SPECTROPHOTOMETRY MEASUREMENT OF SOIL COLOR AND ITS RELATIONSHIP TO MOISTURE AND ORGANIC MATTER

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Abstract
The color of soil samples taken from the Ap horizons of Chernozemic and Gray Wooded (Podzolic) soils was measured spectrophotometrically at moisture levels ranging from air-dryness to field capacity. The Munsell re-notations "hue", "value" and "chroma" were related to the moisture content and the amount and nature of the soil organic matter. The addition of moisture to the Ap horizons from Chernozemic and Gray Wooded soils caused a significant decrease in value but had little effect on the hue and chroma. In Chernozemic soils the average decrease in value was 1.0 unit. This darkening in color occurred primarily in the moisture range between air-dryness and 18%. The decrease in Gray Wooded soils averaged 1.7 units and it occurred throughout the moisture range from air-dryness to 30%. The Gray Wooded soils were significantly higher in color value per unit of organic matter than were the Chernozemic soils. Differences were found in the ultraviolet reflectance spectra of these two kinds of soils and in the E4:E6 ratios of alkali extracts. The ratio of humic to fulvic acid and the amounts of 0.5 N NaOH-extractable humic acid also differed for the Gray Wooded and the Chernozemic soils.

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