I know it's not an answer to your question, but why not mulch them where they lay and put their nutrients back into the soil? Does it harm the lawn to do that?
I'm seriously debating mulching mine in this year but not from a nutritional standpoint. /forums/images/graemlins/cool.gif My trees are all oaks though so maybe it's the rake and blower afterall. /forums/images/graemlins/frown.gif