Weirdly it turned out that our local garage has it on the pump - and is the only place around here to stock it - because they supply for normal domestic use. It does get through it quite quickly and would have been mighty expensive to clear the whole area. Weedkiller did the job but I do like the volcano approach - so satisfying and immediate. Given the geese keep destroying the weed matting in the orchard and I don't want to use weedkillers around them, I might use it for keeping the trees clear too (although will need to do part by hand as I guess tree trunks don't appreciate being scorched).
My friends used Grazon 90 in their orchard to clear nettles & all other weeds . They complied with all the safety requirements and did a section at a time .
Once it had killed the weeds they cut the grass ( at 6 inches tall ) , twice , raked it up each time and burnt it when dry .
The geese were then put in the orchard behind electric fencing for slowing down Mr fox , a night shed ( fox proof) was towed in the orchard to put them in
Their foot deep water bath ( bottom of one of the big square palletized liquid containers with a 2 inch tap drain in it,
It was put on a home made very low trailer that had a drop down access ramp for them to get up to it & a small ramp for them to exit out the water easily .
They moved it around if the grass was suffering , it was power washed out at least once a week .