Third, we buy different sizes of things. Give them incentives. That's one incentive. Maybe you can make the writing easier by finding a writer within the company who is willing to colloborate with a programmer who doesn't like to do the writing part. Focus on repeat offenders.
Some programmers have trouble thinking of article ideas.
Those sorts may sell us one article, and then we'll never hear from them again. They grasp what sort of thing it is we buy, and from then on all they have to do is keep their eyes open for appropriate topics that arise in their own daily work. Those sorts will send us a proposal every few months, and sell us multiple articles each year. That's what I would do. What I wouldn't do is the typical things.