A medium with required properties can be easily created by mixing components that have known particle size. We can add particles that are small to a medium which is made up of  large particles. If we do this, it increases water holding capacity and reduces air pore space which is at container capacity. Common propagation media has same volume of perlite and peat, same volume of perlite and vermiculite, one part of coarse sand and 3 parts of peat, ground pine park.

For outdoor propagation, ideal propagation contains 35 to 25 percent of air space. If irrigation and misting are managed properly in a covered greenhouse then quality liners can be easily produced in propagation media. If there is excessive irrigation and rainfall, porous medium acts an excellent buffer

Fertilization

When roots of seedlings emerge they absorbed nutrients, but excessive nutrients injure tender roots. You can use controlled release fertilizers in propagation medium. However, you should also consider rate of nutrients that are released. Controlled release fertilizers should be predictable over range of temperatures that are possible in a propagation system. Soluble fertilizers can control nutrient levels if they are applied moderately in the propagation medium. However, intense management is required. But they should not be added in propagation medium.  

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