Bill recommends sealing the top of the container with a heavy duty construction garbage bag so no rainwater gets in, he recommends just one early season application of slow-release osmocote, which seems to work fine for him. I don't see explosive growth with this method, but it ain't bad either. I will be seeing him saturday so I will ask him his thoughts. I suppose you can rig an opening so top-application fertilizer can be added, but the idea is to have the plant expect feeding from below, not from above. So the top should be sealed, tho' some people operate their wicking systems with the top open. This results in sun-drying, which requires more watering. With the top sealed you only need to water every 3 days, which is a relief to the busy and the beleaguered. I also have traditional open top watering containers, and I find a thick layer of chunky pine bark keeps the top moist and reduces evaporation. Personally, I also find that a mixture of mycorrizae pro-mix, sand and/or perlite and slow release limestone works great for figs without any additional tinkering with other soils or mixes.