I appreciate the 'free' nature of the task at hand!
One of my favorite topics of discussion recently has been hugelkultur - the burying of wood. This wood, as it decomposes underground and thus locks carbon into the soil, becomes spongey and holds moisture, allowing the surrounding plants to resist drought easier!
These buried branches also activate soil microlife, including very much a plethora of fungi - these fungi help mobilize nutrients throughout the soil, raising fertility levels!
We are having a lot of fun burying wood around the world, taking pictures and coming back to observe the results over the years!