Soil color.
In general, the darker a soil is, the more nutrient it has. The darker colored soil usually contains more decomposed organic matter known as humas.
Gray soils often indicate poor drainage while red soils can indicate very poor soils. These are the general rulers about soil colors. Under certain conditions,a very poor soil can appear as dark black, while a rich healthy soil can appear as red.
Soil texture.
Soil texture refers to the proportion of the sand, silt, and clay in the soil. The size ranger of sand, silt and clay are as follows:
Sand, silt, and clay represent the inorganic soil particles less than 2 mm in diameter. Inorganic soil particles of 2 mm in size or larger are called rock fragments or gravel and pebbles.
Soil texture is important in determining the amount of water retained by the soil and air movement. Fine-textured soil retains more water and has lesser air movement than the coarse-textured soil, but it may be not ideal for plant growth.
The texture of the soil, how it locks and feels, depends upon the amount of sand, silt and clay. Soil texture in a way that create large pores. Clay-sized soil particles fit together in a way that create small pores.
Soil structure
Have you ever played with a dirt clod? A dirt clod is small clump of soil that has formed a rock-like clump. These dirt clods are called peds by geologists. Soil ped is the basic unit of soil structure.
These peds are organized into a repeating pattern that is referred to as soil structure. Between the peds are cracks called "pores" through which soil, air and water are conducted. Soil structure is most commonly described in terms of the shape of the individual peds that occur within a soil horizon. There are a few types of soil structure.
Granular - roughly spherical, like grape nuts. Usually 1-10 mm in diameter. Most common in horizon of organic matter decomposed bind soil grains into granular aggregates.
Platy - flat peds that lie horizontally in the soil. Platy structure can be found in horizon A, B and C . It commonly occurs in horizon A as result of compaction.
Blocky - roughly cube-shaped, with more or less flat surfaces. Sizes commonly range from 5-50 mm across. Blocky structures are typical of horizon B, especially those with a high clay content. They form by repeated expansion and contraction of clay minerals.
Prismatic - larger, vertically elongated blocks, often with five sides. Sizes are commonly 10-100 mm across.
Columnar - the units are similar to prisms and are bounded by flat or slightly rounded vertical faces. The tops of columns, in contrast to those of prisms, are very distinct and normally rounded