If your spruce trees are producing PINE cones, it must mean that the world is
coming to an end. Spruce will fruit heavily when they are under stress to
ensure that thier genetic information will be passed on to another generation.
As for the tilling, what are you doing that for??? Tilling arround the
rootzone of you trees will harm their roots. Also, if you are tilling without
actually adding some sort of organic matter to the soil, you are destroying the
soil structure arround the plants.

Toad