Watch ph level too. Manure, especially when applied regularly over several years can throw ph off....WAY off.
As I mentioned in earlier post, micro nutrients are very important. Zinc, boron, and as Paul mentioned, sulfur have been found to be vital in a plants ability to take up NP&K. And that cation exchange capacity I mentioned is the soil's ability to hold moisture. Low CEC will limit soil's ability to hold nutrients and therefor, effecting availability of nutrients for plants to use. You can apply fertilizer till the cows come home, and if the plant can't take in those nutrients, you just wasted a LOT of money.
Feeding a plant is like feeding a human....It takes a proper balance of ALL required nutrients to keep a person healthy.
From my experience, getting ph in range is the first thing I'd start with.