Cycling of carbon in a paddy field. IV. Organic matter decomposition in the flooding water and surface soil.

Abstract Soil organic matter (SOM) and its fractions play an important role in maintaining or improving soil quality and soil fertility. Therefore, the effects of a 34-year long-term fertilizer regime on six functional SOM fractions under a double-cropping rice paddy field of southern China were studied in the current paper. The field experiment included four different fertilizer treatments: chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM) and without fertilizer input as control (CK). The results showed that coarse unprotected particulate organic matter (cPOM), biochemically, physically–biochemically and chemically protected silt-sized fractions (NH-dSilt, NH-μSilt and H-dSilt) were the main carbon (C) storage fractions under long-term fertilization conditions, accounting for 16.7–26.5, 31.1–35.6, 16.2–17.3 and 7.5–8.2% of the total soil organic carbon (SOC) content in paddy soil, respectively. Compared with control, OM treatment increased the SOC content in the cPOM, fine unprotected POM fraction, pure physically protected fraction and physico-chemically protected fractions by 58.9, 106.7, 117.6 and 28.3%, respectively. The largest proportion of SOC to total SOC in the different fractions was biochemically protected, followed by chemically and unprotected, and physically protected were the smallest. These results suggested that a physical protection mechanism plays an important role in stabilizing C of paddy soil. In summary, the results showed that higher functional SOM fractions and physical protection mechanism play an important role in SOM cycling in terms of C sequestration under the double-cropping rice paddy field.

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Effects of Land Management Change on Spatial Variability of Organic Matter and Nutrients in Paddy Field: A Case Study of Pinghu, China

Environmental Management ◽

10.1007/s00267-004-0053-6 ◽

2004 ◽

Vol 34 (5) ◽

pp. 691-700 ◽

Cited By ~ 24

Author(s):

Xingmei Liu ◽

Jianming Xu ◽

Mingkui Zhang ◽

Bin Zhou

Keyword(s):

Organic Matter ◽

Spatial Variability ◽

Land Management ◽

Paddy Field ◽

Management Change ◽

Land Management Change

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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 ◽

10.1071/sr99043 ◽

2000 ◽

Vol 38 (2) ◽

pp. 345 ◽

Cited By ~ 18

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.

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