A planter when it is full of dirt and plant may weight a lot. It is heavy and difficult to lift when we decide to move it to a new location. When it's full loaded with dirt and plant, it could be more than 20kg. It's a back breaker job. I know because previously, I had that incident.
Here, I'll show a solution to light-weighted your planter. But, firstly we need...

Step 1: Items

1 heavy clay planter
A few dry banana fronds or coconut husks
Dirt

Tool
A shovel

Step 2: The Filling

I fill the planter with the banana fronds just about three quarter of height. For a larger planter, I use both banana fronds and coconut husks. Then, I top it with the dirt.

I notice over a period of time that when I used the coconut husks, the dirt sink much slower that the banana fronds.

Step 3: The Planting

Lastly, I plant it with a coconut seedling. Now, the planter is much easy to handle because the weight is reduce about a least 50%.
No more back breaker for me.