This is an interesting discussion. I think writing good English goes beyond working out the technical meaning. Likewise when we teach learners, especially foreign learners, we can best help them by telling them about style, customary usage and the relevant cultural background. Consider for example the proverb, "We reap what we sow." We do not say, "We reap what we seed." Figuratively and idiomatically we normally say, "We sow the seeds (of discord, victory, etc)..." So "sow" is the natural choice of native speakers.

There may be some difference in UK and US English here as you use "ploughing" not "plowing", but because it's a field, which means it's being planted by a farmer, usually, the word is sowing. Seeding makes sense, too. Growing is not right here. The seeds will grow late, after sowing or seeding.

That's a fairly difficult question. Even some native English speakers would pick seeding, however sowing seems more correct. To make them all sound equally correct I would say: ...is ready to be seeded. ...is ready to grow. If someone said "...is ready for seeding" I would probably never think it was incorrect

"Growing" and "seeding" have very different meanings! Check a dictionary. ;) "Sowing" is the only correct answer.