Soil texture, determined by the measurement of particle size distribution, introduces three variables to create texture classes.
However, if we forget about the three fractions (clay, silt and sand), a the end of the particle sizes are distributed along a continuous axis (one dimension).
Could it be possible to derive a single number to characterize soil texture, to make whatever calculation more useful?
Some people use sometimes sand content, or clay content, reducing the (somewhat arbitrary) three dimensions of texture to a single value, but there should a mathematically more acceptable way to reflect soil particle size distribution withtout loosing too much information?
What do you think?
The average or medial particle size could perhaps be more interesting? Or some sort of the average particle size of the interquartile of the distribution (if it is unimodal...)? Any thoughts?
Not being able to reduce soil texture to a single value often feels constraining to make relevant data analyses...
I do not think; you must analyze the three classes of soil texture (sand,clay, silt)
I agree with Dr Ali Hassan Hommadi in this matter. Actually, soil texture is a method of nomenclature of soil comprising of sand, silt and clay content and naming of soil is done by considering the amount of these three components altogether. As because, each of these particles do play definite role in the soil. Some one may find interest to explain some physico-chemical and biological properties by considering only one components, but this does not mean that other components could not play any role. So it is not scientifically recognized to represent soil texture by one dimensional way.
Dear Dr. Thomas,
I appreciate your logic. It is well known that each soil fraction (sand, silt and clay) plays a distinct role in imparting physical and chemical behavior to a soil. Therefore, determination of percentage of coarse and fine sand, silt and clay fractions will be necessary. As far as integration of these soil fractions into a single variable to decide the texture of soils is concerned, it would be interesting to examine the weighted mean size values of soils where, a summation of product of % value with mean size of each soil fraction is calculated analogous to mean weight diameter (MSW) used for characterizing soil structure.
Simply take for each soil separate (i.e sand, silt or clay), the mean or median value of the range (%) for each textural class in the textural triangle- if you must use one value. For example, for "Sand" as a textural class, it is composed of 90-100% sand, 0-10% clay and 0-14% silt from the textural triangle. You may try the mean value for any of the soil separates you are interested in and see how it goes.
Yes . Soil texture is a nomenclature. Are you looking for engineering applications or agricultural applications. you can try for the three fractions of three different minerological composition . how they work in different percentage. there is always limitation for natural soil, because of the complexity in minerological composition.
I do not think such a reduction is possible, except in a very narrowly specialized application aimed at a narrow category of soils. Mathematically speaking, the very term "distribution" implies the impossibility of reducing it to a single value. A distribution may have various single-valued properties (various means, quantiles, etc) but none of them, individually, really "describes" it, they are just properties.
I came across total surface area of the soil particles as a way to reduce texture to only one dimension.
And actually it makes a lot of sense since surfaces are involved in a lot of processes.
The finer the texture, the larger the surface area, and vice versa.
Soil surface area is an important property of soil which governs surface bound processes like adsorption- desorption, synthesis of new mineral phases etc.. However, processes like water movement , heat flow and gaseous exchange are controlled by relative proportion of different size soil separates. Therefore, in my view soil surface area alone may not help in characterizing soils for their physical and ion exchange properties.
Well, thinking about this one dimension area, if it is applied to a fixed volume (Surface Area/Volume), we would obtain an inverse length unit. For this given volume, it would still relate to a certain extent to the porosity of the soil, and therefore its liquid and gas flow characteristics, ins't it?
I will try to look in other disciplines to see how they deal with this.
There must be such a one-dimension variable somewhere.
In civil engineering for example when looking at hydraulic conductivity of a the liner of a pond for example.
Ok, update:
In fluid dynamics, specific surface area seem to be interesting.
http://perminc.com/resources/fundamentals-of-fluid-flow-in-porous-media/chapter-2-the-porous-medium/specific-surface-area/
Darcy's makes also the use of 'cross sectional area', in m², which could be an interesting contender.
It is just my intuition, but expressing correlation between various variables and soil's specific surface area (as a derivative of soil texutre), would be interesting, to see if any trends emerge.
Anyone interested in this please information here ;)
Maybe it is not powerful enough to be explanatory, maybe not.
I have been looking for some time for the explanation behind the boundaries between different classes of particles.
Why 2µm between clays and silts for example?
What significant difference a 1.99µm soil particle has with a 2.01µm one?
Physically speaking, not much... Or am I missing something?
I guess someone working on standards development may know the reason of this choice.
Properties of particles are not uniform across different particle sizes but change dramatically with size.Clay particles with size less than 2um behave much different from silt size particles.But at the boundary level there may be some overlap,or not so distinct seperation or dividing line.Even for contribution to total surface area,clay paricles may contribute much more than the sand or silt size particles.The most important property of soil, the cation exchange capacity, is mostly contributed by clay particles(clay sized clay minerals).As mentioned by some colleagues,the three soil separates have distinct properties and they contribute differently to over all soil physical and chemical properties.For some specific purpose one may try to have a unified single value for soil textute but that will definetely mask several soil properties which help to understand the soil from agricultural use or other purposes.
Soil clay, silt, sand and organic matter content of the soil, depending on the volume and specific weight values can be obtained depending on the value= CTX
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