Horse manure is considered an excellent fertilizer for roses and fruit trees. However, before using it in the vegetable garden, it must be properly prepared.
If you are lucky enough to live near a horse farm, you can usually get horse manure cheaply. It has been valued for generations as a valuable fertilizer for a wide variety of garden plants. Horse manure contains various nutrients as well as a high amount of fiber, which enriches the soil with humus. This is due to the fact that horses are poor feed converters: Among other things, they cannot digest the cellulose in plants as thoroughly as cattle, sheep and other ruminants. This is an advantage for building up humus in the garden.
The nutrient content of horse manure is relatively low, but the nutrient ratio is quite balanced and suitable for most plants. Fresh manure contains about 0.6 percent nitrogen, 0.3 percent phosphate and 0.5 percent potassium. However, nutrient contents vary quite a bit depending on feeding, urine and bedding percentages.
How to fertilize with fresh horse manure
Fresh horse manure is only suitable as a fertilizer for very robust plants, for example fruit trees. It should be applied well shredded to the base of the tree and, at most, worked flat into the soil or covered with a thin mulch layer of leaves.
Fruit trees and berry bushes are best fertilized with fresh horse manure in late fall. Cover the root area with about a centimeter-high layer (0.4 in). You don’t have to measure with a ruler, though: There is little danger of overfertilizing, as the nutrients are released very slowly and are then available to the plants starting in the spring. One manure fertilization is usually sufficient for two years as a basic supply. Ornamental shrubs such as hedges and roses can also be fertilized with horse manure.
But do not work fresh horse manure as fertilizer into the beds of your vegetable garden to improve the soil in the spring. Fresh manure is much too harsh for most herbaceous plants and is therefore only recommended as a fertilizer to a limited extent. Above all, direct root contact must be avoided at all costs.
Composting horse manure
Experienced amateur gardeners first make manure compost from horse manure and also cattle manure before using it in the garden: Set the compost out separately and, if needed, mix the fresh manure with other organic material such as fall leaves or shredded shrubbery. Because the manure can get very hot during the rotting process, the pile should be no higher than 100 cm (40 in).
The manure is left to rot for at least 12 months without turning and can then be used in the garden. Since it is usually quite dry and incompletely decomposed in the peripheral areas, one usually uses only the inside of the manure compost and rebuilds the rest with fresh horse manure.
The rotted manure is very compatible with plants and is also excellent for soil improvement. For example, you can use it in the spring to prepare beds in the vegetable garden or use it as compost mulch for the ornamental garden.
Problems with horse manure
Horses, like us humans, sometimes need to be treated with antibiotics for bacterial infections. These are excreted by the animals and, depending on the frequency of treatment and dosage, can delay the decomposition of horse manure in compost and also harm soil life. However, the complex molecules are not absorbed by plants.
Nevertheless, if you have a choice, you should preferably obtain your horse manure from robust horse breeds. A good address is, for example, horse farms that breed Icelandic horses, because the small Nordic riding horses are considered very robust and healthy. Fresh horse manure also often contains undigested oat grains that germinate at the edges of the compost. However, they will die in the course of the composting process if you pick them up with the top layer of manure using a digging fork, turn it over and place it back on the pile.