The concern with animal manure composts begins with the recipe and ends with the how it is processed and where it is used. In Fact, the most important considerations for any garden compost, whether it comes from a plant, an animal or a combination of the two, is knowing what it is made of, how it is made and how it is used. What follows is a word of caution and a few reasons gardeners may want to stick to “best” soil management practices by incorporating plant-based composts into their garden rather than “good” management practices using animal manures.
Compost is decomposed organic matter. It is used by tiny soil organisms as food. Bacteria, fungi and small insects living in the soil eat organic matter and leave behind a rich byproduct that plants take up through their roots. Almost anything can be composted if given enough time and the right conditions. However, when it comes to gardening, there are some things that are good to put into a home compost pile and some things that should be left out.
When thoughtfully included as an overall part of soil management, animal manures may make a valuable contribution to the garden. Animal manure compost is often added as under the assumption that they make an excellent “organic.” However, any type of compost including animal based material is more appropriately added to soil as food for the microbes. It is the activity of these tiny underground animals that brings soil to life. Manure is often freely available from facilities that accumulate large amounts of animal waste. When a gardener is on a budget, adding animal manure in small and carefully planned amounts may benefit gardens.
On the other hand, large amounts of animal manures incorporated into soil may create more problems than solutions. Consider horse manure. With horses, food moves quickly from one end of the digestive system to the other. Of course, horses eat plants. Anyone who has ever taken a look at fresh horse manure can testify to seeing undigested plants in the stool. When it is not properly “hot” composted, horse manure will contain viable weed seeds along with the undigested plants.
Sometimes, horses eat plants that have been sprayed with herbicides to rid a pasture of weeds. Horse manures from a source such as this will still contain those chemicals. These broadleaf weed killers are toxic to garden plants. Nightshades such as tomatoes, eggplants and peppers can be killed outright by leftover herbicides in animal manures. When not killed, ornamental plants may become distorted beyond recognition while vegetable plants will be less productive.
The high concentration of salts in horse manures will slowly increase in the soil as each successive application is worked into the garden. These salts may eventually reach toxic levels. Even before salt concentrations hit toxic levels in soil, they will begin to inhibit the uptake of other vital nutrients by plants.
It is difficult for home composters and even livestock facilities to compost some organic materials properly. Hot composting occurs when organic material is layered in a specific manner which will increase its temperature and destroy most weed seeds and many herbicides. This involves layering large amounts of carbon rich materials with small amounts of nitrogen rich materials. Commercial composters are successful at reaching higher composting temperatures because they actively turn, water and aerate their compost piles to ensure a high quality product.
Cold composting on the other hand is a more passive method of simply piling up organic material and allowing it to break down without much input from the composter. Feed lots, horse stables and other livestock facilities rarely have the time or experience to generate a garden-ready product. Their business is to handle livestock which is accompanied by an ever increasing by product they cannot effectively compost.
Many of these animal handling facilities wisely sell or give their waste to commercial composting operations. Most commercial composting companies have the experience to process animal manure properly by adding it to the massive amounts of plant-based material they receive. Professional composters are often happy to provide their clients with information about their composting process and an analysis of their product.
While an offer to pick up all the free animal waste you can haul sounds like a treasure that can’t be passed up, think twice before shoveling it into the back of the family truckster and taking it home to plow into your garden.