In some ways, animal manure is a better sustainable fertilizer for an urban farm than raw organic matter like grasses or woodchips. It doesn't take much time to decompose, like raw organic matter. Think of animals as composting factories: In goes the raw materials in the form of hay, straw, grass, and kitchen scraps, and out comes the fertilizer in the form of manure.
Like organic matter, animal manure feeds the microbes in your soil, but it also contains nutrients that can directly feed your plants.
For annual vegetable and flower gardens, apply a 1- to 2-inch-thick layer of completely decomposed manure annually before the growing season to build and maintain the soil's fertility.
Each type of manure has its own advantages and disadvantages. Generally speaking, using decomposed or aged manures is best for two reasons:
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Composted manures are less smelly (a concern in urban areas when your neighbors are so close).
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Any volatile compounds in the manure that may harm your plants have been broken down.
Even though animals, such as cows, digest their food into a very decomposed form, other animals, such as horses, aren't as efficient, so their manure needs more time to decompose. If you happen to produce your own manure (your animals, that is!), then you need to let it compost or age for at least six months before you use it in your garden.
Don't use dog and cat manures in your garden. Although these manures are plentiful in city areas (just check out the park trash barrels loaded with plastic bags of dog poop), they contain pathogens that can infect humans. So be sure to toss your pets' poop in the trash and look for manures from farm animals instead.
The manure most urban dwellers find at the local garden center or home center comes in bags. The best part about bagged manure is that it has been composted and sometimes sterilized and is ready to use in your garden.
Bulk manure (manure not sold in bags) isn't the norm in most urban areas, but that may be changing in some municipalities. Buying manure in bulk is cheaper if you have a big garden.
Whether the animal manure is in bags or fresh off the farm, you need to know what type of manure you have so you can know how it best can be used in your garden or yard.
| Manure Type | Pros | Cons |
|---|---|---|
| Cow | Good nutrient-balanced manure with few weed seeds |
May have high salt levels |
| Horse | Dry and loaded with undecomposed organic matter | May contain weed seeds Mild smell |
| Chicken | High in nitrogen and good for plants that need an abundance of this nutrient; The high nitrogen content can burn tender plant roots if used fresh | Strong smell |
| Sheep and goat | Dry and well decomposed | Fresh sheep manure can burn tender seedling roots because of the nitrogen content Mild smell |
| Rabbit | Rich in nutrients | Strong smell |
| Worm | Rich in nutrients Can be used fresh or composted; No smell; Easy to raise in urban areas | It takes a lot of worms to make much compost. Best used as a compost tea |