How do they make ‘fast acting slow release’ fertilizer, drugs etc?

Question

I was watching a gardening channel, she said she is adding ‘fast acting slow release’ Nitrogen, I also hear similar stiuff with medical drugs etc.

How do they make Nitrogen behave like that?

How do they time it?

In: Chemistry

Answer 1

I think you probably misheard, as “fast acting” and “slow release” are opposites, and a fertilizer will generally be one or the other. I guess it’s possible that a product will contain a mixture of fast acting and slow release fertilizers, and thus provide the benefits of both?

In any case, whether it’s fertilizer or drugs, the answer is kind of the same: how fast does it dissolve?

Both fertilizer and drugs only get taken up and used when they’re dissolved into a fluid, either the groundwater or your stomach acid. And both of them use a lot of different strategies to change how fast they get dissolved.

One strategy both use is a coating, either on the pill or the grains/tablets of fertilizer. This coating may be mixed with the active ingredient in layers or in a sort of microscopic honeycomb pattern, so that the coating has to dissolve before a bit of the active ingredient gets dissolved. The coating could also be porous, allowing some of the active ingredient to seep through it at a slow, controlled rate.

There are many more strategies when it comes to drugs, and I won’t go into them all here; most essentially boil down to “make the active ingredient dissolve into stomach acid more slowly.” And that’s just oral preparations – there are things like patches which deliver a slow and steady dosage, but that’s another can of worms.