But summun ’ull come ater meä mayhap wi’ ’is kittle o’ steam
Huzzin’ an’ maäzin’ the blessed feälds wi’ the Divil’s oaän teäm.
mean in modern English?
In this poem, Tennyson uses nonstandard spelling to convey the dialect of Lincolnshire where he grew up. His son Hallam wrote:
The Lincolnshire dialect poems are so true in dialect and feeling, that when they were first read in that county a farmer’s daughter exclaimed, “That’s Lincoln labourer’s talk, and I thought Mr Tennyson was a gentleman.”
Hallam Tennyson (1897), Alfred, Lord Tennyson: A Memoir, Volume 2, p. 10.
In standard spelling, the couplet would be:
But someone will come after me mayhap with his kettle of steam
Huzzing and mazing the blessed fields with the Devil’s own team.
Some of the vocabulary is archaic (a common feature of rural dialects): ‘mayhap’ = ‘perhaps’, ‘huzz’ = ‘buzz’, and ‘maze’ = ‘wander’. By “kettle of steam” the farmer means the kind of portable steam engine that was coming into use for ploughing in the 1860s when Tennyson wrote the poem. The farmer would have employed a team of horses, hence the metaphor of the “Devil’s own team”.
Context: this poem is part of a pair, "Northern Farmer - Old Style" and "Northern Farmer - New Style", both written in strong dialect from Tennyson's home county of Lincolnshire, in which Tennyson portrays the differing attitudes of the 'traditional' and 'modern' farmers of the time.
For the specific lines you're asking about:
/iː/(for example, "beän", "peä", etc.) So the second word here is "me", which suggests the first one must be "after": we have "after me".
"kittle o' steam" - given the context of steam, and the again standard contraction "o'" for "of", it seems clear that this means "kettle of steam".
"Huzzin’" - according to this guide to Lincolnshire dialect, this means a whirring noise; perhaps here we could 'translate' it as "buzzing".
/iː/, this should be "fields".
So the lines are, in more standard English:
But someone will come after me, perhaps with his kettle of steam,
Buzzing and [maäzin’?] the blessed fields with the Devil’s own team.
(Actually these are among the lines I find the least difficult to understand in this poem! It's all the rest that are more troublesome.)