Horse manure can be an economical source of organic garden fertiliser. Easily obtained from riding stables, boarding facilities or local farmers, horse manure enriches the surrounding earth as it decomposes, offering nearby plants a ready source of essential nutrients. Unfortunately, fresh horse manure has a high concentration of nitrogen, which can damage fragile roots. Once the manure ages, however, you can add to the garden without fear of chemical burning. As it matures, the harmful compounds in the manure break down, leaving a nourishing, all-purpose plant food behind.
Scoop the horse manure into a single pile, or create several small mounds. Use the blade of a sturdy garden spade to smash any large pieces of dung. While it is not necessary, mixing other organic materials into the manure will enrich the finished product. Add shredded leaves, tree bark or other plant materials and blend them into the manure with a garden rake, creating a homogenous mixture.
Smooth the pile with a rake so that the height is approximately the same as the width. Cover the finished manure heap with a tarpaulin to help keep the compost moist and help the mixture to retain heat.
Turn the manure pile at least once a day. Slide the blade of a garden spade into the manure and flip it over, exposing new material to the open air.
Add water, if needed, to keep the manure heap moist. Sprinkle the water over the compost, 5 litres at a time, until the materials are evenly damp. When the manure loses its distinctive aroma and looks like soil, it is ready to apply to the garden. The ageing process takes two to three months, though it varies according to the quantity of manure being processed and the local weather.
Spread a 10 cm layer of composted horse manure over the garden area. Work the compost into the soil of newly turned plots with a tiller or garden rake; around existing plants, work the compost in with a small hand trowel taking care not to disturb the plant's roots.