Soil stripping and replacement for the rehabilitation of bauxite-mined land at Weipa. III. Simulated long-term soil organic matter development

Soil Research ◽  
2000 ◽  
Vol 38 (2) ◽  
pp. 395 ◽  
Author(s):  
G. D. Schwenke ◽  
D. R. Mulligan ◽  
L. C. Bell
Keyword(s):  
Organic Matter ◽  
Rate Of Change ◽  
Native Forest ◽  
N Losses ◽  
Organic C ◽  
Highly Sensitive ◽  
Long Term Trends ◽  
Undisturbed Forest ◽  
C And N

Long-term trends in soil organic carbon (C) and nitrogen (N) under current and alternative rehabilitation practices at Weipa were simulated using the CENTURY model. After 100 years, predicted organic C in the surface soils (0–20 cm) of each treatment had risen to new dynamic equiliPbria. Since the ‘passive’ pool of recalcitrant organic C, which occupied 47% of organic C, changed little over the simulation period, the new equilibria differed according to initial organic C content. Most organic matter recovery occurred in the ‘slow’ fraction, although the greatest rate of change occurred in the ‘active’ C pool, which stabilised within 50 years at levels similar to the native forest. Similarly, ‘slow’ C accumulated in all treatments to new equilibria which were similar to that in undisturbed forest soil. The main difference between treatments was in the predicted time until a stable equilibrium in the ‘slow’ pool was reached: between 90 and 160 years depending on the soil stripping and replacement operation used. Successful development of new equilibria was highly sensitive to the amount of legume N2 fixation in the system and also to the severity of C and N losses during fire events. Reasonable agreement was found between simulated organic C accumulation and that observed in surveyed rehabilitation of up to 15 years of age (r2 = 0.67 for freshly replaced soils, r2 = 0.72 for soils stockpiled before respreading).

Management effects on the dynamics and storage rates of organic matter in long-term crop rotations

2004 ◽  
Vol 84 (1) ◽  
pp. 49-61 ◽  
Author(s):  
E. A. Paul ◽  
H. P. Collins ◽  
K. Paustian ◽  
E. T. Elliott ◽  
S. Frey ◽  
...  
Keyword(s):  
Organic Matter ◽  
C Sequestration ◽  
Organic C ◽  
Soil C ◽  
Site Analysis ◽  
Laboratory Incubation ◽  
C And N ◽  
A Site ◽  
Management Effects

Factors controlling soil organic matter (SOM) dynamics in soil C sequestration and N fertility were determined from multi-site analysis of long-term, crop rotation experiments in Western Canada. Analyses included bulk density, organic and inorganic C and N, particulate organic C (POM-C) and N (POM -N), and CO2-C evolved during laboratory incubation. The POM-C and POM-N contents varied with soil type. Differences in POM-C contents between treatments at a site (δPOM-C) were related (r2= 0.68) to treatment differences in soil C (δSOC). The CO2-C, evolved during laboratory incubation, was the most sensitive indicator of management effects. The Gray Luvisol (Breton, AB) cultivated plots had a fivefold difference in CO2-C release relative to a twofold difference in soil organic carbon (SOC). Soils from cropped, Black Chernozems (Melfort and Indian Head, SK) and Dark Brown Chernozems (Lethbridge, AB) released 50 to 60% as much CO2-C as grassland soils. Differences in CO2 evolution from the treatment with the lowest SOM on a site and that of other treatments (δCO2-C) in the early stages of the incubation were correlated to δPOM-C and this pool reflects short-term SOC storage. Management for soil fertility, such as N release, may differ from management for C sequestration. Key words: Multi-site analysis, soil management, soil C and N, POM-C and N, CO2 evolution

SOIL ORGANIC MATTER CHARACTERISTICS AFTER LONG-TERM CROPPING TO VARIOUS SPRING WHEAT ROTATIONS

1987 ◽  
Vol 67 (4) ◽  
pp. 845-856 ◽  
Author(s):  
H. H. JANZEN
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Fertility ◽  
Crop Rotation ◽  
Spring Wheat ◽  
N Mineralization ◽  
Soil Layer ◽  
Organic C ◽  
C And N

Soil from a long-term crop rotation study conducted at Lethbridge, Alberta was analyzed to determine the influence of various spring wheat rotations with and without perennial forages on total and mineralizable soil organic matter contents. Crop rotations considered included: continuous wheat (W), fallow-wheat (FW), fallow-wheat-wheat (FWW), and fallow-wheat-wheat-forage-forage-forage (FWWAAA) in which the forage was a mixture of alfalfa and crested wheat grass. The organic C and N contents of soil after 33 yr of cropping were highest in treatments W and FWWAAA, and decreased with increasing frequency of fallow in the rotation. The inclusion of the perennial forage in the rotation did not increase organic C and N levels above those observed in the continuous wheat treatment (W). Differences in levels of mineralizable organic matter among treatments, as measured in laboratory incubations, were much greater than differences in total organic matter content among treatments. In the surface soil layer (0–15 cm), N mineralization was significantly higher in treatment W than in treatments FWW and FWWAAA, and was more than twice that observed in treatment FW. In the subsurface soil layer (15–30 cm), N mineralization was greatest in treatment FWWAAA when sampled just after the plowdown of forage. Effects of crop rotation on C mineralization were similar to those observed for N. Levels of mineralized organic matter were closely related to levels of "light fraction" material (specific gravity < 1.59 g cm−3), which is believed to consist primarily of incompletely decomposed organic matter of plant origin. Differences in amounts of mineralizable organic matter among treatments were attributed to varying frequencies and patterns of crop residue additions. The pronounced effects of crop rotation on the distribution of organic matter among labile and humified organic matter will have a strong impact on soil fertility and may need to be taken into consideration in the development of fertilizer recommendations. It was concluded that inclusion of perennial forages in spring wheat rotations for the purpose of enhancing soil fertility and organic matter levels was not justified under semiarid conditions. Key words: Carbon, nitrogen, mineralization

EFFECT OF FERTILIZER ON SOIL PRODUCTIVITY IN LONG-TERM SPRING WHEAT ROTATIONS

1987 ◽  
Vol 67 (1) ◽  
pp. 165-174 ◽  
Author(s):  
H. H. JANZEN
Keyword(s):  
Organic Matter ◽  
N Fertilization ◽  
N Fertilizer ◽  
Organic N ◽  
Phosphorus Fertilization ◽  
Soil Productivity ◽  
Organic C ◽  
C And N ◽  
N Fertility

Surface soil samples taken from two long-term crop rotations at Lethbridge, Alberta were used to assess the influence of fertilizer N and P on total and mineralizable concentrations of organic C and N in a Dark Brown Chernozemic soil. Rotations sampled were continuous wheat and fallow-wheat-wheat initiated in 1912. In 1967 and 1972, N fertilizer and P fertilizer treatments, respectively, were superimposed over the rotation treatments (which had received no previous fertilizer) to produce a factorial of two N rates (0 and 45 kg N ha−1) by two P rates (0 and 20 kg P ha−1). After 18 yr of application, N fertilizers increased organic C content in both rotations by approximately 14% over that observed in soil receiving no N fertilizer. Organic N contents, similarly, were increased by 15 and 11% in the continuous wheat and fallow-wheat-wheat rotations, respectively. As well, N fertilization increased relative N mineralization potential by 22% in the continuous wheat rotation and by 44% in the fallow-wheat-wheat rotation. Phosphorus fertilization had no significant influence on either total or mineralizable C and N concentrations. Soil pH (measured in dilute CaCl2) was reduced, on average, from 7.2 to 6.9 by 18 annual N applications. These results demonstrate that N fertilization can make significant contributions to the replenishment of organic matter in soil and to the maintenance of indigenous soil N fertility. Key words: Organic matter, nitrogen, carbon, mineralizable nitrogen, mineralizable carbon, pH

Impact of long-term cultivation on the status of organic matter and cadmium in soil

2001 ◽  
Vol 81 (3) ◽  
pp. 349-355 ◽  
Author(s):  
D. F. E. McArthur ◽  
P M Huang ◽  
L M Kozak
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Significant Positive Correlation ◽  
Soil Organic C ◽  
Organic C ◽  
Total Soil ◽  
Total Organic C ◽  
Soil Cd ◽  
Cultivated Soils

Research has suggested a link between the bioavailability of soil Cd and total soil organic matter. However, some research suggested a negative relationship between total soil organic matter and bioavailable soil Cd while other research suggested a positive relationship. This study investigated the relationship between soil Cd and both the quantity and quality of soil organic matter as influenced by long-term cultivation. Two Orthic Chernozemic surface soil samples, one from a virgin prairie and the other from an adjacent cultivated prairie, were collected from each of 12 different sites throughout southern Saskatchewan, Canada. The samples were analyzed for total organic C, total Cd, Cd availability index (CAI), and pH. The nature of the soil organic matter was investigated with 13C Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy (13C CPMAS NMR). The total soil Cd, CAI, and total soil organic C of the cultivated soils were significantly lower than those of the virgin soils whereas the opposite trend was observed for the soil pH and the aromaticity of the organic C. The reduced CAI in the cultivated soils was related to the increase in both the soil pH and the aromaticity of the organic C. No relationship was found between the CAI and the soil organic C content, but a significant positive correlation was found between total organic C and total Cd in both the virgin and the cultivated soils. As well, a significant positive correlation was found between the fraction of total Cd removed from the soil after long-term cultivation and the corresponding fraction of organic C removed. Key words: Long-term cultivation, soil organic matter, 13C CPMAS NMR, cadmium

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.

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