• Authors:
    • Amiro, B. D.
    • Tenuta, M.
    • Glenn, A. J.
    • Maas, S. E.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 5
  • Year: 2013
  • Summary: The long-term use of perennial forages in crop rotations can increase soil carbon (C) and lower nitrous oxide (N2O) emissions compared with continuous annual cropping. However, less is known of the short-term (within 2 yr) benefit of inclusion of perennial forages in an annual crop rotation on net carbon dioxide (CO2) and N2O fluxes. Perennial forage, primarily composed of alfalfa (Medicago sativa L.) and a minor component of timothy grass (Phleum pretense L.) was sown in 2008 on two 4-ha plots previously in annual cropping in the Red River Valley, Manitoba. Spring wheat (Triticum aestivum L.) and industrial rapeseed (Brassica napus L.) were grown on two adjacent plots in 2008 and 2009, respectively. Carbon dioxide and N2O fluxes were measured continuously using the flux-gradient micrometeorological method from 2008 May 01 to 2010 Apr. 30. During the 2-yr study, the newly established perennial forage was nearly twice the sink for atmospheric CO2 (mean and standard deviation of 4480 +/- 1840 kg C ha(-1)) as the annual crops (2470 700 kg C ha(-1)). The annual crop emitted more than four times the N2O (7.8 +/- 0.7 kg N ha(-1)) as the perennial forage stand (1.8 +/- 0.7 kg N ha(-1)). When accounting for harvest C removals (grain, straw, hay) and considering the greenhouse gas (GHG) emissions in CO2-equivalents (eq.), the newly established perennial forage was a net sink of 8470 5640 kg CO2-eq. ha(-1) and the annual crop was a source of 3760 +/- 2450 kg CO2-eq. ha(-1) during the study. The results indicate an immediate reduction in soil GHG emissions with the inclusion of perennial forage in the rotation, primarily from reduced N2O emissions, the lack of crop removal in the forage establishment year and the longer growing season period of net CO2 uptake of the perennial crop.
  • Authors:
    • Zebarth, B.
    • Laganiere, J.
    • Angers, D. A.
    • Rochette, P.
    • Chantigny, M. H.
    • Pelster, D. E.
    • Goyer, C.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 4
  • Year: 2013
  • Summary: Freeze-thaw (FT) cycles stimulate soil nitrogen (N) and carbon (C) mineralization, which may induce nitrous oxide (N2O) emissions. We examined how soybean (Glycine max L.) and corn (Zea mays L.) residue incorporation affect N2O emissions from high C content (35 g kg(-1)) silty clay and low C content (19 g kg(-1)) sandy loam soils over eight 10-d FT cycles, as a function of three temperature treatments [constant at +1 degrees C (unfrozen control), +1 to -3 degrees C (moderate FT), or +1 to -7 degrees C (extreme FT)]. In unamended soils, N2O emissions were stimulated by FT, and were the highest with extreme FT. This was attributed to the increased NO3 availability measured under FT. Application of mature crop residues (C:N ratios of 75 for soybean and 130 for corn) caused rapid N immobilization, attenuating FT-induced N2O emissions in the silty clay. In the sandy loam, residue addition also induced immobilization of soil mineral N. However, N2O emissions under moderate FT were higher with than without crop residues, likely because N2O production in this low-C sandy loam was stimulated by C addition in the early phase of incubation. We conclude that FT-induced N2O emissions could be reduced through incorporation of mature crop residues and the subsequent immobilization of mineral N, especially in C-rich soils.
  • Authors:
    • Messier, C.
    • Olivier, A.
    • Lorente, M.
    • Rivest, D.
  • Source: Science of the Total Environment
  • Volume: 463-464
  • Year: 2013
  • Summary: Agroforestry is increasingly viewed as an effective means of maintaining or even increasing crop and tree productivity under climate change while promoting other ecosystem functions and services. This study focused on soil biochemical properties and resilience following disturbance within agroforestry and conventional agricultural systems and aimed to determine whether soil differences in terms of these biochemical properties and resilience would subsequently affect crop productivity under extreme soil water conditions. Two research sites that had been established on agricultural land were selected for this study. The first site included an 18-year-old windbreak, while the second site consisted in an 8-year-old tree-based intercropping system. In each site, soil samples were used for the determination of soil nutrient availability, microbial dynamics and microbial resilience to different wetting drying perturbations and for a greenhouse pot experiment with wheat. Drying and flooding were selected as water stress treatments and compared to a control. These treatments were initiated at the beginning of the wheat anthesis period and maintained over 10 days. Trees contributed to increase soil nutrient pools, as evidenced by the higher extractable-P (both sites), and the higher total N and mineralizable N (tree-based intercropping site) found in the agroforestry compared to the conventional agricultural system. Metabolic quotient (qCO(2)) was lower in the agroforestry than in the conventional agricultural system, suggesting higher microbial substrate use efficiency in agroforestry systems. Microbial resilience was higher in the agroforestry soils compared to soils from the conventional agricultural system (windbreak site only). At the windbreak site, wheat growing in soils from agroforestry system exhibited higher aboveground biomass and number of grains per spike than in conventional agricultural system soils in the three water stress treatments. At the tree-based intercropping site, higher wheat biomass, grain yield and number of grains per spike were observed in agroforestry than in conventional agricultural system soils, but in the drought treatment only. Drought (windbreak site) and flooding (both sites) treatments significantly reduced wheat yield and 1000-grain weight in both types of system. Relationships between soil biochemical properties and soil microbial resilience or wheat productivity were strongly dependent on site. This study suggests that agroforestry systems may have a positive effect on soil biochemical properties and microbial resilience, which could operate positively on crop productivity and tolerance to severe water stress.
  • Authors:
    • Qian, B.
    • Li, C.
    • Kroebel, R.
    • Desjardins, R. L.
    • Grant, B. B.
    • Smith, W. N.
    • Worth, D. E.
    • McConkey, B. G.
    • Drury, C. F.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 179
  • Year: 2013
  • Summary: Regions in northern latitudes are likely to be strongly affected by climate change with shifts in weather that may be conducive to increased agricultural productivity. In this study the DNDC model was used to assess the effect of climate change on crop production and GHG emissions at long-term experimental sites in Canada. Crop production in the model was parameterized using measured data, and then simulations were performed using historical weather (1961-1990) and future IPCC SRES climate scenarios (2040-2069). The DNDC model predicted that for western Canada under the SRES scenarios and no change in cultivar, yields of spring wheat would increase by 37% and winter wheat by 70%. Corn responded favorably to an increase in heat units at the eastern site with a 60% increase in yields. At all locations, yields were projected to increase further when new cultivars with higher GDD requirements were assumed. These increases were notable considering that the estimated soil water deficit indices indicated that there could be less water available for crop growth in the future. However, when accounting for increased water use efficiency under elevated CO2, DNDC predicted less crop water stress. Nitrous oxide emissions per ton of wheat were projected to increase across most of western Canada by about 60% on average for the A1b and A2 SRES scenarios and by about 30% for the B1 scenario. Nitrous oxide emissions per unit area were predicted to increase under corn production at the eastern location but to remain stable per ton of grain. Model results indicated that climate change in Canada will favor increased crop production but this may be accompanied by an increase in net GHG emissions for small grain production.
  • Authors:
    • Fraser, T. J.
    • Amiro, B. D.
    • Taylor, A. M.
  • Source: Agricultural and Forest Meteorology
  • Volume: 182-183
  • Year: 2013
  • Summary: Eddy covariance flux towers were used to measure net ecosystem production over three adjacent agricultural fields in Manitoba, Canada, from 2009 to 2011. Two fields were converted from long-term perennial hay/pasture to annual cropping, while the third field served as a control field that was maintained as hay/pasture. One converted field had a rotation of oat-canola-oat crops, while the second was hay-oat-fallow. Weather was an important driver of inter-annual variability, with poor yields on all fields in 2011 because of dry conditions in summer, with the summer-fallow condition on one field caused by excess spring moisture not allowing planting. The cumulative net ecosystem production of the oat-canola-oat field showed a net CO2 emission of 100 g Cm-2, the hay-oat-fallow field emitted 500 g Cm-2, and the hay field gained 550 g C m(-2) by the end of the 30-month study period. The hay field had the highest cumulative gross primary production of 2500 g C m(-2), whereas the oat-canola-oat and hay-oat-fallow fields had only about 1400 g C m(-2). The perennial field had the advantage of both early- and late-season growth when crops were absent on the other fields. The hay and hay-oat-fallow fields had comparable cumulative ecosystem respiration (1400 g Cm-2). Manure additions contributed 300 g C m(-2) on the two converted fields. With harvest exports and manure additions included, the oat-canola-oat field was a carbon source of 240 g Cm-2, the hay-oat-fallow field was a source of 415 g C m(-2), and the hay/pasture field was a sink of 120 g C m(-2) over the 30-month period.
  • Authors:
    • Thomas,Amy R. C.
    • Bond,Alan J.
    • Hiscock,Kevin M.
  • Source: Global Change Biology Bioenergy
  • Volume: 5
  • Issue: 3
  • Year: 2013
  • Summary: Reduction in energy sector greenhouse gas GHG emissions is a key aim of European Commission plans to expand cultivation of bioenergy crops. Since agriculture makes up 1012% of anthropogenic GHG emissions, impacts of land-use change must be considered, which requires detailed understanding of specific changes to agroecosystems. The greenhouse gas (GHG) balance of perennials may differ significantly from the previous ecosystem. Net change in GHG emissions with land-use change for bioenergy may exceed avoided fossil fuel emissions, meaning that actual GHG mitigation benefits are variable. Carbon (C) and nitrogen (N) cycling are complex interlinked systems, and a change in land management may affect both differently at different sites, depending on other variables. Change in evapotranspiration with land-use change may also have significant environmental or water resource impacts at some locations. This article derives a multi-criteria based decision analysis approach to objectively identify the most appropriate assessment method of the environmental impacts of land-use change for perennial energy crops. Based on a literature review and conceptual model in support of this approach, the potential impacts of land-use change for perennial energy crops on GHG emissions and evapotranspiration were identified, as well as likely controlling variables. These findings were used to structure the decision problem and to outline model requirements. A process-based model representing the complete agroecosystem was identified as the best predictive tool, where adequate data are available. Nineteen models were assessed according to suitability criteria, to identify current model capability, based on the conceptual model, and explicit representation of processes at appropriate resolution. FASSET, ECOSSE, ANIMO, DNDC, DayCent, Expert-N, Ecosys, WNMM and CERES-NOE were identified as appropriate models, with factors such as crop, location and data availability dictating the final decision for a given project. A database to inform such decisions is included.
  • Authors:
    • Chang, S. X.
    • Wang, S.
    • Jia, Z.
    • Wu, F.
    • Startsev, A.
  • Source: Biology and Fertility of Soils
  • Volume: 49
  • Issue: 5
  • Year: 2013
  • Summary: Biochar produced from plant biomass through pyrolysis has been shown to be much more resistant to biodegradation in the soil as compared with the raw biomass, such as cereal straw that is routinely shredded and discharged on to farm fields in large amounts. Biochar application to soil has also been reported to decrease greenhouse gas (GHG) emissions, although the mechanisms are not fully understood. In this study, the emissions of three main GHGs (CO2, CH4, and N2O) and enzyme activities (urease, beta-glycosidase, and dehydrogenase) were measured during a 100-day laboratory incubation of a Chernozemic soil amended with either straw or its biochar at rates of 0.67 and 1.68 % (based on the amount of C added) for the low and high rates, respectively. The biochar application dramatically reduced N2O emissions, but CO2 or CH4 emissions were not different, as compared with the un-amended soil. At the same C equivalent application rate, CO2 and N2O emission rates were greater while CH4 emission rates were lower in straw than in biochar application treatments. The activities of both the dehydrogenase and beta-glycosidase significantly declined while that of urease significantly increased with the biochar as compared with the straw treatment. We conclude that pyrolysis of cereal straw prior to land application would significantly reduce CO2 and N2O emissions, in association with changed enzyme activities, while increasing the soil C pool through the addition of stable C in the form of biochar.
  • Authors:
    • Nyiraneza, J.
    • Gagnon, B.
    • Ziadi, N.
  • Source: Canadian Journal of Soil Science
  • Volume: 93
  • Issue: 3
  • Year: 2013
  • Summary: Les biosolides papetiers (BP) en combinaison avec les residus industriels alcalins pourraient beneficier aux sols agricoles tout en les detournant des sites d'enfouissement. Une etude en serre a ete menee afin d'evaluer l'effet de trois types de BP a des taux de 0,30, et 60 Mg humide ha(-1), ainsi que cinq sous-produits chaulants a 3 Mg humide ha(-1) avec 30 Mg BP ha(-1) stir le rendement des cultures, l'accumulation des elements nutritifs et les proprietes du sol. Des biosolides de desencrage (BD, C/N de 65) ont ete appliques au soya [Glycine max (L.) Merr.], et deux BP mixtes (BPI, C/N de 31; et BP2, C/N de 14) ont ete appliqu s a du haricot sec (Phaseolus vulgaris L.) et de l'orge (Hordettm vulgare L.), respectivement. Les sous-produits chaulants incluaient des boues de chaux (BC), des cendres de bois de papetieres, de la chaux calcique commerciale (CC), des sous-produits de dissolution magnesien, et des residus de Mg provenant du travail de la fonte et d'electrolyse (MgFE). Par rapport au temoin, BP2 a augment& le rendement de l'orge et l'accumulation totale en Mg et Na, et les deux BP ont augmente l'accumulation du N, P et Ca dans les plants d'orge et de haricot. L'impact des BD sur le soya a ete limite. L'ajout de sous-produits chaulants a BD ou BP n'a pas eu d'incidence sur les parametres culturaux a l'exception de la combinaison avec MgFE qui a fortement reduit la croissance du haricot sec et, dans une moindre mesure, le soya. Le NO3-N du sol a ete immobilise suite a l'application de BD alors qu'il y a eu un relachement net avec les deux BP. La combinaison BP et sous-produits chaulants a produit les plus grands changements dans les proprietes du sol a la recolte. En regle generale, BC et CC ont augmente le pH et le Ca extrait au Mehlich-3, et MgFE a cause une forte augmentation du Mehlich-3 Mg et Na et du Cl soluble a l'eau. Lorsqu'ils sont utilises avec des cultures appropriees, les biosolides de papetieres et les residus alcalins autres que MgFE peuvent ameliorer efficacement la fertilite des sols en fournissant du C organique et des elements nutritifs majeurs pour equilibrer la fertilisation des cultures.
  • Authors:
    • Sheng,Min
    • Lalande,Roger
    • Hamel,Chantal
    • Ziadi,Noura
  • Source: Web Of Knowledge
  • Volume: 369
  • Issue: 1-2
  • Year: 2013
  • Summary: Evidence shows that tillage modifies soil properties, especially phosphorus (P) dynamics. Our objective was to disentangle long-term effects of P-fertilization and tillage on arbuscular mycorrhizal fungal (AMF) proliferation and community structure. Changes in the community structure of AMF and in the density of their hyphae and spores induced by moldboard plow (MP) or no till (NT), and fertilization with 0, 17.5, or 35 kg P ha(-1) were sought in the 0-15 cm and 15-30 cm soil layers after soybean harvest, at a long-term (17 years) experimental site in a humid continental zone of eastern Canada. The relationships among AMF, soil and plant attributes were examined. The 0-15 cm and 15-30 cm soil layers had different properties under NT, but were similar under MP, after 17 years, and MP increased soil available P levels. Phosphorus fertilization increased P levels in soil and in soybean. Treatment effects on AMF spore and hyphal density at 0-15 cm were greater than that at 15-30 cm, whereas effects on AMF community structure did not change with soil depths. At 0-15 cm, P-fertilization increased AMF spore density and reduced AMF hyphal density, and MP reduced AMF spore density. A total of eight AMF phylotypes were detected. Phosphorus fertilization reduced AMF phylotype richness and Shannon diversity index. Soil P availability increased under MP and hence the influence of P-fertilization treatments on the frequency of AMF phylotype detection varied with tillage system; it declined with P-fertilization under MP, but increased under NT. Phosphorus fertilization shifts resource partitioning in AMF propagules rather than in their hyphae, and degrades the genetic diversity of AMF in soil; tillage increases soil P availability and hence aggravates the impact of P-fertilization.
  • Authors:
    • Williams,Terry
    • Hardison,Preston
  • Source: Climatic Change
  • Volume: 120
  • Issue: 3
  • Year: 2013
  • Summary: Traditional knowledge is increasingly recognized as valuable for adaptation to climate change, bringing scientists and indigenous peoples together to collaborate and exchange knowledge. These partnerships can benefit both researchers and indigenous peoples through mutual learning and mutual knowledge generation. Despite these benefits, most descriptions focus on the social contexts of exchange. The implications of the multiple cultural, legal, risk-benefit and governance contexts of knowledge exchange have been less recognized. The failure to consider these contexts of knowledge exchange can result in the promotion of benefits while failing to adequately address adverse consequences. The purpose of this article is to promote awareness of these issues to encourage their wider incorporation into research, policy, measures to implement free, prior and informed consent (FPIC) and the development of equitable adaptation partnerships between indigenous peoples and researchers.