When my wife and I moved into our home, I had a soil sample taken of our lot before I planted grass seed. I guess the builder basically stripped off the top soil because we've got a pretty poor soil base from which to work. I think this is evident b/c despite using a premium grass seed mix (TTTF - winning Colors mix & KBG - Midnight II among others), I get very poor winter color (despite the fact that the seeds I picked are supposed to have very dark winter color), I've got some bare spots (the KBG doesn't seem to have filled in very well) esp. in the back yard, and it still seems be a mottled brown/tan mixed in with the green despite some of the other premium yards in our neighborhood are already a dark green.

I finally went back an re-read my soil sample from two years ago, and I realized that our Phosphorous levels are pathetically low (bottom level for all three soil samples I submitted). I got to realize this when I noticed that it didn't look like either my Kwanzan Cherry or my Crabapple were going to bloom this year, and I thought about the ramifications of such low P levels for my lawn as well. I was able to salvage about a 25% bloom for each tree (and I will further enhance the soil for a full bloom next year) with some triple phosphate, and I started thinking about doing the same for my lawn. At any rate, I put down about 50 lbs. of Triple Phosphate (0-46-0) for 8k sq. ft. of lawn since my P levels were so low to begin with in the hopes of somehow generating some decent root growth for my grass this spring.

My goal is to get ahead of my lawn deficiencies by building up some mineral reserves in the soil and not just applying fertilizer in the spring and fall and just managing to keep pace with the nutritional needs of the grass (which obviously are not being met). I'm also thinking about applying some Potash and applying next weekend to try to kick the K up a bit as well since it was low but not as low as the P. The Nitrogen I'll just add as I go along b/c I don't want to end up with excess top growth that I just have to cut and which makes the grass more susceptible to disease & pests. My father planted the exact grass seed mix and lives 15 minutes down the road from me, and, his lawn is much darker and fuller than mine seems to be. I looked at his soil tests, and the only real discrepancy seems to be the level of Phosphorous in our two soils, so it makes me feel like I'm on the right track with my approach.

Has anybody had issues trying to build back up NPK levels in their soils? Is there a danger to a lawn in adding too much phosphorous? Can you have too much root growth? I had only planned on applying in the spring and fall when the grass was actively growing. Please reassure me if I'm on the right track or help set me straight if I am not. Thanks in advance for any help you could give.