Q.how much compost/manure to use around leyland trees
How much 5-5-5 compost/manure should I use around my Leyland trees? My Leyland trees are 20 ft high and showing signs of turning brown and yellow. I want to add some fertilizer (compost/manure 5-5-5) around the base of each tree, but I don’t know how much to use. They come in 40lb bags.
Joe, Thank You

If your leyland is turning brown and yellow, this could be a sign of disease or insect infestation in which case fertilizing may not correct the issue. I would encourage you to peruse any of the articles below which discuss diseases and infestations:
http://extension.uga.edu/publications/detail.html?number=B1229
http://www.ces.ncsu.edu/depts/ent/notes/O&T/specificplants/note133a/note133a.html
http://www.clemson.edu/extension/hgic/pests/plant_pests/trees/hgic2004.html
http://www.ces.ncsu.edu/depts/pp/notes/Ornamental/odin17/od17.htm
However, if you are pursuing the fertilizing route, evergreen trees need 1/8 bushel of manure per foot of height so in your case (provided I did my math right), that would be 2.5 bushels.
For more information on growing leyland trees, please visit the link below:
https://www.gardeningknowhow.com/ornamental/trees/leyland-cypress/growing-leyland-cypress-trees.htm