• Authors:
    • Dyer, J. A.
    • Worth, D. E.
    • McConkey, B. G.
    • Desjardins, R. L.
    • Shrestha, B. M.
    • Cerkowniak, D. D.
  • Source: Renewable Energy
  • Volume: 63
  • Issue: March
  • Year: 2014
  • Summary: Accounting for greenhouse gas (GHG) emissions at the production stage of a bioenergy crop is essential for evaluating its eco-efficiency. The objective of this study was to calculate the change in GHG emissions for canola (Brassica napus L.) production on the Canadian Prairies from 1986 to 2006. Net GHG emissions in the sub-humid and semi-arid climatic zones were estimated for fallow-seeded and stubble-seeded canola in intensive-, reduced- and no-tillage systems, with consideration given to emissions associated with synthetic nitrogen (N) fertilizer input, mineralized N from crop residues, N leaching and volatilization, farm operations, the manufacturing and transportation of fertilizer, agrochemicals and farm machinery, and emission and removal of CO2 associated with changes in land use (LUC) and land management (LMC). The GHG emissions on an area basis were higher in stubble-seeded canola than in fallow-seeded canola but, the opposite was true on a grain dry matter (DM) basis. Nitrous oxide emissions associated with canola production, CO2 emissions associated with farm energy use and the manufacturing of synthetic N fertilizer and its transportation contributed 49% of the GHG emissions in 1986 which increased to 66% in 2006. Average CO2 emissions due to LUC decreased from 27% of total GHG emissions in 1986 to 8% in 2006 and soil C sequestration due to LMC increased from 8% to 37%, respectively. These changes caused a reduction in net GHG emission intensities of 40% on an area basis and of 65% on a grain DM basis. Despite the reduction in GHG emission intensities, GHG emissions associated with canola in the Prairies increased from 3.4 Tg CO2 equiv in 1986 to 3.8 Tg CO2 equiv in 2006 because of the more than doubling of canola production. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Ruser, R.
    • Stolze, M.
    • Fliessbach, A.
    • Maeder, P.
    • Muller, A.
    • Gattinger, A.
    • Skinner, C.
    • Niggli, U.
  • Source: Science of The Total Environment
  • Volume: 468-469
  • Issue: January
  • Year: 2014
  • Summary: It is anticipated that organic farming systems provide benefits concerning soil conservation and climate protection. A literature search on measured soil-derived greenhouse gas (GHG) (nitrous oxide and methane) fluxes under organic and non-organic management from farming system comparisons was conducted and followed by a meta-analysis. Up to date only 19 studies based on field measurements could be retrieved. Based on 12 studies that cover annual measurements, it appeared with a high significance that area-scaled nitrous oxide emissions from organically managed soils are 492 +/- 160 kg CO2 eq. ha(-1) a(-1) lower than from non-organically managed soils. For arable soils the difference amounts to 497 +/- 162 kg CO2 eq. ha(-1) a(-1). However, yield-scaled nitrous oxide emissions are higher by 41 +/- 34 kg CO2 eq. t(-1) DM under organic management (arable and use). To equalize this mean difference in yield-scaled nitrous oxide emissions between both farming systems, the yield gap has to be less than 17%. Emissions from conventionally managed soils seemed to be influenced mainly by total N inputs, whereas for organically managed soils other variables such as soil characteristics seemed to be more important. This can be explained by the higher bioavailability of the synthetic N fertilisers in non-organic farming systems while the necessary mineralisation of the N sources under organic management leads to lower and retarded availability. Furthermore, a higher methane uptake of 3.2 +/- 2.5 kg CO2 eq. ha(-1) a(-1) for arable soils under organic management can be observed. Only one comparative study on rice paddies has been published up to date. All 19 retrieved studies were conducted in the Northern hemisphere under temperate climate. Further GHG flux measurements in farming system comparisons are required to confirm the results and close the existing knowledge gaps. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Wassmann, R.
    • Sharma, D. K.
    • Sharma, P. C.
    • Kumar, V.
    • Sharma, S.
    • Gathala, M.
    • Rai, M.
    • Tirol-Padre, A.
    • Ladha, J.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 1
  • Year: 2014
  • Summary: Rapid, precise, and globally comparable methods for monitoring greenhouse gas (GHG) fluxes are required for accurate GHG inventories from different cropping systems and management practices. Manual gas sampling followed by gas chromatography (GC) is widely used for measuring GHG fluxes in agricultural fields, but is laborious and time-consuming. The photo-acoustic infrared gas monitoring system (PAS) with on-line gas sampling is an attractive option, although it has not been evaluated for measuring GHG fluxes in cereals in general and rice in particular. We compared N2O, CO2, and CH4 fluxes measured by GC and PAS from agricultural fields under the rice-wheat and maize-wheat systems during the wheat (winter), and maize/rice (monsoon) seasons in Haryana, India. All the PAS readings were corrected for baseline drifts over time and PAS-CH4 (PCH4) readings in flooded rice were corrected for water vapor interferences. The PCH4 readings in ambient air increased by 2.3ppm for every 1000mgcm(-3) increase in water vapor. The daily CO2, N2O, and CH4 fluxes measured by GC and PAS from the same chamber were not different in 93-98% of all the measurements made but the PAS exhibited greater precision for estimates of CO2 and N2O fluxes in wheat and maize, and lower precision for CH4 flux in rice, than GC. The seasonal GC- and PAS-N2O (PN2O) fluxes in wheat and maize were not different but the PAS-CO2 (PCO2) flux in wheat was 14-39% higher than that of GC. In flooded rice, the seasonal PCH4 and PN2O fluxes across N levels were higher than those of GC-CH4 and GC-N2O fluxes by about 2- and 4fold, respectively. The PAS (i) proved to be a suitable alternative to GC for N2O and CO2 flux measurements in wheat, and (ii) showed potential for obtaining accurate measurements of CH4 fluxes in flooded rice after making correction for changes in humidity.
  • Authors:
    • Landis, A. E.
    • Pang, Y. L.
    • Xue, X.
  • Source: Renewable Energy
  • Volume: 66
  • Issue: June
  • Year: 2014
  • Summary: This study examines three agriculture management practices with the aim of improving the environmental performance of corn-derived products such as bioethanol. Corn production is energy intensive and contributes to water quality degradation and global warming, thus affecting the environmental impact of corn-derived ethanol. Life Cycle Assessment (LCA) is used to quantify and compare the environmental impacts of three management strategies: tillage, fertilizer choices and the use of buffer strips to sequester nutrients. Detailed energy, carbon, nitrogen and phosphorus inventories are compiled to represent corn production scenarios within the US Corn Belt. The LCA was developed using GREET 1.8 (Greenhouse Gases, Regulated Emissions, and Energy use in Transportation) and emission factors with statistical analyses to estimate energy consumption, associated air emissions, and aqueous nutrient runoff potentials. Results show that using manure fertilizers as opposed to synthetic fertilizers requires less energy, however the use of manure generates more CH4, N2O, CO2 and results in more variable concentrations of nitrogen and phosphorus leaching from farmlands. No tillage emits less greenhouse gas emissions, sequesters more soil organic carbon and slightly reduces nutrient runoff compared with conventional tillage practices. Building buffer strips of certain widths is an efficient way to reduce N and P discharge to surrounding waters with minimal effect on the energy or global warming profile. Based on the results of the LCA studies, replacing conventional tillage with no till, and installing buffer strips can improve environmental performances of corn derived ethanol. (C) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Li, D.-C.
    • Wang, B.-R.
    • Li, J.-W.
    • Ding, X.-S.
    • Sun, N.
    • Wu, L.-H.
    • Zhang, X.-B.
  • Source: Journal of Integrative Agriculture
  • Volume: 13
  • Issue: 3
  • Year: 2014
  • Summary: Upland red soils have been identified as major CO2 and N2O sources induced by human activities such as fertilization. To monitor characteristics of soil surface CO2 and N2O fluxes in cropland ecosystems after continuous fertilizer applications over decades and to separate the respective contributions of root and heterotrophic respiration to the total soil CO2 and N2O fluxes, the measurements of soil surface CO2 and N2O fluxes throughout the maize growing season in 2009 were carried out based on a fertilization experiment (from 1990) through of the maize (Zea mays L.) growing season in red soil in southern China. Five fertilization treatments were chosen from the experiment for study: zero-fertilizer application (CK), nitrogen-phosphorus-potassium (NPK) fertilizer application only, pig manure (M), NPK plus pig manure (NPKM) and NPK with straw (NPKS). Six chambers were installed in each plot. Three of them are in the inter-row soil (NR) and the others are in the soil within the row (R). Each fertilizer treatment received the same amount of N (300 kg ha(-1) yr(-1)). Results showed that cumulative soil CO2 fluxes in NR or R were both following the order: NPKS>M, NPKM>NPK>CK. The contributions of root respiration to soil CO2 fluxes was 40, 44, 50, 47 and 35% in CK, NPK, NPKM, M and NPKS treatments, respectively, with the mean value of 43%. Cumulative soil N2O fluxes in NR or R were both following the order: NPKS, NPKM>M>NPK>CK, and soil N2O fluxes in R were 18, 20 and 30% higher than that in NR in NPKM, M and NPKS treatments, respectively, but with no difference between NR and R in NPK treatment. Furthermore, combine with soil temperature at -5 cm depth and soil moisture (0-20 cm) together could explain 55-70% and 42-59% of soil CO2 and N2O emissions with root interference and 62-78% and 44-63% of that without root interference, respectively. In addition, soil CO2 and N2O fluxes per unit yield in NPKM (0.55 and 0.10 kg C t(-1)) and M (0.65 and 0.13 g N t(-1)) treatments were lower than those in other treatments. Therefore, manure application could be a preferred fertilization strategy in red soils in South China
  • Authors:
    • Wu, J.
    • Liu, J.
    • Zhou, G.
    • Jiang, P.
    • Chang, S. X.
    • Li, Y.
    • Zhang, J.
    • Shen, Z.
  • Source: Plant and Soil
  • Volume: 376
  • Issue: 1-2
  • Year: 2014
  • Summary: The impact of understory vegetation control or replacement with selected plant species, which are common forest plantation management practices, on soil C pool and greenhouse gas (GHG, including CO2, CH4 and N2O) emissions are poorly understood. The objective of this paper was to investigate the effects of understory vegetation management on the dynamics of soil GHG emissions and labile C pools in an intensively managed Chinese chestnut (Castanea mollissima Blume) plantation in subtropical China. A 12-month field experiment was conducted to study the dynamics of soil labile C pools and GHG emissions in a Chinese chestnut plantation under four different understory management practices: control (Control), understory removal (UR), replacement of understory vegetation with Medicago sativa L. (MS), and replacement with Lolium perenne L. (LP). Soil GHG emissions were determined using the static chamber/GC technique. Understory management did not change the seasonal pattern of soil GHG emissions; however, as compared with the Control, the UR treatment increased soil CO2 and N2O emissions and CH4 uptake, and the MS and LP treatments increased CO2 and N2O emissions and reduced CH4 uptake (P < 0.05 for all treatment effects, same below). The total global warming potential (GWP) of GHG emissions in the Control, UR, MS, and LP treatments were 36.56, 39.40, 42.36, and 42.99 Mg CO2 equivalent (CO2-e) ha(-1) year(-1), respectively, with CO2 emission accounting for more than 95 % of total GWP regardless of the understory management treatment. The MS and LP treatments increased soil organic C (SOC), total N (TN), soil water soluble organic C (WSOC) and microbial biomass C (MBC), while the UR treatment decreased SOC, TN and NO3 (-)-N but had no effect on WSOC and MBC. Soil GHG emissions were correlated with soil temperature and WSOC across the treatments, but had no relationship with soil moisture content and MBC. Although replacing competitive understory vegetation with legume or less competitive non-legume species increased soil GHG emissions and total GWP, such treatments also increased soil C and N pools and are therefore beneficial for increasing soil C storage, maintaining soil fertility, and enhancing the productivity of Chinese chestnut plantations.
  • Authors:
    • Huang, Y.
    • Sun, W.
    • Li, T.
    • Yu, Y.
    • Zhang, W.
  • Source: Environmental Science & Technology
  • Volume: 48
  • Issue: 5
  • Year: 2014
  • Summary: Cropland soils have been shown to emit nitrous oxide (N2O) and methane (CH4) into the atmosphere and to sequester carbon when field management is improved, yet the spatiotemporal changes in the N2O and CH4 emissions and the soil organic carbon (SOC) in China's croplands are unclear with regard to an integrated global warming potential (GWP). This limits our overall evaluation of anthropogenic greenhouse gas (GHG) emissions and impairs effective decision making. On the basis of model simulations primarily from 1980 to 2009, we estimated a 69% increase in the gross GWP of CH4 and N2O emissions, from 244 Tg CO2-equiv yr(-1) in the early 1980s to 413 Tg CO2-equiv yr(-1) in the late 2000s. The SOC was estimated to have increased from 54 Tg CO2-equiv yr(-1) to 117 Tg CO2-equiv yr(-1) during the same period. A reduction in the carbon input during the rice season, along with an improvement of synthetic nitrogen use efficiency in crops to 40%, would mitigate GHG emissions by 111 Tg CO2-equiv yr(-1) and keep SOC sequestration at 82 Tg CO2 yr(-1). Together, this would amount to a reduction of 193 Tg CO2-equiv yr(-1), representing similar to 47% of the gross GWP in the late 2000s. The mitigation of GHG emissions in Henan, Shandong, Hunan, Jiangsu, Hubei, Sichuan, Anhui, Jiangxi, Guangdong and Hebei Provinces could lead to a similar to 66% national improvement and should be given priority.
  • Authors:
    • El-Sharkawy, M.
  • Source: Photosynthetica
  • Volume: 52
  • Issue: 2
  • Year: 2014
  • Summary: Earth's climate has experienced notable changes during the past 50-70 years when global surface temperature has risen by 0.8°C during the 20th century. This was a consequence of the rise in the concentration of biogenic gases (carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone) in the atmosphere that contribute, along with water vapor, to the so-called 'greenhouse effect'. Most of the emissions of greenhouse gases have been, and still are, the product of human activities, namely, the excessive use of fossil energy, deforestations in the humid tropics with associated poor land use-management, and wide-scale degradation of soils under crop cultivation and animal/pasture ecosystems. General Circulation Models predict that atmospheric CO 2 concentration will probably reach 700 mol(CO 2) mol -1. This can result in rise of Earth's temperature from 1.5 to over 5°C by the end of this century. This may instigate 0.60-1.0 m rise in sea level, with impacts on coastal lowlands across continents. Crop modeling predicts significant changes in agricultural ecosystems. The mid- and high-latitude regions might reap the benefits of warming and CO 2 fertilization effects via increasing total production and yield of C 3 plants coupled with greater water-use efficiencies. The tropical/subtropical regions will probably suffer the worst impacts of global climate changes. These impacts include wide-scale socioeconomic changes, such as degradation and losses of natural resources, low agricultural production, and lower crop yields, increased risks of hunger, and above all waves of human migration and dislocation. Due to inherent cassava tolerance to heat, water stress, and poor soils, this crop is highly adaptable to warming climate. Such a trait should enhance its role in food security in the tropics and subtropics.
  • Authors:
    • Yu, Y.
    • Zhang, W.
    • Li, T.
    • Wang, G.
  • Source: PLoS ONE
  • Volume: 9
  • Issue: 4
  • Year: 2014
  • Summary: Dynamics of cropland soil organic carbon (SOC) in response to different management practices and environmental conditions across North China Plain (NCP) were studied using a modeling approach. We identified the key variables driving SOC changes at a high spatial resolution (10 kmx10 km) and long time scale (90 years). The model used future climatic data from the FGOALS model based on four future greenhouse gas (GHG) concentration scenarios. Agricultural practices included different rates of nitrogen (N) fertilization, manure application, and stubble retention. We found that SOC change was significantly influenced by the management practices of stubble retention (linearly positive), manure application (linearly positive) and nitrogen fertilization (nonlinearly positive) - and the edaphic variable of initial SOC content (linearly negative). Temperature had weakly positive effects, while precipitation had negligible impacts on SOC dynamics under current irrigation management. The effects of increased N fertilization on SOC changes were most significant between the rates of 0 and 300 kg ha(-1) yr(-1). With a moderate rate of manure application (i.e., 2000 kg ha(-1) yr(-1)), stubble retention (i.e., 50%), and an optimal rate of nitrogen fertilization (i.e., 300 kg ha(-1) yr(-1)), more than 60% of the study area showed an increase in SOC, and the average SOC density across NCP was relatively steady during the study period. If the rates of manure application and stubble retention doubled (i.e., manure application rate of 4000 kg ha(-1) yr(-1) and stubble retention rate of 100%), soils across more than 90% of the study area would act as a net C sink, and the average SOC density kept increasing from 40 Mg ha(-1) during 2010s to the current worldwide average of similar to 55 Mg ha(-1) during 2060s. The results can help target agricultural management practices for effectively mitigating climate change through soil C sequestration.
  • Authors:
    • Sui, P.
    • Chen, Y.
    • Zhang, M.
    • Gao, W.
    • Yang, X.
  • Source: Journal of Cleaner Production
  • Volume: 76
  • Issue: August
  • Year: 2014
  • Summary: Increasing atmospheric concentrations of greenhouse gases has caused grievous global warming and associated consequences. Lowering carbon footprint to promote the development of cleaner production demands the immediate attention. In this study, the carbon footprint calculations were performed on five cropping systems in North China Plain from 2003 to 2010. The five cropping systems included sweet potato -> cotton -> sweet potato -> winter wheat-summer maize (SpCSpWS, 4-year cycle), ryegrass-cotton -> peanut -> winter wheat-summer maize (RCPWS, 3-year cycle), peanut -> winter wheat-summer maize (PWS, 2-year cycle), winter wheat-summer maize (WS, 1-year cycle), and continuous cotton (Cont C), established in a randomized complete-block design with three replicates. We used a modified carbon footprint calculation with localized greenhouse gas emissions parameters to analyze the carbon footprint of each cropping system per unit area, per kg biomass, and per unit economic output. Results showed that the lowest annual carbon footprint values were observed in SpCSpWS among the five cropping systems, which were only 27.9%, 28.2% and 25.0% of those in WS rotation system (the highest carbon footprint) in terms of per unit area, per unit biomass, and per unit economic output, respectively. The five cropping systems showed the order of SpCSpWS < Cont C < RCPWS < PWS < WS sorting by their annual carbon footprint calculated by all the three metrics above-mentioned. Results revealed that appropriate diversified crop rotation systems could contribute to decreased carbon footprint compared with conventional intensive crop production system in North China Plain. (C) 2014 Elsevier Ltd. All rights reserved.