Soil C and N turnover after incorporation of chopped maize, barley straw and blue grass in the field: Evaluation of the DAISY soil–organic-matter submodel

An area of native savanna on an Oxisol in the Eastern Plains of Colombia was opened and sown to various rotations of grass or grass-legume pasture with rice. After 4.5 years, the soil was sampled for studying the effect of land conversion on soil aggregation and on the distribution of total and particulate soil organic matter across the aggregate size classes. The size distribution of undisturbed aggregates did not vary among treatments. Five different methods were used to measure wet aggregate stability (WAS). The choice of method affected the WAS average across treatments as well as the differences among treatments. The only consistent observation was the lower WAS under monocropped rice compared with the other treatments. Inclusion of a legume in a pasture hardly affected aggregate stability. In contrast to the WAS measurements, which were carried out with soil aggregates of 1-2 mm, wet sieving of whole-soil samples revealed additional differences among treatments: large macroaggregates (>2 mm) proved less stable under those treatments that involved soil disturbance through ploughing and harvesting. Total soil C and N content did not vary among treatments, despite considerable differences in plant production levels. The C concentration, but not the N concentration, declined with decreasing aggregate size. The distribution of whole-soil C and N content across aggregate size classes depended more on the amount of soil in a certain size class than on the size class's C or N concentration. Those treatments that involved frequent soil disturbance had a smaller fraction of large macroaggregates (>2 mm) and, as a consequence, less C and N in the large macroaggregate fraction. The particulate organic matter (POM) fraction accounted for only 6.2-8.5% of total soil carbon. The small size of this pool makes it unlikely that POM can serve in these Oxisols for estimating the amount of soil organic matter with medium turnover rate, as suggested by others.

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Soil organic matter in fire-affected pastures and in an Araucaria forest in South-Brazilian Leptosols

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2012000500011 ◽

2012 ◽

Vol 47 (5) ◽

pp. 707-715 ◽

Cited By ~ 11

Author(s):

Mariana da Luz Potes ◽

Deborah Pinheiro Dick ◽

Graciele Sarante Santana ◽

Michely Tomazi ◽

Cimélio Bayer

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Grazing Intensity ◽

Soil C ◽

Araucaria Forest ◽

Physical Fractionation ◽

C Stocks ◽

Native Pasture ◽

Soil C And N ◽

C And N

The objective of this work was to evaluate the distribution pattern and composition of soil organic matter (SOM) and its physical pools of Leptosols periodically affected by fire over the last 100 years in South Brazil. Soil samples at 0-5, 5-10, and 10-15 cm depths were collected from the following environments: native pasture without burning in the last year and grazed with 0.5 livestock per hectare per year (1NB); native pasture without burning in the last 23 years and grazed with 2.0 livestock per hectare per year (23NB); and an Araucaria forest (AF). Physical fractionation was performed with the 0-5 and 5-10 cm soil layers. Soil C and N stocks were determined in the three depths and in the physical pools, and organic matter was characterized by infrared spectroscopy and thermogravimetry. The largest C stocks in all depths and physical pools were found under the AF. The 23NB environment showed the lowest soil C and N stocks at the 5-15 cm depth, which was related to the end of burning and to the higher grazing intensity. The SOM of the occluded light fraction showed a greater chemical recalcitrance in 1NB than in 23NB. Annual pasture burning does not affect soil C stocks up to 15 cm of depth.

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Top-down and bottom-up controls on soil carbon and nitrogen cycling with repeated burning across four ecosystems

10.1101/565135 ◽

2019 ◽

Cited By ~ 1

Author(s):

Adam F. A. Pellegrini ◽

Sarah E. Hobbie ◽

Peter B. Reich ◽

Ari Jumpponen ◽

E. N. Jack Brookshire ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Soil Carbon ◽

Fire History ◽

Tree Cover ◽

Top Down ◽

Bottom Up ◽

Soil C ◽

Soil C And N ◽

C And N

AbstractFires shape the biogeochemistry and functioning of many ecosystems, but fire frequencies are changing across large areas of the globe. Frequent fires can change soil carbon (C) and nitrogen (N) storage through both “top-down” pathways, by altering inputs through shifting plant composition and biomass, and “bottom-up” ones, by altering losses through decomposition and turnover of soil organic matter. However, the relative importance of these different pathways and the degree to which they regulate ecosystem responses to decades of changing fire frequencies is uncertain. Here, we sampled soils and plant communities in four North American and African sites spanning tropical savanna, temperate coniferous savanna, temperate broadleaf savanna, and temperate coniferous forest that each contained multiple plots repeatedly burned for 33-61 years and nearby plots that were protected from fire over the same period. The sites varied markedly in temperature, precipitation, species composition, fire history and soil chemistry; thus they represent a broad test for the generality of fire impacts on biogeochemical cycling. For all four sites, bulk soil C and N by were 25-180% higher in unburned vs. frequently burned plots, with greater soil losses occurring in areas with greater declines in tree cover and biomass inputs into soils. Fire reduced the activity of soil extracellular enzymes that hydrolyze labile C and N from soil organic matter by two- to ten-fold, whereas tree cover was the predominant control on the oxidation of recalcitrant C compounds. C-acquisition enzyme activity tended to decline with decreasing soil N, suggesting that N losses may contribute to limited decomposition, buffering systems against increased losses of soil C with fire. In conclusion, variability in how fire alters soil C and N across ecosystems can be explained partly by fire-driven changes in tree cover and biomass, but the slower turnover of organic matter we observed may offset some of the reduction of C inputs from plants after fire.

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Post-thinning soil organic matter evolution and soil CO2 effluxes in temperate radiata pine plantations: impacts of moderate thinning regimes on the forest C cycle

Canadian Journal of Forest Research ◽

10.1139/x2012-137 ◽

2012 ◽

Vol 42 (11) ◽

pp. 1953-1964 ◽

Cited By ~ 4

Author(s):

Irene Fernandez ◽

Juan Gabriel Álvarez-González ◽

Beatríz Carrasco ◽

Ana Daría Ruíz-González ◽

Ana Cabaneiro

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Radiata Pine ◽

Soil Samples ◽

Mitigation Strategies ◽

Change Scenario ◽

Soil C ◽

C Storage ◽

C Cycle ◽

C And N

Forest ecosystems can act as C sinks, thus absorbing a high percentage of atmospheric CO2. Appropriate silvicultural regimes can therefore be applied as useful tools in climate change mitigation strategies. The present study analyzed the temporal changes in the effects of thinning on soil organic matter (SOM) dynamics and on soil CO2 emissions in radiata pine ( Pinus radiata D. Don) forests. Soil C effluxes were monitored over a period of 2 years in thinned and unthinned plots. In addition, soil samples from the plots were analyzed by solid-state 13C-NMR to determine the post-thinning SOM composition and fresh soil samples were incubated under laboratory conditions to determine their biodegradability. The results indicate that the potential soil C mineralization largely depends on the proportion of alkyl-C and N-alkyl-C functional groups in the SOM and on the microbial accessibility of the recalcitrant organic pool. Soil CO2 effluxes varied widely between seasons and increased exponentially with soil heating. Thinning led to decreased soil respiration and attenuation of the seasonal fluctuations. These effects were observed for up to 20 months after thinning, although they disappeared thereafter. Thus, moderate thinning caused enduring changes to the SOM composition and appeared to have temporary effects on the C storage capacity of forest soils, which is a critical aspect under the current climatic change scenario.

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Effects of climate change on soil organic matter chemical composition and carbon content in different physical fractions

10.5194/egusphere-egu21-9216 ◽

2021 ◽

Author(s):

Moritz Mohrlok ◽

Victoria Martin ◽

Alberto Canarini ◽

Wolfgang Wanek ◽

Michael Bahn ◽

...

Keyword(s):

Climate Change ◽

Organic Matter ◽

Chemical Composition ◽

Soil Organic Matter ◽

Soil C ◽

Size Classes ◽

Soil Fractions ◽

Total Soil ◽

C And N ◽

Amp Clay

Soil organic matter (SOM) is composed of many pools with different properties (e.g. turnover times) which are generally used in biogeochemical models to predict carbon (C) dynamics. Physical fractionation methods are applied to isolate soil fractions that correspond to these pools. This allows the characterisation of chemical composition and C content of these fractions. There is still a lack of knowledge on how these individual fractions are affected by different climate change drivers, and therefore the fate of SOM remains elusive. We sampled soils from a multifactorial climate change experiment in a managed grassland in Austria four years after starting the experiment to investigate the response of SOM in physical soil fractions to temperature (eT: ambient and elevated by +3&#176;C), atmospheric CO2-concentration (eCO2: ambient and elevated by +300 ppm) and to a future climate treatment (eT x eCO2: +3&#176;C and + 300 ppm). A combination of slaking and wet sieving was used to obtain three size classes: macro-aggregates (maA, > 250 &#181;m), micro-aggregates (miA, 63 &#181;m &#8211; 250 &#181;m) and free silt & clay (sc, < 63 &#181;m). In both maA and miA, four different physical OM fractions were then isolated by density fractionation (using sodium polytungstate of &#961; = 1.6 g*cm-3, ultrasonication and sieving): Free POM (fPOM), intra-aggregate POM (iPOM), silt & clay associated OM (SCaOM) and sand-associated OM (SaOM). We measured C and N contents and isotopic composition by EA-IRMS in all fractions and size classes and used a Pyrolysis-GC/MS approach to assess their chemical composition. For eCO2 and eT x eCO2 plots, an isotope mixing-model was used to calculate the proportion of recent C derived from the elevated CO2 treatment. Total soil C and N did not significantly change with treatments.&#160; eCO2 decreased the relative proportion of maA-mineral-associated C and increased C in fPOM and iPOM. About 20% of bulk soil C was represented by the recent C derived from the CO2 fumigation treatment. This significantly differed between size classes and density fractions (p < 0.001), which indicates inherent differences in OM age and turnover. Warming reduced the amount of new C incorporated into size classes. We found that each size class and fraction possessed a unique chemical fingerprint, but this was not significantly changed by the treatments. Overall, our results show that while climate change effects on total soil C were not significant after 4 years, soil fractions showed specific effects. Chemical composition differed significantly between size classes and fractions but was unaffected by simulated climate change. This highlights the importance to separate SOM into differing pools, while including changes to the molecular composition might not be necessary for improving model predictions.&#160;&#160;&#160;&#160;

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Soil organic matter as influenced by straw management practices and inclusion of grass and clover seed crops in cereal rotations

Soil Research ◽

10.1071/sr01103 ◽

2003 ◽

Vol 41 (1) ◽

pp. 95 ◽

Cited By ~ 17

Author(s):

D. Curtin ◽

P. M. Fraser

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Management Practices ◽

Degree Days ◽

Straw Management ◽

Soil C ◽

Total Soil ◽

C And N ◽

Second Year ◽

Seed Crops

In New Zealand, cereal straw has traditionally been burned to facilitate seedbed preparation for the succeeding crop. Because of concerns over the decline of organic matter and the associated deterioration in soil structure, farmers are interested in incorporating crop residues as a means of maintaining organic matter levels. In a 6-year trial on a Wakanui silt loam on the Canterbury Plains, we evaluated the effects of 3 straw management practices (i.e. straw incorporation, burning of straw, and straw removal) on total and labile soil organic matter. A fourth treatment was included to evaluate the local practice of including seed crops (grass and clover) in cereal rotations. The seed crops were grown every second year, the crop sequence being cereal–ryegrass–cereal–clover–cereal–clover. The rate of straw (wheat) decomposition was determined using a litter bag technique, with the bags being buried at a depth of 15 cm for intervals of up to 19 months. In the straw-incorporated treatment, about 25 t/ha of straw (~11 t C/ha) was returned to the soil during the trial. However, there was no significant effect (P > 0.05) of straw management treatments on total soil C (or N), or on labile organic matter pools, although there was a tendency for higher levels of mineralisable C and N where straw was incorporated. Measured straw decomposition rates were consistent with predictions of the Douglas-Rickman residue decomposition model. Under the relatively warm conditions of the Canterbury Plains (thermal time typically >4000 degree-days per year, calculated as the sum of daily degree-days above a base temperature of 0�C), about three-quarters of incorporated straw decomposed within a year. Of the 11 t C/ha of straw-C incorporated, we estimated that only about 1 t C/ha would remain in the soil at the time of sampling. An increase in soil C by this amount would not be detectable (total soil C was about 55 t/ha in the upper 15 cm). Growing seed crops every second year increased several of the labile organic pools (mineralisable C and N, light fraction C and N, microbial biomass) in the 0–7.5 and 7.5 cm soil layers and this may have beneficial effects (e.g. improved N supply) on the succeeding cereal crop. However, the seed crops did not significantly increase total soil organic matter within the 6 years.

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Changes in the soil C and N contents, C decomposition and N mineralization potentials in a rice paddy after long-term application of inorganic fertilizers and organic matter

Soil Science & Plant Nutrition ◽

10.1080/00380768.2016.1155169 ◽

2016 ◽

Vol 62 (2) ◽

pp. 212-219 ◽

Cited By ~ 21

Author(s):

Weiguo Cheng ◽

Agnes T. Padre ◽

Chizuru Sato ◽

Hiroyuki Shiono ◽

Satoshi Hattori ◽

...

Keyword(s):

Organic Matter ◽

N Mineralization ◽

Rice Paddy ◽

Inorganic Fertilizers ◽

Soil C ◽

C Decomposition ◽

Soil C And N ◽

C And N

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Effects of manure quality and application forms on soil C and N turnover of a subtropical oasis soil under laboratory conditions

Biology and Fertility of Soils ◽

10.1007/s00374-003-0689-z ◽

2004 ◽

Vol 39 (3) ◽

pp. 165-171 ◽

Cited By ~ 33

Author(s):

Florian Wichern ◽

Torsten M�ller ◽

Rainer Georg Joergensen ◽

Andreas Buerkert

Keyword(s):

Soil C ◽

N Turnover ◽

Laboratory Conditions ◽

Soil C And N ◽

C And N ◽

Application Forms

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Mineralisation of organic matter in intact versus sieved/refilled soil cores

Soil Research ◽

10.1071/sr01003 ◽

2002 ◽

Vol 40 (1) ◽

pp. 149 ◽

Cited By ~ 15

Author(s):

R. Stenger ◽

G. F. Barkle ◽

C. P. Burgess

Keyword(s):

Organic Matter ◽

N Mineralisation ◽

Soil Cores ◽

Nitrogen Mineralisation ◽

Soil C ◽

Soil Microbial ◽

Conditioning Period ◽

Incubation Study ◽

Soil C And N ◽

C And N

In a 6-month laboratory incubation study, we compared the net C and N mineralisation of the soil organic matter (SOM) of 3 pasture soils and the mineralisation of glucose-C in intact versus sieved/refilled soil cores. The main questions were whether the net C and N mineralisation differed between intact and sieved/refilled soil cores after a conditioning period of 4 weeks, and how much the C and N mineralisation of SOM differed among the similarly managed pasture soils. Apart from the net nitrogen mineralisation in one soil, there were no significant differences in cumulated mineralisation of C or N from SOM between the core types. In a fine-textured soil, net mineralisation of glucose-C differed significantly between core types, which was attributed to the different distribution of the amended glucose in intact and sieved/refilled cores. Net C and N mineralisation of SOM were closely correlated in the sieved/refilled cores, whereas no significant correlation was found in the intact cores. Expressing net C and N mineralisation as percentages of total soil C and N showed a more than 2-fold maximum difference between the soils in spite of similar long-term organic matter input. Subsequent studies should be done using more replicates and wider diameter, better controllable cores on ceramic plates. CO2, net nitrogen mineralisation (NNM), soil microbial biomass.

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