Sexual references in Heaney's 'Digging'?

Hey everyone,

I've read quite a few of Heaney's poems and the cleverly embedded sexual references in some made me chuckle.

I'm studying the poem 'Digging' atm, are there any sexual references in this poem, and what is its purpose, or am i simply overanalyzing the notion of "digging into the soggy peat". can it mean the fertility of land, and how it is rich in memories and gives birth to new talents (like seamus and his elderrs)?

Here's the poem, thanks guys...

Between my finger and my thumb
The squat pen rests: snug as a gun.

Under my window, a clean rasping sound
When the spade sinks into gravelly ground:
My father, digging. I look down
Till his straining rump among the flowerbeds
Bends low, comes up twenty years away
Stooping in rhythm through potato drills
Where he was digging.

The coarse boot nestled on the lug, the shaft against the inside knee was levered firmly.
He rooted out tall tops, buried the bright edge deep
To scatter new potatoes that we picked
Loving their cool hardness in our hands.

By God, the old man could handle a spade.
Just like his old man.

...

The cold smell of potato mould, the squelch and slap
Of soggy peat, the curt cuts of an edge
Through living roots awaken in my head.
But I've no spade to follow men like them.

Between my finger and my thumb
The squat pen rests.
I'll dig with it.

Seamus Heaney