I have since done a little searching through Google and come up with the following:
Whoever wrote it was trying a variation on a 1915 poem of similar title, and humour, by the Australian, Tom Skeyhill. Our local poet, if local he was, did not add his name, but he appeared to be making a fair copy, for his handwriting was good, though not his spelling - unless he was being deliberately playful in his misspellings. Here is an exact transcription:
In my little wet home in the trench
Were hail storms continuale drench
Theirs a died Cow close by with
It hoofs towards the sky and it
gives such a Beautifill stench
O in Land in place of a flour thers
lots of wed mud and some straw
and J Johnsons they tear though
the rained soden air to my little wet
home in the trench.
Now the snipers they keep on the go so
you have to keep your napper down
low for the star shells at night
courses a doust of a light and it courses
Poetry is essentially about craft, but it is impossible in these rhymes to be sure where craftsmanship ends and naivety or casualness begins. The first five lines are limerick in form (as in Skeyhill's original) - only slightly subverted by the continuation of lines 3 and 4 beyond the rhyming words (by and sky). The second five are also limerick - but the poet either cannot, or chooses not to, find the third rhyme for flour and straw, which would close and clinch it.
The feature of the misspellings that struck me was that the majority are good spellings of 'wrong' words - Were for Where, Theirs for There's, died for dead etc - as if they had been purposely placed to annoy a teacher. Beautifill is an exception - but in context the fill seems apter than the ful would have been.
J Johnsons (line 8) are Jack Johnsons: 'German shells bursting with black smoke. After the boxer Jack Johnson 1878- 1946, the first black American world heavyweight champion' (see Battlefield Colloquialisms of the Great War (WW1) by Paul Hinckley). I take these to be tearing through rather than tearing though the rain-sodden air. That must be a slip?
The second verse is much more obviously unfinished - comprising 4 and a bit lines of inchoate limerick instead of 5. Was there more to come on another page or was inspiration tiring?
Suggested exercises for students of WW1 poetry - first, to 'correct' all the deviations in spelling in the poem above; second, to discuss whether such corrections improve it or not: third to compare the poem with Skeyhill's and other versions; fourth, to try and compose a parody for modern times ('My Little Wet Home in the Trench' itself derives from a sentimental poem 'My Little Grey Home in the West' by D. Eardley-Wilmot).