^^agree with RadaR, and N+P based substrate is the way to go. However, it's quite expensive on larger tanks. I'm the same as RadaR, Columbo flora base was the best planted substrate i have used. I haven't used the ADA substrates, they are very expensive. Apparently the Florabase, Oliver Knott etc etc are all made by the same company. The ADA Amazonia is the only soil based substrate that is made independently.
and just before anyone say's that these are great for 'root feeders' lol, these substrates are used so the N and P leech into the water column. There is also some certain control of C02 with these substrates. Thus creating a balance in a tank more quickly than other tanks with inert substrates. I know i'll be using the Columbo stuff again in the near future.