1.
If you dig a substance in, or dig it into the soil, you mix it into the soil by digging.
I usually ~ a small barrow load of compost in late summer...
To dig calcium into the soil, he warned, does not help the plant.
PHRASAL VERB: V P n (not pron), V n P n
2.
When soldiers ~ or dig themselves in, they dig trenches and prepare themselves for an attack by the enemy.
The battalion went directly to the airport to begin digging in...
The enemy must be digging themselves in now ready for the attack...
Our forces are dug in along the river.
PHRASAL VERB: V P, V pron-refl P, V-ed P
3.
If someone digs in, or digs into some food, they start eating eagerly. If you tell someone to ~, you are inviting them to start eating, and encouraging them to eat as much as they want. (INFORMAL)
‘Listen,’ said Daisy, digging into her oatmeal...
Pull up a chair and ~!
= tuck in
PHRASAL VERB: V P n, V P