Neil wrote...
A friend of mine has provided me with 4 bags of horse manure for my
veg plot. There's a fair chance I wont use it all straight away - any
ideas how long it will store, and how best to store it ? Currently its
sat in plastic horse feed bags.

Four bags and you can't use it all?
You either have very big bags or a very small plot. We spread two large
tipper trailer loads of horse manure on a different quarter of our allotment
each year (4 year rotation), it's 4+ inches deep at least. Then we rotovate
it in and plant that quarter with the spuds, amongst other things. You can
see the soil has changed colour, gone darker, blacker, by the next spring.

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Regards
Bob H
17mls W. of London.UK