Denitrification and denitrifying efficiencies in sediments of Port Phillip Bay: direct determinations of biogenic N2 and N-metabolite fluxes with implications for water quality

1999 ◽  
Vol 50 (6) ◽  
pp. 589 ◽  
Author(s):  
David T. Heggie ◽  
Graham W. Skyring ◽  
Joseph Orchardo ◽  
Andrew R. Longmore ◽  
Geoffrey J. Nicholson ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Sedimentary Facies ◽  
Precision Measurements ◽  
Organic C ◽  
Redfield Ratio ◽  
Tightly Coupled ◽  
C And N ◽  
Muddy Sediments ◽  
Nitrate And Nitrite

High-precision measurements of N2 in benthic chamber waters indicated that denitrification occurs within the major sedimentary facies in Port Phillip Bay. The integrated fluxes of biogenic N2 , ammonia, nitrate and nitrite showed that the stoichiometric relationship between organic C and N in the muddy sediments, occupying about 70% of the seafloor, was 5.7, this being similar to the Redfield ratio of 6.6. High denitrifying efficiencies (75–85%; denitrification rates ~1.3 mmol N2 m–2 day–1) at organic carbon loadings of ~15–25 mmol m–2 day–1 indicate that most N processed through the sediments was returned to the overlying waters as biologically (generally) unavailable N2. At sites of high organic carbon loadings to the sediments (>100 mmol m–2 day–1) denitrification rates and denitrifying efficiencies were near zero and most N is returned to the Bay waters as biologically available ammonium. In chambers ‘spiked’ with 15NO3 , denitrifyers used nitrate produced in the sediments in situ, rather than the exogenous nitrate in overlying waters. The sedimentary microbial processes of ammonification, nitrification and denitrification are therefore tightly coupled.

Soil organic carbon and nitrogen sequestration and turnover in aggregates under subtropical leucaena–grass pastures

Soil Research ◽  
2018 ◽  
Vol 56 (6) ◽  
pp. 632 ◽  
Author(s):  
Kathryn Conrad ◽  
Ram C. Dalal ◽  
Ryosuke Fujinuma ◽  
Neal W. Menzies
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Aggregates ◽  
Soil Mass ◽  
Δ13c And Δ15n ◽  
Organic C ◽  
Carbon And Nitrogen ◽  
Nitrogen Sequestration ◽  
C And N

Stabilisation and protection of soil organic carbon (SOC) in macroaggregates and microaggregates represents an important mechanism for the sequestration of SOC. Legume-based grass pastures have the potential to contribute to aggregate formation and stabilisation, thereby leading to SOC sequestration. However, there is limited research on the C and N dynamics of soil organic matter (SOM) fractions in deep-rooted legume leucaena (Leucaena leucocephala)–grass pastures. We assessed the potential of leucaena to sequester carbon (C) and nitrogen (N) in soil aggregates by estimating the origin, quantity and distribution in the soil profile. We utilised a chronosequence (0–40 years) of seasonally grazed leucaena stands (3–6 m rows), which were sampled to a depth of 0.3 m at 0.1-m intervals. The soil was wet-sieved for different aggregate sizes (large macroaggregates, >2000 µm; small macroaggregates, 250–2000 µm; microaggregates, 53–250 µm; and <53 µm), including occluded particulate organic matter (oPOM) within macroaggregates (>250 µm), and then analysed for organic C, N and δ13C and δ15N. Leucaena promoted aggregation, which increased with the age of the leucaena stands, and in particular the formation of large macroaggregates compared with grass in the upper 0.2 m. Macroaggregates contained a greater SOC stock than microaggregates, principally as a function of the soil mass distribution. The oPOM-C and -N concentrations were highest in macroaggregates at all depths. The acid nonhydrolysable C and N distribution (recalcitrant SOM) provided no clear distinction in stabilisation of SOM between pastures. Leucaena- and possibly other legume-based grass pastures have potential to sequester SOC through stabilisation and protection of oPOM within macroaggregates in soil.

scholarly journals Total C and N storage and organic C pools of a Red-Yellow Podzolic under conventional and no tillage at the Atlantic Forest Zone, south-eastern Brazil

Soil Research ◽  
2003 ◽  
Vol 41 (4) ◽  
pp. 717 ◽  
Author(s):  
L. F. C. Leite ◽  
E. S. Mendonça ◽  
P. L. O. A. Machado ◽  
E. S. Matos
Keyword(s):  
Organic Carbon ◽  
Atlantic Forest ◽  
Soil Management ◽  
Microbial Biomass C ◽  
No Tillage ◽  
Forest Zone ◽  
Organic C ◽  
C Stocks ◽  
C And N ◽  
The Impact

A 15-year experiment in a clayey Red-Yellow Podzolic in the tropical highlands of Viçosa, Brazil, was studied in 2000, aiming to evaluate the impact of different management systems (no tillage, disk plowing, heavy scratcher + disk plowing, and heavy scratched) on the total organic carbon (TOC), total nitrogen (TN), and several organic carbon pools. A natural forest, adjacent to the experimental area, was used as reference. The greatest TOC and TN as well as microbial biomass C (CMB), light fraction C (CFL), and labile organic carbon (CL) stocks were observed in the Atlantic Forest, compared with all other systems. The long-term cultivation (±70 years) of this area, prior to the installation of the experiment, has led to soil degradation, slowing the C recovery. No tillage had the higher C and N stocks and greater CL pool at the surface (0–10 cm), indicating improvement in soil nutrient status, although none of the systems presented potential to sequester C-CO2. Sustainable tropical agricultural systems should involve high residue input and conservative soil management in order to act as a C-CO2 sink. The C stocks in the CMB, CFL, and CL compartments were more reduced in relation to the natural vegetation with higher intensity management than the TOC stocks. This result indicates that these C compartments are more sensitive to changes in the soil management.

No-tillage and nitrogen application affects the decomposition of 15N-labelled wheat straw and the levels of mineral nitrogen and organic carbon in a Vertisol

2007 ◽  
Vol 47 (7) ◽  
pp. 862 ◽  
Author(s):  
R. C. Dalal ◽  
W. M. Strong ◽  
J. E. Cooper ◽  
A. J. King
Keyword(s):  
Organic Carbon ◽  
Wheat Straw ◽  
Residence Time ◽  
Mean Residence Time ◽  
No Tillage ◽  
Tillage Practice ◽  
Straw Decomposition ◽  
Mineral N ◽  
Organic C ◽  
C And N

No-tillage (NT) practice, where straw is retained on the soil surface, is increasingly being used in cereal cropping systems in Australia and elsewhere. Compared to conventional tillage (CT), where straw is mixed with the ploughed soil, NT practice may reduce straw decomposition, increase nitrogen immobilisation and increase organic carbon in the soil. This study examined 15N-labelled wheat straw (stubble) decomposition in four treatments (NT v. CT, with N rates of 0 and 75 kg/ha.year) and assessed the tillage and fertiliser N effects on mineral N and organic C and N levels over a 10-year period in a field experiment. NT practice decreased the rate of straw decomposition while fertiliser N application increased it. However, there was no tillage practice × N interaction. The mean residence time of the straw N in soil was more than twice as long under the NT (1.2 years) as compared to the CT practice (0.5 years). In comparison, differences in mean residence time due to N fertiliser treatment were small. However, tillage had generally very little effect on either the amounts of mineral N at sowing or soil organic C (and N) over the study period. While application of N fertiliser increased mineral N, it had very little effect on organic C over a 10-year period. Relatively rapid decomposition of straw and short mean residence time of straw N in a Vertisol is likely to have very little long-term effect on N immobilisation and organic C level in an annual cereal cropping system in a subtropical, semiarid environment. Thus, changing the tillage practice from CT to NT may not necessitate additional N requirement unless use is made of additional stored water in the soil or mineral N loss due to increased leaching is compensated for in N supply to crops.

scholarly journals Long-term tillage and crop rotation effects on soil quality, organic carbon, and total nitrogen

2014 ◽  
Vol 94 (3) ◽  
pp. 303-315 ◽  
Author(s):  
Laura L. Van Eerd ◽  
Katelyn A. Congreves ◽  
Adam Hayes ◽  
Anne Verhallen ◽  
David C. Hooker
Keyword(s):  
Organic Carbon ◽  
Winter Wheat ◽  
Soil Quality ◽  
Crop Rotation ◽  
Total Nitrogen ◽  
Total N ◽  
Organic C ◽  
C And N ◽  
Production Practices

Van Eerd, L. L., Congreves, K. A., Hayes, A., Verhallen, A. and Hooker, D. C. 2014. Long-term tillage and crop rotation effects on soil quality, organic carbon, and total nitrogen. Can. J. Soil Sci. 94: 303–315. Long-term studies allow for quantification of the effects of crop production practices, such as tillage and crop rotation, on soil quality and soil C and N stores. In two experiments at Ridgetown, ON, we evaluated the long-term (11 and 15 yr) effect of tillage system and crop rotation on soil quality via the Cornell Soil Health Assessment (CSHA) at 0–15 cm and soil organic C (SOC) and total N at 5-, 10-, and 20-cm increments to 120 cm depth. The CSHA soil quality score and SOC and total N were higher with no-till (NT) than fall moldboard plough with spring cultivation (conventional tillage, CT) and rotations with winter wheat [soybean–winter wheat (S-W) and soybean–winter wheat–corn (S-W-C)] compared with rotations without winter wheat. In both long-term trials, NT had ca. 21 Mg ha−1more or 14% higher SOC than CT in the 0- to 100-cm soil profile, a trend which contrasts previous research in eastern Canada. Thus, the two long-term trial results at Ridgetown suggest that to improve soil quality and storage of C and N, growers on clay loam soil in southwestern Ontario should consider adopting NT production practices and including winter wheat in the rotation.

scholarly journals Nitrate uptake and carbon exudation – do plant roots stimulate or inhibit denitrification?

2020 ◽  
Author(s):  
Pauline Sophie Rummel ◽  
Reinhard Well ◽  
Birgit Pfeiffer ◽  
Klaus Dittert ◽  
Sebastian Floßmann ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Plant Growth ◽  
Nitrate Uptake ◽  
N Uptake ◽  
Root Exudation ◽  
Mineral N ◽  
Double Labeling ◽  
Organic C ◽  
C And N

Abstract Background and aims Plant growth affects soil moisture, mineral N and organic C availability in soil, all of which influence denitrification. With increasing plant growth, root exudation may stimulate denitrification, while N uptake restricts nitrate availability. Methods We conducted a double labeling pot experiment with either maize (Zea mays L.) or cup plant (Silphium perfoliatum L.) of the same age but differing in size of their shoot and root systems. The 15N gas flux method was applied to directly quantify N2O and N2 fluxes in situ. To link denitrification with available C in the rhizosphere, 13CO2 pulse labeling was used to trace C translocation from shoots to roots and its release by roots into the soil. Results Plant water and N uptake were the main factors controlling daily N2O + N2 fluxes, cumulative N emissions, and N2O production pathways. Accordingly, pool-derived N2O + N2 emissions were 30–40 times higher in the treatment with highest soil NO3− content and highest soil moisture. CO2 efflux from soil was positively correlated with root dry matter, but we could not detect any relationship between root-derived C and N2O + N2 emissions. Conclusions Root-derived C may stimulate denitrification under small plants, while N and water uptake become the controlling factors with increasing plant and root growth.

scholarly journals Implications of carbon saturation model structures for simulated nitrogen mineralization dynamics

2014 ◽  
Vol 11 (23) ◽  
pp. 6725-6738 ◽  
Author(s):  
C. M. White ◽  
A. R. Kemanian ◽  
J. P. Kaye
Keyword(s):  
Soil Texture ◽  
N Mineralization ◽  
Plant Residues ◽  
Short Term ◽  
Organic C ◽  
Soil C ◽  
Biogeochemical Models ◽  
Tightly Coupled ◽  
C And N ◽  
Model Structures

Abstract. Carbon (C) saturation theory suggests that soils have a limited capacity to stabilize organic C and that this capacity may be regulated by intrinsic soil properties such as clay concentration and mineralogy. While C saturation theory has advanced our ability to predict soil C stabilization, few biogeochemical ecosystem models have incorporated C saturation mechanisms. In biogeochemical models, C and nitrogen (N) cycling are tightly coupled, with C decomposition and respiration driving N mineralization. Thus, changing model structures from non-saturation to C saturation dynamics can change simulated N dynamics. In this study, we used C saturation models from the literature and of our own design to compare how different methods of modeling C saturation affected simulated N mineralization dynamics. Specifically, we tested (i) how modeling C saturation by regulating either the transfer efficiency (ε, g C retained g−1 C respired) or transfer rate (k) of C to stabilized pools affected N mineralization dynamics, (ii) how inclusion of an explicit microbial pool through which C and N must pass affected N mineralization dynamics, and (iii) whether using ε to implement C saturation in a model results in soil texture controls on N mineralization that are similar to those currently included in widely used non-saturating C and N models. Models were parameterized so that they rendered the same C balance. We found that when C saturation is modeled using ε, the critical C : N ratio for N mineralization from decomposing plant residues (rcr) increases as C saturation of a soil increases. When C saturation is modeled using k, however, rcr is not affected by the C saturation of a soil. Inclusion of an explicit microbial pool in the model structure was necessary to capture short-term N immobilization–mineralization turnover dynamics during decomposition of low N residues. Finally, modeling C saturation by regulating ε led to similar soil texture controls on N mineralization as a widely used non-saturating model, suggesting that C saturation may be a fundamental mechanism that can explain N mineralization patterns across soil texture gradients. These findings indicate that a coupled C and N model that includes saturation can (1) represent short-term N mineralization by including a microbial pool and (2) express the effects of texture on N turnover as an emergent property.

scholarly journals Assessment of Microbial Biomass Carbon and Nitrogen in Some Tea Soils of Bangladesh

1970 ◽  
Vol 25 (1) ◽  
pp. 21-25
Author(s):  
SM Abdur Rahman ◽  
ARM Solaiman
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Microbial Biomass Carbon ◽  
Microbial Biomass C ◽  
Biomass Carbon ◽  
Total N ◽  
Organic C ◽  
Biomass N ◽  
C And N ◽  
Tea Garden

Microbial biomass carbon (C) and nitrogen (N) and their contribution to soil organic carbon and total N contents were assessed in soils collected from Bilashchara Tea Estate under Bangladesh Tea Research Institute (BTRI), Srimangal of Moulavibazar district, and Sripur Tea Garden under Jaintapur of Sylhet district. Microbial biomass C and N in Bila shchara Tea Estate soils varied from 90.4-144.0 and 20.5-29.0 mg/kg soil, and that of Sripur Tea Garden soils varied from 120.7-362.0 and 26.6-59.5 mg/kg soil, respectively. Within the two tea growing areas biomass C/N ratios ranged from 3.35-6.12. Relationships between biomass C and organic carbon and biomass N and total N were positively correlated. The contribution of biomass C to soil organic C was 1.23%, ranging from 0.9-1.55% and the contribution of biomass N to total N content of the soils ranged from 1.19-2.89%. Keywords: Biomass carbon (C); Biomass nitrogen (N); Organic C; Total N; Tea soilDOI: http://dx.doi.org/10.3329/bjm.v25i1.4850 Bangladesh J Microbiol, Volume 25, Number 1, June 2008, pp 21-25

Soil properties in organic olive orchards following different weed management in a rolling landscape of Andalusia, Spain

2012 ◽  
Vol 29 (1) ◽  
pp. 83-91 ◽  
Author(s):  
María-Auxiliadora Soriano ◽  
Sonia Álvarez ◽  
Blanca B. Landa ◽  
José A. Gómez
Keyword(s):  
Organic Carbon ◽  
Soil Properties ◽  
Weed Management ◽  
C:N Ratio ◽  
Principal Component ◽  
Soil Management ◽  
Exchange Capacity ◽  
Management Systems ◽  
Organic C ◽  
C And N

AbstractThis study evaluated the most significant physical, chemical and biological soil properties from a group of organic olive farms located in a typical olive-growing area of Andalusia, Spain, after 5 or more years since the shift from conventional to organic farming, and compared soils with those in nearby undisturbed (U) natural areas. Two soil management systems implemented in these organic olive farms to control weeds, tillage (T), characterized by non-inverting-shallow tillage in spring, and mechanical mowing (M), were compared and evaluated against the U areas. Organic olive orchards showed similar productivity (average fruit yield of 3130 kg ha−1 yr−1) as the conventional, rain-fed olive groves in the same area, with no significant differences due to soil management systems. Soil properties in the olive orchards (i.e. texture, pH, organic carbon (C), organic nitrogen (N), C:N ratio, cation exchange capacity (CEC) and exchangeable potassium) were in the suitable range for olive farming in both soil managements, although organic C and N, saturated hydraulic conductivity and available water-holding capacity (AWC) of the soil were lower than in the U areas. A principal component analysis (PCA) for soil properties in topsoil (0–10 cm depth) distinguished the T from M olive orchards and U areas, and determined organic C and N as the most significant soil properties to characterize them. Average values of soil organic carbon (SOC) stocks for the surface layer (0–10 cm depth) were 18.6, 59.3 and 67.8 Mg ha−1, for T and M soil management systems and U areas, respectively. This indicates that the sustainability of organic olive orchards could be significantly improved by shifting to M soil management to decrease soil erosion and depletion of SOC.

Effects of nitrogen fertilizer and manure application on storage of carbon and nitrogen under continuous maize cropping in Arenosols and Luvisols of Zimbabwe

2015 ◽  
Vol 154 (2) ◽  
pp. 242-257 ◽  
Author(s):  
L. MUJURU ◽  
L. RUSINAMHODZI ◽  
J. NYAMANGARA ◽  
M. R. HOOSBEEK
Keyword(s):  
Organic Carbon ◽  
Soil Quality ◽  
Nitrogen Fertilizer ◽  
Sandy Soils ◽  
Crop Productivity ◽  
Clayey Soils ◽  
Total Organic Nitrogen ◽  
Organic C ◽  
Continuous Maize ◽  
C And N

SUMMARYSoil organic matter (SOM) is important for long-term crop productivity through maintenance of soil quality and is also now receiving attention due to its potential for climate change mitigation. The objectives of the present study were to investigate the effects of 9 years of fertilization on soil organic carbon (SOC) and total organic nitrogen (TON) and their fractions for the 0–50 cm profile in clayey (Luvisols) and sandy (Arenosols) soils in Murewa District, Zimbabwe. Three treatments were assessed: unfertilized (Control), nitrogen fertilizer (Nfert) and nitrogen fertilizer plus cattle manure (Nfert+manure). Density fractionation was used to assess the distribution of SOC and TON in three SOM fractions and their sensitivity to fertilization in fields 0–50 m away from homesteads (Homefields) and > 100 m away from homesteads (outfields). The relationship between light and heavy fraction organic carbon (C) were analysed to determine equilibrium levels that give an indication of carbon storage potential. In clayey soils total organic C under Nfert+manure was 4% higher than Nfert and 16% higher than the control. In sandy soils, SOC stocks were lowest in the control and highest in Nfert treatments at all depths. Nine years of fertilization significantly influenced SOC concentrations and storage up to 20 cm depth, below which stocks and concentrations of C and N were statistically insignificant. Distribution of C and N in density fractions showed greater stabilization under Nfert+manure in clayey soils, whereas it was greater under Nfert in sandy soils. Estimation of equilibrium levels suggested that homefields had potential to store more C, whereas outfields and control treatments had limited capacity due to attainment of lower equilibrium levels. Application of manure can be a low-cost alternative for enhancing soil quality and promoting soil C sequestration under conventionally tilled continuous maize cropping systems in Zimbabwe.

Annual variation of tissue biomass and carbon and nitrogen content in the freshwater bivalve Corbicula fluminea relative to downstream dispersal

1989 ◽  
Vol 67 (1) ◽  
pp. 82-90 ◽  
Author(s):  
Carol J. Williams ◽  
Robert F. McMahon
Keyword(s):  
Seasonal Variation ◽  
Organic Carbon ◽  
Nitrogen Content ◽  
C:N Ratio ◽  
Corbicula Fluminea ◽  
Dry Weight ◽  
Power Station ◽  
Organic C ◽  
Tissue Weight ◽  
C And N

Tissue dry weight biomass, ash-free dry weight, organic carbon content, nitrogen content, and organic carbon: nitrogen ratio (C:N) of individuals of Corbicula fluminea were monitored monthly over an annual reproductive cycle in a population living in an inlet from which a power station drew cooling water; the same variables were monitored for clams trapped on traveling screens in power station water intake embayments. These measurements were used to determine the relationship between tissue condition and downstream dispersal behavior. The ratio of dry tissue weight to dry shell weight showed marked seasonal variation: it was minimal during reproduction and maximal during overwintering, nonreproductive periods. Fractional ash content increased and organic content decreased during reproduction as shelled juveniles accumulated in the inner demibranchs. Seasonal variation in tissue organic C and N biomass corresponded directly to variation in dry tissue weight. Tissue C:N ratio was 6.0:1 in overwintering individuals and 4.9:1 during reproduction, indicating reduction of non-proteinaceous energy reserves. Reduction of the C:N ratio, dry tissue weight, and C and N biomass during reproduction suggests transfer of organic biomass to gamete production. Dry tissue weight, tissue organic C and N biomass, and C:N ratio were also reduced in individuals impinging on traveling screens, indicating poor nutritional status. Passive adult downstream dispersal onto traveling screens occurred only before periods during which clams incubated eggs and embryonic stages on the gills and released juveniles. Thus, downstream dispersal apparently allows relocation of individuals in poor nutritional condition to microhabitats more favorable for acquisition of energy for reproductive effort.

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