• 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:
    • Liu, W. Z.
    • Li, J.
    • Yang, X. Y.
    • Chen, C.
    • Cleverly, J.
    • He, L.
    • Yu, Q.
  • Source: Agronomy Journal
  • Volume: 106
  • Issue: 4
  • Year: 2014
  • Summary: Crop production and water use in rainfed cropland are vulnerable to climate change. This study was to quantify diverse responses of winter wheat ( Triticum aestivum L.) yield and water use to climate change on the Loess Plateau (LP) under different combinations of climatic variables. The crop model APSIM was validated against field experimental data and applied to calculate yield and water use at 18 sites on the LP during 1961 to 2010. The coefficient of variation of yield ranged from 12 to 66%, in which the vulnerability of yield increased from the southeast (12%) to the northwest (66%). This change was attributed to the gradual increase in precipitation variation from the southeast to the northwest. An obvious warming trend during 1961 to 2010 resulted in a significant decrease in the growth duration by 1 to 5 d decade -1. The yield at 12 sites was significantly reduced by 120 to 720 kg ha -1 decade -1. Evapotranspiration was significantly decreased by 1 to 26 mm decade -1; however, water use efficiency at most sites showed no significant trend. Eighteen sites were classified into three climatic zones by cluster analysis: high temperature-high precipitation-low radiation (HHL), medium temperature-medium precipitation-medium radiation (MMM), and low temperature-low precipitation-high radiation (LLH). The trend of decreasing yield was smallest in the HHL cluster because of a minimal reduction in precipitation, while decreasing trends in yield and evapotranspiration were larger in the LLH and MMM because of larger reductions in precipitation. The results imply that among strategies such as breeding for long duration or drought tolerance, modification of the planting date will be necessary to avoid high temperatures associated with climate change.
  • Authors:
    • Yilmaz, G.
    • Bilgili, A. V.
    • Ikinci, A.
  • Source: Turkish Journal of Agriculture & Forestry
  • Volume: 37
  • Issue: 6
  • Year: 2013
  • Summary: Broad interest in reducing greenhouse gas emissions requires a better understanding of controls on carbon dioxide (CO2) release under different agricultural management practices. The objective of this study was to investigate and model seasonal variation of soil CO2 emissions from an apple orchard field (Malus domestica L. 'Starkrimson'). Soil CO2 emissions from an apple orchard managed with common practices were measured weekly over a 3-year period (May 2008 to May 2011) from both under the crowns of trees (CO2-UC) and between rows (CO2-BR) using a soda lime technique and were modeled using available environmental data. The study area is located in the Harran Plain of southeastern Turkey and has a semiarid climate. The weekly soil CO2 emissions ranged from 87.8 to 1428 kg week(-1) ha(-1), from 74.6 to 835 kg week(-1) ha(-1), and from 88.6 to 1087 kg week(-1) ha(-1) for CO2-UC, CO2-BR, and the average of both (CO2-AVG), respectively, and showed a pronounced seasonal pattern with the lowest emissions in winter (January and February) and the highest emissions during the growing season (April to December). Relative to 2008 emissions, 2009 CO2 emissions increased by approximately 75%, and 2010 emissions increased by approximately 88%. Comparison of 3 models (multiple linear regression, principal component regression, and multivariate adaptive regression splines) showed that multivariate adaptive regression splines provided the best performance in modeling soil CO2 emissions, explaining overall variation of 64%, 56%, 76%, and 53% in CO2-AVG for the first, second, third, and all three 3 periods, respectively. In conclusion, overall findings showed that soil CO2 emissions could be modeled by available environmental data such as air and soil temperature.
  • Authors:
    • Cowie, B. A.
    • Thornton, C. M.
    • Dalal, R. C.
  • Source: SCIENCE OF THE TOTAL ENVIRONMENT Special Issue: SI
  • Volume: 465
  • Year: 2013
  • Summary: The continuing clearance of native vegetation for pasture, and especially cropping, is a concern due to declines in soil organic C (SOC) and N, deteriorating soil health, and adverse environment impact such as increased emissions of major greenhouse gases (CO2, N2O and CH4). There is a need to quantify the rates of SOC and N budget changes, and the impact on greenhouse gas emissions from land use change in semi-arid subtropical regions where such data are scarce, so as to assist in developing appropriate management practices. We quantified the turnover rate of SOC from changes in delta C-13 following the conversion of C-3 native vegetation to C-4 perennial pasture and mixed C-3/C-4 cereal cropping (wheat/sorghum), as well as delta N-15 changes following the conversion of legume native vegetation to non-legume systems over 23 years. Perennial pasture (Cenchrus ciliaris cv. Biloela) maintained SOC but lost total N by more than 20% in the top 0-0.3 m depth of soil, resulting in reduced animal productivity from the grazed pasture. Annual cropping depleted both SOC and total soil N by 34% and 38%, respectively, and resulted in decreasing cereal crop yields. Most of these losses of SOC and total N occurred from the >250 mu m fraction of soil. Moreover, this fraction had almost a magnitude higher turnover rates than the 250-53 mu m and <53 mu m fractions. Loss of SOC during the cropping period contributed two-orders of magnitude more CO2-e to the atmosphere than the pasture system. Even then, the pasture system is not considered as a benchmark of agricultural sustainability because of its decreasing productivity in this semi-arid subtropical environment. Introduction of legumes (for N-2 fixation) into perennial pastures may arrest the productivity decline of this system. Restoration of SOC in the cropped system will require land use change to perennial ecosystems such as legume-grass pastures or native vegetation. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Tahmasebi, P.
    • Raiesi, F.
    • Salek-Gilani, S.
    • Ghorbani, N.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 96
  • Issue: 2-3
  • Year: 2013
  • Summary: Agricultural abandonment is known to influence plant cover composition and C inputs into the soil with a consequence for changes in soil organic matter (SOM) storage and dynamics in rangeland ecosystems. This study was conducted on a chronosequence of high altitude rangelands (1) cultivated with rainfed wheat (CR0), (2) abandoned for 4 (AR4), 12 (AR12) and 45 (AR45) years and (3) uncultivated (reference) rangelands (UR) with three replicates in Zagros Mountains, Central Iran. We studied the changes in the concentrations and stocks of bulk soil organic carbon (OC), total N, particulate organic C (POC) and N (PON), dissolved organic C (DOC), microbial biomass C (MBC), and potentially mineralizable C (Min-C) at 0-0.15 and 0.15-0.3 m soil depths. Results showed that the concentrations and stocks of OC, N, and labile fractions increased with the abandonment of agriculture at both soil sampling depths. After 4-45 years of agricultural abandonment, soil OC and N stocks increased logarithmically by 3.8-46 % and 2.8-32 % in the whole 0-0.3 m, respectively. Although, the stocks of labile fractions decreased slightly 4 years after agricultural abandonment, there were considerable increases (logarithmic) in these fractions after 12-45 years of abandonment (POC, 65-148 %; PON, 68-147 %; DOC, 76-139 %; MBC, 24-62 %). The study shows that rangelands abandoned for 45 years contained lower soil OC and N concentrations and stocks compared to uncultivated rangelands, reflecting 45 years of abandonment would not be sufficient for SOM to attain the level of uncultivated rangelands. The present study provided evidence that the rate of increases in POC and DOC stocks was greater than that of OC and MBC stocks, demonstrating POC and DOC fractions of total SOM pool may be suitable and sensitive indicators for detecting the effects of agricultural abandonment on soil OC changes and storage in these restored semi-arid rangelands. Soil bulk density decreased, while the mean weight diameter (MWD) and aggregate ratio as measures of aggregate stability increased considerably within the abandoned rangelands with increasing time of abandonment. Results from a multivariate analysis suggested that soil variables such as bulk density, OC, TN, DOC, POC, PON, MBC, MWD and metabolic quotient (qCO(2)) were successful in separating land uses. In brief, the abandonment of agricultural activities in previously cultivated high altitude rangelands can potentially lead to an increase of total and labile SOM and also sequestration of C in these semi-arid rangelands.
  • Authors:
    • Campbell, C. A.
    • Desjardins, R. L.
    • Smith, W. N.
    • McConkey, B. G.
    • Shrestha, B. M.
    • Grant, B. B.
    • Miller, P. R.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 1
  • Year: 2013
  • Summary: There is uncertainty about how crop rotation and tillage affect soil organic C (SOC) on the Canadian prairies. We compared SOC amount and change (SOC) for one continuous crop and four 3-yr fallow-containing crop rotations under no-tillage (NT), and two fallow-containing crop rotations under minimum-tillage (MT), from 1995 to 2005 in semiarid southwestern Saskatchewan. After 11 yr, SOC (0- to 15-cm depth) was 0.2 Mg C ha -1 higher under continuous crop compared with fallow-containing systems. There were no significant differences in SOC and SOC among fallow-containing rotations or between MT and NT. Total C inputs were weakly ( R2=0.18) but significantly ( P<0.05) correlated to SOC, which changed by0.33 Mg C ha -1 for each Mg ha -1 C input above or below 2.4 Mg C ha -1 yr -1. Carbon inputs were typically less than this amount and SOC generally decreased over the experiment. Simulations of SOC with the Century model were consistent with our observations regarding SOC per unit of C input. There was slight loss of SOC for the above-average precipitation regime during the study. Simulations also supported our finding that SOC differences between crop mix and tillage systems may require several decades to become distinguishable in this semiarid climate with small and variable C inputs.
  • Authors:
    • Isaev, S.
    • Mavlyanov, D.
    • Esanbekov, M.
    • Khasanova, F.
    • Sultonov, M.
    • Karaev, S.
    • Kobilov, R.
    • Ibragimov, N.
    • Kholov, B.
    • Bekenov, M.
    • Martynova, L.
    • Ibraeva, M.
    • Otarov, A.
    • Yuldashev, T.
    • Glazirina, M.
    • Sommer, R.
    • Abdurahimov, S.
    • Ikramov, R.
    • Shezdyukova, L.
    • Pauw, E. de
  • Source: Agriculture Ecosystems and Environment
  • Volume: 178
  • Year: 2013
  • Summary: Climate change (CC) may pose a challenge to agriculture and rural livelihoods in Central Asia, but in-depth studies are lacking. To address the issue, crop growth and yield of 14 wheat varieties grown on 18 sites in key agro-ecological zones of Kazakhstan, Kyrgyzstan, Uzbekistan and Tajikistan in response to CC were assessed. Three future periods affected by the two projections on CC (SRES A1B and A2) were considered and compared against historic (1961-1990) figures. The impact on wheat was simulated with the CropSyst model distinguishing three levels of agronomic management. Averaged across the two emission scenarios, three future periods and management scenarios, wheat yields increased by 12% in response to the projected CC on 14 of the 18 sites. However, wheat response to CC varied between sites, soils, varieties, agronomic management and futures, highlighting the need to consider all these factors in CC impact studies. The increase in temperature in response to CC was the most important factor that led to earlier and faster crop growth, and higher biomass accumulation and yield. The moderate projected increase in precipitation had only an insignificant positive effect on crop yields under rainfed conditions, because of the increasing evaporative demand of the crop under future higher temperatures. However, in combination with improved transpiration use efficiency in response to elevated atmospheric CO 2 concentrations, irrigation water requirements of wheat did not increase. Simulations show that in areas under rainfed spring wheat in the north and for some irrigated winter wheat areas in the south of Central Asia, CC will involve hotter temperatures during flowering and thus an increased risk of flower sterility and reduction in grain yield. Shallow groundwater and saline soils already nowadays influence crop production in many irrigated areas of Central Asia, and could offset productivity gains in response to more beneficial winter and spring temperatures under CC. Adaptive changes in sowing dates, cultivar traits and inputs, on the other hand, might lead to further yield increases.
  • Authors:
    • Govindaraj, M.
    • Prabukumar, G.
    • Arunachalam, P.
    • Kannan, P.
  • Source: African Journal of Agricultural Research
  • Volume: 8
  • Issue: 21
  • Year: 2013
  • Summary: Atmospheric rise of CO 2, N 2O and CH 4 over years, accelerated increase in global temperature, has led to uncertainty in monsoon rainfall and also leading to recurrence of drought, which in turn is severely affecting crop productivity and livelihood security of the farmers in Semi Arid Tropics. Agriculture contributes considerable amount of CO 2, N 2O and CH 4 emission into the atmosphere through different soil and crop management practices. Nevertheless agricultural activities contribute to global warming. The medium of crop production, soil is one of the major sinks of global warming gaseous and it helps to sequester more carbon and cut the N 2O emission by adopting smart soil and crop management techniques. Biochar is one of the viable organic amendments to combat climate change and sustain the soil health with sustainable crop production. It is an anaerobic pyrolysis product derived from organic sources and store carbon on a long term basis in the terrestrial ecosystem and also capable of reducing greenhouse gases (GHG) emission from soil to the atmosphere. Biochar application improved the soil health, increase the carbon capture and storage, reduce the GHG emission and enhance the crop yield with sustained soil health, which enables to meet out the food grain needs of the ever growing population.
  • Authors:
    • Armstrong, R.
    • Norton, R.
    • Chen, D.
    • Lam, S. K.
    • Mosier, A. R.
  • Source: The Journal of Agricultural Science
  • Volume: 151
  • Issue: 2
  • Year: 2013
  • Summary: The effect of elevated carbon dioxide (CO2) concentration on greenhouse gas (GHG) emission from semi-arid cropping systems is poorly understood. Closed static chambers were used to measure the fluxes of nitrous oxide (N2O), CO2 and methane (CH4) from a spring wheat (Triticum aestivum L. cv. Yitpi) crop-soil system at the Australian grains free-air carbon dioxide enrichment (AGFACE) facility at Horsham in southern Australia in 2009. The targeted atmospheric CO2 concentrations (hereafter CO2 concentration is abbreviated as [CO2]) were 390 (ambient) and 550 (elevated) mu mol/mol for both rainfed and supplementary irrigated treatments. Gas measurements were conducted at five key growth stages of wheat. Elevated [CO2] increased the emission of N2O and CO2 by 108 and 29%, respectively, with changes being greater during the wheat vegetative stage. Supplementary irrigation reduced N2O emission by 36%, suggesting that N2O was reduced to N-2 in the denitrification process. Irrigation increased CO2 flux by 26% at ambient [CO2] but not at elevated [CO2], and had no impact on CH4 flux. The present results suggest that under future atmospheric [CO2], agricultural GHG emissions at the vegetative stage may be higher and irrigation is likely to reduce the emissions from semi-arid cropping systems.
  • Authors:
    • Radhouane, L.
  • Source: Journal of Agriculture and Environment for International Development
  • Volume: 107
  • Issue: 1
  • Year: 2013
  • Summary: Global temperature is increasing and that the main cause is the accumulation of carbon dioxide and other greenhouse gases in the atmosphere as a result of human activities. The economic costs alone will be very large: as extreme weather events such as droughts and floods become more destructive and frequent; communities, cities, and island nations are damaged or inundated as sea level rises; and agricultural output is disrupted. Impacts on ecosystems and biodiversity are also likely to be devastating. But what about Climate change impacts on water resources and agriculture in North African regions and especially on Tunisia country? North Africa is vulnerable to climate change impacts. Scenarios predict an average rise in annual temperatures, higher than the average expected for the planet. Heat waves would then be more numerous, longer and more intense. North Africa would be particularly affected by droughts that would be more frequent, more intense and longer-lasting. The projections also announce a drop of 4 to 27% in annual rainfall. The water deficit will be worsened by increased evaporation and coastal aquifers will become more salty. The sea level could rise by 23-47 cm. by the end of the 21st century. Many Mediterranean regions would then run a major risk of being submerged and eroded. In North Africa, rising temperatures associated with climate change are expected to decrease the land areas suitable for agriculture, shorten the length of growing seasons and reduce crop yields. In these countries, we estimate that a 1°C rise in temperature in a given year reduces economic growth in that year by about 1.1 points. The decrease in annual precipitation that is predicted for Northern Africa in the 21st century will exacerbate these effects, particularly in semiarid and arid regions that rely on irrigation for crop growth. These effects of climate change are more dramatic for Tunisia country especially for water resources and arable cropland. The African countries face numerous environmental challenges and have to reconcile many conflicting priorities, from promoting economic diversification, ensuring water supply and food security, and furthering environmental protection and conservation to adapting to the impacts of global warming.