What makes a substrate good for plants?

[Jaap]

Hello,

sorry if this sounds stupid but I was thinking what makes a good substrate good? Apart from being NPK or nutrient rich, which again if you dose via water column it might be unecessary, what makes a substrate good for a heavily planted tank? e.g not being porous, getting packed after some time, lack of oxygenation due to compact feature of substre....I don't really know but I am throughing ideas out there!!!

Thanks

 

[hotweldfire]

High CEC I guess. Being able to absorb nutrients from the water column and provide to plan roots.

 

[Jim]

Plain and simply an anchor for the root system.

 

[nayr88]

Plain and simply an anchor for the root system.

2nd that