If horses have a non-conducive digestive system for manure heaps, and weeds grow in the soil from therewithin, why is it recommended to use fresh horse muck for hot beds ??? All these different opinions seem to cancel each other out .
Good question, why use fresh manure.
Our hot beds were a wooden box made by my Father into which would go straw then a good layer of fresh manure more straw and a good covering of soil.
The heat caused by the reaction of the fresh manure would raise the temperature of the soil into which we could plant those items needing some root warmth to grow, Dad would grow a melon on the hot bed a luxury when I was a kid.
ON the farm where there was a heap of organic or animal waste mainly horse dung a hole would be dug in the steaming pile some soil shovelled in and a plant put in to grow on the rising warmth helping the plant.
At the end of its use the whole box was emptied straw and all onto the compost, we had a large brick midden full of the stuff, my job was to fork it over now and then and then the now mature horse manure would go in the base of the potato trenches or be spread on the soil as it was dug over.
There were no organic fertilisers for gardeners back then and electric cable warming boxes with thermostat which I have now would have been beyond the reach of gardeners, forever putting a penny in the meter.
Boxes of seed or seedlings could be put on the hot bed to give some bottom heat, a couple of batons across the top with the boxes on the batons would raise them so it was not too warm for some plants.
Any seed in the mix would be killed by the rising heat and smothered by the straw.