Soil structure can begin to evolve from a single grain of massive form. When coming from a single grain, the development starts from the binding of soil particles form a clump (cluster) which later became ped. There are five main mechanisms that unites these particles, namely:
1. Activities during the growing root penetration.
2. Water movement which followed the direction of root growth leads to soil erosion and breakdown which then triggers the formation ped.
3. Activities exit and entry of soil fauna.
4. wetting and drying that expands and constrict the particles.
5. Disbursement, freezing, expanding and wrinkling particles.
Lump (ped) of land that form, should be stable, and stability ped formed depends on two conditions, namely:
a. The integrity of the soil surface at the time of rehydration, and the strength of the bond between colloidal particles in the ped when wet,
b. Ped resilience can be determined by wet screening method.
In this method, the dry soil is placed in a colander and then dipped into the water, the water immediately pervasive and urgent air trapped in the pore spaces of land, ped is not strong against this pressure will be broken and damaged, dropped through holes sieve. Ped-ped ped left is stable against water.
Generally, there are three groups of materials colloidal (diameter <1 m) which acts as an adhesive, the particles in the formation of soil aggregates, namely: (1) The clay mineral colloids, (2) iron oxides and manganese colloidal, and (3) colloidal organic matter, including results and overhaul activity of microbial cells. By the time the water evaporates, the plates will be adjacent clay and assisted by the adhesive, then there was a clumping (aggregation).
Figure 1:32. Sketches of the Land Aggregation Mechanism
Based on the above, the role of soil structure is very important for the agricultural world and the growth of plants. Without good soil structure, growth, development and production plant will be disrupted. How to determine the structure of the soil on the ground? And how the structure of the land in a farm. To answer this question must be observed in the field through practical observation soil structure.