When spring feeding with bonemeal for trees & shrubs and sulphate of potash for fruit trees and shrubs, I have the following questions:

When there is weed suppressant matting and bark mulch/stone chippings on top, is it alright to sprinkle the food on top of this and let it work its way down to the soil or should the covering be pulled back,food administered and then recovered?

The instructions give a spreading rate per metre but how does this translate into per tree/shrub? Is just a handful per tree/shrub alright as a rule of thumb?