• Authors:
    • Don, A.
    • Poeplau, C.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 4
  • Year: 2014
  • Summary: Bioenergy has to meet increasing sustainability criteria in the EU putting conventional bioenergy crops under pressure. Alternatively, perennial bioenergy crops, such as Miscanthus, show higher greenhouse gas savings with similarly high energy yields. In addition, Miscanthus plantations may sequester additional soil organic carbon (SOC) to mitigate climate change. As the land-use change in cropland to Miscanthus involves a C-3-C-4 vegetation change (VC), it is possible to determine the dynamic of Miscanthus-derived SOC (C-4 carbon) and of the old SOC (C-3 carbon) by the isotopic ratio of C-13 to C-12. We sampled six croplands and adjacent Miscanthus plantations exceeding the age of 10 years across Europe. We found a mean C-4 carbon sequestration rate of 0.78 +/- 0.19 Mg ha(-1) yr(-1), which increased with mean annual temperature. At three of six sites, we found a significant increase in C-3 carbon due to the application of organic fertilizers or difference in baseline SOC, which we define as non-VC-induced SOC changes. The Rothamsted Carbon Model was used to disentangle the decomposition of old C-3 carbon and the non-VC-induced C3 carbon changes. Subsequently, this method was applied to eight more sites from the literature, resulting in a climate-dependent VC-induced SOC sequestration rate (0.40 +/- 0.20 Mg ha(-1) yr(-1)), as a step toward a default SOC change function for Miscanthus plantations on former croplands in Europe. Furthermore, we conducted a SOC fractionation to assess qualitative SOC changes and the incorporation of C-4 carbon into the soil. Sixteen years after Miscanthus establishment, 68% of the particulate organic matter (POM) was Miscanthus-derived in 0-10 cm depth. POM was thus the fastest cycling SOC fraction with a C-4 carbon accumulation rate of 0.33 +/- 0.05 Mg ha(-1) yr(-1). Miscanthus-derived SOC also entered the NaOCl-resistant fraction, comprising 12% in 0-10 cm, which indicates that this fraction was not an inert SOC pool.
  • 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:
    • Zheng, J. F.
    • Pan, G. X.
    • Li, L. Q.
    • Zhang, X. H.
    • Zhang, A F.
    • Liu, Y. M.
    • Kibue, G. W.
    • Ye, Y. X.
    • Liu, X. Y.
    • Zheng, J. W.
  • Source: Agricultural Systems
  • Volume: 129
  • Year: 2014
  • Summary: Biochar's effects on improving soil fertility, enhancing crop productivity and reducing greenhouse gases (GHGs) emission from croplands had been well addressed in numerous short-term experiments with biochar soil amendment (BSA) mostly in a single crop season/cropping year. However, the persistence of these effects, after a single biochar application, has not yet been well known due to limited long-term field studies so far. Large scale BSA in agriculture is often commented on the high cost due to large amount of biochar in a single application. Here, we try to show the persistence of biochar effects on soil fertility and crop productivity improvement as well as GHGs emission reduction, using data from a field experiment with BSA for 5-crop seasons in central North China. A single amendment of biochar was performed at rates of 0 (C0), 20 (C20) and 40 t ha -1 (C40) before sowing of the first crop season. Emissions of CO 2, CH 4 and N 2O were monitored with static closed chamber method throughout the crop growing season for the 1st, 2nd and 5th cropping. Crop yield was measured and topsoil samples were collected at harvest of each crop season. BSA altered most of the soil physico-chemical properties with a significant increase over control in soil organic carbon (SOC) and available potassium (K) content. The increase in SOC and available K was consistent over the 5-crop seasons after BSA. Despite a significant yield increase in the first maize season, enhancement of crop yield was not consistent over crop seasons without corresponding to the changes in soil nutrient availability. BSA did not change seasonal total CO 2 efflux but greatly reduced N 2O emissions throughout the five seasons. This supported a stable nature of biochar carbon in soil, which played a consistent role in reducing N 2O emission, which showed inter-annual variation with changes in temperature and soil moisture conditions. The biochar effect was much more consistent under C40 than under C20 and with GHGs emission than with soil property and crop yield. Thus, our study suggested that biochar amended in dry land could sustain a low carbon production both of maize and wheat in terms of its efficient carbon sequestration, lower GHGs emission intensity and soil improvement over 5-crop seasons after a single amendment.
  • 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:
    • Druschke, C. G.
    • Secchi, S.
  • Source: Journal of Soil and Water Conservation
  • Volume: 69
  • Issue: 2
  • Year: 2014
  • Summary: Female agricultural land ownership and operatorship are on the rise in Iowa and across the nation, but little research exists that explores agricultural conservation outreach to women and gendered differences in conservation knowledge and attitudes. The authors surveyed all agricultural landowners and operators in the Clear Creek Watershed in eastern Iowa about conservation knowledge and attitudes, as well as preferred sources of information about conservation. Clear Creek is a high-visibility watershed for conservation outreach for several reasons, including its long-standing watershed stakeholder council and its connection to the impaired Iowa River. Analysis of the survey results demonstrated that female respondents had significantly lower levels of knowledge about best management practices and significantly more positive attitudes towards conservation and collaboration than men. Meanwhile, women looked to the same sources for conservation information as male respondents, including neighbors, friends, and conservation agencies like the Natural Resources Conservation Service, Cooperative Extension, and the Farm Service Agency. These gendered results have significant consequences for the future of agricultural conservation practice and policy and for the subsequent health of the nation's soils and waterways. While lacking in knowledge about specific conservation practices, female respondents valued conservation practices, looked to government agencies for information about conservation, and expressed interest in collaborating with government entities for conservation on their land. Agricultural conservation practitioners can use these findings to tailor outreach efforts that will more effectively reach the nation's female landowners and operators.
  • Authors:
    • Billen, G.
    • Anglade, J.
    • Garnier, J.
    • Benoit, M.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 100
  • Issue: 3
  • Year: 2014
  • Summary: In the Seine Basin, characterised by intensive arable crops, most of the surface and groundwater is contaminated by nitrate (NO3-). The goal of this study is to investigate nitrogen leaching on commercial arable crop farms in five organic and three conventional systems. In 2012-2013, a total of 37 fields are studied on eight arable crop rotations, for three different soil and climate conditions. Our results show a gradient of soil solution concentrations in function of crops, lower for alfalfa (mean 2.8 mg NO3-N l(-1)) and higher for crops fertilised after legumes (15 mg NO3-N l(-1)). Catch crops decrease nitrate soil solution concentrations, below 10 mg NO3-N l(-1). For a full rotation, the estimated mean concentrations is lower for organic farming, 12 +/- 5 mg NO3-N l(-1) than for conventional farming 24 +/- 11 mg NO3-N l(-1), with however a large range of variability. Overall, organic farming shows lower leaching rates (14-50 kg NO3-N ha(-1)) than conventional farms (32-77 kg NO3-N ha(-1)). Taking into account the slightly lower productivity of organic systems, we show that yield-scaled leaching values are also lower for organic (0.2 +/- 0.1 kg N kg(-1) N year(-1)) than for conventional systems (0.3 +/- 0.1 kg N kg(-1) N year(-1)). Overall, we show that organic farming systems have lower impact than conventional farming on N leaching, although there is still room for progress in both systems in commercial farms.
  • Authors:
    • Al-Mansour, F.
    • Jejcic, V.
  • Source: Proceedings of the 42nd International Symposium on Agricultural Engineering, Actual Tasks on Agricultural Engineering, Opatija, Croatia, 25-28 February, 2014
  • Year: 2014
  • Summary: An analysis of the carbon footprint of conventional, integrated and organic crop production, and three sizes of farms was made. Conventional tillage and direct seeding were used in mentioned production systems. For the analysis of the carbon footprint, CO 2 emissions from fossil fuel (direct energy) consumed in the process of production of corn (for silage and grain), wheat, rapeseed, and sunflower were used. In addition to emissions from fossil fuels used in the production of mentioned crops, greenhouse gas emissions resulting from the use of organic and mineral fertilizers in the production and converted to CO 2 equivalents were also used. In the case of conventional production mineral fertilizers were used, in integrated production combination of mineral fertilizers and organic fertilizers and in organic production only organic fertilizer was used. The sum of emissions arising from fossil fuel use and emissions from fertilizers used in the cultivation process, make final emission from crop production. It was estimated that the emissions of CO 2/t of yields in conventional and integrated production are about the same. In organic production emissions of CO 2/t of yields are higher in comparison with emissions CO 2/t of yields in conventional and integrated farming. CO 2 emissions in conventional and organic production (CO 2/t of yield) are in the following proportions: corn for grain 1:1.34, corn for silage 1:1.52, wheat 1:1.53, rapeseed 1:1.47 and sunflower 1:1.2 (the higher is the number of organic production).
  • Authors:
    • Badyopadhyay, K. K.
    • Patle, G. T.
    • Mukesh Kumar
  • Source: Journal of Applied and Natural Science
  • Volume: 6
  • Issue: 2
  • Year: 2014
  • Summary: Indian agriculture has changed considerably in the past several decades. Since post green revolution era, Indian farming basically shifted from the conventional farming system to towards the mechanized farming system and relies heavily on agricultural inputs such as chemical fertilizers, pesticides, heavy farm machineries and irrigation, which are dependent on fossil fuels. Large scale use of these inputs also contributed in emission of greenhouse gases which are mainly responsible for global warming and consequently climate change. Agriculture plays a unique role in the climate change mitigation because of its potential to lower greenhouse gases emissions through carbon sequestration. Organic agriculture is being considered as one of the appropriate farming systems that could serve the twin objectives of climate change mitigation and adaptation. Compared to conventional agriculture, organic agriculture is considered to be more energy efficient and effective both in reducing green house gases emission mainly due to the less use of chemical fertilizers and fossil fuel and enhancing the soil organic carbon. Promotion and adaptation of organic farming in developing country like India can serve as mitigation strategy of climate change.
  • Authors:
    • Gimeno, B. S.
    • Gattinger, A.
    • Lassaletta, L.
    • Aguilera, E.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 168
  • Year: 2013
  • Summary: Mediterranean croplands are seasonally dry agroecosystems with low soil organic carbon (SOC) content and high risk of land degradation and desertification. The increase in SOC is of special interest in these systems, as it can help to build resilience for climate change adaptation while contributing to mitigate global warming through the sequestration of atmospheric carbon (C). We compared SOC change and C sequestration under a number of recommended management practices (RMPs) with neighboring conventional plots under Mediterranean climate (174 data sets from 79 references). The highest response in C sequestration was achieved by those practices applying largest amounts of C inputs (land treatment and organic amendments). Conservation tillage practices (no-tillage and reduced tillage) induced lower effect sizes but significantly promoted C sequestration, whereas no effect and negative net sequestration rates were observed for slurry applications and unfertilized treatments, respectively. Practices combining external organic amendments with cover crops or conservation tillage (combined management practices and organic management) showed very good performance in C sequestration. We studied separately the changes in SOC under organic management, with 80 data sets from 30 references. The results also suggest that the degree of intensification in C input rate is the main driver behind the relative C accumulation in organic treatments. Thus, highest net C sequestration rates were observed in most eco-intensive groups, such as "irrigated", "horticulture" and controlled experiments ("plot scale"). (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Jolejole, M. C.
    • McCarthy, N.
    • Lipper, L.
    • Branca, G.
  • Source: Agronomy for Sustainable Development
  • Volume: 33
  • Issue: 4
  • Year: 2013
  • Summary: Agriculture production in developing countries must be increased to meet food demand for a growing population. Earlier literature suggests that sustainable land management could increase food production without degrading soil and water resources. Improved agronomic practices include organic fertilization, minimum soil disturbance, and incorporation of residues, terraces, water harvesting and conservation, and agroforestry. These practices can also deliver co-benefits in the form of reduced greenhouse gas emissions and enhanced carbon storage in soils and biomass. Here, we review 160 studies reporting original field data on the yield effects of sustainable land management practices sequestering soil carbon. The major points are: (1) sustainable land management generally leads to increased yields, although the magnitude and variability of results varies by specific practice and agro-climatic conditions. For instance, yield effects are in some cases negative for improved fallows, terraces, minimum tillage, and live fences. Whereas, positive yield effects are observed consistently for cover crops, organic fertilizer, mulching, and water harvesting. Yields are also generally higher in areas of low and variable rainfall. (2) Isolating the yield effects of individual practices is complicated by the adoption of combinations or "packages" of sustainable land management options. (3) Sustainable land management generally increases soil carbon sequestration. Agroforestry increases aboveground C sequestration and organic fertilization reduces CO2 emissions. (4) Rainfall distribution is a key determinant of the mitigation effects of adopting specific sustainable land management practices. Mitigation effects of adopting sustainable land management are higher in higher rainfall areas, with the exception of water management.