Soil StructureLecturer: Miss MooreStudent: Jhon - Pierre Maxwell

WHAT IS SOIL STRUCTURE:

It is the aggregation of individual particles that gives the soil its structure. In undistributed soils, these aggregates form different shapes known as peds. It is the shape and alignment of the peds, which, combined with particle size/texture, determine the size and number of pore spaces through which water, air, roots and soil organisms can pass.

GRADES OF SOIL STRUCTUREThere are four major grades of structure rated from

0 to 3 as follows: 0 is structure less: has no observable

aggregation or no definite orderly arrangement of natural lines of weakness.

1 is weak structure: is poorly formed from indistinct aggregation that can barely be observable in place.

2 is moderate structure: is well formed from distinct aggregates that are moderately durable and evident but not distinct in undistributed soil.

3 is strong structure: is well formed from distinct aggregates that are durable and quite evident in undisturbed soil.

TYPES OF SOIL STRUCTURE (PED)

Single Grained Granular Platy Blocky Prismatic Columnar

It should be noted, however, that some soils may be structure less(sand) some may have more than one ped structure, and most are likely to have a distinctive ped in each horizon

Structure less

Two Ped Structure Distinctive Ped Horizon

AGRICULTURAL VALUE

Granular: Fairly productive; well aerated and drained – good for roots

Platy: The least productive; hinders water and air movement; restricts roots.

Blocky: Productive: usually well drained and aerated.

Prismatic: Usually quite productive: formed by wetting and drying; adequate water movement and root development

Columnar: Quite productive (if water available)