I've just spent all morning taking down half a dozen elder trees, the roots of which threatened to undermine an old wooden stable block. The stumps are about 9 inches in diameter. I realise that there are specially formulated stump-killing chemicals I can buy but in trying to save myself a trip to an out of town farming supplier, I wondered if any of the following might do the trick if very carefully dribbled into holes drilled into the top of the stumps around and parallel to the inner bark: Glyphosate concentrate, creosote substitute or diesel oil. I'm not daft enough to get any of the above into the soil and would only use minimal quantities. Oh and it's my own land too.