This Is What the Color of Your Garden Soil Means :- Pedogenic processes in soils are inferred from the colours of the soil. The primary colouring factors found in soils are iron, organic matter, and, to a lesser degree, manganese. The original colour of the mineral grains is revealed when these agents are not masking them.
This Is What the Color of Your Garden Soil Means
In nature, most granules of minerals are grey. Figures 3 and 4 illustrate the colour contrast between two soils with comparable texture and structure but different colour schemes. The matrix colour is the colour that predominates by volume in a soil horizon when there are many colours present.
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Soil Color :- It has been discovered that the characteristic of soil that most represents its pedogenic environment and past is its colour. The two main factors influencing soil colour are organic matter and iron oxides.
While iron oxides provide a spectrum of soil colours depending on the iron’s oxidation state, organic stuff darkens soil. Comparing soil samples to the colour chips in the Munsell soil colour charts is the most used technique for identifying the colour of the soil.
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Hue (base colour), value (lightness or darkness), and chroma (intensity of fundamental hue) are the three terms used to describe colour in the Munsell colour system.
Air-dried bulk soil samples are subjected to colour determinations; however, more complex color-determination systems have also been proposed.
Some forensic soil analysts have recommended basing colour determinations on the clay fraction of the soil because it accounts for the majority of the colour of a bulk soil sample. The clay fraction contains clay particles that are intimately bound to soil humus (forming the clay–humus complex) and clay particles coated with iron oxides.
The colours of the soil sample after air-drying, soaking, removing organic matter, removing iron oxide, and ashing have been suggested by other forensic soil scientists. The geographical origins of the soils being studied determine how well these treatments work to distinguish colours across soils from various regions.
According to a UK study by the Home Office Central Research Establishment, a significant degree of soil discrimination across different sites can be achieved by combining the colours of air-dried, wet, and ashed samples.
However, colour determinations following a different regimen of treatments (air-drying and moistening of bulk samples; organic matter and iron oxide removal from clay fractions) provide the highest discriminatory power, according to a similar study carried out by the Japanese National Research Institute of Police Science.
Munsell colours in the latter study were transformed into x-, y-, and z-coordinates: the x-coordinate indicates the hue, with basic hues from 2.5YR to 5GY, given numerical values from 1 to 10; the y-coordinate indicates the value; and the z-coordinate indicates the chroma.
The Euclidean distance d2 between the colour coordinates of the soil samples is the basis for colour comparisons between various soil samples. Soil sample pairs with d2 ≤ 1 were deemed indistinguishable from one another. 97% of 190 pairs of soil sample pairs from various sites were found to differ using this method.
Site selection and climate
Color:- The mineral content of the soil, in addition to its water and organic content, affects its colour. For instance, soils rich in humus are dark brown to black, soils heavy in iron are reddish, and soils high in calcium are often white. Just around 5% of organic matter is needed for soil to turn black when it gets moist.
In addition to reflecting the climate’s temperature and moisture content, soil colour also reflects the age of the soil. Topsoil in cooler climates typically has a grey to black colour due to humus buildup.
Soils in humid, warm climates typically have a greater yellowish-brown to red colour, which is influenced by the hydration of ferric oxide and the substantial weathering of the parent mineral. In warm, humid climates, the organic content quickly minerals out, so that humus buildup is insufficient to significantly affect the colour of the soil.
Because of their low organic content, arid soils typically have light colours that mostly reflect the colour of the minerals in them.
Water after rain momentarily darkens the colour of the soil by absorbing more light. Furthermore, soil colour may change over time due to moisture. For instance, iron oxides are typically found in the ferrous state in anaerobic, wet environments.
These may impart a faint bluish-gray hue on the soil. A greyish matrix with a mottled, rusty, or streaky look could be an indication of uneven or poorly drained soils. In the absence of organic material, a blackish colour could be an indication of manganese oxide staining.
The rate at which soil warms in the spring and cools in the autumn is influenced by colour. Regardless of moisture content, darker soils absorb more heat than lighter-colored, more reflecting soils (Oke, 1987).
Higher moisture content soils warm more slowly than drier soils because they are darker and absorb more solar radiation (Fig. 5.8). Due of water’s high specific heat, which requires a lot of energy to warm, there appears to be an abnormality.
Thus, compared to clayey soils of the same colour, the surfaces of sandy and coarse soils warm and cool more quickly. The air and fruit near the ground can warm significantly at night due to the soil’s rapid cooling (heat loss).
In the spring, reflective ground cover can slow down soil warming, but in the autumn, it can mitigate the decline. Under mulches, there is a comparable variance in the daily temperature of the soil (Whiting et al., 1993; see Fig 4.71). On the other hand, early soil warming in vineyards is frequently improved by plastic mulches (Ballif and Dutil, 1975).
