• Authors:
    • Shang, Z. H.
    • Chen, X. P.
    • Pan, J. L.
    • Dai, W. A.
    • Wang, X. M.
    • Ma, L. N.
    • Guo, R. Y.
  • Source: Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 11
  • Year: 2013
  • Summary: Soil carbon and nitrogen in vegetable fields are the core elements of soil quality and environmental pollution. The decrease of soil C/N ratio of vegetable fields under greenhouse conditions causes an imbalance in soil carbon and nitrogen content. An effective way of adjusting soil carbon and nitrogen conditions in vegetable fields has been by improving soil quality and decreasing environmental pollution. Furthermore, there has been little research on soil carbon and nitrogen mineralization under greenhouse conditions in the Tibetan region. After transformations of alpine meadows and farmlands into solar greenhouse vegetable fields, there was the need to study the characteristics and processes of soil mineralization. In this study therefore, carbon and nitrogen mineralization in soils of alpine grassland, farmland and greenhouse (1-year, 5-year) were analyzed in an indoor incubation experiment. The results showed that soil carbon mineralization in different soil types mainly occurred during the first seven days (0-7 d) after treatment. Soil carbon mineralization was higher under alpine grassland than in farmland and 5-year greenhouse conditions ( P0.05). This was attributed to soil nutrient and soil microbial environment sensitivity to temperature. Soil CO 2-C accumulation in farmland soil was higher than in alpine grassland soil. It was also higher in alpine grassland soil than in the 1-year greenhouse and 5-year greenhouse soils. However, the differences in soil organic carbon mineralization and accumulation among alpine grassland, farmland, 1-year greenhouse and 5-year greenhouse soil conditions were not significant ( P>0.05) at 28 days after treatment. Soil nitrogen mineralization mainly happened in different soil types during the first three days (3 d) after treatment. With delayed incubation, the main process of soil nitrogen mineralization was nitrogen fixation. Soil inorganic nitrogen content in alpine grassland, farmland, 1-year greenhouse and 5-year greenhouse soils at 28 days after incubation were 29.04%, 75.94%, 66.86% and 65.70% of that at 0 day, respectively. The results showed that soil nitrogen mineralization capacity of alpine grassland soil was stronger than farmland, 1-year greenhouse and 5-year greenhouse soils. Soil nitrogen mineralization capacity of farmland was weaker than alpine grassland, 1-year greenhouse and 5-year greenhouse. Also soil nitrogen mineralization capacities of 1-year greenhouse and 5-year greenhouse were similar. Moreover, soil mineralization processes were similar among different soil conditions.
  • 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:
    • Marschner, P.
    • Khan, K. S.
    • Malik, M. A.
    • Fayyaz-ul, H.
  • Source: Journal of soil science and plant nutrition
  • Volume: 13
  • Issue: 4
  • Year: 2013
  • Summary: A 72-day greenhouse pot experiment was conducted with a sandy loam or a silt loam soil to examine the effects of farmyard manure (FYM), poultry litter (PL) and biogenic waste compost (BWC) at 10 g dw kg(-1) soil on microbial biomass and activity and growth and nutrient uptake by wheat. Soil samples were collected at days 0, 14, 28, 42, 56 and 72 after planting. Growth and nutrient uptake by wheat were determined on day 72. All three amendments increased microbial biomass C, N and P, dehydrogenase activity, plant growth and nutrient uptake with a greater effect by FYM and PL than by BWC. All amendments increased microbial biomass C, N and P and enzyme activity particularly on day 0. These microbial parameters decreased after day 0 indicating microbial biomass turnover. All amendments increased plant growth and nutrient uptake. It is concluded that organicamendments can stimulate microbial growth and nutrient uptake as well as plant growth and nutrient uptake. Microbes can increase plant nutrient availability by nutrient mobilisation but also because nutrients taken up by the microbial biomass initially could become available to plants when the microbial biomass turns over as the easily available C is depleted.
  • Authors:
    • Prochnow, A.
    • Olesen, J. E.
    • Meyer-Aurich, A.
    • Brunsch, Reiner
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 18
  • Issue: 7
  • Year: 2013
  • Summary: Agricultural lands have been identified to mitigate greenhouse gas (GHG) emissions primarily by production of energy crops and substituting fossil energy resources and through carbon sequestration in soils. Increased fertilizer input resulting in increased yields may reduce the area needed for crop production. The surplus area could be used for energy production without affecting the land use necessary for food and feed production. We built a model to investigate the effect of changing nitrogen (N) fertilizer rates on cropping area required for a given amount of crops. We found that an increase in nitrogen fertilizer supply is only justified if GHG mitigation with additional land is higher than 9-15 t carbon dioxide equivalents per hectare (CO2-eq.(.)/ha). The mitigation potential of bioenergy production from energy crops is most often not in this range. Hence, from a GHG abatement point of view land should rather be used to produce crops at moderate fertilizer rate than to produce energy crops. This may change if farmers are forced to reduce their N input due to taxes or governmental regulations as it is the case in Denmark. However, with a fertilizer rate 10 % below the economical optimum a reduction of N input is still more effective than the production of bioenergy unless mitigation effect of the bioenergy production exceeds 7 t carbon dioxide (CO2)-eq.(.)/ha. An intensification of land use in terms of N supply to provide more land for bioenergy production can only in exceptional cases be justified to mitigate GHG emissions with bioenergy under current frame conditions in Germany and Denmark.
  • Authors:
    • Keeton, W. S.
    • Mika, A. M.
  • Source: GCB Bioenergy
  • Volume: 5
  • Issue: 3
  • Year: 2013
  • Summary: With growing interest in wood bioenergy there is uncertainty over greenhouse gas emissions associated with offsetting fossil fuels. Although quantifying postharvest carbon (C) fluxes will require accurate data, relatively few studies have evaluated these using field data from actual bioenergy harvests. We assessed C reductions and net fluxes immediately postharvest from whole-tree harvests (WTH), bioenergy harvests without WTH, and nonbioenergy harvests at 35 sites across the northeastern United States. We compared the aboveground forest C in harvested with paired unharvested sites, and analyzed the C transferred to wood products and C emissions from energy generation from harvested sites, including indirect emissions from harvesting, transporting, and processing. All harvests reduced live tree C; however, only bioenergy harvests using WTH significantly reduced C stored in snags (P<0.01). On average, WTH sites also decreased downed coarse woody debris C while the other harvest types showed increases, although these results were not statistically significant. Bioenergy harvests using WTH generated fewer wood products and resulted in more emissions released from bioenergy than the other two types of harvests, which resulted in a greater net flux of C (P<0.01). A Classification and Regression Tree analysis determined that it was not the type of harvest or amount of bioenergy generated, but rather the type of skidding machinery and specifics of silvicultural treatment that had the largest impact on net C flux. Although additional research is needed to determine the impact of bioenergy harvesting over multiple rotations and at landscape scales, we conclude that operational factors often associated with WTH may result in an overall intensification of C fluxes. The intensification of bioenergy harvests, and subsequent C emissions, that result from these operational factors could be reduced if operators select smaller equipment and leave a portion of tree tops on site.
  • Authors:
    • Jaroslav, B.
    • Moudry, J.
    • Jelinkova, Z.
    • Moudry, J., Jr.
    • Marek, K.
    • Petr, K.
  • Source: Journal of Food, Agriculture & Environment
  • Volume: 11
  • Issue: 3/4
  • Year: 2013
  • Summary: The study presents a comparison of an effect of greenhouse gas emission load on the environment caused within the production of crops (rye, wheat, potato, carrot, cabbage, onion and tomato) under conventional and organic farming system in the Czech Republic. For evaluation, the simplified LCA analysis focused on evaluation of greenhouse gas emission load, expressed in carbon dioxide equivalents, was used. Outputs were converted into 1 kg of agricultural production. Within the evaluation of agricultural phase, total emissions from the cultivation of crops and emissions from particular parts of agricultural phase (agricultural engineering, fertilizers, pesticides, seeds and seedlings, field emission) were surveyed. The results show that except for onion growing, there is a reduction of emissions for all studied crops.
  • Authors:
    • Gottschall, N.
    • Drury, C. F.
    • Gregorich, E. G.
    • Topp, E.
    • Sunohara, M. D.
    • Nangia, V.
    • Lapen, D. R.
  • Source: Journal of Environmental Management
  • Volume: 129
  • Year: 2013
  • Summary: Controlled tile drainage can boost crop yields and improve water quality, but it also has the potential to increase GHG emissions. This study compared in-situ chamber-based measures of soil CH4, N2O, and CO2 fluxes for silt loam soil under corn and soybean cropping with conventional tile drainage (UTD) and controlled tile drainage (LID). A semi-empirical model (NEMIS-NOE) was also used to predict soil N2O fluxes from soils using observed soil data. Observed N2O and CH4 fluxes between UTD and CID fields during the farming season were not significantly different at 0.05 level. Soils were primarily a sink for CH4 but in some cases a source (sources were associated exclusively with CTD). The average N2O fluxes measured ranged between 0.003 and 0.028 kg N ha(-1) day(-1). There were some significantly higher (p <= 0.05) CO2 fluxes associated with LID relative to UTD during some years of study. Correlation analyses indicated that the shallower the water table, the greater the CO2 fluxes. Higher corn plant C for CTD tended to offset estimated higher CTD CO2 C losses via soil respiration by similar to 100-300 kg C ha(-1). There were good fits between observed and predicted (NEMIS-NOE) N2O fluxes for corn (R-2 = 0.70) and soybean (R-2 = 0.53). Predicted N2O fluxes were higher for CID for approximately 70% of the paired-field study periods suggesting that soil physical factors, such as water-filled pore space, imposed by CTD have potentially strong impacts on net N fluxes. Model predictions of daily cumulative N2O fluxes for the agronomically-active study period for corn-CTD and corn-UTD, as a percentage of total N fertilizer applied, were 3.1% and 2.6%, respectively. For predicted N2O fluxes on basis of yield units, indices were 0.0005 and 0.0004 (kg N kg(-1) crop grain yield) for CTD and UTD corn fields, respectively, and 0.0011 and 0.0005 for CTD and UTD soybean fields, respectively.
  • Authors:
    • Penttila,T.
    • Minkkinen,K.
    • Ojanen,P.
  • Source: Forest Ecology and Management
  • Volume: 289
  • Issue: February
  • Year: 2013
  • Summary: We estimated the soil CO2 balance of 68 forestry-drained boreal peatland sites in Finland by subtracting the litter input to soil from the CO2 efflux from soil. We also measured soil-atmosphere fluxes of CH4 and N2O and the CO2 sink of the growing tree stand in order to assess the current greenhouse gas impact of the study sites. The soil was, on average, a CO2 source of +190 +/- 70 g m(-2) year(-1) at the fertile Herb-rich and Vaccinium myrtillus type sites, but a CO2 sink of -70 +/- 30 g m(-2) year(-1) at the poor Vaccinium vitis-idaea and Dwarf shrub type sites. The source increased at the fertile and the sink decreased at the poor sites as the water table deepened. The source at the fertile sites also increased by increasing temperature sum, the highest CO2 sources being around +1000 g m(-2) year(-1) at well drained sites in Southern Finland. Both fertile and poor sites had a climate cooling impact. The sink in CO2 equivalents at the fertile sites was -690 +/- 90 g m(-2) year(-1) and at the poor sites -540 +/- 70 g m(-2) year(-1). The greater sink at the fertile sites was due to clearly better tree growth, their tree stand CO2 sink being -880 +/- 60 g m(-2) year(-1) compared to the -490 +/- 60 g m(-2) year(-1) at the poor sites. Ditching-based forestry can be climatically sustainable at nutrient-poor boreal peatlands since the peat soil continues to be a CO2 sink even after drainage. At the fertile sites, forestry will inevitably lead to loss of carbon in the long term, unless the tree biomass is stored after cuttings, for example in wooden buildings or as biochar in agricultural soils. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Omonode, R.
    • Vyn, T.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 6
  • Year: 2013
  • Summary: Simultaneous application of nitrification inhibitors and fertilizer N has the potential to delay nitrification processes and reduce atmospheric N loss through N2O emissions. A 2-yr study was conducted to assess the effects of newly available water-soluble nitrapyrin (Instinct) [2-chloro-6-(trichloromethyl) pyridine] on the nitrification kinetics and N2O emissions from urea-NH4NO3 (UAN) band applied to somewhat poorly drained and moderately well-drained silt loam soils in Indiana. The UAN fertilizer, with or without nitrapyrin, was injected post-emergence between corn (Zea mays L.) rows that were 76 cm apart. Soil samples were taken at various increments from the band centers at 1- to 2-wk intervals for up to 14 wk and analyzed for NH4- and NO3-N concentrations. Nitrification rates were determined using appropriate kinetic models. Greenhouse gas samples were collected weekly for 7 to 10 wk and biweekly thereafter for an additional 2 to 4 wk. Our results showed that UAN nitrification followed first-order kinetics, with significantly greater nitrification rate constants without nitrapyrin. On average, UAN half-life was about 15 d without nitrapyrin and 25 d when coapplied with nitrapyrin. Nitrapyrin reduced N2O emissions by up to 44% from sidedress-applied UAN, even though emission quantities varied by location and year due to differences in soil moisture, temperature, and precipitation. These latter variables plus soil NH4-N concentrations, in various combinations, accounted for 40 to 50% of the total variability associated with N2O emissions. These results can help inform UAN management decisions with regard to use of N stabilizers with UAN in the midwestern United States.
  • Authors:
    • Boettcher, U.
    • Pahlmann, I.
    • Kage, H.
    • Sieling, K.
  • Source: Biomass & Bioenergy
  • Volume: 57
  • Year: 2013
  • Summary: In 2009, the Renewable Energy Directive (RED), established sustainability criteria for biofuels including legal thresholds for specific greenhouse gas (GHG) emissions, expressed as g CO(2)eq per MJ of biofuel. Because biofuels are a major market for winter oilseed rape (WOSR), investigating the possible impact of the RED on WOSR cropping practices is prudent. This study analyses GHG emissions for WOSR cropping practices (namely N fertilization intensity, tillage method and crop rotation) basing on a 6-year field trial in a high yielding area of northern Germany. Using the International Panel on Climate Change (IPCC) methodology the field emissions of nitrous oxide (N2O) are calculated from the nitrogen (N) inputs to the cropping system. Results showed that the predominant source of GHG emissions is the N related emissions from production of fertilizer and N2O field emissions. Specific GHG emissions are lowest without N fertilizer but rise continuously with increasing N rates. Yield per ha also responded to N fertilization resulting in lowered acreage productivity when reducing GHG emissions by reducing N fertilization level. Most calculated scenarios and cropping systems result in a drastic decrease of N fertilization to achieve thresholds, causing substantial yield losses. To a certain extent, the required drastic reduction of N fertilization in some scenarios is driven by using the IPCC methodology for calculating N2O emissions. Therefore characteristics of this methodology are also discussed within this study. To mitigate the impact of the RED on WOSR, peas (legumes) may be a possible preceding crop to WOSR. (C) 2013 Elsevier Ltd. All rights reserved.