The main four types of soil structure are columns, blocky, granular and plate-like. Soil structure is based on the shape that is takes from its chemical and physical properties. To determine the soil structure, study a sample of undisturbed soil in your hand and see how each individual unit of soil lines up.
Soil is considered column type when it's shaped in blocks and the related cracks are generally longer in the vertical shape and not the horizontal shape. The column soil structure has good water penetration, drainage and aeration. This type of soil is capped with salt and is found in arid regions.
With blocky soil structure, the size of the soil will be large and cracks in it will go in a vertical and horizontal direction. Soil with a blocky texture has a good level of water penetration and a moderate level of drainage and aeration. The blocks of soil are usually between 1.5 and 5.0 centimeters in diameter.
The granular soil structure is like the blocky structure but the soil is usually smaller than a half centimeter in diameter. The cracks are the same in quantity and go horizontal and vertical. The water penetration is good, but this is the best type of soil for drainage and aeration. It is common to find the granular soil structure where roots have grown in surface horizons.
Plate-like soil structure is usually found in compacted soil and the cracks are stretched more horizontally than they are vertically. It allows moderate water penetration, aeration and drainage.