Horse manure is still a natural source of nutrients for the garden. Well rotted manure also improves the soil structure and the ability to retain moisture. The condition is that the manure mixed with straw or similar material. In horses, however, one uses in the stables especially "sawdust" instead of straw. The disadvantage is that this sawdust degrades very slowly and in this process, especially nitrogen has the ground instead of adding. Let this horse manure especially first good composting. Mix the manure with other garden waste and let this mixture well composted.