First time growing asparagus! Placed 2nd year roots in the ditch with compost mixed in, covered it and watered it twice. The asparagus stalks appeared about 10 days later and were way more than 2 inches tall. Can I still fill in the ditch without harming the plants?
It depends. But in your case, it should be fine: the plant seem vigorous, so it will not have problem to "dig" the new soil.
Else, usually we do it in two year period: the first year we cover only half of the ditch, and the next year the rest. We do this especially if we got asparagus from seeds, so the root may not be well developed in the next few years, but we need to move the roots (so more space).