In the Sabbath year the ground is allowed to lie fallow...
or rather, left to rest
in this rest it replenishes (or renews) the nutrients it needs to grow the crops again for the next 6 years
the nutrients however - i guess - would mainly come from the death of the last crops which are no longer maintained and allowed to decompose - similar to how a forest fire would severely enrich the soil
if that's a correct understanding of agriculture...
then our Sabbath is only possible because of the death of Jesus
because He dies, we can have rest in Him..
as His body is the manner in how we are renewed...
as we take Him in and now grow in Him