Where there's muck there's brass the saying goes. In this case well rotted horse manure purchased by my father for the allotment. The straw bedding used in stables combines with the droppings and urine to make a well balanced mixture.
 "Well rotted" is the mantra where compost is concerned. Fresh muck can scorch plants because it's too potent at that stage and soil can become depleted of nitrogen processing uncomposted materials. Once the processes of decomposition are well advanced the goodness and organic matter is readily absorbed into the soil structure.
 Following a "no-dig" or at least "low-dig" philosophy spreading the muck as a surface mulch is fine for building soil fertility.