Why does my fertilized lawn look even better where I also planted tree food spikes?

I can't complain about my lawn (well, I guess I can hence this message) but I'd like to know why my lawn looks even better in little circles around where I've inserted some basic food spikes to feed trees and shrubs. The lawn is even more vibrant and a darker green.
On the lawn itself I'm doing basic things: using Turf Builder as prescribed, aerating twice a year, watering 2-3 times a week. I'm in San Francisco, so climate is not too hot. Again, it looks decent overall, but markedly better where the spikes have gone.
Obviously, the spikes are providing even more nutrients, and, it seems to me, that means I could be fertilizing my lawn even better. But, I'm a little hesitant to just up the dosage of the Scott's as I think that's a surefire way to burn out the lawn.
Is there a particular extra ingredient in tree / shrub spikes that I might consider?
Thanks,
- TK
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On 2 Jul 2006 13:02:29 -0700, snipped-for-privacy@hotmail.com wrote:

The grass is feeding off of the nitrogen from the tree fertilizer spikes.

You could apply the fertilizer more often and at a lower rate. That is, apply the same amount of fertilizer but twice as often. You can safely add organic fertilizers in addition to the lawn fertilizer. Unless your lawn is very dry, I doubt there will be any burning. I hold off fertilizing during drought times, unless I'm using an organic fertilizer. Over-fertilization using inorganic fertilizers can cause a variety of undesirable conditions.

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I live just a bit south of you, in San Jose. What I do, is ever year around april/may is I core the lawn with an aerator. Then I use a spreader to distribute a 50/50 mix of blood and bone meal, and follow that by raking in a layer of composted steer manure.
Lawn seems to like it, and stays healthy enough. Turning greener, suggests it lacks nitrogen. So try adding a slow source of nitrogen, such as blood meal. This time of year the ground is just too dry to easily work into the soil.
-S
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