Now showing 1 - 7 of 7
  • Publication
    Assessing the sensitivity of fertilizer types and soil variables on nitrous oxide emissions in permanent grasslands using the DNDC model
    The adoption and use of improved methodologies including models that reflect more robust emissions accounting procedures and the identification of specific mitigation options for agricultural greenhouse gases are a global concern. In Ireland, country-specific N2O emission factors (EFs) are constrained primarily by short-term measurements and limited coverage of regulating factors. Simulation of N2O emissions from grassland silage plots managed for 42 years with different slurry treatments was performed using the DeNitrification-DeComposition (DNDC95) model. The objective was to assess the long-term impact of management practices on N2O fluxes and EFs, and the sensitivity of the outputs to key inorganic and organic fertilizer management and soil variables. The DNDC performed well for urea, cattle slurry and pig slurry applied at variable rates, delivering EFs on-average of 0.35±0.02, 1.80±0.28 and 1.53±0.41%, respectively. Variation in the derived-EFs could be explained by differences in nitrogen inputs (49%), rainfall (16%) and temperature (10%) and are close to national estimates. Sensitivity analysis of the model demonstrated that N2O EFs were higher with ammonium sulphate compared to CAN and urea fertilizers, and with urea-N at higher rates. The replacement of slurry either after the second or third silage cut by urea decreased EFs significantly. There was a strong correlation with the sensitivity of N2O EFs to soil texture, bulk density, pH and organic carbon (R2=0.96-0.99). The resulting-EFs ranged from 0.28 to 0.41% for urea, 1.12 to 2.07% for cattle slurry, and 1.05 to 1.65% for pig slurry, and the corresponding values on-average were 0.35±0.02, 1.74±0.17 and 1.39±0.12%. These findings show that DNDC95, although requiring more improvement, could provide an accurate representation of the effect of soils, climate and management practices on N2O fluxes and subsequent estimates of disaggregated EFs.
  • Publication
    Strategic Management of Grazing Grassland Systems to Maintain and Increase Organic Carbon in Soils
    Understanding management-induced C sequestration potential in soils under agriculture, forestry, and other land use systems and their quantification to offset increasing greenhouse gases are of global concern. This chapter reviews management-induced changes in C storage in soils of grazing grassland systems, their impacts on ecosystem functions, and their adaptability and needs of protection across socio-economic and cultural settings. In general, improved management of grassland/pasture such as manuring/slurry application, liming and rotational grazing, and low to medium livestock units could sequester C more than under high intensity grazing conditions. Converting cultivated land to pasture, restoration of degraded land, and maximizing pasture phases in mixed-cropping, pasture with mixed-livestock, integrated forestry-pasturage of livestock (silvopastoral) and crop-forestry-pasturage of livestock (agro-silvopastoral) systems could also maintain and enhance soil organic C density (SOCρ). In areas receiving low precipitation and having high erodibility, grazing exclusion might restore degraded grasslands and increase SOCρ. Yet, optimizing C sequestration rates, sowing of more productive grass varieties, judicial inorganic and organic fertilization, rotational grazing, and other climate-resilient approaches could improve overall farm productivity and profitability and attain sustainability in livestock farming systems.
  • Publication
    Soil-Atmosphere Exchange of NH3 and NOx in Differently Managed Vegetation Types of Southern Germany
    Ammonia (NH3) and Nitrogen Oxides (NOx = NO + NO2) emissions from soils and vegetation, and their subsequent deposition are key factors in global Nitrogen (N) cycling and have important functions in atmospheric and ecosystem degradation processes. To better understand their contribution, NH3 and NOx gases were simultaneously measured from differently managed vegetation types using a dynamic-chamber method. Biomass and N yields were higher from unfertilized clover-grass than fertilized oilseed radish. Summer cuts of clover-grass resulted in 137% higher biomass and 2.7-3.7% N concentrations than autumn cuts. Mulching reduced the re-growth and biomass production in clover-grass by 16% compared to cutting. The relative loss of NH3 through mulching was higher from the clover-grass (2.18%) than in the oilseed radish (0.08%). The total NH3 release over the four cuts of the clover-grass was 0.58% of the N removed. The influence of biomass-N, either mulched or cut, on the total NOx emission was temporary, resulted in net deposition (0.02-0.15% of the added/removed biomass-N). The ecosystems acted as sources for NH3, with the rate being weakly related to the added biomass-N, air temperature and humidity (R2 = 0.58, p<0.07), and sinks for NOx, with the rate influenced significantly by sunshine hours, precipitation and amount of biomass-N added (R2 = 0.87, p<0.001). We conclude that cutting clover-grass multiple times could be a good option to reduce the emissions of reactive N species and increase fodder yields with moderate N. Additionally, clover-grass could be superior for soil conservation measures over oilseed radish. Results imply further studies on the annual exchanges of gaseous N between the ecosystems and the atmosphere through long-term measurements.
  • Publication
    Turnover of Chicken Manure in Some Upland Soils of Asia: Agricultural and Environmental Perspectives
    Recycling of organic manure/waste is an important global issue to improve soil productivity for sustaining agricultural production as well as to preserve the environment. In Asia, rearing of poultry especially chicken is becoming one of the key industrial sectors and the wastes from clean-out operations may contribute largely to plant nutrients. Thus, some recent research works on the use of chicken manure (CM) in the uplands of tropical Asia are reviewed. Relative loss of the added CM-C was averaged 83% during a 90-day incubation and in-situ retention of labile organic-C was poor in 2 years, signifying long-term episodes to sequestrate its inherent low C. Ammonification of the added CM was rapid during 1-2 weeks followed by oxidation of NH4+. The high pH of CM remarkably influenced nitrification either after a lag phase or immediately after application, ensuing NO3- leaching to occur under favourable conditions. Net mineralization/ nitrification was greater with CM than with other wider C/N ratio organic residues. CM-N recovery was relatively low, indicating immobilization and other N loss processes. Likewise, a large N2O loss of added CM-N with or without other N sources under field (0.99%) and laboratory (6.66%) conditions was observed, along with presumable NH3 volatilization. Composted CM/litter could reduce the loss by limiting the transformation of organic N. Application of CM (fresh/composted) either alone or with inorganic fertilizers demonstrated crop yield benefits and reduced the use of the latter as well as a noticeable residual effect to the succeeding crops. Results suggest that strategic but agro-economically viable composting might have great advantages in synchronizing CM-N release with plant uptake and in reducing appreciable amounts of labile C and gaseous N loss under upland conditions and thus, in minimizing environmental risk.
  • Publication
    Evidence of aerobic and anaerobic methane oxidation coupled to denitrification in agricultural soils
    Agricultural soils may act as either a source or a sink for atmospheric methane (CH4) depending on soil type, aeration, water regimes, nutrient availability and environmental variables. The interaction between CH4 and nitrogen (N) has been identified as one of the major gaps in the global carbon (C) and N cycles. Methane is being considered as a low-cost electron donor for coexisting denitrifiers and the denitrification process may be coupled to either aerobic CH4 oxidation involving direct nitrate/nitrite reduction (partial denitrification), or anaerobic relating predominantly to nitrite/nitric oxide reduction (complete denitrification). It is evidenced from isotopic studies that CH4 production and oxidation could take place simultaneously in agricultural soils at water content above field capacity, linking to the presence of anaerobic microsites and aerobic-anaerobic interface. This results in either aerobic or anaerobic CH4 oxidation coupled to the highest N2O emissions, demonstrating a close relationship between CH4 oxidation and denitrification (partial) processes. Besides the involvement of a microbial consortium in the interactive process, recent advancement with microbiological techniques prove the occurrence of the coupled process by combining aerobic methanotrophs and denitrifiers, as well as oxidization of ammonium and metabolic by-products, releasing N2O as a terminal product. However, the apparent anaerobic phenomenon lacks known genes for dinitrogen (N2) production, but subsequent isotopic labelling reveals that methanotrophs could bypass the denitrification intermediate N2O to produce N2 and oxygen that oxidizes CH4. Further investigations using both advanced molecular microbiology and isotope tracing techniques are necessary to elucidate the nature of the processes, better understand the mechanisms in agricultural soils and develop biotechnological solutions to the issues concerning particularly to climate change.
  • Publication
    Contrasting Effects of Forest Type and Stand Age on Soil Microbial Activities: An Analysis of Local Scale Variability
    Understanding the functioning of different forest ecosystems is important due to their key role in strategies for climate change mitigation, especially through soil C sequestration. In controlled laboratory conditions, we conducted a preliminary study on six different forest soils (two coniferous, two deciduous, and two mixed sites comprising trees of different ages) collected from the same region. The aim was to explore any differences and assess seasonal changes in soil microbial parameters (basal respiration BR, microbial biomass Cmic, metabolic quotient qCO2, dehydrogenase activity DHA, and Cmic:Corg ratio). Indicator- and forest-specific seasonality was assessed. In addition to litter input, soil parameters (pH, nutrient content, texture and moisture) strongly regulated the analyzed microbial indicators. PCA analysis indicated similarity between mature mixed and deciduous forests. Among annual mean values, high Cmic and DHA with simultaneously low qCO2 suggest that the mature deciduous stand was the most sustainable in microbial activities among the investigated forest soils. Research on the interrelationship between soil parameters and forest types with different tree ages needs to be continued and extended to analyze a greater number of forest and soil types.
      105Scopus© Citations 6
  • Publication
    Variations in Soil Properties and CO2 Emissions of a Temperate Forest Gully Soil along a Topographical Gradient
    Although forest soils play an important role in the carbon cycle, the influence of topography has received little attention. Since the topographical gradient may affect CO2 emissions and C sequestration, the aims of the study were: (1) to identify the basic physicochemical and microbial parameters of the top, mid-slope, and bottom of a forest gully; (2) to carry out a quantitative assessment of CO2 emission from these soils incubated at different moisture conditions (9% and 12% v/v) and controlled temperature (25 °C); and (3) to evaluate the interdependence between the examined parameters. We analyzed the physicochemical (content of total N, organic C, pH, clay, silt, and sand) and microbial (enzymatic activity, basal respiration, and soil microbial biomass) parameters of the gully upper, mid-slope, and bottom soil. The Fourier Transformed Infrared spectroscopy (FTIR) method was used to measure CO2 emitted from soils. The position in the forest gully had a significant effect on all soil variables with the gully bottom having the highest pH, C, N concentration, microbial biomass, catalase activity, and CO2 emissions. The sand content decreased as follows: top > bottom > mid-slope and the upper area had significantly lower clay content. Dehydrogenase activity was the lowest in the mid-slope, probably due to the lower pH values. All samples showed higher CO2 emissions at higher moisture conditions, and this decreased as follows: bottom > top > mid-slope. There was a positive correlation between soil CO2 emissions and soil microbial biomass, pH, C, and N concentration, and a positive relationship with catalase activity, suggesting that the activity of aerobic microorganisms was the main driver of soil respiration. Whilst the general applicability of these results to other gully systems is uncertain, the identification of the slope-related movement of water and inorganic/organic materials as a significant driver of location-dependent differences in soil respiration, may result in some commonality in the changes observed across different gully systems.
      43Scopus© Citations 3