• Authors:
    • Kroetsch, D.
    • Vandenbygaart, A. J.
    • Gregorich, E. G.
    • Lobb, D.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 4
  • Year: 2012
  • Summary: Erosion influences the lateral and vertical distribution of soil in agricultural landscapes. A better understanding of the effects of erosion and redistribution on soil organic carbon (C) within croplands would improve our knowledge of how management practices may affect global C dynamics. In this study, the vertical and lateral distribution of soil organic C was characterized to evaluate the amounts and timescales of soil organic C movement, deposition and burial over the last 50 years in different agroecosystems across Canada. There was strong evidence that a substantial portion of eroded sediment and soil organic C was deposited as colluvium close to its source area, thereby burying the original topsoil. The deepest aggraded profile was in a potato field and contained over 70 cm of deposited soil indicating an accumulation rate of 152 Mg ha yr -1; aggraded profiles in other sites had soil deposition rates of 40-90 Mg ha -1 yr -1. The largest stock of soil organic C was 463 Mg ha -1 (to 60 cm depth) and soil C deposition ranged from about 2 to 4 Mg ha -1 yr -1 across all sites. A distinct feature observed in the aggraded profiles at every site was the presence of a large increase in soil organic C concentration near the bottom of the A horizon; the concentration of this C was greater than that at the soil surface. Compared to aggraded profiles, the SOC concentration in eroded profiles did not differ with depth, suggesting that dynamic replacement of soil organic C had occurred in eroded soils. A large amount of soil organic C is buried in depositional areas of Canadian croplands; mineralization of this stock of C appears to have been constrained since burial, but it may be vulnerable to future loss by management practices, land use change and a warming climate.
  • Authors:
    • Williams, C.
    • Walling, S.
    • Sample, D.
    • Radloff, G.
    • Jackson, R.
    • Hull, S.
    • Ventura, S.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 1
  • Year: 2012
  • Authors:
    • Kasimir-Klemedtsson, A.
    • Rutting, T.
    • Weslien, P.
    • Klemedtsson, L.
  • Source: Nutrient Cycling in Agroecosytems
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: The emissions of the greenhouse gas nitrous oxide (N2O) were measured from a non nitrogen fertilized carrot (Daucus carota ssp. sativa) field on an organic soil in Sweden during one cropping and post-harvest season. The cumulative emission during the measuring period of 149 days was 41 (+/- 2.8) kg N2O ha(-1). Dividing the measuring period into a cropping and a post-harvest period revealed that the presence of carrots strongly stimulated N2O emissions, as the emission during the cropping period was one order of magnitude higher compared to the post-harvest period. The N2O emission from the carrot field were higher than fluxes reported from cereal crop and grass production, but in the same order as reported fluxes from vegetable cropping on organic soils. In conclusion, our results indicate that the cultivation of root vegetable, such as carrots, on organic soil can be a high point source for N2O emissions.
  • Authors:
    • Lutzow, M. von
    • Schilling, B.
    • Reischl, A.
    • Haug, S.
    • Hangen, E.
    • Geuss, U.
    • Sporlein, P.
    • Wiesmeier, M.
    • Kogel-Knabner, I.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Precise estimations of soil organic carbon (SOC) stocks are of decided importance for the detection of C sequestration or emission potential induced by land use changes. For Germany, a comprehensive, land use-specific SOC data set has not yet been compiled. We evaluated a unique data set of 1460 soil profiles in southeast Germany in order to calculate representative SOC stocks to a depth of 1 m for the main land use types. The results showed that grassland soils stored the highest amount of SOC, with a median value of 11.8 kg m -2, whereas considerably lower stocks of 9.8 and 9.0 kg m -2 were found for forest and cropland soils, respectively. However, the differences between extensively used land (grassland, forest) and cropland were much lower compared with results from other studies in central European countries. The depth distribution of SOC showed that despite low SOC concentrations in A horizons of cropland soils, their stocks were not considerably lower compared with other land uses. This was due to a deepening of the topsoil compared with grassland soils. Higher grassland SOC stocks were caused by an accumulation of SOC in the B horizon which was attributable to a high proportion of C-rich Gleysols within grassland soils. This demonstrates the relevance of pedogenetic SOC inventories instead of solely land use-based approaches. Our study indicated that cultivation-induced SOC depletion was probably often overestimated since most studies use fixed depth increments. Moreover, the application of modelled parameters in SOC inventories is questioned because a calculation of SOC stocks using different pedotransfer functions revealed considerably biased results. We recommend SOC stocks be determined by horizon for the entire soil profile in order to estimate the impact of land use changes precisely and to evaluate C sequestration potentials more accurately.
  • Authors:
    • Khizar, A.
    • Abbasi, M. K.
  • Source: Ecological Engineering
  • Volume: 39
  • Issue: February
  • Year: 2012
  • Summary: Application of organic amendments to soil is an important management strategy for enhancing the restoration of degraded soils and providing better soil conditions to below-ground soil microbial composition and above-ground plant community development. This study was conducted to investigate the effect of organic amendments (poultry manure - PM; white clover residues - WCR), a mineral N fertilizer (urea N - UN), or mixtures of these fertilizers on microbial activity and nitrogen (N) mineralization through both soil analysis (laboratory incubation) and aboveground maize (Zea mays L) growth (pot experiment). In the incubation experiment, soil was amended with PM, WCR, PM + WCR, UN, UN + PM, UN + WCR, and UN + PM + WCR at the rate equivalent to 200 mg N kg(-1) soil. Pot experiment was conducted in a glasshouse using same amendments to examine the response of maize seedlings to these treatments. Organic amendments and UN applied alone or in mixtures increased soil microbial biomass compared to the control. Among N amendments, the highest evaluation of CO2-C (47.7 mg kg(-1) day(-1)), microbial biomass C (434 mg kg) and microbial biomass N (86 mg kg(-1)) were recorded in the UN + PM + WCR while the lowest values were recorded in UN. It is estimated that 9-18% of the applied N had been assimilated into microbial N pool after 105 days. Mineralization of N was higher in the fertilized soil and ranged between 85 and 192 mg N kg(-1) compared with 46 mg N kg(-1) in the control. The net cumulative N mineralized (NCNM) ranged between 43 and 169 mg kg(-1) while the net cumulative N nitrified (NCNN) ranged between 16 and 69%. Combined application of UN + PM + WCR exhibited the highest NCNM and NCNN. On average, percentage conversion of added N into NO3--N was: 21% from organic sources, 40% from UN and 52% from UN + organic sources. The apparent recovery of added N (ANR) from PM, WCR and PM + WCR was 20, 24 and 45%, respectively, while UN, UN + PM, UN + WCR and UN + PM + WCR exhibited 50, 57, 64, and 73% ANR, respectively. Results obtained from the pot experiment (on maize) were consistent with the total mineral N (TMN) released from different amendments and highly significant correlations existed between TMN and plant dry matter yield (r(2) = 0.92) and TMN and N uptake of plants (r(2) = 0.89). The present study demonstrates the existence of substantial amount of N reserve present in organic substrates, which can be transformed into inorganic N pool and can be taken into account as potential sources in the management of the nutrient poor soils and crop growth. (C) 2011 Published by Elsevier B.V.
  • Authors:
    • Schmidt, J. E.
    • Thomsen, S. T.
    • Jensen, M.
    • Heiske, S.
    • Hauggaard-Nielsen, H.
    • Carter, M. S.
    • Johansen, A.
    • Ambus, P.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: One way of reducing the emissions of fossil fuel-derived carbon dioxide (CO2) is to replace fossil fuels with biofuels produced from agricultural biomasses or residuals. However, cultivation of soils results in emission of other greenhouse gases (GHGs), especially nitrous oxide (N2O). Previous studies on biofuel production systems showed that emissions of N2O may counterbalance a substantial part of the global warming reduction, which is achieved by fossil fuel displacement. In this study, we related measured field emissions of N2O to the reduction in fossil fuel-derived CO2, which was obtained when agricultural biomasses were used for biofuel production. The analysis included five organically managed feedstocks (viz. dried straw of sole cropped rye, sole cropped vetch and intercropped ryevetch, as well as fresh grassclover and whole crop maize) and three scenarios for conversion of biomass into biofuel. The scenarios were (i) bioethanol, (ii) biogas and (iii) coproduction of bioethanol and biogas. In the last scenario, the biomass was first used for bioethanol fermentation and subsequently the effluent from this process was utilized for biogas production. The net GHG reduction was calculated as the avoided fossil fuel-derived CO2, where the N2O emission was subtracted. This value did not account for fossil fuel-derived CO2 emissions from farm machinery and during conversion processes that turn biomass into biofuel. The greatest net GHG reduction, corresponding to 700800 g CO2 m(-2), was obtained by biogas production or coproduction of bioethanol and biogas on either fresh grassclover or whole crop maize. In contrast, biofuel production based on lignocellulosic crop residues (i.e. rye and vetch straw) provided considerably lower net GHG reductions (=215 g CO2 m(-2)), and even negative numbers sometimes. No GHG benefit was achieved by fertilizing the maize crop because the extra crop yield, and thereby increased biofuel production, was offset by enhanced N2O emissions.
  • Authors:
    • Leytem, A. B.
    • Venterea, R. T.
    • Fixen, P. E.
    • Snyder, C. S.
    • Liebig, M. A.
    • Del Grosso, S. J.
    • Cavigelli, M. A.
    • McLain, J. E.
    • Watts, D. B.
  • Source: Frontiers in Ecology and the Environment
  • Volume: 10
  • Issue: 10
  • Year: 2012
  • Summary: The use of commercial nitrogen (N) fertilizers has led to enormous increases in US agricultural productivity. However, N losses from agricultural systems have resulted in numerous deleterious environmental impacts, including a continuing increase in atmospheric nitrous oxide (N2O), a greenhouse gas (GHG) and an important catalyst of stratospheric ozone depletion. Although associated with about 7% of total US GHG emissions, agricultural systems account for 75% of total US N2O emissions. Increased productivity in the crop and livestock sectors during the past 30 to 70 years has resulted in decreased N2O emissions per unit of production, but N2O emissions from US agriculture continue to increase at a rate of approximately 0.46 teragrams of carbon dioxide equivalents per year (2002-2009). This rate is lower than that during the late 20th century. Improvements in agricultural productivity alone may be insufficient to lead to reduced emissions; implementing strategies specifically targeted at reducing N2O emissions may therefore be necessary. Front Ecol Environ 2012; 10(10): 537-546, doi:10.1890/120054
  • Authors:
    • Chidthaisong, A.
    • Lu, Y.
    • Yuan, Q.
    • Klose, M.
    • Conrad, R.
  • Source: Soil Biology and Biochemistry
  • Volume: 49
  • Issue: June
  • Year: 2012
  • Summary: Straw amendment is a common practice for improving the fertility of rice field soils, but it also enhances production of the greenhouse gas methane. To quantify carbon flux partitioning and priming effects due to straw amendment, we measured delta C-13 in CH4 and CH4 precursors produced in anoxic slurries of soil from Italy, China and Thailand after addition of straw from either rice (C3 plant) or maize plants (C4 plant), which have different delta C-13 signatures. The delta C-13 values of the CH4, acetate and CO2 produced were similar when expressed as the difference to the delta C-13 value of the straw applied. These results indicated that the C-13-isotopic fractionation involved in methanogenic decomposition was similar for rice straw and maize straw. However, measurement of CH4 produced in soil without or with straw showed that isotopic fractionation during methanogenic degradation of straw was smaller than during degradation of soil organic matter. Isotopic fractionation during hydrogenotrophic methanogenesis, measured in the presence of methyl fluoride, with straw was also smaller than with soil organic matter. The results show that C-13-isotopic analysis after application of rice straw and maize straw is a convenient approach for quantifying carbon flux partitioning during methanogenic degradation of straw and soil organic matter. In our experiments, straw degradation accounted for most of the CH4 production and caused a negative priming effect on the methanogenic degradation of soil organic matter. (c) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Griffis, T. J.
    • Fassbinder, J. J.
    • Baker, J. M.
  • Source: Agricultural and Forest Meteorology
  • Volume: 153
  • Issue: February
  • Year: 2012
  • Summary: Separation of the photosynthetic (F-P) and respiratory (F-R) fluxes of net CO2 exchange (F-N) remains a necessary step toward understanding the biological and physical controls on carbon cycling between the soil, biomass, and atmosphere. Despite recent advancements in stable carbon isotope partitioning methodology, several potential limitations can cause uncertainty in the partitioned results. Here, we combined an automated chamber system with a tunable diode laser (TDL) to evaluate carbon isotope partitioning under controlled environmental conditions. Experiments were conducted in a climate controlled greenhouse utilizing both soybean (C-3 pathway) and corn (C-4 pathway) treatments. Under these conditions, net exchange of (CO2)-C-13 and (CO2)-C-12 was obtained with an improved signal to noise ratio. Further, the chamber system was used to estimate soil evaporation (E) and plant transpiration (T), allowing for an improved estimate of the total conductance to CO2 (g(c)). This study found that the incorporation of short-term and diel variability in the isotope composition of respiration (delta(R)) caused F-P to nearly double in the corn system while only slightly increasing in the soybean system. Variability in both g(c) and the CO2 bundle sheath leakage factor for C-4 plants (phi) also had a significant influence on F-P. In addition, chamber measurements of F-N and its isotope composition (delta(N)) indicated that post-illumination processes caused a decrease in plant respiration for up to 3 h following light termination. Finally, this study found systematic differences between the isotope and temperature-regression partitioning methods on the diel time scale. Published by Elsevier B.V.
  • Authors:
    • Felzer, B. S.
  • Source: Ecological Modelling
  • Volume: 240
  • Issue: August
  • Year: 2012
  • Summary: Future climate projections indicate that Pennsylvania will get significantly warmer and wetter due to continued increases in atmospheric greenhouse gas (GHG) concentrations. Using the Terrestrial Ecosystem Model version Hydro2 (TEM-Hydro2), this study explores the effect of different climate and land use scenarios on carbon, nitrogen, and water dynamics during the 20th and 21st centuries. TEM-Hydro2 runs are forced by historical 20th century climate data and by 21st century climate projections from the NCAR CCSM3.0 IPCC A2 and B1 scenarios, a relatively high and low GHG emissions scenario, respectively. Regrowing forests are the only ecosystem with positive Net Carbon Exchange (NCE) and sequestered more than 12,000 g C m(-2) during the 20th century. The highest rates of leaching of dissolved inorganic nitrogen (DIN) occurred in fertilized croplands in the 20th century. Twenty first century runoff increases by 30% in the A2 scenario and 20% in the B1 scenario, but DIN leaching only increases in the A2 scenario. DIN leaching depends upon both runoff and available inorganic nitrogen, which decreases due to high productivity and enhanced plant nitrogen uptake. The effect of increasing urbanization in the 21st century is to reduce NCE by about 34% in both climate scenarios, while water runoff increases by 5% and DIN leaching decreases by 17%. The reduced leaching is the result of converting agricultural land to suburban areas, which are a combination of turflawn and forests, both of which have lower leaching rates than croplands or pastures. Incorporating realistic forest stand age substantially increases the NCE but has little effect on runoff or DIN leaching. Maize yields decrease in the A2 scenario due to the excessive leaching, but increase in the B1 scenario. These results illustrate why it is important to include scenarios of both GHG emissions and realistic land use changes in model projections of the regional impacts of climate change in the 21st century. (C) 2012 Elsevier B.V All rights reserved.