PH of 6.2 is good:
Toxicity is highly unlikely. Dr. Earth Soft Rock Phosphate is only 2% P as plant available Phosphoric Acid, the rest of the P is probably around 25%-30% bound up in insoluble minerals.
It's a mystery. I've never applied Soft Rock Phosphate that way, I never put anything on top of the soil other than compost or other organic mulch.
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