Short-term effects of incubated legume and grass materials on soil acidity and C and N mineralisation in a soil of north-east Australia

Soil Research ◽  
2002 ◽  
Vol 40 (7) ◽  
pp. 1231 ◽  
Author(s):  
M. Marx ◽  
B. Marschner ◽  
P. N. Nelson
Keyword(s):  
Plant Material ◽  
Organic Anion ◽  
Perennial Grass ◽  
Plant Residues ◽  
N Mineralisation ◽  
Organic C ◽  
North East ◽  
Ash Alkalinity ◽  
C And N ◽  
Grass Growth

Perennial grass growth forms the basis of beef production systems in northern Australia. To improve pasture productivity the woody legume Stylosanthes has been introduced into these native pastures. However, the growth of legumes has been recognised to be a major factor in soil acidification, thereby reducing soil fertility. In order to determine impacts of Stylosanthes scabra (stylo) or Urochloa mosambicensis (urochloa) residues on soil pH, acid neutralising capacity (ANC), and C and N mineralisation, their tops and roots were incubated at a rate equivalent to 10 t dry matter/ha at 25�C for 25 days in topsoil samples of a Mottled-Subnatric Yellow Sodosol from a long-term field experiment under urochloa or under stylo cover. The amount of CO2-C released during the first 2 days of incubation was correlated with the decrease in dissolved organic C. Plant material addition immediately raised the pH and ANC relative to the control. This was related to the amount of ash alkalinity of the plant residues added to the soil. Since the ash alkalinity is a measure for the organic anion content of plant material, it was concluded that the pH buffering was due to protonation of organic anions. During incubation, net N mineralisation was only observed in the urochloa soil amended with stylo leaves. In all other treatments, N added in the residues was immobilised by microorganisms due to the high availability of easily degradable C-sources. Consequently, there was no further change in pH or ANC during incubation, since no significant amounts of H+ were produced or consumed during N conversion processes.

Decomposition of plant material in Australian soils. III. Residual organic and microbial biomass C and N from isotope-labelled legume material and soil organic matter, decomposing under field conditions

Soil Research ◽  
1985 ◽  
Vol 23 (4) ◽  
pp. 603 ◽  
Author(s):  
JN Ladd ◽  
M Amato ◽  
JM Oades
Keyword(s):  
Microbial Biomass ◽  
South Australia ◽  
Experimental Period ◽  
Decay Rates ◽  
Microbial Biomass C ◽  
Plant Residues ◽  
Total Biomass ◽  
Organic C ◽  
Air Temperatures ◽  
C And N

After eight years decomposition of 14C, 15N-labelled legume (Medicago littoralis) material previously mixed into topsoils (0-10 cm) at four field sites in South Australia, residual organic 14C and 15N to 30 cm depth accounted for respectively 11-13% of input 14C, and 31-38% of input 15N. About 90% of the residual organic 14C and 70-80% of the residual l15N was recovered in topsoils. For sites in similar rainfall areas, soils of heavier texture retained slightly greater amounts of 14C and15N-labelled residues. Throughout the eight-year experimental period, the rates of decline of residual organic 14C and 15N exceeded those of native soil organic C and N. A comparison of the decline of organic 14C in topsoils, averaged for the four South Australian sites, with the average decline reported for 14C-labelled plant residues in soils at English and Nigerian field sites, suggests that net decomposition rates doubled approximately for an 8-9�C rise in mean annual air temperatures. Microbial biomass 14C and 15N of topsoils with time accounted for decreasing proportions of total biomass C and N, and of residual organic I4C and I5N. The relatively greater retention after eight years of biomass 14C and 15N in soils of heavier texture is consistent with the concept that the net decay of C and N in soils is dependent upon the turnover of biomass C and N, and that decay rates are decreased in soils which have the greater capacity to protect decomposer populations.

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 Modelling greenhouse gas emission from organic soils (PEAT-GHG-model)

2017 ◽  
pp. 141-148
Author(s):  
A.N. Polevoy ◽  
A.Yu. Mykytiuk
Keyword(s):  
Plant Material ◽  
Greenhouse Gas Emission ◽  
Soil Layer ◽  
N2o Emission ◽  
Organic Soils ◽  
Plant Residues ◽  
Nitrogen Absorption ◽  
C And N ◽  
Carry Over ◽  
Form Transformation

It is considered that the organic substance of plant residues as well as one of the soil are subdivided into two active compartments and an inert compartment: resistant plant material - RPM, decomposition plant material - DPM, inert organic material - IOM are distinguished, as well as pools of microbiological biomass, BIO, and humus, HUM. All major processes of C and N turnover are included in a model; their intensity is described by a first-order equation. CO2 and CH4 emission under decomposition is studied. Main processes of nitrogen form transformation are simulated under the influence of environmental factors: ammonification, nitrification, denitrification, immobilization, nitrogen absorption by the plant rootage, carry-over of nitrates outside the soil layer of 0 - 50 cm during moisture infiltration, N2O emission under nitrification and denitrification.

Manipulation of rhizosphere organisms to enhance glomalin production and C sequestration: Pitfalls and promises

2014 ◽  
Vol 94 (6) ◽  
pp. 1025-1032 ◽  
Author(s):  
F. L. Walley ◽  
A. W. Gillespie ◽  
Adekunbi B. Adetona ◽  
J. J. Germida ◽  
R. E. Farrell
Keyword(s):  
Plant Growth ◽  
Mycorrhizal Fungi ◽  
Plant Growth Promoting Rhizobacteria ◽  
C Sequestration ◽  
Ionization Mass ◽  
Edge Structure ◽  
Organic C ◽  
Soil C ◽  
N Storage ◽  
C And N

Walley, F. L., Gillespie, A. W., Adetona, A. B., Germida, J. J. and Farrell, R. E. 2014. Manipulation of rhizosphere organisms to enhance glomalin production and C-sequestration: Pitfalls and promises. Can. J. Plant Sci. 94: 1025–1032. Arbuscular mycorrhizal fungi (AMF) reportedly produce glomalin, a glycoprotein that has the potential to increase soil carbon (C) and nitrogen (N) storage. We hypothesized that interactions between rhizosphere microorganisms, such as plant growth-promoting rhizobacteria (PGPR), and AMF, would influence glomalin production. Our objectives were to determine the effects of AMF/PGPR interactions on plant growth and glomalin production in the rhizosphere of pea (Pisum sativum L.) with the goal of enhancing C and N storage in the rhizosphere. One component of the study focussed on the molecular characterization of glomalin and glomalin-related soil protein (GRSP) using complementary synchrotron-based N and C X-ray absorption near-edge structure (XANES) spectroscopy, pyrolysis field ionization mass spectrometry (Py-FIMS), and proteomics techniques to characterize specific organic C and N fractions associated with glomalin production. Our research ultimately led us to conclude that the proteinaceous material extracted, and characterized in the literature, as GRSP is not exclusively of AMF origin. Our research supports the established concept that GRSP is important to soil quality, and C and N storage, irrespective of origin. However, efforts to manipulate this important soil C pool will remain compromised until we more clearly elucidate the chemical nature and origin of this resource.

scholarly journals Perennial herbaceous legumes as live soil mulches and their effects on C, N and P of the microbial biomass

2003 ◽  
Vol 60 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Gustavo Pereira Duda ◽  
José Guilherme Marinho Guerra ◽  
Marcela Teixeira Monteiro ◽  
Helvécio De-Polli ◽  
Marcelo Grandi Teixeira
Keyword(s):  
Microbial Biomass ◽  
Soil Depth ◽  
Vegetation Management ◽  
Pueraria Phaseoloides ◽  
Organic C ◽  
Arachis Pintoi ◽  
Factorial Combination ◽  
C And N ◽  
Microbial C ◽  
Macroptilium Atropurpureum

The use of living mulch with legumes is increasing but the impact of this management technique on the soil microbial pool is not well known. In this work, the effect of different live mulches was evaluated in relation to the C, N and P pools of the microbial biomass, in a Typic Alfisol of Seropédica, RJ, Brazil. The field experiment was divided in two parts: the first, consisted of treatments set in a 2 x 2 x 4 factorial combination of the following factors: live mulch species (Arachis pintoi and Macroptilium atropurpureum), vegetation management after cutting (leaving residue as a mulch or residue remotion from the plots) and four soil depths. The second part had treatments set in a 4 x 2 x 2 factorial combination of the following factors: absence of live mulch, A. pintoi, Pueraria phaseoloides, and M. atropurpureum, P levels (0 and 88 kg ha-1) and vegetation management after cutting. Variation of microbial C was not observed in relation to soil depth. However, the amount of microbial P and N, water soluble C, available C, and mineralizable C decreased with soil depth. Among the tested legumes, Arachis pintoi promoted an increase of microbial C and available C content of the soil, when compared to the other legume species (Pueraria phaseoloides and Macroptilium atropurpureum). Keeping the shoot as a mulch promoted an increase on soil content of microbial C and N, total organic C and N, and organic C fractions, indicating the importance of this practice to improve soil fertility.

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.

Distribution of carbon and nitrogen in a long-term cropping system and permanent pasture system

1993 ◽  
Vol 44 (6) ◽  
pp. 1323 ◽  
Author(s):  
FA Robertson ◽  
RJK Myers ◽  
PG Saffigna
Keyword(s):  
Microbial Biomass ◽  
Crop Residues ◽  
Perennial Grass ◽  
Cropping System ◽  
N Availability ◽  
Continuous Cropping ◽  
Organic C ◽  
Soil Microbial ◽  
Permanent Pasture ◽  
Standing Dead

Nitrogen (N) limitation to productivity of sown perennial grass pastures on the brigalow lands of S.E. Queensland contrasts with adequate N supply to annual crops grown on the same soil. In order to understand this anomaly, the distribution of N and carbon (C) under permanent green panic pasture and under continuous cropping with grain sorghum was compared in an 18 month field study. Total soil N and organic C (0-10 cm) were, respectively, 0.37 and 3.20% under green panic and 0.23 and 2.31% under sorghum. Soil microbial biomass (0-28 cm) contained 246 kg N and 1490 kg C ha-1 under green panic and 147 kg N and 744 kg C ha-1 under sorghum. Enhanced microbial growth under pasture was attributed to the continuous input of available C from surface litter and roots. The C/N ratio of pasture residues was high (greater than 50) and conducive to immobilization of N. Availability of N under pasture was further reduced by approximately 50% of plant N being immobilized in standing dead tissue. Under sorghum, the microbial biomass was well supplied with N, but was limited by C availability. The soil under sorghum received a single large C input when crop residues were returned after harvest. The differences in N availability, and hence productivity, of these soils under cropping and permanent pasture were due primarily to differences in the timing and quality of C inputs.

scholarly journals Simulating soil organic C dynamics in managed grasslands under humid temperate climatic conditions

2020 ◽  
Author(s):  
Asma Jebari ◽  
Jorge Álvaro-Fuentes ◽  
Guillermo Pardo ◽  
María Almagro ◽  
Agustin del Prado
Keyword(s):  
Field Experiments ◽  
Model Performance ◽  
Climatic Conditions ◽  
Plant Residue ◽  
Plant Residues ◽  
Organic C ◽  
Natural Grasslands ◽  
Rothc Model ◽  
Below Ground ◽  
Intensively Managed

Abstract. Temperate grasslands are of paramount importance in terms of soil organic carbon (SOC) dynamics. Globally, research on SOC dynamics has largely focused on forests, croplands and natural grasslands, while intensively managed grasslands has received much less attention. In this regard, we aimed to improve the prediction of SOC dynamics in managed grasslands under humid temperate regions. In order to do so, we modified and recalibrated the SOC model RothC, originally developed to model the turnover of SOC in arable topsoils, which requires limited amount of readily available input data. The modifications proposed for the RothC are: (1) water content up to saturation conditions in the soil water function of RothC to fit the humid temperate climatic conditions, (2) entry pools that account for particularity of exogenous organic matter (EOM) applied (e.g., ruminant excreta), (3) annual variation in the carbon inputs derived from plant residues considering both above- and below-ground plant residue and rhizodeposits components as well as their quality, and (4) the livestock treading effect (i.e., poaching damage) as a common problem in humid areas with higher annual precipitation. In the paper, we describe the basis of these modifications, carry out a simple sensitivity analysis and validate predictions against data from existing field experiments from four sites in Europe. Model performance showed that modified RothC reasonably captures well the different modifications. However, the model seems to be more sensitive to soil moisture and plant residues modifications than to the other modifications. The applied changes in RothC model could be appropriate to simulate both farm and regional SOC dynamics from managed grassland-based systems under humid temperate conditions.

Sign in / Sign up

Export Citation Format

Share Document