Like everyone has said, only if those are your wishes. I like the idea, but used in a way like this:
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Coral reef burial sounds pretty cool, you get to become part of an ecosystem. I also like the idea of being planted with a tree - that sounds really nice. Somewhere deep in a forest where my tree will hopefully live for a long time and thrive. I love the idea of becoming part of a tree.
Now that I think about it, another thing that really needs to be considered is what sort of things these bodies will be fertilizing. If it's crops that are to be eaten by humans (or even animals) some people may be angry or horrified to find out they're eating food fertilized by human beings, so that may be a problem. Another thing if its crops, not everyone would be able to be made into fertilizer - some people die of diseases that probably wouldn't be healthy to put into soil. So you couldn't mandate everyone being turned into fertilizer - there would have to be a screening process no matter what.