production in upland fields.