Boiling water will make a very effective weed destroyer. It will also
destroy nematodes (spell?) and other life in the soil at the time of
appliction.

Boiled water will have the disolved gases evaporated away from the surface
and some of the heavier minerals will plate out onto the kettle element,
some of the suspended solids will also stick to the kettle.

This will affect what chemical reactions may occur in the soil when the
water is used, but would probably make very little difference in practical
terms.

Biological hazards may be done in with a good boil....

Peter