MSU fertilizer vs coconut chips
 

It is very nice to use a fertilizer (MSU) perfectly balanced for demineralized or tap water. But I read somewhere that some orchid medium (bark) can change the nutrient availability for the plant.

My question is: does coconut chips make nitrogen, phosphorus or potassium or micronutrients less available to orchids?

I think as bark decays it can affect the nutrients. Chc decays much slower than bark, so while I suppose it could have the same effect, it would occur much more slowly.

It used to be that orchids were grown in bark, with added peat moss, leaf mold, and the like, gleaned from the garden and forests. They tended to decompose rapidly. It is the microorganisms that do the decomposing that consume nitrogen, so plants were often subjected to nitrogen deficiencies. Hence the invention of high-nitrogen fertilizers.

As WR states, the slower decomposition rates of modern medium components minimizes that excess nitrogen demand, so it's not an issue.

One caveat is that if you let your potting medium go for a long time between replacements, that issue can rear its head, but by then you will have lost the roots, too, so a nitrogen deficiency is the least of your worries.

any oganic media brakes down and can buffer the fertilizer and it can also hold salts if you notice salt around the rim or bottom of your pot you might want to flush them or repot , each media hold more salts then others and buffers more then others.

Also, plants growing on windowsills grow much slower than plants grown in greenhouses or under lights, and nitrogen is not used as rapidly, so there is always enough for the plants.