Hating to waste a perfectly good (if trivial) feature, I'd suggest putting the Rotten Plant trash item to use. Make it recyclable into a new type of fertilizer: Compost. Every good farmer ought to be able to put that into practice. I can't see that a recycling machine ought to be required - perhaps a Tractor (new equipment?, with further expansion possibilities). But that's optional. A spade/hoe is enough if the volume is low (which I expect it to be), so just shovel it into the earth. Leave it as an option to consider the tile fertilized once mixed, or to harvest the tile as a Compost item to save the fertilizer for later application.
I'd like to see some kind of composting feature in general so we can put all our unwanted and not-really-profitable-enough-to-ship items to better use.
I think they mean items that clog up inventory space, like algae, which you can eat, or other things like flowers, maybe fiber, etc. I'd like to see some sort of crafting system put in for items that are just kind of there, like seaweed, algae, clay, etc.
I get what they're trying to say, yes. But algae and seaweed are for cooking or can be shipped, fiber is a godsend for scarecrows and Junimo huts and other crafts. Clay lost a bit of usefulness with the removal from Keg recipe, and currently is only for silos or retaining soil (and you can get by with just one silo and a chest). Flowers may stand to benefit from additional uses.
Hmm, that was over a month ago so I forgot what I was thinking. But I'm guessing I meant any food/plants that has no immediate or significantly relevant use, and whose monetary value is measly compared to vastly more profitable crops, should be able to turned into compost or something that can be put to better use. Basically, yes, you can ship for them for profit, but the profit would be so marginal that I feel they could be put to better use instead.
In the compost thread of thought, perhaps putting algae, seaweed, or clay into the recycle machine could produce compost, and with enough compost you could craft it into your choice of first-tier fertilizers.