Since poop is the solid waste that the majority of organisms produce, how is it so packed with nutrients that plants like?
In: Biology
Plants have to take in all of their chemical nutrients in the simplest form possible and then from those base structures create more complex chemical structures as needed, as they don’t have mouths and digestive systems. Animals can eat complex chemicals and break them down into simpler ones either to use them in that form, or use them to construct complex structures anything that can’t be used as a building block or broken down will be disposed of as waste.
Poop is “waste” in the sense that the animal’s gut has extracted everything it can from the food. That doesn’t mean it’s extracted every usable nutrient – it just means that the animal’s body has done all it can. There’s still stuff that can be used, if only it breaks down more.
So you take the poop and work it into the soil. Bacteria in the soil continue to work on whatever is left in the poop – bits of plant material, carbohydrate, etc. The bacteria excrete their _own_ waste, which is even more broken down into its constituent parts. That’s what plants need.
Plants don’t consume poop directly, but bacteria and fungi do. While doing so they break down and sort of “simplify” the components and the byproduct of that is available for plants to use.
What is in your poop is not useful to your body cause you can’t use it, but it doesn’t mean it has no value to other types of life, that consume nutrients differently and metabolize them in other manners. It’s how available the nutrients are to a certain being that make it “food” or not
To give you another example: a cow can digest grass, but you can’t.
Edit: it’s impressive how all comments are about the cow and the grass
Plants “eat” air and light. That’s not everything they need, so they use their roots to gather the last little bits from rocks. Animals eat plants or animals that ate plants. Animal poop is predigestested rocks for plants.
Because plants and humans function in completely different ways. It’s similar to how plants “fart” oxygen and then we use there oxygen farts to breath, in exchange for the CO2 that we breath back out
Poop is waste not because its substance has no value, but because it’s all the stuff the body has no use for extras of.
Plant mass is made out of like 98% water and carbon dioxide from the air. They need very little in terms of everything else, which is how you can grow multiple huge plants in a row from a single small pot without really using up the soil that much.
What they do need are basic elements and simple chemical compounds, which they get from bacteria breaking anything organic down.
Food as organic matter gets more complex as you go up the food chain and each member of the food chain is responsible for making more complex organic matter to serve as food. Each step along the chain also produces waste to return to the lower levels. In fact only a minuscule percentage of food taken up at each animal level serves to benefit the organism. Most is returned in fecal matter, but the rest when the animal dies.
Decomposers scavenge dead and decaying organic matter and turn it into raw elements and simple compounds and minerals. Plants take this up and incorporate the organic matter into their tissues. Pretty much all fungi are chemotroph decomposers.
Then chemotrophs that are herbivorous take those plants and incorporate them into their tissues and produce waste that ideally gets returned to the plants.
Herbivores serve as food for carnivores and incorporate their flesh into their tissues. They provide a waste product that returns the herbivore back to the environment.
Plants and people are opposite ends of a cycle.
People breathe in oxygen and breathe out carbon dioxide. Plants take in carbon dioxide and put out oxygen. We need their waste and they need ours.
The same goes for using poop as fertilizer. The things we DON’T need are exactly what the plants do need.
manure contains essential nutrients for plants, like nitrates and phosphates, and it contains lots and lots of the kind of bacteria that breakdown organic waste to release those nutrients.
because plants require those nutrients to grow, they gradually deplete them from the soil the plant is growing in. without a replacement source of nutrients the plants growth will slow down or stop. adding manure to the soil allows the plants to continue growing.
In addition to what’s said here (and maybe not strictly speaking answering the exact question asked), part of the reason poop would be bad for you if you ate is that it contains a bunch of stuff that would give you diseases that the body was trying to get out. But plants and humans are not very closely related, meaning that it’s difficult for something that infects humans to also infect a plant, and vice-versa.
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