Answer: d. using a color reference chart
Step-by-step explanation:
The soil color depends upon various factors such as the mineral content, moisture content, organic matter content and others. The use of Munsell color chart is ideal for the determination of the color of the soil. This chart has three components that include the hue (specific color), chroma (color intensity) and value (darkness or lightness) these three components are compared and judged for each soil sample. This involves the visual matching the three components with that of the soil sample. It is the most reliable approach for the classification of the soil color.