• Authors:
    • Domene, X.
    • Alcaniz, J. M.
    • Marks, E. A. N.
  • Source: Regular Article
  • Volume: 385
  • Issue: 1-2
  • Year: 2014
  • Summary: Background and aims Biochar has demonstrably improved crop yields in weathered and acidic soils, but studies in calcareous soils are particularly lacking, so biochar effects on plant growth was investigated under these conditions. Methods Six biochars were obtained from different feedstocks and production technologies. Chemical characterization of fresh biochars included total and extractable nutrients, labile carbon, and Fourier transform infrared spectroscopy. Extractable nutrients were also evaluated in biochar-soil mixtures with a basic (pH >8.2) test soil. Bioassays with lettuce and ryegrass were carried out to relate biochar chemical properties to effects on plant biomass. Results A sewage sludge slow pyrolysis char was stimulatory to plant growth, as was a slow pyrolysis pine wood char at an intermediate concentration, while gasification and fast-pyrolysis pine and poplar wood chars were strongly inhibitory, with reductions in biomass at realistic application rates of 519 t ha(-1). Conclusions Statistical comparison of plant responses with biochar composition led to the assessment that plant responses were most correlated with volatile matter content and total P content, whose availability was likely regulated by pH and Ca content. Potential effects of phytotoxins were considered, but these were seen to be much less probable than effects due to nutrient availability.
  • Authors:
    • Siegfried, W.
    • Rohr, C.
    • Riemann, D.
    • Retso, D.
    • Pribyl, K.
    • Nordl, O.
    • Litzenburger, L.
    • Limanowka, D.
    • Labbe, T.
    • Kotyza, O.
    • Kiss, A.
    • Himmelsbach, I.
    • Glaser, R.
    • Dobrovolny, P.
    • Contino, A.
    • Camenisch, C.
    • Burmeister, K.
    • Brazdil, R.
    • Bieber, U.
    • Barriendos, M.
    • Alcoforado, M.
    • Luterbacher, J.
    • Gruenewald, U.
    • Herget, J.
    • Seneviratne, S.
    • Wagner, S.
    • Zorita, E.
    • Werner, J.
    • Pfister, C.
    • Wetter, O.
    • Soderberg, J.
    • Spring, J.
  • Source: Climatic Change
  • Volume: 125
  • Issue: 3-4
  • Year: 2014
  • Summary: The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring-summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km(2), we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models.
  • Authors:
    • Rappaport, A. G.
    • Mitra, S.
    • Francis, B.
    • Harris, R.
    • Thomson, A. M.
    • Reeves, J. B.
    • Ebinger, M. H.
    • Wielopolski, L.
    • Rice, C. W.
    • Izaurralde, R. C.
    • Etchevers, J. D.
    • Sayre, K. D.
    • Govaerts, B.
    • McCarty, G. W.
  • Source: PLOS ONE
  • Volume: 8
  • Issue: 1
  • Year: 2013
  • Summary: Three advanced technologies to measure soil carbon (C) density (g C m -2) are deployed in the field and the results compared against those obtained by the dry combustion (DC) method. The advanced methods are: (a) Laser Induced Breakdown Spectroscopy (LIBS), (b) Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS), and (c) Inelastic Neutron Scattering (INS). The measurements and soil samples were acquired at Beltsville, MD, USA and at Centro International para el Mejoramiento del Maiz y el Trigo (CIMMYT) at El Batan, Mexico. At Beltsville, soil samples were extracted at three depth intervals (0-5, 5-15, and 15-30 cm) and processed for analysis in the field with the LIBS and DRIFTS instruments. The INS instrument determined soil C density to a depth of 30 cm via scanning and stationary measurements. Subsequently, soil core samples were analyzed in the laboratory for soil bulk density (kg m -3), C concentration (g kg -1) by DC, and results reported as soil C density (kg m -2). Results from each technique were derived independently and contributed to a blind test against results from the reference (DC) method. A similar procedure was employed at CIMMYT in Mexico employing but only with the LIBS and DRIFTS instruments. Following conversion to common units, we found that the LIBS, DRIFTS, and INS results can be compared directly with those obtained by the DC method. The first two methods and the standard DC require soil sampling and need soil bulk density information to convert soil C concentrations to soil C densities while the INS method does not require soil sampling. We conclude that, in comparison with the DC method, the three instruments (a) showed acceptable performances although further work is needed to improve calibration techniques and (b) demonstrated their portability and their capacity to perform under field conditions.
  • Authors:
    • Ganeshan, V.
    • Pramanik, P.
    • Das, T. K.
    • Bhattacharyya, R.
    • Saad, A. A.
    • Sharma, A. R.
  • Source: Web Of Knowledge
  • Volume: 96
  • Issue: 2-3
  • Year: 2013
  • Summary: We evaluated impacts of conservation agriculture (zero tillage, bed planting and residue retention) on changes in total soil N (TSN) and aggregate-associated N storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum) and wheat (Triticum aestivum) crops were grown during the first 3 years (2008-2011) and in the last year, maize (Zea mays) and wheat were cultivated. Results indicate that after 4 years the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had 15 % higher TSN concentrations than conventional tillage and bed planting plots (CT-B) (0.63 g kg(-1) soil) in the 0-5 cm soil layer. CT-B plots had lower soil bulk density that ZT plots in that layer. Plots under ZT-B (0.57 Mg ha(-1)) contained 20 % higher TSN stock in the 0-5 cm soil layer than CT-B plots (0.48 Mg ha(-1)). However, tillage had no impact on TSN concentration or stock in the sub-surface (5-15 and 15-30 cm) soil layers. Thus, in the 0-30 cm soil layer, ZT-B plots contained 6 and 5 % higher (P > 0.05) TSN stock compared with CT-B (2.15 Mg N ha(-1)) and CT-F (2.19 Mg N ha(-1)) plots respectively after 4 years. Plots that received cotton/maize + wheat residue (C/M + W RES) contained 16 % higher TSN concentration than plots with residues removed (N RES; 0.62 g kg(-1) soil) in the surface (0-5 cm) layer. Plots with only cotton/maize residue (C/M RES) or only wheat residue (W RES) retention/incorporation had similar TSN concentrations and stocks in the subsurface layer. Plots under ZT-B also had more macroaggregates (0.25-8 mm) and greater mean weight diameter with lower silt + clay sized particles than CT-B plots in that layer. A greater proportion of large macroaggregates (2-8 mm) in the plots under C/M + W RES compared with N RES were observed. In the 5-15 cm soil layer ZT-B and C/M + W RES treated plots had more macroaggregates and greater mean weight diameter than CT-B and N RES treated plots, respectively. Because of the greater amount of large aggregates, plots under ZT-B and C/M + W RES had 49 and 35 % higher large macroaggregate-associated N stocks than CT-B (38 kg TSN ha(-1)) and N RES (40 kg TSN ha(-1)) plots, respectively, in the 0-5 cm soil layer, although aggregates had similar TSN concentrations in all plots. Both tillage and residue retention had greater effects on aggregate-associated N stocks in the 5-15 cm layers. In addition to N content within large macroaggregates, small macroaggregate-associated N contents were also positively affected by ZT-B and C/M + W RES. Tillage and residue retention interaction effects were not significant for all parameters. Thus, the adoption of ZT in permanent beds with crop residue addition is a better management option for improvement of soil N (and thus possibly a reduced dose of fertilizer N can be adopted in the long run), as the management practice has the potential to improve soil aggregation with greater accumulation of TSN within macroaggregates, and this trend would likely have additive effects with advancing years of the same management practices in this region.
  • Authors:
    • Kennedy, A. C.
    • Bary, A. I.
    • Cogger, C. G.
    • Fortuna, A. M.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 6
  • Year: 2013
  • Summary: Biosolids have the potential to improve degraded soils in grain-fallow rotations. Our objectives were to determine if repeated biosolids applications in wheat ( Triticum aestivum L.) - fallow could supply adequate but not excessive N for grain production and increase soil C without creating a high risk of P loss. A replicated on-farm experiment was established in 1994 in central Washington, comparing anaerobically digested biosolids with anhydrous NH 3 and a zero-N control. Biosolids were applied at 5, 7, and 9 Mg ha -1 every fourth year through 2010 and incorporated 10 cm deep, while anhydrous NH 3 plots received 56 kg ha -1 N every second year. Grain yield and protein were determined. Soil chemical, biological, and bulk density analyses were made in 2012. Medium and high biosolids rates significantly increased grain yield (3.63 vs. 3.13 Mg ha -1) and protein (103 vs. 85 g kg -1) compared with anhydrous NH 3 averaged across all crops. The medium biosolids rate had significantly lower bulk density (1.05 vs. 1.22 g kg -1) and greater total C (0-10-cm depth) (16.9 vs. 9.4 g kg -1), mineralizable N (156 vs. 52 mg kg -1), and extractable P (114 vs. 16 mg kg -1) than anhydrous NH 3. The P index site vulnerability increased from low for anhydrous NH 3 to medium for the biosolids treatments. Soil NO 3-N was nearly always <10 mg N kg -1 soil (0-30-cm depth). Medium and high biosolids rates significantly increased bacteria/fungi ratios, Gram-negative bacteria, and anaerobic bacteria markers compared with anhydrous NH 3. Biosolids can be an agronomically and environmentally sound management practice in wheat-fallow systems.
  • Authors:
    • Singh, B. R.
    • Demessie, A.
    • Lal, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 3
  • Year: 2013
  • Summary: Conversion of forests to farm lands without trees and farm lands with scattered trees (traditional agroforestry systems) may lead to decline of soil organic carbon (SOC) and N stocks provided that they have similar original status. This study was conducted on soils with the age chronosequences of 12, 20, 30, 40, 50 years of farm (F), traditional agroforestry (AF) and the adjacent natural forest (NF) lands. We studied the changes in the concentration and stocks of SOC, total N and their distribution in the soil profile of an Andic Paleustalfs in Gambo District, Southern Ethiopia. Soil samples were collected at 10, 20, 40, 60, 100 cm depth interval from pits of 1 m depth in all land use types and they were analyzed for their SOC and N stock. The results showed that the greater proportion of SOC and N was concentrated in 0-20 cm depth and that their concentration in AF and F land uses was significantly lower than that under the NF. Soils in traditional agroforestry land use showed a trend of higher SOC stocks in all chronosequences than those under the corresponding farm lands. The SOC stock under the chronosequence of 12-50 years of AF and F land uses varied from 28.2 to 98.9 Mg ha(-1) or 12 to 43 % of the stock under the NF. The SOC was less by 6.2 Mg ha(-1) year(-1) for AF(12) and 0.9 Mg ha(-1) year(-1) for AF(50) compared with NF. The corresponding values for farm lands were 6.6 and 1.3 Mg ha(-1) year(-1). The N values of all land uses were also less than that of the NF. The SOC and N stocks tended to be less in farm lands than in the traditional agroforestry. However, the SOC stocks were not significantly higher with AF compared with F suggesting that the parkland systems as practiced is not sufficient to overcome other effects of cultivation.
  • Authors:
    • Ruane, A. C.
    • Oppenheimer, M.
    • Debats, S. R.
    • Bradley, B. A.
    • Beukes, H.
    • Estes, L. D.
    • Schulze, R.
    • Tadross, M.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 12
  • Year: 2013
  • Summary: Crop model-specific biases are a key uncertainty affecting our understanding of climate change impacts to agriculture. There is increasing research focus on intermodel variation, but comparisons between mechanistic (MMs) and empirical models (EMs) are rare despite both being used widely in this field. We combined MMs and EMs to project future (2055) changes in the potential distribution (suitability) and productivity of maize and spring wheat in South Africa under 18 downscaled climate scenarios (9 models run under 2 emissions scenarios). EMs projected larger yield losses or smaller gains than MMs. The EMs' median-projected maize and wheat yield changes were -3.6% and 6.2%, respectively, compared to 6.5% and 15.2% for the MM. The EM projected a 10% reduction in the potential maize growing area, where the MM projected a 9% gain. Both models showed increases in the potential spring wheat production region (EM=48%, MM=20%), but these results were more equivocal because both models (particularly the EM) substantially overestimated the extent of current suitability. The substantial water-use efficiency gains simulated by the MMs under elevated CO 2 accounted for much of the EM-MM difference, but EMs may have more accurately represented crop temperature sensitivities. Our results align with earlier studies showing that EMs may show larger climate change losses than MMs. Crop forecasting efforts should expand to include EM-MM comparisons to provide a fuller picture of crop-climate response uncertainties.
  • Authors:
    • Jair Andrade, H.
    • Alvarado, J.
    • Segura, M.
  • Source: Revista Colombia Forestal
  • Volume: 16
  • Issue: 1
  • Year: 2013
  • Summary: The increase in greenhouse gas emissions from anthropogenic sources has resulted in climate change, which affects all living beings. Coffee (Coffea arabica L.) plantations, in monoculture or together with timber species such as salmwood (Cordia alliodora), mitigate climate change due to fixation of atmospheric CO 2 that is deposited in biomass and soils. This study was carried out in the municipality of Libano, Tolima, Colombia with the objective of defining which of the following coffee production systems store more soil organic carbon (SOC): (1) monoculture, (2) agroforestry systems (AFS) with salmwood, and (3) AFS with plantain. Farms with those systems that are the most dominant in the study zone were selected. From each system, five repetitions were identified to be analyzed with a completely randomized design. In each plot or repetition, five samples for bulk density (BD) using the cylinder method and a composite sample for concentration of SOC were taken and analyzed using the Walkley and Black approach. The systems of production did not significantly (p >0.05) affect either the BD or the concentration of SOC. However, AFS with plantain tended to have less BD than monoculture and AFS with salmwood (0.830.03 vs 0.880.03 vs 0.920.04 g.cm -3, respectively). These systems of production stored between 50 and 54 t.ha -1 of SOC in the top 30 cm, which indicates their capacity for climate change mitigation.
  • Authors:
    • Priesack, E.
    • Palosuo, T.
    • Osborne, T. M.
    • Olesen, J. E.
    • O'Leary, G.
    • Nendel, C.
    • Kumar, S. Naresh
    • Mueller, C.
    • Kersebaum, K. C.
    • Izaurralde, R. C.
    • Ingwersen, J.
    • Hunt, L. A.
    • Hooker, J.
    • Heng, L.
    • Grant, R.
    • Goldberg, R.
    • Gayler, S.
    • Doltra, J.
    • Challinor, A. J.
    • Biernath, C.
    • Bertuzzi, P.
    • Angulo, C.
    • Aggarwal, P. K.
    • Martre, P.
    • Basso, B.
    • Brisson, N.
    • Cammarano, D.
    • Rotter, R. P.
    • Thorburn, P. J.
    • Boote, K. J.
    • Ruane, A. C.
    • Hatfield, J. L.
    • Jones, J. W.
    • Rosenzweig, C.
    • Ewert, F.
    • Asseng, S.
    • Ripoche, D.
    • Semenov, M. A.
    • Shcherbak, I.
    • Steduto, P.
    • Stoeckle, C.
    • Stratonovitch, P.
    • Streck, T.
    • Supit, I.
    • Tao, F.
    • Travasso, M.
    • Waha, K.
    • Wallach, D.
    • White, J. W.
    • Williams, J. R.
    • Wolf, J.
  • Source: Nature Climate Change
  • Volume: 3
  • Issue: 9
  • Year: 2013
  • Summary: Projections of climate change impacts on crop yields are inherently uncertain(1). Uncertainty is often quantified when projecting future greenhouse gas emissions and their influence on climate(2). However, multi-model uncertainty analysis of crop responses to climate change is rare because systematic and objective comparisons among process-based crop simulation models(1,3) are difficult(4). Here we present the largest standardized model intercomparison for climate change impacts so far. We found that individual crop models are able to simulate measured wheat grain yields accurately under a range of environments, particularly if the input information is sufficient. However, simulated climate change impacts vary across models owing to differences in model structures and parameter values. A greater proportion of the uncertainty in climate change impact projections was due to variations among crop models than to variations among downscaled general circulation models. Uncertainties in simulated impacts increased with CO2 concentrations and associated warming. These impact uncertainties can be reduced by improving temperature and CO2 relationships in models and better quantified through use of multi-model ensembles. Less uncertainty in describing how climate change may affect agricultural productivity will aid adaptation strategy development and policy making.
  • Authors:
    • Lonergan, V. E.
    • Andersson, K. O.
    • Rawson, A.
    • Murphy, B. M.
    • Simmons, A. T.
    • Badgery, W. B.
    • van de Ven, R.
  • Source: Soil Research
  • Volume: 51
  • Issue: 7-8
  • Year: 2013
  • Summary: The potential to change agricultural land use to increase soil carbon stocks has been proposed as a mechanism to offset greenhouse gas emissions. To estimate the potential carbon storage in the soil from regional surveys it is important to understand the influence of environmental variables (climate, soil type, and landscape) before land management can be assessed. A survey was done of 354 sites to determine soil organic carbon stock (SOC stock; Mg C/ha) across the Lachlan and Macquarie catchments of New South Wales, Australia. The influences of climate, soil physical and chemical properties, landscape position, and 10 years of land management information were assessed. The environmental variables described most of the regional variation compared with management. The strongest influence on SOC stock at 0-10cm was from climatic variables, particularly 30-year average annual rainfall. At a soil depth of 20-30cm, the proportion of silica (SiO2) determined by mid-infrared spectra (Si-MIR) had a negative relationship with SOC stock, and sand and clay measured by particle size analysis also showed strong relationships at sites where measured. Of the difference in SOC stock explained by land use, cropping had lower soil carbon than pasture in rotation or permanent pasture at 0-10cm. This relationship was consistent across a rainfall gradient, but once soil carbon was standardized per mm of average annual rainfall, there was a greater difference between cropping and permanent pasture with increasing Si-MIR in soils. Land use is also regulated by climate, topography, and soil type, and the effect on SOC stock is better assessed in smaller land-management units to remove some variability due to climate and soil.