My garden has an very high level of phosphorous in the soil and has not been producing for years. What to do?

I think I've killed my garden over the years, burning leaves and downed limbs there every fall and tilling the ash in the spring. I've only tried to maintain the ph at normal. My nitrogen and potash levels are almost not even registering they are so low. But I have added 3/4 ton of composted cow manure this year to balance them. Just the phosphorous remains.