The speaker is a field, and it speaks directly to a sower. It calls itself open and submissive, ready to receive whatever is scattered. The first stanza accepts that sunshine, rain and air will help crops and weeds grow alike, though people tend to look after one and ignore the other.
The second stanza turns more desperate. The speaker admits its breast is rocky, gravelly and hard, not a good place for crops to take root. So it makes an unusual request: if you can't sow crops, sow weeds, as long as they wake something in me. Weeds are tough and full of life, and the speaker would rather grow something unwanted than stay barren sand.
The mood is humble, bare and quietly urgent. The field could stand for a person who feels unworthy or neglected, and who longs for any purpose at all. That reading is an inference, but the poem's closing line, "It will give me significance," strongly suggests it.