Gardening with horse manure is an effective way to improve the quality of your garden soil. Horse manure will add nutrients to the soil and improve its composition, so that sandy soil retains moisture more effectively and heavy clay soils drain better. Horse manure is a good choice for gardeners because it is often readily available and inexpensive, or even free. Proper application is the key to good results with horse manure.
Decide the best time to apply the manure. There is the chance that fresh horse manure will harbor E.coli bacteria that could contaminate any food you grow in the garden. Fortunately, it is possible to time the application to prevent contamination. If you are applying the manure to a flower garden, feel free to use horse manure throughout the growing season. For vegetables that are in direct contact with the soil, such as potatoes, apply the manure at least four months before harvesting the garden. For vegetables and fruits that don't come into direct contact with the soil, such as tomatoes and blueberries, apply the horse manure at least three months before harvesting.
Determine how much bedding and what type is included with the manure. Horse manure is a good source of nutrients, including nitrogen. Horse manure often comes with remnants of the bedding used in the horses stall, however, and that can create problems. Woody bedding, such as shavings and sawdust, tie up the nitrogen in the manure as well as the nitrogen in the soil. This can lead to a nitrogen deficiency in the plants, characterized by yellow, stunted plants. If there is a good deal of woody bedding mixed with the manure, or you notice that your plants seem stunted or yellow, you may want to add a nitrogen fertilizer to the soil.
Load the horse manure into a wheelbarrow and disperse with a shovel. Toss the manure over the garden area and then work it into the soil with a hoe. You should work to a depth of about three inches. The amount of manure you apply is flexible. Aim for about one inch of coverage across the surface of the soil before mixing it in.