Properties and Genesis of Soils Developed in Very Firm Till in Northeastern Iowa

The Lawu volcano was sampled from an altitude of 500-3, 300 m and investigated morphologically, mineralogically and chemically. The soil organic matter was analysed in respect of its C, H, O and N content. Comparison of soils in a monsoon climate with those formed in a wet climate showed that the process of laterization proceeded to higher altitudes in a monsoon climate. It seems possible to recognize the following belts: a zone from 3, 300 to 2, 500 m altitude with brown podzolic soils, 2, 000-1, 400 m with brown forest soils, 1, 400-1, 000 m with latosolic brown forest soils and 1, 000-300 m with brown and reddish-brown latosolic soils. Organic acid was a more important soil-forming factor than CO2 at altitudes > 1, 000 m and under a monsoon climate. An explanation is proposed for the curious trends of C/N ratios of the soil and organic matter and for the trends in the clay's molar Al2O3/Fe2O3 ratios.-From authors' summary. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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Cyclic salt as a dominant factor in the genesis of soils in South-Eastern Australia.

Australian Journal of Agricultural Research ◽

10.1071/ar9540448 ◽

1954 ◽

Vol 5 (3) ◽

pp. 448 ◽

Cited By ~ 15

Author(s):

RG Downes

Keyword(s):

Physical Properties ◽

Dominant Factor ◽

Annual Rainfall ◽

Arid Soils ◽

South Eastern ◽

Eastern Australia ◽

Average Annual Rainfall ◽

Soil Distribution ◽

Genesis Of Soils ◽

South Eastern Australia

A theory is presented suggesting that during the Recent Arid Period the rainfall was approximately half that of the present day and enabled cyclic salt to be accumulated in areas in south-eastern Australia, where it does not 'accumulate at present. The salinization and subsequent desalinization during the wetter conditions since the Arid Period have operated with varying degrees of intensity to produce solods, solodic and solonized soils over large areas. However, irrespective of the degree of intensity, some of the pre-Arid soils because of their chemical or physical properties have been able to resist these processes and remain unaffected. Five "pedogenetic zones" have been defined according to the degrees of intensity with which the salinization and desalinization processes are thought to have operated, and it is found that soil distribution and morphology is correlated with these defined zones. The zone in which the effect has been most intense has an average annual rainfall at present of between 20 and 30 in., and the most widespread soils, those formerly called red and yellow podzolics, are solodic soils and solods. The theory provides a reasonable explanation for the anoxalous distribution of soils within the "podzol" zone where those showing the greatest degree of horizon differentiation (solods and solodic soils) occur in the driest parts. In addition, the postulated processes for the formation of the soils provide a reason why molybdenum deficiency is so common on these soils in zone 3.

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Genesis of soils across a late Quaternary volcanic landscape in the humid tropical island of Leyte, Philippines

Soil Research ◽

10.1071/sr08012 ◽

2008 ◽

Vol 46 (5) ◽

pp. 403 ◽

Cited By ~ 8

Author(s):

Ian A. Navarrete ◽

Kiyoshi Tsutsuki ◽

Renzo Kondo ◽

Victor B. Asio

Keyword(s):

Late Quaternary ◽

Chemical Properties ◽

Morphological Characteristics ◽

Soil Formation ◽

Principal Component ◽

Clay Content ◽

Soil Thickness ◽

Tropical Island ◽

Tropical Condition ◽

Genesis Of Soils

This study evaluated the characteristics and genesis of soils across a young volcanic landscape in the humid tropical island of Leyte, Philippines. Five representative soil pedons (P1–P5) derived from late Quaternary volcanoclastics (i.e. fragmental) on a hillslope sequence were examined and sampled. Results revealed that the soils have generally similar morphological characteristics particularly in terms of soil colour (10YR 3/3–10YR 5/6) and soil structure (granular to subangular blocky), but differed in terms of soil thickness and clay content, which was higher in P3 than the other pedons across the landscape. The high porosities of the soils were the results of high organic matter, the dominance of noncrystalline (short-range order) minerals, as well as the isovolumetric weathering in the subsoils. All soils have very similar chemical properties (e.g. acidic, high organic carbon, low exchangeable bases), except soils from the middle backslope position (P3), which have high cation exchange capacity because higher exchangeable Ca and K result in a higher base saturation. Allophane, goethite, ferrihydrite, and gibbsite are the dominant clay minerals in the soils. Principal component analysis revealed that P3 was distinct from pedons P1, P2, P4, and P5, suggesting that it was substantially different from all other soils across the landscape. Soil formation was relatively fast due to the easy weatherability of the parent materials, high rainfall, and good drainage of the soils along the landscape. This study revealed that on young volcanic soils under humid tropical condition, topography greatly influenced soil development.

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