Make a Soil Texture Ternary Plot

Visually classify soil samples by texture based on their ratios of sand, clay, and silt

Soil texture is a key property that influences water retention, drainage, and fertility. It is defined by the relative proportions of sand, silt, and clay in a soil sample. In this example, we'll visualize soil texture on a ternary plot, where each vertex represents one of the three components. By plotting a sample's composition, users can identify its USDA soil texture class and explore how varying sand, silt, and clay proportions affect classification boundaries.

Define soil texture regions geometrically as polygons:

In[1]:=

polygons=Polygon

Number of points: 4

Embedding dimension: 3

,Polygon

Number of points: 4

Embedding dimension: 3

,Polygon

Number of points: 3

Embedding dimension: 3

,Polygon

Number of points: 6

Embedding dimension: 3

,Polygon

Number of points: 4

Embedding dimension: 3

,Polygon

Number of points: 5

Embedding dimension: 3

,Polygon

Number of points: 3

Embedding dimension: 3

,Polygon

Number of points: 5

Embedding dimension: 3

,Polygon

Number of points: 7

Embedding dimension: 3

,Polygon

Number of points: 4

Embedding dimension: 3

,Polygon

Number of points: 3

Embedding dimension: 3

,Polygon

Number of points: 5

Embedding dimension: 3

;

Define styling options for each polygon:

In[2]:=

colors=

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In[3]:=

regionStyles=MapDirectiveOpacity[0.5`],EdgeForm

,#&,colors

Out[3]=

DirectiveOpacity[0.5],EdgeForm

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,DirectiveOpacity[0.5],EdgeForm

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,DirectiveOpacity[0.5],EdgeForm

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,DirectiveOpacity[0.5],EdgeForm

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,DirectiveOpacity[0.5],EdgeForm

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Assign each polygon its colour and opacity:

In[4]:=

regions=Thread[{regionStyles,polygons}];

Define labels corresponding to each region:

In[5]:=

labels={"Silt","Silty clay loam","Silty clay","Silt loam","Clay loam","Loam","Sandy clay","Sandy clay loam","Sandy loam","Loamy sand","Sand","Clay"};

Define some data points representing a set of soil samples, were each entry represents a relative quantity of sediment in the format {sand, clay, silt}:

In[6]:=

data={.4,.3,.3}+#&/@RandomReal[1,{40,3}]

Out[6]=

{{1.282,1.01856,0.499304},{0.51407,0.950089,0.518348},{0.656066,0.4201,0.761945},{0.771961,1.22045,0.782103},{0.608762,0.33885,1.15159},{0.982249,0.88236,1.2878},{0.912718,0.483265,0.667048},{0.823423,0.524028,0.623597},{1.30314,1.17953,1.16644},{1.04991,0.384283,0.611994},{0.775802,0.343128,1.04534},{0.623826,0.740817,0.377569},{1.1019,1.01001,0.567008},{1.21282,1.17655,0.687763},{1.18465,0.633312,0.529771},{0.505655,0.882967,0.353184},{0.486742,0.933768,0.327258},{0.858549,1.28132,1.24019},{1.08983,1.18872,0.944397},{0.6675,0.921892,0.824652},{0.707179,0.796258,1.27752},{0.808475,0.455509,0.900804},{1.02486,0.392505,0.361746},{1.08902,0.626504,0.82041},{1.06625,0.70195,0.783033},{1.00165,0.763445,0.81569},{0.579127,1.1572,1.15189},{0.97829,0.983877,1.19395},{1.1878,0.788962,1.11159},{1.13711,1.21323,0.794698},{0.81323,0.854726,0.845654},{0.958121,0.374615,0.788886},{0.829804,0.766408,0.844968},{0.932995,1.01278,0.690816},{0.97976,0.50738,1.12267},{0.420372,0.920579,0.64998},{0.464601,0.777572,0.674119},{0.940463,0.351154,0.988801},{0.506287,0.839181,0.485115},{0.622244,0.942069,1.1035}}

Make the final soil texture ternary plot:

In[7]:=

LegendedLabeledTernaryListPlotdata,FrameLabel{None,Style["Clay (%)",14],Style["Silt (%)",14]},Prologregions,PlotMarkersAutomatic,GridLinesThread#,Opacity0.5`,

,Thread#,Opacity0.5`,

,Thread#,Opacity0.5`,

&@Range[0,1,.05],ImageSizeMedium,Text[Style["Sand (%)",{14,Darker[Gray]}]],Bottom,SwatchLegend[Reverse[colors],Reverse[labels],LegendLayout{"Column",1}]

Out[7]=

External Links

Source Metadata

Citation:
- USDA Soil Texture Calculator

See Also

Publisher Information

Contributed by: Phileas Dazeley-Gaist