• Authors:
    • Ladoni,M.
    • Basir,A.
    • Kravchenko,A.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 3
  • Year: 2015
  • Summary: Active fractions of soil C such as particulate organic C (POC) and short-term mineralizable C (SMC) respond faster than total organic C (TOC) to management induced changes in soil C. However, the active fractions of organic C can possibly have larger variability that decreases the detectability of management effects on soil C. The objectives of this study were to (i) assess the relative usefulness of TOC, POC, and SMC as criteria of management induced changes on soil C and (ii) investigate if using auxiliary soil and topographical information can aid in increasing the usefulness of these criteria in studies conducted across large spatial scales. Data were collected at locations with two contrasting topographical positions (slope and depression) within 10 agricultural fields in conventional and cover crop based row crop managements at the 0- to 20-, 35- to 50-, and 70- to 90-cm depths. The results showed that to detect differences between the management systems with an acceptable type II error of 0.20, an 80% difference in TOC and a 50% difference in SMC were needed. The statistical power for POC was never in an acceptable range. The use of auxiliary soil and topography information via analysis of covariance decreased the sizes of the minimal detectable differences. Given the faster reaction to management of SMC as compared with TOC, and its lower variability as compared with POC, we recommend SMC as the preferred C fraction for detecting treatment induced differences in organic C stocks in agricultural field experiments, especially in deeper soil layers. © Soil Science Society of America, 5585 Guilford Rd., Madison Wl 53711 USA.
  • Authors:
    • Messerli,J.
    • Bertrand,A.
    • Bourassa,J.
    • Belanger,G.
    • Castonguay,Y.
    • Tremblay,G.
    • Baron,V.
    • Seguin,P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 3
  • Year: 2015
  • Summary: The increase in atmospheric carbon dioxide concentration ([CO 2]) and consequent increase in air temperature is expected to have significant effects on plant growth and nutritive value. Studies examining the effects of elevated [CO 2] on plants under field conditions have been limited by the inherent difficulty to modify air composition in open air. Here we describe an efficient and inexpensive open-top chamber (OTC) system designed to study the effects of elevated atmospheric [CO 2] and temperature on perennial alfalfa-timothy ( Medicago sativa L.)-( Phleum pratense L.) mixture. The design and construction of these OTCs are described in detail, along with cost estimation for each component. Eight OTCs, each with 1.2 m 2 of ground area (four with elevated [CO 2] and four with ambient [CO 2]) were fabricated and four control plots of the same dimension were established to assess the chamber effects on plant responses to CO 2. The [CO 2] in elevated-CO 2 chambers fell 93% of the time within 20% of the targeted 600 mol mol -1 CO 2, based on 10 min averages. The CO 2 consumption in elevated-CO 2 chambers averaged 3.0 kg CO 2 m -2 d -1. To ensure that the environment within OTCs was similar to the surrounding field, growing conditions were determined in all chambers and control plots. Adequate light transmission was observed compared to control plots (93%) and the temperature increase was 0.7°C on average. After two growing seasons of continued use, this system has proven its effectiveness for studying the effects of CO 2 and climate change in the field at low cost.
  • Authors:
    • Niero,Monia
    • Ingvordsen,Cathrine H.
    • Peltonen-Sainio,Pirjo
    • Jalli,Marja
    • Lyngkjaer,Michael F.
    • Hauschild,Michael Z.
    • Jorgensen,Rikke B.
  • Source: Agricultural Systems
  • Volume: 136
  • Year: 2015
  • Summary: The paper has two main objectives: (i) to assess the eco-efficiency of spring barley cultivation for malting in Denmark in a future changed climate (700 ppm [CO2] and +5 degrees C) through Life Cycle Assessment (LCA) and (ii) to compare alternative future cultivation scenarios, both excluding and including earlier sowing and cultivar selection as measures of adaptation to a changed climate. A baseline scenario describing the current spring barley cultivation in Denmark was defined, and the expected main deviations were identified (differences in pesticide treatment index, modifications in nitrate leaching and change in crop yield). The main input data originate from experiments, where spring barley cultivars were cultivated in a climate phytotron under controlled and manipulated treatments. Effects of changed climate on both crop productivity and crop quality were represented, as well as impacts of predicted extreme events, simulated through a long heat-wave. LCA results showed that the changed climatic conditions will likely increase the negative impacts on the environment from Danish spring barley cultivation, since all environmental impact categories experienced increased impact for all investigated scenarios, except under the very optimistic assumption that the pace of yield improvement by breeding in the future will be the same as it was in the last decades. The main driver of the increased environmental impact was identified as the reduction in crop yield. Therefore, potential adaptation strategies should mainly focus on maintaining or improving crop productivity. The LCA also showed that selection of proper cultivars for future climate conditions including the challenge from extreme events is one of the most effective ways to reduce future environmental impacts of spring barley. Finally, if yield measurements are based on relative protein content, the negative effects of the future climate seem to be reduced. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Smith,E. G.
    • Janzen,H. H.
    • Larney,F. J.
  • Source: Canadian Journal of Soil Science
  • Volume: 95
  • Issue: 2
  • Year: 2015
  • Summary: Long-term cropping system studies offer insights into soil management effects on agricultural sustainability. In 1995, a 6-yr bioassay study was superimposed on a long-term crop rotation study established in 1951 at Lethbridge, Alberta, to determine the impact of past cropping systems on soil quality, crop productivity, grain quality, and the relationship of yield productivity to soil quality. All plots from 13 long-term crop rotations were seeded to wheat ( Triticum aestivum L.) in a strip plot design [control, nitrogen (N) fertilizer]. Prior to seeding, soils were sampled to determine soil chemical properties. Total wheat production for the last 4 yr of the study was used as the measure of productivity. The 1995 soil analysis indicated crop rotations with less frequent fallow and with N input had higher soil quality, as indicated by soil organic carbon (SOC) and light fraction carbon (LF-C) and N (LF-N). SOC had a positive relationship to total wheat yield, but was largely masked by the application of N in this bioassay study. Frequent fallow in the previous crop rotation lowered productivity. The concentration of LF-C had a negative relationship, whereas LF-N had a positive relationship to total wheat yield, with and without N fertilization in this bioassay study. Grain N concentration was higher with applied N and when the long-term rotation included the addition of N by fertilizer, livestock manure, annual legume green manure or legume hay. This study determined that long-term imposition of management practices have lasting effects on soil quality and crop productivity.
  • Authors:
    • Yoshida,H.
    • Nielsen,M. P.
    • Scheutz,C.
    • Jensen,L. S.
    • Christensen,T. H.
    • Nielsen,S.
    • Bruun,S.
  • Source: Acta Agriculturae Scandinavica, Section B — Soil & Plant Science
  • Volume: 65
  • Issue: 6
  • Year: 2015
  • Summary: Application of sewage sludge on agricultural land becomes more and more common in many parts of the world in order to recycle the nutrients from the sludge. A range of sewage sludge stabilization techniques are available to make the sludge more stable prior to storage, transportation, and application. These stabilization techniques include dewatering, drying, anaerobic digestion, composting, and reed bed sludge treatment. However, very few studies have investigated the effect of these techniques after the sludge has been applied to agricultural land. The objective of the current study was therefore to investigate the effect of sewage sludge stabilization techniques on the C and N mineralization and gaseous emissions from soil. A soil incubation was conducted to determine the rate of C and N mineralization and N 2O and CH 4 emissions of sewage sludge stabilized using different techniques. Unstabilized sludge released up to 90% of their C content as CO 2, part of which could be caused by release of CO 2 from carbonates. Compared with this, sludge stabilization including anaerobic digestion and drying resulted in a reduction of the C mineralization rate of about 40%. Liming reduced C mineralization with around 29%, while treatment in a reed bed system reduced it by 74%. The current study thus clearly demonstrated that stabilization techniques resulted in sludge that was more stable once they were applied to agricultural land. Stabilization also reduced the N immobilization phase, potentially improving the value of the sludge as a fertilizer. Emissions of CH 4 were also reduced through sludge stabilization and mainly occurred after application of easily degradable sludge types, which is likely to have enhanced the creation of anaerobic microsites. The stabilization processes also decreased emissions of N 2O. The results for both CH 4 and N 2O indicate that the stabilization tends to reduce the chance of developing conditions where these gases could be produced.
  • Authors:
    • Aldana Jague,E.
    • Sommer,M.
    • Saby,N. P. A.
    • Cornelis,J. -T
    • Van Wesemael,B.
    • Van Oost,K.
  • Source: Soil & Tillage Research
  • Volume: 156
  • Issue: 3
  • Year: 2015
  • Summary: The identification of soil management strategies as well as the evaluation of their effectiveness requires detailed information on the spatial and temporal patterns of soil organic carbon storage. High-resolution SOC profile data are generally not available and traditional methods for collecting these are time consuming and costly. Recent studies use geo-statistical approaches to assess the three-dimensional patterns of SOC storage. However, there is still a large discrepancy between the continuous and high resolution mapping of the horizontal SOC variability on the one hand, and the coarse and discontinuous mapping of the vertical SOC profile on the other. In this study, we combine spectroscopic techniques with spatial modeling in a small, cultivated catchment in Germany and we evaluate the contribution of soil redistribution processes and topographical parameters to the observed spatial and vertical patterns. Using high-resolution data from soil cores, we evaluated the robustness of a third order polynomial function to model the vertical SOC profile. Using a crossvalidation, our results show that this approach results in a robust model (RSME=0.24%) and performs better than the widely used exponential depth model (RMSE=0.39%). In a next step, we evaluated the relationship between the parameters of the SOC depth model and co-variables including soil redistribution (inferred from 137Cs data) and topographical indices using a multiple linear regression model. The performance was calculated by cross-validation and we found a low robustness of the models because of the low number of profiles (i.e. n =19). A statistical evaluation of the co-variables highlighted two key factors influencing the SOC vertical distribution. Soil redistribution processes mainly influenced the surface SOC content (first centimeters) whereas the shape of the depth distribution was controlled by slope curvature alone. The mapping of polynomial parameters was validated using an external SOC profile dataset and showed a poor prediction of the surface content but a good prediction of the depth distribution once the surface SOC content is known (RMSE=0.15-0.25%C). This suggests that estimating the vertical SOC profile from topsoil data by applying remote sensing data, in combination with our SOC profile model, is promising and can will result in an accurate mapping of 3D SOC patterns at a very high resolution. © 2015 Elsevier B.V.
  • Authors:
    • Huffman,T.
    • Liu JianGui
    • McGovern,M.
    • McConkey,B.
    • Martin,T.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 205
  • Year: 2015
  • Summary: Accurate estimation of greenhouse gas emissions and detailed monitoring of the carbon cycle are important for mitigation of and adaptation to climate change. On agricultural land, annual herbaceous vegetation is not considered a carbon sink, whereas perennial woody vegetation accumulates biomass over multiple years and does represent a carbon sink. This paper presents a study to estimate aboveground woody carbon stock in 1990 and its annual change from 1990 to 2000 on Canada's cropland. The cropland was stratified into zones according to soils, climate and cropping systems, within which sample plots were randomly selected and paired aerial photographs corresponding to circa 1990 and 2000 were interpreted to detect changes in perennial woody vegetation such as trees, shrubs, orchards and vineyards. Woody biomass volumes lost as a result of land use change and gained as a result of planting and growth were estimated using species composition and growth rates typical of each zone, as obtained from published literature, forest reports and charts and forestry expert knowledge. Census of agriculture data was used to scale up the sample level results to zone and national levels. Results showed that on Canada's cropland, the aboveground woody carbon stock in 1990 was 33.78.8 Tg. Between 1990 and 2000, the area covered by woody vegetation was affected negatively by removals and positively through planting and natural regeneration, leading to a net reduction in area. There was an annual increase of about 78.3 Gg over all cropland in Canada, with a net decrease in some ecozones. Although this is a comparatively small increase with a large uncertainty, it indicates that changes in woody carbon on cropland in Canada over the 1990-2000 period were relatively insignificant. Further studies may be needed to refine the carbon estimates and reduce uncertainties.
  • Authors:
    • Karki,S.
    • Elsgaard,L.
    • Kandel,T. P.
    • Lærke,P. E.
  • Source: Environmental Monitoring and Assessment
  • Volume: 187
  • Issue: 3
  • Year: 2015
  • Summary: Empirical greenhouse gas (GHG) flux estimates from diverse peatlands are required in order to derive emission factors for managed peatlands. This study on a drained fen peatland quantified the annual GHG balance (Carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and C exported in crop yield) from spring barley (SB) and reed canary grass (RCG) using static opaque chambers for GHG flux measurements and biomass yield for indirectly estimating gross primary production (GPP). Estimates of ecosystem respiration (ER) and GPP were compared with more advanced but costly and labor-intensive dynamic chamber studies. Annual GHG balance for the two cropping systems was 4.0 ± 0.7 and 8.1 ± 0.2 Mg CO2-Ceq ha(-1) from SB and RCG, respectively (mean ± standard error, n = 3). Annual CH4 emissions were negligible (<0.006 Mg CO2-Ceq ha(-1)), and N2O emissions contributed only 4-13 % of the full GHG balance (0.5 and 0.3 Mg CO2-Ceq ha(-1) for SB and RCG, respectively). The statistical significance of low CH4 and N2O fluxes was evaluated by a simulation procedure which showed that most of CH4 fluxes were within the range that could arise from random variation associated with actual zero-flux situations. ER measured by static chamber and dynamic chamber methods was similar, particularly when using nonlinear regression techniques for flux calculations. A comparison of GPP derived from aboveground biomass and from measuring net ecosystem exchange (NEE) showed that GPP estimation from biomass might be useful, or serve as validation, for more advanced flux measurement methods. In conclusion, combining static opaque chambers for measuring ER of CO2 and CH4 and N2O fluxes with biomass yield for GPP estimation worked well in the drained fen peatland cropped to SB and RCG and presented a valid alternative to estimating the full GHG balance by dynamic chambers.
  • Authors:
    • Knapp,A. K.
    • Hoover,D. L.
    • Wilcox,K. R.
    • Avolio,M. L.
    • Koerner,S. E.
    • Pierre,K. J. la
    • Loik,M. E.
    • Luo,Y. Q.
    • Sala,O. E.
    • Smith,M. D.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Climate change is intensifying the hydrologic cycle and is expected to increase the frequency of extreme wet and dry years. Beyond precipitation amount, extreme wet and dry years may differ in other ways, such as the number of precipitation events, event size, and the time between events. We assessed 1614 long-term (100 year) precipitation records from around the world to identify key attributes of precipitation regimes, besides amount, that distinguish statistically extreme wet from extreme dry years. In general, in regions where mean annual precipitation (MAP) exceeded 1000 mm, precipitation amounts in extreme wet and dry years differed from average years by ~40% and 30%, respectively. The magnitude of these deviations increased to >60% for dry years and to >150% for wet years in arid regions (MAP 99th percentile of all events); these occurred twice as often in extreme wet years compared to average years. In contrast, these large precipitation events were rare in extreme dry years. Less important for distinguishing extreme wet from dry years were mean event size and frequency, or the number of dry days between events. However, extreme dry years were distinguished from average years by an increase in the number of dry days between events. These precipitation regime attributes consistently differed between extreme wet and dry years across 12 major terrestrial ecoregions from around the world, from deserts to the tropics. Thus, we recommend that climate change experiments and model simulations incorporate these differences in key precipitation regime attributes, as well as amount into treatments. This will allow experiments to more realistically simulate extreme precipitation years and more accurately assess the ecological consequences.
  • Authors:
    • Kurganova,I.
    • Lopes de Gerenyu,V.
    • Kuzyakov,Y.
  • Source: Catena; ScienceDirect
  • Volume: 122
  • Year: 2015
  • Summary: Most land use changes (LUC) significantly affect the amount of carbon (C) sequestered in vegetation and soil, thereby, shifting the C balance in ecosystems. Disintegration of the USSR and the followed collapse of collective farming system have led to abandonment of more than 58millionha (Mha) of former croplands in Russia and Kazakhstan that comprise together about 90% of land area in the former USSR. This was the most widespread and abrupt LUC in the 20th century in the northern hemisphere. The spontaneous withdrawal of croplands in 1990s caused several benefits for environment including substantial C sequestration in post-agrogenic ecosystems. The new estimations of net ecosystem production (NEP) and changes in soil organic carbon stocks ({increment}SOC) in post-agrogenic ecosystems presented here are based on the uniform bio-climatic approach, and hereby, allow to update C balance of the former USSR. The total extra C sink in abandoned croplands in Russia (45.5Mha) and Kazakhstan (12.9Mha) is estimated to be 155±27MtCyr-1 and 31±2MtCyr-1, respectively. This additional C sink could cover about 18% of the global CO2 release due to deforestation and other land use changes or compensate annually about 36% and 49% of the current fossil fuel emissions in Russia and Kazakhstan, respectively. The extra C sink to the post-agrogenic ecosystems in Russia and Kazakhstan contributes possibly about 1/3 part to the total current C balance of the former USSR. Hence, the disintegration of the former USSR significantly affected national and global C budget over few decades after LUC. © 2015 Elsevier B.V.