Bigyin,
You have probably been asked this question once or twice before,but why did you cut down mature olive trees in the first place ?
If the answer is, they were in the wrong place,you could have simply had the loading shovel pick them up and move them to my land !
This would have solved two problems at once,you would have no tree roots to dispose of and I would have nice old mature olive tree's to replace the hundreds of tree's that the local farmers have grubbed out of my land, over the last thirty years.