The management of organic matter in tropical soils: what are the priorities?

There is a need to quantitatively assess the soil fertility status of tropical soils. Descriptive summaries help describe the effectiveness of liming programs, nutritional limitation in soils and the relative risk of off-field nutrient transport. A database of 1,168 soil test results collected from 1989 to 1999 from nearly 400 cultivated farms in Puerto Rico was used. Samples were analyzed for pH, organic matter (Walkley-Black method), extractable phosphorus (P) (Olsen and Bray 1), and exchangeable bases (NH4Oac method) by a commercial laboratory. Thirty-six percent of the samples had acidity problems (pH <5.5). Twenty-three percent of the samples had low organic matter content (<20 g/kg), and 16% had high category (>40 g/kg) values. Fifty-three and 56% of the samples showed a need to fertilize with magnesium (Mg) and potassium (K), respectively, because they had values below the suggested critical levels of 2.5 cmolc/kg for soil exchangeable Mg and of 0.4 cmolc/kg for K. On the basis of current soil fertility criteria, P fertilization would be required in 69% of the samples with pH less than 7.3, but only in 28% of the samples with pH greater than or equal to 7.3. Although the soils grouped with pH >7.3 had a greater proportion of samples in the "extremely high" soil test P category, the potential environmental impact may be lessened because the climatic and topographic conditions where these soils occur favor less runoff. Follow-up studies are needed to assess the spatial variability and the temporal dynamics of the nutritional status of soils of Puerto Rico.

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The Types and The Amounts of Organic Matter Influence Carbon Dioxide Production in The Reclaimed-Mine Tropical Soils

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/239/1/012012 ◽

2019 ◽

Vol 239 ◽

pp. 012012

Author(s):

A R Saidy ◽

A Hayati ◽

M Septiana

Keyword(s):

Carbon Dioxide ◽

Organic Matter ◽

Tropical Soils ◽

Carbon Dioxide Production

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Analysis of VNIR (400–1100 nm) spectral signatures for estimation of soil organic matter in tropical soils of Thailand

International Journal of Remote Sensing ◽

10.1080/0143116031000139944 ◽

2004 ◽

Vol 25 (3) ◽

pp. 643-652 ◽

Cited By ~ 32

Author(s):

K. W. Daniel ◽

N. K. Tripathi ◽

K. Honda ◽

E. Apisit

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Tropical Soils ◽

Spectral Signatures

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Tropical forest soil carbon stocks do not increase despite 15 years of doubled litter inputs

Scientific Reports ◽

10.1038/s41598-019-54487-2 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 5

Author(s):

Emma J. Sayer ◽

Luis Lopez-Sangil ◽

John A. Crawford ◽

Laëtitia M. Bréchet ◽

Ali J. Birkett ◽

...

Keyword(s):

Organic Matter ◽

Tropical Forest ◽

Critical Role ◽

Tropical Soils ◽

Soil Geochemistry ◽

Soil Minerals ◽

Litter Addition ◽

Lowland Tropical Forest ◽

Tropical Forest Soil ◽

Underlying Mechanisms

AbstractSoil organic carbon (SOC) dynamics represent a persisting uncertainty in our understanding of the global carbon cycle. SOC storage is strongly linked to plant inputs via the formation of soil organic matter, but soil geochemistry also plays a critical role. In tropical soils with rapid SOC turnover, the association of organic matter with soil minerals is particularly important for stabilising SOC but projected increases in tropical forest productivity could trigger feedbacks that stimulate the release of stored SOC. Here, we demonstrate limited additional SOC storage after 13–15 years of experimentally doubled aboveground litter inputs in a lowland tropical forest. We combined biological, physical, and chemical methods to characterise SOC along a gradient of bioavailability. After 13 years of monthly litter addition treatments, most of the additional SOC was readily bioavailable and we observed no increase in mineral-associated SOC. Importantly, SOC with weak association to soil minerals declined in response to long-term litter addition, suggesting that increased plant inputs could modify the formation of organo-mineral complexes in tropical soils. Hence, we demonstrate the limited capacity of tropical soils to sequester additional C inputs and provide insights into potential underlying mechanisms.

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Mobility of metsulfuron-methyl in tropical soils

Soil Research ◽

10.1071/s97008 ◽

1997 ◽

Vol 35 (6) ◽

pp. 1291 ◽

Cited By ~ 2

Author(s):

B. S. Ismail ◽

K. Kalithasan

Keyword(s):

Organic Matter ◽

Soil Column ◽

Organic Matter Content ◽

Tropical Soils ◽

Matter Content ◽

Fresh Weight ◽

Downward Movement ◽

Natural Conditions ◽

Metsulfuron Methyl ◽

Rainfall Total

The mobility of metsulfuron-methyl in 5 soil series with different organic contents was determined in a greenhouse as well as under natural conditions. In these studies, the movement and biological activity of metsulfuron-methyl were determined by the bioassay method using long bean as a bioassay species. Bioactivity and movement of the herbicide down the soil profile were inversely related to the organic matter content of the soil. Phytotoxic levels of metsulfuron-methyl were restricted to the 10-cm depth of the column containing Selangor Series soil except when it received 40 mL of water daily (depth, 10–15 cm). In Munchung Series, the phytotoxic level was also mainly in the 5–10 cm layer. However, when the column received 40 mL daily or every 4 days, the residue was detected in 15–20 cm and 10–15 cm zones, respectively. The phytotoxic level moved downward to the 20–25 cm layer both in Sogomana and Holyrood Series when 40 mL of water was given daily. A phytotoxic level of metsulfuron herbicide was detected in the 20–25 cm layer when the soil column containing Serdang Series was leached with 40 mL of water every 4 days or with 20 mL daily; the phytotoxic level was detected at a depth of 25–30 cm when this soil was watered daily with 40 mL. The downward movement of metsulfuron under natural conditions showed a pattern similar to that found under simulated conditions. Phytotoxic effects of the residue could be detected in the 25–30 cm and 15–20 cm zone of Serdang and Holyrood Series, respectively, after exposure to 20 days of rainfall (total 111·9 mm). Phytotoxic residue in both Sogomana and Munchung Series soil was detected in the 10–15 cm layer, and in the 5–10 cm layer for Selangor Series soil, after exposure to 20 days of rainfall. After exposure to 40 days of rainfall (total 152·8 mm) under natural conditions, the residue could be detected in the 15–20 cm layer of Selangor Series. The phytotoxic level moved deeper in soil with low organic matter after exposure to 40 days of rainfall. Fresh weight reduction was greater in the 20–30 cm layer in Serdang Series than in the top layer.

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Sulfur forms in bulk soils and alkaline soil extracts of tropical mountain ecosystems in northern Thailand

Soil Research ◽

10.1071/sr01001 ◽

2002 ◽

Vol 40 (1) ◽

pp. 161 ◽

Cited By ~ 9

Author(s):

A. Möller ◽

K. Kaiser ◽

N. Kanchanakool ◽

C. Anecksamphant ◽

W. Jirasuktaveekul ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Tropical Soils ◽

Forest Site ◽

Alkaline Soil ◽

Northern Thailand ◽

Total N ◽

Soil Extracts ◽

Organic C ◽

Organic S

Sulfur, besides phosphorus, is crucial for the nutrition of plants on tropical soils. Its availability is closely related to the turnover of soil organic matter. To get a better insight into transformation of soil S forms during the decomposition of organic matter, we studied inorganic and organic S pools in bulk samples and alkaline extracts of soils under different land uses representative of the tropical highlands of northern Thailand. Samples were taken from a cabbage cultivation, a Pinus reforestation, a secondary forest, and a primary forest. Total S ranged from 483 549 mg/kg in the subsoil to 1909 376 mg/kg in the organic layers, which is relatively high for tropical soils. The major S component in soil was organic S, comprising 75–99&percnt; of total S. Organic S was significantly correlated with total S, organic C, and total N, indicating that there is a close relationship between C, N, and S cycling in soil. C-bonded S was the predominant form in the topsoils (35–99&percnt; of total S) but its presence decreased with soil depth. The maximum concentrations of ester SO4-S were found in the A horizons (128 49 mg/kg), whereas the concentrations of inorganic SO4-S were small in all horizons. Compared with the forest site, the cabbage cultivation site was strongly depleted in S. C-bonded S was more depleted than ester SO4-S. A comparison of the S forms in NaOH extracts with S forms in bulk soil and C forms as indicated by 13C-NMR spectroscopy showed (i) that the extracts were very representative of soil organic S fractions and (ii) that ester SO4-S was mainly associated with O-substituted aliphatic C. In contrast, C-bonded S seemed to be connected to more-or-less all C binding types. transformation of soil organic matter, sulfate.

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