heavily
He came down the stairs, treading as heavily as he could.

gently, lightly, softly
carefully, cautiously, gingerly, warily
The government will have to tread carefully in handling this issue. (figurative)
She trod gingerly. It would be risky to hurry.

with care, with caution
down
She planted the seeds and trod the earth down.

in (BrE)
Billy trod in a big puddle.

into (BrE)
Some cake crumbs had been trodden into the carpet.

on (BrE)
Be careful not to tread on the flowers.

Tread is used with these nouns as the object:
grape, ground, path