It is not only the nutrients in the manures that helps the plants, it is also the microbial life. Even bagged Big Box Store composted manures and compost generally have excellent microbial life in it. When you open up a bag of Kellogs compost from Home Depot for example, you can often see lots of white filaments or dots in the compost. Those white strands are beneficial soil organism probably some fungi or actinomycetes that can greatly benefit plants.
I've found that top dressing with a bit of composted manures and compost on a quarterly if not more frequent schedule greatly increases the health and vigor of my trees. The living life in composted manures and compost seems to have something that artificial NPK and even boxed organic fertilizers don't have. When using these living organisms, the results won't happen overnight. It can take 2 weeks to a couple months before your plants will start looking much greener and showing increased vigor.
Simon
for trees fungi is very important
and while manure can help it along, you really dont need it
and woody substance will work
i have a few inches of woody mulch around all of my plants.
pine bark is excellent, i love the small stuff as it breaks down faster
you have to add more, but it mimics the forest more in that respect.
i recently found a compost (made local)
that has no animal products, and i am very happy with the stuff.
i went into a wooded area near my house
a place that was never cleared by humans.
i did not see 1 plant with a nitrogen, potassium, or any other deficiency...
LOL