Whate are dispersion and flocculation?

First, what is dispersion? Dispersion is when clay particles are kept separate from one another like opposite ends of a magnet. In fact, clay particles are very similar to the negative ends of a magnet. Certain minerals bring clay particles together (with their positive charges). Others keep them repelled.

Flocculation is the opposite of dispersion. Flocculation is the process where individual clay particles are pulled together. This clumping is called aggregation. Soil aggregates are cemented clusters of sand, silt, and clay that create pore space in the soil—allowing water movement and air exchange. This is one of the most important keys to healthy soil.

Dispersion creates terrible soil structure. So how does it happen? Dispersion and flocculation are chemical phenomena, driven by the balance of cations in the soil. Calcium has a very high flocculation power, while sodium and potassium cause dispersion. The general balance between Ca and Mg compared to sodium is what determines flocculation/dispersion. Too much sodium—from the use of toxic fertilizers, over-application of compost, or the use of poor irrigation water—will cause dispersion. Alternatively, too little calcium may be the issue, making soil testing and mineral amendments of utmost importance in low pH soils!

Electrical conductivity influences dispersion as well. EC is simply a measure of the total ions in the soil solution. Low EC increases dispersion. Low EC, high sodium soils are considered sodic, which is a huge challenge for soil health.

Things to remember:

• Don’t create sodic soil. Be careful with what you apply.

• Get a soil test and balance the cations.

• Don’t ignore your soil’s physical structure. It’s super important!