How is the art of writing portrayed in the poem "Digging"?

In the poem “Digging,” Heaney barely discusses the art of writing but envisions it as an act analogous to farming. The only times he directly mentions writing are in the first and last stanzas. Instead, he devotes most of the poem to describing others digging and cultivating plants—a process similar to writing.

With his pen poised, the poet is about to start composing and suddenly hears his father outside digging in a flowerbed. He flashes back twenty years to see his father

stooping in rhythm through potato drills
Where he was digging.

Farming is hard work and so is writing; both processes hold hope for a successful harvest. Just as his father labors to produce potatoes, the poet ponders to collect and present images and ideas to create poetry. His father digs with a “rhythm”; similarly, the poet creates rhythm through beats, pacing, and meter. For his father, the fruits of his (and the poet as a young boy) manual labor are

new potatoes that we picked,
Loving their cool hardness in our hands.

These crops are prized for their substantiality as well as purpose: to feed and sustain the family. The poet does not point out a specific work for the reader to admire but presents the poem “Digging” as evidence of his own artistic labor; he allows the poem to speak for itself.

The instrument for writing—a pen—is compared to the tool for digging, the spade. In fact, the way the poet’s father positions and wields the digging tool is similar to the way the poet holds his writing instrument. Heaney describes his father positioning the spade:

The coarse boot nestled on the lug, the shaft
Against the inside knee was levered firmly.

Similarly, for the poet,

between my finger and my thumb
The squat pen rests.
I’ll dig with it.

The poet will dig mentally to excavate words and images to create pieces of writing. His father “rooted out” or sought potatoes. His grandfather burrowed into the earth to seek peat, probably for fuel and/or fertilizer.

Nicking and slicing neatly, heaving sods
Over his shoulder, going down and down
For the good turf. Digging.

Similarly, the poet edits, discards words and ideas, and hones his poetry. Heaney presents the act of digging by his father and grandfather as an extended metaphor for his own act of writing. All of the men labor as artists to create works of art: flowers, food, fuel, or literature.

What is the personal nature of the poem "Digging"?

The personal nature of this poem relates to the way in which it is a meditation of how Seamus Heaney, the poet, is following in his father's footsteps, though in a radically different way, which the figurative langauge employed in the poem helps us to see is not actually that different after all.

The poem discusses the way that his father and his grandfather cut turf and presents us with an evocation of their way of life and how they took pride in their work:

My grandfather cut more turf in a day
Than any other man on Toner's bog.

The poet remembers seeing how his grandfather worked, "Nicking and slicing neatly" and going "down and down." The poem ends with the determination of the speaker to "dig" in the same way as his father and grandfather dug, but with his pen, making a link between his writing and his rich cultural heritage. The personal nature of this poem therefore stems from the way in which the poet examines what he does and creates an imaginative link between his profession as a poet and what his father and grandfather did.