• Authors:
    • Young, M. A.
    • Roy, J. L.
    • Bekele, A.
  • Source: Soil Science
  • Volume: 178
  • Issue: 7
  • Year: 2013
  • Summary: Topsoil (TS) shortage often limits the successful reclamation of older mined sites. We evaluated the effectiveness of one-time application of biochar or oxidized lignite (humalite) alone or in combination with a mix of conventional organic materials to reconstruct functioning TS using subsoil (SS) as a substrate. Biochar or humalite carbon (C) represented a stable form of C, whereas C from a mix of sawdust, wheat straw, and alfalfa (labile organic mix (LOM)) represented the labile C fraction. The amount and composition of organic amendment mix were determined so that organic C levels of reconstructed TS would be equivalent to that of the native TS in the long-term. Three SS substrates differing in texture (clay, loam, and sand) and organic C levels were used in the study. We used field pea (Pisum sativum L.) and barley (Hordeum vulgare L.) as test crops in rotation in four sequential greenhouse studies. All treatments except the control SS and TS received supplemental fertilizer nutrients. Plant biomass yield and tissue concentrations were evaluated at the end of each study, whereas soil nutrient levels were assessed at the end of Study II and Study IV. Labile organic mix amendment alone was superior in biomass production relative to any of the other treatments at the early stages of the study. Cumulative biomass yield of SS amended with either biochar or humalite in the presence of LOM was statistically identical for clay and sand soils. These values were also statistically indistinguishable from the fertilized native TS control treatment for the clay soil but not for the sand soil. Humalite application at a high rate (76 g/kg soil) increased soil CEC, decreased soil pH and P concentration, and increased both soil and plant tissue B concentrations. Our data show that a functioning TS can be reconstructed using either biochar or humalite in the presence of LOM and adequate supplemental fertilizers particularly N and P. Detailed characterization of organic amendments is recommended to avoid undesirable effects emanating from their use. Field-based long-term studies are needed to confirm the longevity of benefits of using these amendments.
  • Authors:
    • Stevenson, F. C.
    • Vanasse, A.
    • Legere, A.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 3
  • Year: 2013
  • Summary: Combining low-input systems with conservation tillage may be feasible for field crops under northeastern conditions. This study compared the effects of herbicide-free (HF), organic (ORG), conventional (CONV), and herbicide-tolerant (GM) cropping systems applied to three 20 yr-old tillage treatments (MP, moldboard plow; CP, chisel plow; NT, no-till) on weed biomass and crop productivity in a 4-yr barley ( Hordeum vulgare L.)-red clover ( Trifolium pratense L.)-corn ( Zea mays L.)-soybean [ Glycine max (L.) Merr.] rotation. Barley yield (4.5 Mg ha -1), and red clover forage yield (two cuts: 5.3 Mg ha -1) were similar across treatments. With MP and CP tillage, silage corn yield for CONV and GM systems (15 Mg ha -1) was 25% greater than for HF and ORG (11 Mg ha -1), whereas HF-NT and ORG-NT systems produced no harvestable yield. Soybean yield for HF-MP and ORG-MP systems was similar to that for CONV and GM (2.4 Mg ha -1), whereas yield in for the HF and ORG systems with CP and NT was half or less than for other treatments. Some form of primary tillage (CP or MP) was needed in corn and soybean to achieve adequate weed control and yield in the ORG and HF systems. Midseason weed proportion of total biomass was greater in the HF and ORG systems with CP and NT, and provided good yield prediction in corn ( R2=0.74) and soybean ( R2=0.84). Nutrient availability appeared adequate in corn following N 2-fixing red clover but limiting in NT and CP for soybean following corn. Improving crop sequence, fertilization, and weed management will be key to the adoption of low-input systems using conservation tillage practices in cool, humid climates.
  • Authors:
    • Jayet, P.-A.
    • Castell, J.-F.
    • Szopa, S.
    • Clerino, P.
    • Leconte-Demarsy, D.
    • Humblot, P.
  • Source: ECOLOGICAL ECONOMICS
  • Volume: 85
  • Year: 2013
  • Summary: As a result of anthropogenic activities, ozone is produced in the surface atmosphere, causing direct damage to plants and reducing crop yields. By combining a biophysical crop model with an economic supply model we were able to predict and quantify this effect at a fine spatial resolution. We applied our approach to the very varied French case and showed that ozone has significant productivity and land-use effects. A comparison of moderate and high ozone scenarios for 2030 shows that wheat production may decrease by more than 30% and barley production may increase by more than 14% as surface ozone concentration increases. These variations are due to the direct effect of ozone on yields as well as to modifications in land use caused by a shift toward more ozone-resistant crops: our study predicts a 16% increase in the barley-growing area and an equal decrease in the wheat-growing area. Moreover, mean agricultural gross margin losses can go as high as 2.5% depending on the ozone scenario, and can reach 7% in some particularly affected regions. A rise in ozone concentration was also associated with a reduction of agricultural greenhouse gas emissions of about 2%, as a result of decreased use of nitrogen fertilizers. One noteworthy result was that major impacts, including changes in land use, do not necessarily occur in ozone high concentration zones, and may strongly depend on farm systems and their adaptation capability. Our study suggests that policy makers should view ozone pollution as a major potential threat to agricultural yields. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Laerke, P. E.
    • Elsgaard, L.
    • Kandel, T. P.
  • Source: GCB Bioenergy
  • Volume: 5
  • Issue: 5
  • Year: 2013
  • Summary: Cultivation of bioenergy crops has been suggested as a promising option for reduction of greenhouse gas (GHG) emissions from arable organic soils (Histosols). Here, we report the annual net ecosystem exchange (NEE) fluxes of CO2 as measured with a dynamic closed chamber method at a drained fen peatland grown with reed canary grass (RCG) and spring barley (SB) in a plot experiment (n=3 for each cropping system). The CO2 flux was partitioned into gross photosynthesis (GP) and ecosystem respiration (R-E). For the data analysis, simple yet useful GP and R-E models were developed which introduce plot-scale ratio vegetation index as an active vegetation proxy. The GP model captures the effect of temperature and vegetation status, and the R-E model estimates the proportion of foliar biomass dependent respiration (R-fb) in the total R-E. Annual R-E was 1887 +/- 7 (mean +/- standard error, n=3) and 1288 +/- 19g CO2-Cm-2 in RCG and SB plots, respectively, with R-fb accounting for 32 and 22% respectively. Total estimated annual GP was -1818 +/- 42 and -1329 +/- 66g CO2-Cm-2 in RCG and SB plots leading to a NEE of 69 +/- 36g CO2-C m(-2)yr(-1) in RCG plots (i.e., a weak net source) and -41 +/- 47g CO2-C m(-2)yr(-1) in SB plots (i.e., a weak net sink). Standard errors related to spatial variation were small (as shown above), but more significant uncertainties were related to the modelling approach for establishment of annual budgets. In conclusion, the bioenergy cropping system was not more favourable than the food cropping system when looking at the atmospheric CO2 emissions during cultivation. However, in a broader GHG life-cycle perspective, the lower fertilizer N input and the higher biomass yield in bioenergy cropping systems could be beneficial.
  • Authors:
    • Osborne, B.
    • Richards, M.
    • Khalil, M. I.
    • Williams, M.
    • Mueller, C.
  • Source: Atmospheric Environment
  • Volume: 81
  • Issue: December
  • Year: 2013
  • Summary: Model simulations of C and N dynamics, based on country-specific agricultural and environmental conditions, can provide information for compiling national greenhouse gas (GHG) inventories, as well as insights into potential mitigation options. A multi-pool dynamic model, `ECOSSE' (v5 modified), was used to simulate coupled GHGs and soil organic carbon (SOC) stock changes. It was run for an equivalent time frame of 8 years with inputs from conventionally-tilled arable land cropped with spring barley receiving N fertilizer as calcium ammonium nitrate at 135-159 kg N ha(-1) and crop residues (3 t ha-1 yr-1). The simulated daily N2O fluxes were consistent with the measured values, with R-2 of 033 (p < 0.05) and the total error and bias differences were within 95% confidence levels. The measured seasonal N2O losses were 0.39-0.60% of the N applied, with a modelled estimate of 0.23-0.41%. In contrast, the measured annual N2O loss (integrated) was 0.35% and the corresponding simulated value of 0.45% increased to 0.59% when the sum of the daily fluxes was taken into account. This indicates intermittent gas samplings may miss the peak fluxes. On an 8-year average the modelled N2O emission factor (EF) was 0.53 0.03%. The model successfully predicted the daily heterotrophic respiration (RH), with an R-2 of 0.45 (p <0.05) and the total error and bias differences were within the 95% confidence intervals. The simulated and measured total RH (3149 versus 3072 kg C ha(-1) yr(-1)) was within the cropland average values previously reported. The total measured CH4 fluxes indicated that the unfertilized treatments were a small source (-2.29 g C ha(-1) yr(-1)), whilst the fertilized treatments were a sink (+3.64). In contrast, the simulated values suggested a sink (26.61-31.37 g C ha(-1) yr(-1)), demonstrating fertilizer-induced decreases in CH4 oxidation. On average, based on the simulated SOC content a loss of 516 kg C ha(-1) yr(-1) was indicated, which is within the uncertainty range for temperate regions. Results suggest that the model is suitable for estimating the GHG balance of arable fields. However, further refinements and analyses to fully determine and narrow down the uncertainty ranges for GHG estimates are required. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Armstrong, R.
    • Norton, R.
    • Chen, D.
    • Lam, S. K.
  • Source: Plant and Soil
  • Volume: 364
  • Issue: 1-2
  • Year: 2013
  • Summary: This study investigated the residual contribution of legume and fertilizer nitrogen (N) to a subsequent crop under the effect of elevated carbon dioxide concentration ([CO2]). Field pea (Pisum sativum L.) was labeled in situ with N-15 (by absorption of a N-15-labeled urea solution through cut tendrils) under ambient and elevated (700 mu mol mol(-1)) [CO2] in controlled environment glasshouse chambers. Barley (Hordeum vulgare L.) and its soil were also labeled under the same conditions by addition of N-15-enriched urea to the soil. Wheat (Triticum aestivum L.) was subsequently grown to physiological maturity on the soil containing either N-15-labeled field pea residues (including N-15-labeled rhizodeposits) or N-15-labeled barley plus fertilizer N-15 residues. Elevated [CO2] increased the total biomass of field pea (21 %) and N-fertilized barley (23 %), but did not significantly affect the biomass of unfertilized barley. Elevated [CO2] increased the C:N ratio of residues of field pea (18 %) and N-fertilized barley (19 %), but had no significant effect on that of unfertilized barley. Elevated [CO2] increased total biomass (11 %) and grain yield (40 %) of subsequent wheat crop regardless of rotation type in the first phase. Irrespective of [CO2], the grain yield and total N uptake by wheat following field pea were 24 % and 11 %, respectively, higher than those of the wheat following N-fertilized barley. The residual N contribution from field pea to wheat was 20 % under ambient [CO2], but dropped to 11 % under elevated [CO2], while that from fertilizer did not differ significantly between ambient [CO2] (4 %) and elevated [CO2] (5 %). The relative value of legume derived N to subsequent cereals may be reduced under elevated [CO2]. However, compared to N fertilizer application, legume incorporation will be more beneficial to grain yield and N supply to subsequent cereals under future (elevated [CO2]) climates.
  • Authors:
    • Shahamat, E. Z.
    • Salehi, M.
    • Taki, M.
    • Mobtaker, H. G.
  • Source: AGRICULTURAL ENGINEERING INTERNATIONAL CIGR JOURNAL
  • Volume: 15
  • Issue: 4
  • Year: 2013
  • Summary: The nonparametric method of data envelopment analysis (DEA) was used to investigate the energy efficiency and CO 2 emission of barley farm in Hamedan province of Iran. The method was used based on eight energy inputs including human labor, machinery, diesel fuel, fertilizers, farmyard manure, biocide, electricity and seed energy and single output of barley yield and technical, pure technical, scale and cross efficiencies were calculated using CCR and BCC models. The results showed that the average values of technical, pure technical and scale efficiency scores of farmers were 0.788, 0.941 and 0.833, respectively. Also, energy saving target ratio for barley production was calculated as 11.45%, indicating that by following the recommendations of this study, about 2,865 MJ ha -1 of total input energy could be saved with the same constant level of barley yield. Moreover the contribution of chemical fertilizer input from total saving energy was 34.88% which was the highest share followed by diesel fuel (25.88%) and electricity (20.89%) energy inputs. On one hand, optimization of energy use improved the energy use efficiency, energy productivity and net energy by 12.94%, 15.55% and 6.16%, respectively. On the other hand, total greenhouse gases (GHG) emission was 885.56 kg CO 2eq ha -1, which indicated that, the total CO 2 emissions can be reduced by 11.06%.
  • Authors:
    • Robertson, F.
    • Nash, D.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 165
  • Year: 2013
  • Summary: The extent to which soil C storage can be increased in Australian agricultural soils by adoption of improved management practices is poorly understood. There is a pressing need for such information in order to evaluate the potential for soil C sequestration to offset greenhouse gas emissions. In this study we used the RothC model to assess whether soil C accumulation under cropping using stubble retention and pasture rotations could be a significant offset for greenhouse gas emissions. We chose eight regions to represent the climatic range of the Victorian cropping industry: Walpeup, Birchip, Horsham, Bendigo, Rutherglen, Lismore, Bairnsdale and Hamilton (annual rainfall 330-700 mm). For each region, we chose two representative soil types, varying in clay and total organic C contents. For each region x soil combination, we compared the effects of five rotations: Canola-wheat-pulse-barley (C-W-P-B); Canola-wheat-triticale (C-W-T); Canola-wheat-barley-5 year perennial pasture (C-W-B-Pt5); Canola-wheat-fallow (C-W-F) and Continuous pasture (Pt). We compared the cropping rotations with cereal stubble burnt and with cereal stubble retained and, for two regions, with cereal stubble grazed by sheep. The results of the simulations showed that, across all scenarios, the equilibrium C density varied between 19 and 135 t C/ha to 300 mm depth, with potential soil C change being strongly influenced by crop yield, crop rotation, climate, initial soil C content, stubble management and continuity of management The simulations suggested that soil C stocks could be increased under a crop-pasture rotation (C-W-B-Pt5) with stubble retention, with rates of increase of 0.3-0.9 t C/ha yr over 25 years. If all of Victoria's cropland were converted to C-W-B-Pt5 rotation with stubble retention, and if 50% of the modelled potential C change were achieved, this would represent 3.0-4.5 MtCO(2)-e/year, equivalent to 2.5-3.7% of Victoria's greenhouse emissions. Less C accumulation would be possible under continuous cropping with stubble retention; even using the most conservative rotation (C-W-T) rates of C change varied from loss of 0.3 t C/ha yr to accumulation of 0.5 t C/ha yr over 25 years. If all of Victoria's cropland were converted to C-W-T rotation with stubble retention, and if 50% of the modelled potential C change were achieved, this would be equivalent to 0.8-2.3 MtCO(2)-e/year, or 0.7-1.9% of Victoria's greenhouse emissions. It would generally take 10-25 years for the soil C changes to become measurable using conventional soil sampling and analytical methods. Thus we conclude that, with current technology, the potential for significant and verifiable soil C accumulation in Victoria's croplands is limited.
  • Authors:
    • Liu, S. G.
    • Tan, Z. X.
  • Source: Applied and Environmental Soil Science
  • Volume: 2013
  • Issue: 2013
  • Year: 2013
  • Summary: Terrestrial carbon (C) sequestration through optimizing land use and management is widely considered a realistic option to mitigate the global greenhouse effect. But how the responses of individual ecosystems to changes in land use and management are related to baseline soil organic C (SOC) levels still needs to be evaluated at various scales. In this study, we modeled SOC dynamics within both natural and managed ecosystems in North Dakota of the United States and found that the average SOC stock in the top 20 cm depth of soil lost at a rate of 450 kg C ha -1 yr -1 in cropland and 110 kg C ha -1 yr -1 in grassland between 1971 and 1998. Since 1998, the study area had become a SOC sink at a rate of 44 kg C ha -1 yr -1. The annual rate of SOC change in all types of lands substantially depends on the magnitude of initial SOC contents, but such dependency varies more with climatic variables within natural ecosystems and with management practices within managed ecosystems. Additionally, soils with high baseline SOC stocks tend to be C sources following any land surface disturbances, whereas soils having low baseline C contents likely become C sinks following conservation management.
  • 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.