Motivation of site visitors

Good evening. I have a small website dedicated to one graphic editor well-known in not-so- narrow circles ... The website itself is in the format of a blog in which lessons \ articles and so on are published according to this graphic editor. Authors except me, still <10, but each writing (or rather translating from English at a given link) 1-2 lessons ceases to write. I don’t know if they are becoming uninteresting, bored, or they are getting busy. But I would like to know how to motivate the user? Whatever he throws this occupation ...
In principle, there are not so few visitors on the site (now from 100 to 150 per day), and another unpleasant question arises - there is no feedback. Previously, he was - at least 10-15 comments (normal, not seospam), and now 1-2 and a few comments from the authors themselves ... And yet, it would not be bad if at least one person in 1000 would like to share something something interesting for the community and become a new author.
Searching in Google and Yandex, I did not find anything sane about this topic, can you, good hubrochelovek, can you advise something? Thank you in advance =)

Shl. I was always “afraid” to ask a question in the Habré — after all I suddenly ask for a common truth, which everyone has known for a long time, except for my province)) ... So do not judge strictly, if that)