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Properties of Puddled Soils and Their Relationships

M. J. Islam
Principal Scientific Officer
Training Division, Bangladesh Rice Research Institute, Gazipur, Bangladesh

G. Mowla
Training Division, Bangladesh Rice Research Institute, Gazipur, Bangladesh

S. S. Parul
Training Division, Bangladesh Rice Research Institute, Gazipur, Bangladesh

P. B. Leeds-Harrison
Head (Irrigation Water Management)
Irrigation Water Management Dept., Silsoe College, MK45 4DT, Cranfield Unversity, England, UK

Abstract/ Executive Summary:

Different laboratory and field experiments were conducted with sandy loam, clay loam and clay soil to determine the shrink-swell behaviour and other properties of puddled soils which might help to predict the nature and magnitude of cracking in these soils. The shrinkage characteristic curves, developed for these puddled soils, were not exactly the same as the general theoretical form of the shrinkage characteristic curves. Among the studied soils, the linear shrinkage was the highest in clay soil followed by clay loam. A good relationship between the three dimensional shrinkage of the soil bin experiment and the cumulative linear shrinkage of the laboratory experiment were observed. This study revealed that the increasing pattern of curves for coefficient of linear extensibility from saturation to oven dry soil is almost the same as the linear shrinkage curves. It was also observed that the bulk density and shear strength gradually increased as the soils dried. The moisture content around cracks in the surface layer was about 2% less than the 100 mm away of same layer from the cracks. The absorption of moisture by puddled soil was higher than in the clod state. On the other hand, the reverse result was observed when the soil was dried.

Keywords: Puddled soil, Shrinkage-swelling, Cracking

Location:

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land management

Objectives:

To determine the parameters describing the behaviour of puddled soils
To use it a tool to predict the nature and magnitude of cracking in puddled soils and thereof

Methodology:

The study was conducted in Silsoe College, UK. In order to determine the shrinkage characteristic.Different soils (sandy loam, clay loam and clay soil) were wetted and puddled until it became a homogeneous paste .Semi circular brass shrinkage moulds measuring 140 mm long and 40 mm wide were filled with the paste (British Standard, 1990). After filling the mould with puddled paste, surplus paste was removed. The specimens were allowed to dry at room temperature. Three dimensional measurements of the samples were taken daily by a Vernier calliper to determine their volume. These readings were continued until the samples became air-dry. The volume of the oven-dry specimens was also measured by a water displacement method. The shrinkage characteristic curves for different soils were determined. Linear shrinkage was calculated from the shrinkage mould specimens. For each soil, five replicate samples were used. The linear shrinkage of the soils were calculated as a percentage of the original length of the specimens by using the following equation (British Standard, 1990): Percent of linear shrinkage = (1- LD/LO) x 100, Where, LD = length of the oven dry specimen (mm), LO = original length of the specimen (mm). The coefficient of linear extensibility (COLE) was determined as (Bronswijk and Evers Vermeer, 1990): COLE = (Vwet /Vdry)1/3-1. Where, Vwet = volume of wet soil, Vdry = volume of dry soil. The data from the shrinkage mould specimens were used to determine the bulk density at different moisture contents with the following equation: Bulk density = [{(Weight of the specimen (gm)} / {Volume of the specimen (cm³)}]. Puddled soils were placed on a porous sintered glass plate of given pore diameter. Removal of water from the open manometer limb places a suction head on the soil. The applied suctions (pressure head) were varied from zero to five KPa (0-50 cm). A total of nine porous plates (three plates for each sample) were used. Shear strength was measured on each porous plate by a small shear vane of 19 mm diameter (Serota and Jangle, 1972). Puddled soils were separately placed in 100 ml beakers. Initially a certain height was provided in each beaker. The height was measured from the top of the beakers by a digital calliper. The beakers were allowed to dry at room temperature. The change in surface elevation of the samples and corresponding depletion of moisture content was recorded until they reached the air-dry condition. The 20 m x 1.5 m x 1.5 m bin was made of render bricks and sealed at the bottom. Nine plots were made in the bin each of 1 m x 1 m and were surrounded by plastic lawn edging. Replicated soil samples were collected around the crack and 100 mm away from the crack at different stages of crack formation of puddled soils. A laboratory study was conducted using porous brass boxes for the three soils. Air-dry ground soil < 1.0 mm) was placed in three boxes with a filter paper beneath the soil. Clods (5-12.5 mm diameter) of the similar soil with the same moisture content were placed in another three boxes. The samples were set on a tray and allowed to saturate for seven days. The soils in the boxes (except the clods) were puddled. Finally the samples were allowed to dry for 20 days at room temperature and the weight of the samples was recorded daily to determine moisture depletion pattern.

Source of Information: Progress. Agric. 16(1): 5-11, 2005 ; ISSN 1017-8139

Article Link (Online Journal):

Funding Source:

1.

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Total Budget (Tk.) :

Achievement/Findings:

From these studies it could be concluded that, the puddled soils exhibit the normal shrinkage, residual shrinkage and zero shrinkage stages though the curves remain above the 1:1 line. Puddled soils change from normal shrinkage to residual shrinkage when they reach a moisture ratio of 0.6-0.8. At the early stage, the vertical shrinkage of puddled soils was equal to the volume of water losses and the shrinkage of clay loam and clay soil continued until they became oven-dried. The moisture content around cracks of the surface layer was appx. < 2% than the same layer at 100 mm away from the crack where there was no crack. The difference of moisture content between surface layer and 10 mm depth was noticeable (1.0%, 4.0% and 2.4% for the sandy loam, clay loam and clay soil respectively). The moisture depletion rate of the clod was higher than in the puddled form of the same soil. At the early stage of puddling (up to three days) the difference wss high, then it rapidly reduced and remained almost same at the latter part of drying.

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