Agricultural policy in the US shapes a lot of this, though, via subsidies. The financial system also shapes this through its lending policies. The implements of industrialized farming are what the ag lending sector is designed around; try to step out of that mainstream and you will have trouble accessing capital.
Wheat, corn, and soybeans are heavily subsidized by the US gov't and vegetables are not at all. Every little tiny program to subsidize vegetable growers is picked at every year (happening right now in my state legislature) -- it's always a fight to preserve.
The agricultural lending system in the US is fascinating. Look up Farm Credit Administration. We have a weird and unique system of paragovernmental financial institutions in the US that do farm lending, and even though it's not technically government-backed lending, everyone sees it as such, and so there are some interesting distortions in the market (compared to a more "free-market" system). It does seem quite centered around US gov't subsidies and farm/ag policies.
That's because wheat, corn, and soybeans are staples, while vegetables are luxury food items, especially fresh ones. At no point in history, regular people in agricultural societies ate as much vegetables as we do right now. The diets has always been based in overwhelming majorities on grains, roots and beans, and in places with lactose tolerance, also on dairy.
A single bell pepper today costs something between $1 and $2 where I am. Imagine the government subsidizes bell peppers so that they cost $.50. As a single bell pepper has less than 50 calories, you couldn't base your diet on it, you would still need some more calorie-rich food to actually give you required energy. Since vegetables (except root vegetables) are not calorie-dense, you'd need to eat seeds (e.g. grains) or oils anyway.
That's why, if your goal is to enable the nation to feed itself, you should rather subsidize the staples, not luxury consumption.
Corn and soy are not staples for humans, they're staples for industry. What doesn't get exported is used for livestock feed, ethanol, and filler for unhealthy foods. It makes a very small sector of our economy rich, it destroys huge swaths of our nation's ecology, and that result damages the health of animals (including us).
Feeding the nation isn't hard. We could feed this nation five times over with the amount of food we produce. The problem is, we'd probably shrivel up and die, because wheat, corn and soy aren't enough to keep a population healthy. We could actually produce more nutrition and calories with a fraction of the land just by switching from corn to oats. But then you'd be producing less, and hence selling less. That's not as profitable!
And vegetables are luxuries in the same sense that "nutrition" is a luxury. Just because humanity has historically had a shit diet (since the adoption of agriculture) doesn't mean it's a great idea to stop eating vegetables, or produce less of them. We get plenty of calories already - too many in fact. And most of the ones we do get are more harmful than good.
It would be better to get people to eat more of those low-calorie vegetables as it would help stem the American obesity crisis. And as we've seen in this report, vegetables already contain fewer nutrients than they did before - a reason to consume more of them, not less!
Rich nations don't have problems supplying calories. In fact they have the opposite problem, people eat too many calories. There is an obesity crisis underway.
Wheat, corn, and soybeans are heavily subsidized by the US gov't and vegetables are not at all. Every little tiny program to subsidize vegetable growers is picked at every year (happening right now in my state legislature) -- it's always a fight to preserve.
The agricultural lending system in the US is fascinating. Look up Farm Credit Administration. We have a weird and unique system of paragovernmental financial institutions in the US that do farm lending, and even though it's not technically government-backed lending, everyone sees it as such, and so there are some interesting distortions in the market (compared to a more "free-market" system). It does seem quite centered around US gov't subsidies and farm/ag policies.