Don't get me wrong, I really like the idea of it, I think grains are lowest-tier food and I would much prefer to eat the produce you describe. However, grains

Don't get me wrong, I really like the idea of it, I think grains are lowest-tier food and I would much prefer to eat the produce you describe. However, grains are the staple food, not just in the US, but around the world. To my knowledge no other method than having fields of grains buffed with fertilizer comes close to its caloric output. You're saying it requires "no inputs", but it actually requires a lot of land. The inputs you describe are plentiful, land is scarce. If soil really does get used up as some scientists predict, we might naturally shift towards these kinds of farming, but we might also figure out a way to replenish the soil.