• Authors:
    • Pan, G.
    • Smith, P.
    • Nayak, D.
    • Zheng, J.
    • Cheng, K.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 4
  • Year: 2013
  • Summary: To assess the topsoil carbon sequestration potential (CSP) of China's cropland, two different estimates were made: (i) a biophysical potential (BP) using a saturation limit approach based on soil organic carbon (SOC) accumulation dynamics and a storage restoration approach from the cultivation-induced SOC loss, and (ii) a technically attainable potential (TAP) with a scenario estimation approach using SOC increases under best management practices (BMPs) in agriculture. Thus, the BP is projected to be the gap in recent SOC storage to either the saturation capacity or to the SOC storage of uncultivated soil, while the TAP is the overall increase over the current SOC storage that could be achieved with the extension of BMPs. The recent mean SOC density of China's cropland was estimated to be 36.44t/ha, with a BP estimate of 2.21 Pg C by a saturation approach and 2.95 Pg C by the storage restoration method. An overall TAP of 0.62 Pg C and 0.98 Pg C was predicted for conservation tillage plus straw return and recommended fertilizer applications, respectively. This TAP is comparable to 40-60% of total CO2 emissions from Chinese energy production in 2007. Therefore, carbon sequestration in China's cropland is recommended for enhancing China's mitigation capacity for climate change. However, priority should be given to the vast dry cropland areas of China, as the CSP of China is based predominantly on the dry cropland.
  • Authors:
    • Saad, A. A.
    • Das, S.
    • Sharma, A. R.
    • Bhattacharyya, R.
    • Das, T. K.
    • Pathak, H.
  • Source: European Journal of Agronomy
  • Volume: 51
  • Year: 2013
  • Summary: Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008-2011) and in the last year, maize (Zea mays L), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (similar to 5.5 Mg ha(-1)) in the 0-5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0-5 and 5-15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0-30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+W RES) contained similar to 13% higher total SOC concentration than no residue treated plots (N RES; similar to 7.6 g kg(-1)) in the 0-5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had similar to 17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding similar to 16% higher estimated root (and rhizodeposition) C input in the 0-30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, similar to 7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and if, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity. (c) Elsevier B.V. All rights reserved.
  • Authors:
    • Cantarella, H.
    • Rossetto, R.
    • Gava, G. J. C.
    • Andrade, C. A.
    • Vargas, V. P.
    • Duarte-Neto, P. J.
    • Pitombo, L. M.
    • de Sousa Neto, E. R.
    • Zotelli, L. C.
    • Filoso, S.
    • do Carmo, J. B.
    • Neto, A. E.
    • Martinelli, L. A.
  • Source: GCB Bioenergy
  • Volume: 5
  • Issue: 3
  • Year: 2013
  • Summary: Bioethanol from sugarcane is becoming an increasingly important alternative energy source worldwide as it is considered to be both economically and environmentally sustainable. Besides being produced from a tropical perennial grass with high photosynthetic efficiency, sugarcane ethanol is commonly associated with low N fertilizer use because sugarcane from Brazil, the world's largest sugarcane producer, has a low N demand. In recent years, several models have predicted that the use of sugarcane ethanol in replacement to fossil fuel could lead to high greenhouse gas (GHG) emission savings. However, empirical data that can be used to validate model predictions and estimates from indirect methodologies are scarce, especially with regard to emissions associated with different fertilization methods and agricultural management practices commonly used in sugarcane agriculture in Brazil. In this study, we provide in situ data on emissions of three GHG (CO2, N2O, and CH4) from sugarcane soils in Brazil and assess how they vary with fertilization methods and management practices. We measured emissions during the two main phases of the sugarcane crop cycle (plant and ratoon cane), which include different fertilization methods and field conditions. Our results show that N2O and CO2 emissions in plant cane varied significantly depending on the fertilization method and that waste products from ethanol production used as organic fertilizers with mineral fertilizer, as it is the common practice in Brazil, increase emission rates significantly. Cumulatively, the highest emissions were observed for ratoon cane treated with vinasse (liquid waste from ethanol production) especially as the amount of crop trash on the soil surface increased. Emissions of CO2 and N2O were 6.9kgha1yr1 and 7.5kgha1yr1, respectively, totaling about 3000kg in CO2 equivalent ha1yr1.
  • Authors:
    • Hunter, C.
    • Slee, B.
    • Feliciano, D.
    • Smith, P.
  • Source: Environmental Science & Policy
  • Volume: 25
  • Year: 2013
  • Summary: Challenging greenhouse gas (GHG) emission reduction targets were set in Scotland by the Climate Change (Scotland) Act in June 2009. The national objective is to reduce GHG emissions by 42% by 2020 and 80% by 2050 compared to 1990 levels. The GHG emission reduction targets apply both to the traded and non-traded sectors, thus including the rural land use sector. In North East Scotland, rural land uses cover the majority of the land area, with agriculture and forestry representing about 86% and sporting land about 10% of the total area. The objectives of this study were to provide guidance for the development of a regional GHG inventory to estimate methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions from rural land uses in North East of Scotland, to compare with that of the United Kingdom (UK), and discuss the advantages of regional GHG inventories for rural land uses. The study mainly followed the guidance of the IPCC (Intergovernmental Panel on Climate Change) Revised Guidelines for National Greenhouse Gas Inventories and adapts these to the region level. Data available for North East Scotland allowed an assessment of annual GHG emissions from livestock and grassland, cropland management and sporting land, as well as carbon sequestered by forests, between 1999 and 2010. Estimated GHG emissions of 1420 ktCO(2)e from livestock, grassland and cropland management obtained in this study for 2009 compare well with estimates for the same region from larger-scale inventories. The methodology described, including the steps undertaken for data collection, the shortcomings found and strategies to overcome these, could be applied to other UK or European regions.
  • Authors:
    • Emmerling, C.
    • Fries, J.
    • Froeba, N.
    • Felten, D.
  • Source: Renewable Energy
  • Volume: 55
  • Year: 2013
  • Summary: Biomass for bioenergy is an important option within global change mitigation policies. The present research focused on energy net production, net reduction of greenhouse gases (GHG) (considered as CO2-equivalents), and energy output:input ratio of the energy cropping systems 'rapeseed', 'maize', and 'Miscanthus'. The system-specific main products were biodiesel (rapeseed), electricity from biogas (maize), and Miscanthus chips (loose, chopped material); the related substituted fossil resources were diesel fuel (rapeseed), electricity from the German energy mix (maize), and heating oil (Miscanthus). However, research did not aim for a direct quantitative comparison of the crops. The study followed a case study approach with averaged data from commercial farms within an enclosed agricultural area (<5 km(2)) in Western Germany. Cultivation techniques were considered as communicated by farmers and operation managers; the diesel fuel consumption of agricultural machinery was modeled using an online-based calculator of the German Association for Technology and Structures in Agriculture (KTBL). Overall, rounded net energy production amounted to 66 GJ ha(-1) (rapeseed), 91 GJ ha(-1) (maize), and 254 GJ ha(-1) yr(-1) (Miscanthus); the related energy output:input ratios were 4.7 (rapeseed), 5.5 (maize), and 47.3 (Miscanthus), respectively. Compared to the respective fossil fuel-related energy supply, CO2-equivalent reduction potential ranged between 30 and 76% for electrical energy from maize biomass, 29 -82% for biodiesel from rapeseed, and 96-117% for Miscanthus chips, depending on whether or not the accruing by-products rapeseed cake, glycerin (rapeseed cropping system), and waste heat (maize) were considered. True 'CO2-neutrality' was only reached by the Miscanthus cropping system and was related to an additional credit from carbon sequestration in soil during the cultivation period; thus, this cropping system could be attributed to be a CO2-sink. The study indicated that bioenergy can be produced sustainably under commercial farming conditions in terms of a significantly reduced consumption of natural resources.
  • Authors:
    • Cao, Y.
    • Drake, B.
    • Elliott, J.
    • Firbank, L. G.
    • Gooday, R.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 173
  • Year: 2013
  • Summary: Several influential reports have suggested that one of the most appropriate responses to expected food shortages and ongoing environmental degradation is sustainable intensification, i.e. the increase of food production with at worst no increase in environmental harm, and ideally environmental benefit. Here we sought evidence of sustainable intensification among British farmers by selecting innovative arable, dairy, mixed and upland farms and analysing their own data on yields, inputs and land use and management for 2006 and 2011. The evidence was obtained by interview, and was interpreted in terms of the ecosystem services of food production (GJ ha(-1), where area took into account estimated area to grow any imported animal feeds), regulation of climate, air and water quality (modelled emissions of GHGs (CO(2)e ha(-1)), ammonia (kg ha(-1)) and nitrate loss (kg ha(-1))) and biodiversity (using an index based on the presence of habitats and management). Several farms have increased both food production and other ecosystem services over this time by increasing yields, using resources more efficiently and/or enhancing biodiversity, and sometimes by reducing livestock numbers and increasing cropping. The motivation has been to improve farm profitability through increasing food production, reducing input costs and accessing public payments through agri-environment schemes and generating renewable energy. Such sustainable intensification was not achieved by farmers who increased meat or milk yields. Sustainable intensification can be achieved when the correct drivers are in place to influence the actions of individual farmers. Also, it is possible to indicate sustainable intensification by using a small number of high-level indicators derived from data that farmers already hold, though such an approach may not capture the impacts of farmer innovative practices.
  • Authors:
    • Gonzalez, A.
    • Tapasco, J.
    • Graefe, S.
  • Source: Fruits
  • Volume: 68
  • Issue: 4
  • Year: 2013
  • Summary: Introduction. The cultivation of high-value fruit species is a profitable agricultural activity in many tropical countries; however, intensive fruit cultivation may depend on high amounts of external inputs. The objective of our study was to quantify and compare the resource use during the cultivation of eight tropical fruit species (Rubus glaucus, Solanum quitoense, Passiflora edulis, Cyphomandra betacea, Physalis peruviana, Ananas comosus, Persea americana and Mangifera indica) commonly cultivated in Colombia. It further aimed to identify greenhouse gas (GHG) emissions in the selected production systems and to highlight the potential to contribute to climate change mitigation efforts. Materials and methods. The analysis was based on data from agricultural databases and applied a life-cycle assessment with energy use and GHG emissions as impact categories. Furthermore, economic indicators were taken into account with the aim of integrating the environmental and economic goals of production systems. Results and discussion. Among the eight fruit species studied, mango (Mangifera indica) was found to have the lowest and tree tomato (Cyphomandra betacea) the highest emission profile. The variability in resource use among growers of the same species was high, indicating the need to improve management abilities at the farm level. Mineral fertilizer production was the highest contributor to GHG emissions. GHG- and energy-efficient management alternatives would have a high potential to reduce the carbon footprint of fruit cultivation.
  • Authors:
    • Partington, D. L.
    • Phelan, A. J.
    • Zollinger, R. P.
    • Fogarty, K. M.
    • Armstrong, R. D.
    • Hill, P. A.
    • Officer, S. J.
    • Harris, R. H.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 2
  • Year: 2013
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas released from high rainfall cropping soils, but the role of management in its abatement remains unclear in these environments. To quantify the relative influence of management, nitrogen (N) fertiliser and soil nitrification inhibitor was applied to separate but paired raised bed and conventionally flat field experiments in south west Victoria, to measure emissions and income from wheat and canola planted 2 and 3 years after conversion from a long-term pasture. Management included four different rates of N fertiliser, top-dressed with and without the nitrification inhibitor Dicyandiamide (DCD), which was applied in solution to the soil in the second year of experimentation. Crop biomass, grain yield, soil mineral N, soil temperature and soil water and N2O flux were measured. Static chamber methodology was used to identify relative differences in N2O loss between management. In the second crop (wheat) following conversion, N2O losses were up to 72 % lower (P < 0.05) in the furrows, receiving the lower rate of N fertiliser compared with the highest rate, with less frequent reductions observed in the third crop (canola); losses of N2O from the beds was unaffected by N rate, perhaps from nitrate leakage into the adjacent furrow of the raised bed experiment. On the nearby flat experiment, nitrate leaching may have diminished the effects of N rate and DCD on N2O flux. Furthermore the extra N did not significantly increase grain yield in either the wheat or canola crops on both experiments. The application of DCD in the canola crop temporarily reduced (P < 0.05) N2O production by up to 84 % from the beds, 83 % in the adjacent furrows and 75 % on the flat experiment. Grain yield was not significantly (P < 0.001) affected however, canola income was reduced by $1407/ha and $1252/ha, compared with no addition of inhibitor on the respective bed and flat experiments. Although N2O fluxes are driven by environmental episodic events, management will play a role in N2O abatement. However, DCD currently appears economically unfeasible and matching N fertiliser supply to meet crop demand appears a better option for minimising N2O losses from high rainfall cropping systems.
  • Authors:
    • Herrmann, A.
  • Source: BioEnergy Research
  • Volume: 6
  • Issue: 1
  • Year: 2013
  • Summary: Several European countries have expanded the traditional use of anaerobic digestion, i.e. waste treatment, to energy generation through attractive incentives. In some countries, it is further promoted by additional payments to generate biogas from biomass. This review aims to summarise agronomic aspects of methane production from maize, to address resulting abiotic environmental effects and to highlight challenges and prospects. The opportunities of biogas production are manifold, including the mitigation of climate change, decreasing reliance on fossil fuels and diversification of farm income. Although the anaerobic digestion of animal manure is regarded as the most beneficial for reducing greenhouse gas (GHG) emission from manure storage, the energy output can be substantially enhanced by co-digesting manure and maize, which is the most efficient crop for substrate provision in many regions. Although first regarded as beneficial, the rush into biogas production strongly based on maize (Zea mays ssp. mays) is being questioned in view of its environmental soundness. Main areas of concern comprise the spatial concentration of biogas plant together with the high amount of digestate and resulting pollution of surface and ground water, emission of climate-relevant gases and detrimental effects of maize cultivation on soil organic matter degradation. Key challenges that have been identified to enhance the sustainability of maize-based biogas production include (1) the design of regionally adapted maize rotations, (2) an improved management of biogas residues (BR), (3) the establishment of a more comprehensive data base for evaluating soil C fluxes in maize production as well as GHG emissions at the biogas plant and during BR storage and (4) the consideration of direct and indirect land use change impact of maize-based biogas production.
  • Authors:
    • Liu, H. B.
    • Li, M. F.
    • Sheng, Q. K.
    • Wu, W.
    • Guo, P. T.
    • Wang, Z. Y.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 3
  • Year: 2013
  • Summary: Soil organic matter (SOM) is an important soil property that affects physical, chemical, and biological properties of soil. Accurate estimation of SOM variability could provide critical information for understanding nutrients cycling and sediment. In the current study, artificial neural networks (ANNs) were developed to predict SOM variability based on topographic variables (topographic wetness index, relative position index, slope length and elevation) in hilly areas. A total of 265 soil samples collected from a depth of 0-20 cm were used to calibrate and validate the models. The best performed ANN model was compared with multiple linear regression (MLR) equation. The performance accuracy was evaluated by Pearson's correlation coefficient (r), mean error (ME), mean squared error (MSE), root mean squared error (RMSE), and coefficient of determination (R-2). In terms of MSE and r, the ANN model with topographic wetness index, relative position index, and slope length outperformed other ANNs. The best performed ANN model was also superior to the MLR equation. Values of ME, RMSE, and R-2 were -0.0337 g/kg, 1.0919 g/kg, and 0.8714 for ANN model, and were 0.1574 g/kg, 1.3296 g/kg, and 0.8172 for MLR equation, respectively. The results of ANN and MLR suggested that topographic wetness index was the most important topographic indicator affecting SOM variability in the current study area.