SFG is about promotion of the method itself, a guy and other people are living of this “product”. Book is quite good. It helped me in the beginning of my gardening journey.
Don, as i understand, spacing for SFG is also about each square being planted by it’s own veg and that makes a difference (difference in foliage, root space, take-up of nutrients etc).
It mostly designed to have different crops in small space.
If i would sow parsnips this way, i should sow/thin 10cm apart each way. I wonder what the harvest would be like. Just one example with same doubts as yours.
I think we are mostly planting one veg in bigger quantity here (2m long bed of fava beans for example) and with a bit of companion planting here and there.
And i never thought i would use rows so much, i was so against it! I started with wild sowings/plantings 🙂 , then using close spacing and so on.
Now it’s a combination of everything that works and it’s a continious learning process. 🙂
I’m so happy to be a gardener, it’s alive and it’s fun, dinamic, did i mentioned fun? 🙂 And food…
Btw, Charles has good tips on spacing for a lot of veg in his books. With many it’s also explained why.