Labile soil organic matter pools under a mixed grass/lucerne pasture and adjacent native bush in Western Australia

Soil Research ◽  
2007 ◽  
Vol 45 (5) ◽  
pp. 333 ◽  
Author(s):  
A. J. Macdonald ◽  
D. V. Murphy ◽  
N. Mahieu ◽  
I. R. P. Fillery
Keyword(s):  
Organic Matter ◽  
Plant Material ◽  
Surface Soil ◽  
Organic C ◽  
Soil Solutions ◽  
Mixed Grass ◽  
N Enrichment ◽  
Organic Matter Fractions ◽  
Cp Mas Nmr ◽  
13C Cp Mas Nmr

Total C and N were measured in whole soils (0–0.15, 0.15–0.35, and 0.35–0.65 m), light organic matter fractions (<1 g/cm3 (LF 1.0) and 1.0–1.7 g/cm3 (LF 1.7)) in surface soils, and in leaf litter collected from a mixed grass/lucerne pasture and adjacent native bush at Moora, Western Australia. The C content of the plant material and light fractions was characterised by 13C cross-polarisation/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR) spectroscopy. Water-extractable organic C (WEOC) and N (WEON) were measured in soil, and dissolved organic C (DOC) and N (DON) were measured in soil solutions. In addition, both NO3-N and NH4-N (SMN) were measured in soil solutions and water extracts. Total soil C (0–0.65 m) did not differ significantly between land uses, but there was clear evidence of N enrichment under the pasture system, which contained significantly (P < 0.05) more total N in the surface soil (0–0.15 m) compared with that under native bush. The significantly (P < 0.05) smaller C/N ratios of the surface soil, plant litter, and light fractions (LF 1.0 and 1.7) under the pasture provided further evidence of N enrichment. The 13C CP/MAS NMR spectra for plant material and light fractions did not differ greatly between landuses, but in both cases the O-alkyl : alkyl carbon ratio declined with increasing density. The decomposition and subsequent mineralisation of the relatively N-rich organic matter fractions in the pasture system may have contributed to the significantly (P < 0.05) greater DOC, DON, and SMN concentration measured in soil solutions under pasture compared with those under native bush.

Soil stripping and replacement for the rehabilitation of bauxite-mined land at Weipa. I. Initial changes to soil organic matter and related parameters

Soil Research ◽  
2000 ◽  
Vol 38 (2) ◽  
pp. 345 ◽  
Author(s):  
G. D. Schwenke ◽  
D. R. Mulligan ◽  
L. C. Bell
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Field Experiments ◽  
Surface Soil ◽  
Soil Disturbance ◽  
Microbial Biomass C ◽  
Low Grade ◽  
Double Pass ◽  
Organic C ◽  
The Difference

At Weipa, in Queensland, Australia, sown tree and shrub species sometimes fail to establish on bauxite-mined land, possibly because surface-soil organic matter declines during soil stripping and replacement. We devised 2 field experiments to investigate the links between soil rehabilitation operations, organic matter decline, and revegetation failure. Experiment 1 compared two routinely practiced operations, dual-strip (DS) and stockpile soil, with double-pass (DP), an alternative method, and subsoil only, an occasional result of the DS operation. Other treatments included variations in stripping-time, ripping-time, fertiliser rate, and cultivation. Dilution of topsoil with subsoil, low-grade bauxite, and ironstone accounted for the 46% decline of surface-soil (0–10 cm) organic C in DS compared with pre-strip soil. In contrast, organic C in the surface-soil (0–10 cm) of DP plots (25.0 t/ha) closely resembled the pre-strip area (28.6 t/ha). However, profile (0–60 cm) organic C did not differ between DS (91.5 t/ha), DP (107 t/ha), and pre-strip soil (89.9 t/ha). Eighteen months after plots were sown with native vegetation, surface-soil (0–10 cm) organic C had declined by an average of 9% across all plots. In Experiment 2, we measured the potential for post-rehabilitation decline of organic matter in hand-stripped and replaced soil columns that simulated the DS operation. Soils were incubated in situ without organic inputs. After 1 year’s incubation, organic C had declined by up to 26% and microbial biomass C by up to 61%. The difference in organic C decline between vegetated replaced soils (Expt 1) and bare replaced soils (Expt 2) showed that organic inputs affect levels of organic matter more than soil disturbance. Where topsoil was replaced at the top of the profile (DP) and not ploughed, inputs from volunteer native grasses balanced oxidation losses and organic C levels did not decline.

scholarly journals Soil organic matter pools under management systems in Quilombola Territory in Brazilian Cerrado

2017 ◽  
Vol 21 (4) ◽  
pp. 254-260 ◽  
Author(s):  
Robervone S. de M. P. do Nascimento ◽  
Maria L. G. Ramos ◽  
Cícero C. de Figueiredo ◽  
Antonio M. M. Silva ◽  
Stefany B. Silva ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Sensu Stricto ◽  
Management Systems ◽  
Perennial Crop ◽  
Organic C ◽  
Natural Pasture ◽  
Labile C ◽  
Organic Matter Fractions ◽  
Total Organic C

ABSTRACT The aim of this study was to evaluate the stable and labile fractions of soil organic matter and carbon (C) management index in cultivated areas with conservation and conventional management used by Quilombola farmers in the Goiás state, Brazil. The management systems were studied in the areas of Cerradão: Native Cerrado; Pasture; Conventional grain cultivation; Conservation cultivation of perennial crop; and in the sensu stricto Cerrado: Native Cerrado; Natural pasture; Conventional grain cultivation; Conventional cultivation of perennial crop. The study was considered as observational, with five replicates. Total organic C, fractions of humic substances, labile C and C management index were determined. The Cerradão phytophysiognomy had the highest total organic C values and stable soil organic matter fractions. The native areas had low levels of labile C. The conservation cultivation of perennial crop showed the largest accumulation of total organic C in the different fractions of soil organic matter and the highest rates of C management index.

13C CP/MAS-NMR spectra of organic matter as influenced by vegetation, climate, and soil characteristics in soils from Murcia, Spain

2002 ◽  
Vol 82 (4) ◽  
pp. 403-411 ◽  
Author(s):  
A. Faz Cano ◽  
A R Mermut ◽  
R. Ortiz ◽  
M B Benke ◽  
B. Chatson
Keyword(s):  
Organic Matter ◽  
Functional Groups ◽  
Plant Community ◽  
Nmr Spectra ◽  
Climatic Conditions ◽  
Parent Material ◽  
Mas Nmr ◽  
Soil Parameters ◽  
Organic C ◽  
Cp Mas Nmr

Soils in southern Spain are low in organic matter (OM) and nutrients. Understanding the nature and dynamics of OM has potential to improve soil management technologies for sustainable crop production. The objective of this work was to establish the distribution of functional groups in organic-C from these soils using 13C CP/MAS-NMR spectroscopy and to investigate the influence of vegetation, climatic conditions, soil parameters, parent material, and soil order on these functional groups. No statistically significant variability in the distribution of organic-C groups was found as a result of the influence of either soil order or parent material. The content of O-alkyl-C in the soils under the Rhamno-Quercetum plant community was higher (95% probability) than in the soils under the Paronychio-Sideritidetum plant community. Soils located in the mesomediterranean climatic zone displayed a higher content of O-alkyl-C and a lower content of aromatic-C compared to the soils located in the thermomediterranean zone. These differences were statistically significant at 95% of probability. Vegetation and climatic conditions appear to play a major role in the OM decomposition processes in this region. Statistically significant and positive correlations were found between alkyl-C and both cation exchange capacity (CEC) and clay content indicating the recalcitrant nature of these organic compounds. Key words: Organic matter composition, Spanish soils, 13C CP/MAS-NMR spectra, Mediterranean soils, Alfisols, Mollisols, Aridisols

scholarly journals New molecular evidence for surface and sub-surface soil erosion controls on the composition of stream DOM during storm events

2017 ◽  
Author(s):  
Marie Denis ◽  
Laurent Jeanneau ◽  
Patrice Petitjean ◽  
Anaëlle Murzeau ◽  
Marine Liotaud ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Erosion ◽  
Soil Solution ◽  
Surface Runoff ◽  
Surface Soil ◽  
Molecular Evidence ◽  
Storm Events ◽  
Soil Solutions ◽  
Chemical Segregation ◽  
Dom Composition

Abstract. Storm events are responsible for more than 60 % of the export of dissolved organic matter (DOM) from headwater catchments due to an increase in both the discharge and concentration. The latter was attributed to changing water pathways inducing the mobilization of DOM from the surface soil horizons. Recent molecular investigations have challenged this view and hypothesized (i) a contribution of an in-stream partition of organic matter (OM) between eroded particles and the dissolved fraction and (ii) the modification of the composition of soil DOM during storm events. To investigate these assumptions, soil solutions in the macropores, surface runoff and stream outlet were sampled at high frequency during three storm events in the Kervidy-Naizin catchment, part of the French critical zone observatory AgrHys. The molecular composition of the DOM was analysed by thermally assisted hydrolysis and methylation (THM) with tetramethylammonium hydroxide (TMAH) coupled to a gas chromatograph and a quadrupole mass spectrometer. These analyses highlighted a modification of the DOM composition in soil solution controlled by the water-table dynamic and pre-event hydrological conditions. These findings fits with the mechanism of colloidal and particulate destabilization in the soil macroporosity. The different behaviour observed for lignins, carbohydrates and fatty acids highlights a potential chemical segregation based on their hydrophobicity. The composition of surface runoff DOM is similar to the DOM composition in soil solution and could be generated by the same mechanism. The DOM composition in both soil solution and surface runoff corresponds to the stream DOM composition observed during storm events. On the basis of these results, modifications of the stream DOM composition during storm events seem to be due to surface and sub-surface soil erosion rather than in-stream production.

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