Crops use something like 1% of the resources to grow that meat does. It's not just about where carbon is stored, but land and water usage and where carbon is produced (cows fart. a lot.). Overall plant-based diets are far superior for the planet than meat-based diets, and contrary to popular opinion they don't have to suck.
Water and land usage is also A: grossly overstated (you can't grow anything except grass on most land) and B: cited as something against all meat when chickens, goats, ducks, geese and pigs use far less of both. At that point, substantiate or correct your statement to 'beef'.
The overwhelming majority of soy grown globally is fed to livestock. That's definitely does not fall under your category of "can't grow anything except grass on most land".
"More than three-quarters (77%) of global soy is fed to livestock for meat and dairy production. Most of the rest is used for biofuels, industry or vegetable oils. Just 7% of soy is used directly for human food products"
The proportion is lower for corn, but only because a huge chunk is being used for fuel. If we exclude that, it would still be the overwhelming majority.
https://www.ers.usda.gov/webdocs/charts/104842/corn_dom_use....
How do you plan on solving the problem of eating the bits of soy plants that humans can't eat?
Is this really a problem? No one is suggesting we stop eating fruit just because we cant eat the leaves, branches, and roots.
You could feed it to cows, in which case it gets turned into cow and fertiliser, or you can let it pile up and rot, emitting massive amounts of carbon dioxide and methane.
Sounds like the South Indian Sambar with rice meets this criteria.
Or rice-dal-subji combo in North Indian cuisine.