How to Read Sand Silt Clay Triangle

Measuring Soil Texture in the Laboratory

Key points

• Particle size analysis breaks a soil into texture classes – sand, silt or dirt.


• Soil texture influences nutrient retention, water storage and drainage.


• Particles greater than ii mm are removed before analysis.


• The soil textural triangle is used to determine soil type based on sand, silt and clay percentages.

Background

Particle size analysis (PSA) determines the relative amounts of sand, silt and clay in a soil. These size fractions are the mineral component of a soil and together determine soil texture. PSA is a laboratory culling to field texturing (run into Measuring Soil Texture in the Field fact sheet) and offers a more reliable determination of particle size distribution. There is only an estimate correlation betwixt hand texturing and PSA (McDonald et al., 1998), considering hand texturing relies on qualitative interpretation of texture while PSA measures exact amounts of individual particle sizes.

Soil texture is an inherent soil quality property that has a major influence on several other properties that influence agricultural potential (White, 1997). In detail soil texture influences nutrient retention, water storage and drainage. Soils with a higher proportion of sand retain less nutrients and water compared to clay soils.

Mineral components of soil

Fibroid fragments

Greater than ii mm and include coarse quartz, rock fragments and cemented material. This is commonly called the 'gravel fraction'.

Sand

Incorporate quartz and resistant chief minerals such as mica. Sand particles are between two mm and xx microns in size (Note: there are thousand microns in 1 mm).

Silt

Silts are typically composed of quartz and minor mineral particles such as feldspars and mica, and are between 2 and xx microns in diameter.

Dirt

Clays are fabricated up of secondary clay minerals and oxides/oxyhydroxides of iron and aluminium, and are less than 2 microns in bore.

S-western Commonwealth of australia

Soil information from a range of projects conducted beyond the country is constantly added to the soils database managed by the Department of Agriculture and Food, Western Australia. Figure one, taken from McArthur (1991), shows the soil types feature of due south-western Australia.

Effigy 1: Feature soils of the agricultural region of southward-western Australia. Image courtesy of Natural Resources Cess Group, DAFWA.

Particle Size Analysis

PSA is a reliable, reproducible technique that eliminates factors that may affect field texture such as organic matter content, clay mineralogy, cation composition and the presence of cementing agents (Bowman and Hutka, 2002). The method comprises two parts, dispersion of the soil and separation of the particles into size groups.

Dispersion and pre-treatment

Pre-treatment of the soil may be needed to remove organic matter and salts such as gypsum. Iron oxides, calcium carbonate and magnesium carbonate should also be removed equally they are common cementing agents in Australian soils (Bowman and Hutka, 2002). Pre-handling of the soil will allow information technology to disperse completely.

Fractionation

Fractionation involves removing each particle size group (sand, silt and clay) from a pretreated soil and h2o mixture settled in a cylinder (figure ii). This is achieved by allowing the soil particles of unlike size to settle out of solution at unlike times (minor dirt particles take the longest). The fractions are after dried and weighed and the sand, silt and clay must add

up to 100%. Some calculations are needed for this method including the use of a scaling factor for the pipette analysis and a adding for the sieve analysis. For a consummate method, refer to Bowman and Hutka (2002).

Figure 2: Cylinder used for fractionation of sand, silt and clay particles. The sand fraction settles first followed by the silt and then the dirt fractions.

Using the soil texture triangle

The soil texture triangle (figure 3) is used to convert particle size distribution into a recognised texture class based on the relative amounts of sand, silt and dirt as a percentage, for example:

Effigy 3: Once soil fractionation is consummate a soil textural triangle is used to make up one's mind soil texture. Image adapted from Chase and Gilkes (1992).

A – Sand fifty% + Silt 30% + Clay 20% = SILTY LOAM

The grid on the triangle allows you to move to the left or the right of your position running parallel with either side of the triangle. Information technology is best to start at the base with the sand. Position your finger along the base line at the 50% mark. Move your finger upwardly the line running parallel with the right side of the triangle. Simultaneously use another finger to trace a line from the 30% silt marking until the two see. Your two fingers will always meet at clay for the remaining percentage, in this case 20%. This is e'er the instance that the first two sizes chosen volition lead you to the 3rd.

B – Sand fourscore% + Silt 5% + Clay 15% = SANDY LOAM

Trace your finger forth the 80% sand line while simultaneously tracing another finger forth the 5% silt line until the 2 meet. This should be where dirt is 15%.

Further reading and references

Bowman GM and Hutka J (2002) Particle Size Analysis. In Soil Physical Measurement and Interpretation for Land Evaluation

(Eds Northward McKenzie, M Coughlan, H Cresswell) pp 224-239. CSIRO Publishing: Victoria.

Chase N and Gilkes R (1992) Subcontract Monitoring Handbook. The Academy of Western Australia: Nedlands, WA.

McKenzie NJ, Jacquier DJ, Isbell RF, Dark-brown KL (2004) Australian Soils and Landscapes An Illustrated Compendium. CSIRO Publishing: Collingwood, Victoria.

NLWRA (2001) Australian Agricultural Cess 2001. National State and Water Resources Audit.

Authors: Katharine Dark-brown ( The Academy of Western Commonwealth of australia) and Andrew Wherrett (Department of Agriculture and Food, Western Australia).

This soilquality.org.au fact-canvass has been funded by the Salubrious Soils for Sustainable Farms plan, an initiative of the Australian Government's Natural Heritage Trust in partnership with the GRDC, and the WA NRM regions of Avon Catchment Quango and Due south Declension NRM, through National Activity Plan for Salinity and H2o Quality and National Landcare Plan investments of the WA and Australian Governments.

The Chief Executive Officer of the Department of Agronomics and Food, The Country of Western Australia and The Academy of Western Australia take no liability whatsoever by reason of negligence or otherwise arising from the apply or release of this information or whatsoever function of it.

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Source: https://soilquality.org.au/factsheets/soil-texture-measuring-in-the-lab

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