• Authors:
    • Clay, G. D.
    • Worrall, F.
  • Source: Biomass and Bioenergy
  • Volume: 64
  • Issue: May
  • Year: 2014
  • Summary: Calluna vulgaris can and does grow in areas considered unsuitable for production of biomass crops. In the UK, Calluna vegetation is regularly controlled by burn management and if instead the lost biomass could be harvested would it represent a viable energy crop? This study used established techniques for other energy crops to assess the energy yield, energy efficiency and the greenhouse gas savings represented by cropping of Calluna under two scenarios; only harvested on the area currently under burn management; and harvested on the present total area of Calluna in the UK. The study can consider biomass potential across the UK and can include altitude changes. The study can show that Calluna would represent an efficient energy crop in areas where it would not be possible to revert to functioning peat bogs. The energy efficiency was 65 +/- 19 GJ(output) GJ(input)(-1) with GHG savings of up to 11 tonnes CO2eq, ha(-1) yr(-1). When considered across the UK the potential energy production was up to 40.7 PJ yr(-1) and the potential greenhouse gas saving was upto -2061 ktonnes CO2eq yr(-1) if the all Calluna could be brought into production and substituted for coal. (c) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Hastings, A.
    • Robson, P.
    • Clifton-Brown, J.
    • Zatta, A.
    • Monti, A.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 4
  • Year: 2014
  • Summary: To date, most Miscanthus trials and commercial fields have been planted on arable land. Energy crops will need to be grown more on lower grade lands unsuitable for arable crops. Grasslands represent a major land resource for energy crops. In grasslands, where soil organic carbon (SOC) levels can be high, there have been concerns that the carbon mitigation benefits of bioenergy from Miscanthus could be offset by losses in SOC associated with land use change. At a site in Wales (UK), we quantified the relatively short-term impacts (6 years) of four novel Miscanthus hybrids and Miscanthus x giganteus on SOC in improved grassland. After 6 years, using stable carbon isotope ratios (C-13/C-12), the amount of Miscanthus derived C (C4) in total SOC was considerable (ca. 12%) and positively correlated to belowground biomass of different hybrids. Nevertheless, significant changes in SOC stocks (0-30 cm) were not detected as C4 Miscanthus carbon replaced the initial C3 grassland carbon; however, initial SOC decreased more in the presence of higher belowground biomass. We ascribed this apparently contradictory result to the rhizosphere priming effect triggered by easily available C sources. Observed changes in SOC partitioning were modelled using the RothC soil carbon turnover model and projected for 20 years showing that there is no significant change in SOC throughout the anticipated life of a Miscanthus crop. We interpret our observations to mean that the new labile C from Miscanthus has replaced the labile C from the grassland and, therefore, planting Miscanthus causes an insignificant change in soil organic carbon. The overall C mitigation benefit is therefore not decreased by depletion of soil C and is due to substitution of fossil fuel by the aboveground biomass, in this instance 73-108 Mg C ha(-1) for the lowest and highest yielding hybrids, respectively, after 6 years.
  • Authors:
    • Camargo, L. A.
    • Panosso, A. R.
    • Marques Junior, J.
    • Bahia, A. S. R. de S.
    • Siqueira, D. S.
    • Scala Junior, N. la
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 192
  • Year: 2014
  • Summary: Soil CO 2 emission (FCO 2) is a main contributor of atmospheric carbon transfer and is the subject of research aimed at developing effective methods for characterizing and mitigating CO 2 emissions. The FCO 2 is related to various soil properties including porosity, density and moisture, which are in turn related to gas transfer, O 2 uptake and CO 2 release, as well as mineralogical components (particularly iron oxides, which are closely associated with aggregation and protection of soil organic matter). As estimated by diffuse reflectance spectroscopy (DRS), soil iron oxides such as hematite (Hm) and goethite (Gt) can be useful in determining FCO 2. The main objective of this experiment was to assess the usefulness of the mineralogical properties Hm, Gt, and iron oxides extracted by dithionite-citrate-bicarbonate (Fe d) to estimate the FCO 2 in a sugarcane area under green harvest in southeastern Brazil. The experiment was conducted using an irregular 50 m *50 m grid containing 89 sampling points 0.50-10 m apart to assess the soil properties. The FCO 2 at each sampling point was measured at the beginning of crop growth and 54 days after planting with the use of two portable LI-COR LI-8100 Soil CO 2 Flux Systems. The soil properties studied were found to be spatially dependent and exhibited well-defined anisotropy (particularly the mineralogical properties Hm, Gt and Fe d). The first two components of a principal component analysis (PC1 and PC2) jointly accounted for 73.4% of the overall result variability with PC1 essentially related to the physical and mineralogical properties of the soil. Based on a multiple linear regression analysis, free water porosity (FWP) and Hm accounted for 71% of the FCO 2 variability. Our results indicate that soil preparation and management practices in mechanically harvested sugarcane affect some factors inherent in the soil forming processes, including physical and mineralogical properties, which in turn affect FCO 2. These results affirm the potential of DRS as an auxiliary tool for determination of properties that are typically associated with FCO 2. In addition, the ensuing method allows for large-area FCO 2 mapping to developing greenhouse gas emission inventories for agricultural soils.
  • Authors:
    • Singh, B.
    • Smider, B.
  • Source: Agriculture Ecosystems and Enviroment
  • Volume: 191
  • Issue: SI
  • Year: 2014
  • Summary: Intensive greenhouse industry wastes large amounts of nutrient-rich green waste through improper disposal practices. Converting this greenhouse waste into biochar for soil application offers a viable option to recycle nutrients and long-term C storage. This study was carried out to evaluate the agronomic potential of a biochar produced from tomato green waste in two contrasting soils. We also estimated the amount of waste generated from intensive greenhouse tomato production in Australia. From weekly measurements of leaf picking over a 13-week period, we estimate approximately 133 Mg ha -1 year -1 of green waste on fresh weight basis. Biochar, produced by slowly pyrolysing the green waste at 550°C, had very high-pH (12.1), electrical conductivity (EC, 54.2 dS m -1), ash content (560 g kg -1) and CaCO 3 equivalence (330 g kg -1). Agronomic performance of the biochar was evaluated by growing Hybrid sweet corn ( Zea mays var. rugosa cv - Sentinel) in the greenhouse for 7 weeks. We used three levels of biochar (0, 5 and 15 g kg -1 soil) in a factorial combination with three fertiliser rates (0, 50 and 100% of the recommended rate) applied to two contrasting soils (an Orthic Tenosol and a Red Ferrosol). Biochar application to the Ferrosol significantly increased the shoot dry matter of corn and contrastingly decreased the yield in case of the Tenosol. The positive effect of the biochar in the Ferrosol was attributed to release of nutrients from the biochar and biochar's liming effect and associated increased availability of nutrients. However, in poorly buffered Tenosol the application of biochar produced phytotoxic effects due to excessive soluble salts and high pH. The uptake of most nutrient elements increased in the corn shoot in the Ferrosol and decreased in the Tenosol. Although the biochar produced from green waste was highly alkaline and contained excessive soluble salts, given the right soil properties it can be a good soil ameliorant. The true agronomic potential of the biochar should be further evaluated in different soil types under field conditions.
  • Authors:
    • Sanginga, P.
    • Amede, T.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION Pages:
  • Volume: 69
  • Issue: 4
  • Year: 2014
  • Authors:
    • Mary, B.
    • Jeuffroy, M. H.
    • Amosse, C.
    • David, C.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 98
  • Issue: 1
  • Year: 2014
  • Summary: Nitrogen (N) management is a key issue in livestock-free organic grain systems. Relay intercropping with a legume cover crop can be a useful technique for improving N availability when two cash crops are grown successively. We evaluated the benefits of four relay intercropped legumes (Medicago lupulina, Medicago sativa, Trifolium pratense and Trifolium repens) on N dynamics and their contribution to the associated and subsequent cash crops in six fields of organic farms located in South-East France. None of the relay intercropped legumes affected the N uptake of the associated winter wheat but all significantly increased the N uptake of the succeeding spring crop, either maize or spring wheat. The improvement of the N nutrition of the subsequent maize crop induced a 30 % increase in grain yield. All relay intercropped legumes enriched the soil-plant system in N through symbiotic fixation. From 71 to 96 % of the N contained in the shoots of the legumes in late autumn was derived from the atmosphere (Ndfa) and varied between 38 and 67 kg Ndfa ha(-1). Even if the cover crop is expected to limit N leaching during wintertime, the presence of relay intercropped legumes had no significant effect on N leaching during winter compared to the control.
  • Authors:
    • Gundersen, P.
    • Stefansdottir, H. M.
    • Vesterdal, L.
    • Kiar, L. P.
    • Barcena, T. G.
    • Sigurdsson, B. D.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 8
  • Year: 2014
  • Summary: Northern Europe supports large soil organic carbon (SOC) pools and has been subjected to high frequency of land-use changes during the past decades. However, this region has not been well represented in previous large-scale syntheses of land-use change effects on SOC, especially regarding effects of afforestation. Therefore, we conducted a meta-analysis of SOC stock change following afforestation in Northern Europe. Response ratios were calculated for forest floors and mineral soils (0-10 cm and 0-20/30 cm layers) based on paired control (former land use) and afforested plots. We analyzed the influence of forest age, former land-use, forest type, and soil textural class. Three major improvements were incorporated in the meta-analysis: analysis of major interaction groups, evaluation of the influence of nonindependence between samples according to study design, and mass correction. Former land use was a major factor contributing to changes in SOC after afforestation. In former croplands, SOC change differed between soil layers and was significantly positive (20%) in the 0-10 cm layer. Afforestation of former grasslands had a small negative (nonsignificant) effect indicating limited SOC change following this land-use change within the region. Forest floors enhanced the positive effects of afforestation on SOC, especially with conifers. Meta-estimates calculated for the periods 30 years since afforestation revealed a shift from initial loss to later gain of SOC. The interaction group analysis indicated that meta-estimates in former land-use, forest type, and soil textural class alone were either offset or enhanced when confounding effects among variable classes were considered. Furthermore, effect sizes were slightly overestimated if sample dependence was not accounted for and if no mass correction was performed. We conclude that significant SOC sequestration in Northern Europe occurs after afforestation of croplands and not grasslands, and changes are small within a 30-year perspective.
  • Authors:
    • Grassini, P.
    • Gayler, S.
    • Sanctis, G. de
    • Deryng, D.
    • Corbeels, M.
    • Conijn, S.
    • Boogaard, H.
    • Biernath, C.
    • Basso, B.
    • Baron, C.
    • Adam, M.
    • Ruane, A. C.
    • Rosenzweig, C.
    • Jones, J. W.
    • Lizaso, J.
    • Boote, K.
    • Durand, J. L.
    • Brisson, N.
    • Bassu, S.
    • Hatfield, J.
    • Hoek, S.
    • Izaurralde, C.
    • Jongschaap, R.
    • Kemanian, A. R.
    • Kersebaum, K. C.
    • Kim, S. H. (et al)
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 7
  • Year: 2014
  • Summary: Potential consequences of climate change on crop production can be studied using mechanistic crop simulation models. While a broad variety of maize simulation models exist, it is not known whether different models diverge on grain yield responses to changes in climatic factors, or whether they agree in their general trends related to phenology, growth, and yield. With the goal of analyzing the sensitivity of simulated yields to changes in temperature and atmospheric carbon dioxide concentrations [CO 2], we present the largest maize crop model intercomparison to date, including 23 different models. These models were evaluated for four locations representing a wide range of maize production conditions in the world: Lusignan (France), Ames (USA), Rio Verde (Brazil) and Morogoro (Tanzania). While individual models differed considerably in absolute yield simulation at the four sites, an ensemble of a minimum number of models was able to simulate absolute yields accurately at the four sites even with low data for calibration, thus suggesting that using an ensemble of models has merit. Temperature increase had strong negative influence on modeled yield response of roughly -0.5 Mg ha -1 per °C. Doubling [CO 2] from 360 to 720 mol mol -1 increased grain yield by 7.5% on average across models and the sites. That would therefore make temperature the main factor altering maize yields at the end of this century. Furthermore, there was a large uncertainty in the yield response to [CO 2] among models. Model responses to temperature and [CO 2] did not differ whether models were simulated with low calibration information or, simulated with high level of calibration information.
  • Authors:
    • Poskitt, J.
    • McNamara, N. P.
    • Briones, M. J. I.
    • Crow, S. E.
    • Ostle, N. J.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 9
  • Year: 2014
  • Summary: Partially decomposed plant and animal remains have been accumulating in organic soils (i.e. >40% C content) for millennia, making them the largest terrestrial carbon store. There is growing concern that, in a warming world, soil biotic processing will accelerate and release greenhouse gases that further exacerbate climate change. However, the magnitude of this response remains uncertain as the constraints are abiotic, biotic and interactive. Here, we examined the influence of resource quality and biological activity on the temperature sensitivity of soil respiration under different soil moisture regimes. Organic soils were sampled from 13 boreal and peatland ecosystems located in the United Kingdom, Ireland, Spain, Finland and Sweden, representing a natural resource quality range of C, N and P. They were incubated at four temperatures (4, 10, 15 and 20°C) at either 60% or 100% water holding capacity (WHC). Our results showed that chemical and biological properties play an important role in determining soil respiration responses to temperature and moisture changes. High soil C : P and C : N ratios were symptomatic of slow C turnover and long-term C accumulation. In boreal soils, low bacterial to fungal ratios were related to greater temperature sensitivity of respiration, which was amplified in drier conditions. This contrasted with peatland soils which were dominated by bacterial communities and enchytraeid grazing, resulting in a more rapid C turnover under warmer and wetter conditions. The unexpected acceleration of C mineralization under high moisture contents was possibly linked to the primarily role of fermented organic matter, instead of oxygen, in mediating microbial decomposition. We conclude that to improve C model simulations of soil respiration, a better resolution of the interactions occurring between climate, resource quality and the decomposer community will be required.
  • Authors:
    • Billen, N.
    • Kuzyakov, Y.
    • Fan, M. S.
    • Chen, H. Q.
    • Stahr, K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 98
  • Issue: 2
  • Year: 2014
  • Summary: Field measurements of net ecosystem CO2 exchange (NEE) with high temporal resolution are essential to construct a meaningful ecosystem C balance. The objectives of this study were to monitor NEE in high temporal resolution in cropland and grassland between middle August and middle November (2006) at Kleinhohenheim, Germany and to evaluate NEE in autumn. A fully automated temperature controlled closed chamber system with an infrared CO2 analyzer was used to measure NEE. The measured NEE varied between the two ecosystems depending on changes in above-ground vegetation and environmental factors. The diurnal NEE pattern of daytime CO2 uptake and night time CO2 release was evident in the grassland, but not in the cropland as the crops were harvested at the beginning of the measurement period. The grassland generally showed higher night time NEE, but lower daytime NEE than the cropland. Night time NEE showed exponential dependence on air and soil temperature, resulting in Q(10) of 1.8 and 1.9 (for air temperature), 2.3 and 2.4 (for soil temperature) in the grassland and cropland, respectively. The average daily NEE was 2.77 and 1.86 g CO2-C m(-2) day(-1) in the cropland and grassland, respectively. Both ecosystems were sources of CO2, during 3 months in autumn, but the grassland emitted less CO2 by 87.9 g CO2-C m(-2) than the cropland.