Seamus Heaney Follower.

His shoulders globed like a full sail strung:

 this is suggesting that he stands tall, his shoulders are broad and well tailored to suit this job that he does. His father is strong, and because of his build he is able to lough the feilds well and with great skill.

The horses strained at his clicking tongue:

this phrase suggests that the horses listen to every instruction his father gives, this makes him powerful and skillful, he knows what he is doing.

With a single pluck/Of reins, the sweating team turned around:

this phrase is suggesting an action that is done dyuring the plowing process, it dosent take two or three plucks of the reins for the 'team' to know what to do, the process runs so smoothly as Heaney's father is so skillful, it only takes one.

Dipping and rising to his plod:

this phrase is suggesting that the young Heaney is on his fathers shoulders, as his father plods along Heaney dips and rises, he is following the path of how his father walked. This also links with the line ' like a full sail strung', this is because waves also dip and rise, waves link with sails, sails are on ships.

I stumbled in his hob-nailed wake:

this phrase suggests that Seamus Heaney followed his dad as a young child, in many things than just ploughing, in a deeper sense the word 'stumbled' may mean that he has tried to follow in his fathers footsteps all his life, however he dosent feel he can take over his fathers jobs, he struggles to do them, he stumbles. 

I was a nuisance, tripping, falling/Yapping always:

this phrase suggests that Heaney was a nuisance of a child, it is clearly stated in the line. Like the line 'i stumbled in his hob-nailed wake', it tells you that he struggled to follow in his fathers footsteps as a child. he didnt feel his talent and skill lay with farming, and being able to plough like his dad. The word 'yapping' could be classed as onomatopoeia.

A young animal, the stage of still being classed as a baby. They are just learning how to survive, they take great care in watching their mother/father so they know how to survive when they grow older, they might not do things perfectly and it may take time to learn these skills.  

Towards the end of the poem, the last few lines show a change of relationship, instead of Heaney following his father, his father is following him. This makes us think that he is older now, his father is now a  memory, never forgotten and forever there.