What a Load of Manure!
By Melissa Conroy
Some enterprising soul discovered long ago that the manure animals so generously produce make soil rich, fertile and perfect for growing crops. People have been using manure to fertilize their fields and gardens for thousands of years, and even today many gardeners eagerly visit their local stable or barn to fill their trucks with nature’s bounty. Since most farms and animal operations have manure in abundance and are glad to rid themselves of some of it, any gardener near a stable or barn has access to nature’s most perfect fertilizer.
But just how does manure work? It actually offers two benefits. First, manure helps condition the soil by adding organic matter. Herbivores excrete high amounts of plant material in their manure, and this organic matter helps clay-heavy soil drain water better, sandy soil retain water, and all types of soil attract beneficial bacteria and worms. If you have poor-quality soil, manure can help you turn your garden into a welcome spot for seeds and plants.
Second, manure provides a generous dose of important nutrients to soil. As most gardeners know, crops leech nutrients out of soil: farm a plot of land for a couple years without fertilizing it, and crop production will plummet. This is where manure comes in handy: manure contains nitrogen, phosphorus, and potassium, three of the fourteen nutrients that plants need to complete their full life cycle. In particular, most grain crops need high levels of nutrients, so it is not surprising that farmers have long depended on manure to grow corn, wheat and other important grains.
However, not all manure is the same. Manure can come from a variety of animals. Horse, cow, and poultry manure is quite popular with gardeners, but other types of manure are also used for soil. In fact, you can even purchase “zoo doo” from zoos such as Seattle’s Woodland Park that sell the waste of their many exotic animals to the public. Manure from horses that are bedded down on sawdust will be quite different in consistency and nutrition content than manure from a chicken farm. Manure quality can be affected by what type of animal produced the manure, the animal’s bedding and feed, its age and how it was stored.
Another important distinction is the difference between fresh and aged manure. Manure straight from the animal contains high levels of ammonia, and fresh poultry manure also has high levels of salts: these elements can easily burn plants. In addition, fresh manure often contains seeds, and these seeds may fill your garden with unwanted weeds. Finally, fresh manure may contain harmful bacteria such as e-coli. Aged manure that has had time to compost is generally bacteria and seed-free, but it has lower levels of nitrogen and doesn’t usually contain the levels of nutrition that fresh manure does. However, aged manure is gentler and safer on plants, and if the manure is properly aged, you can plant soon after you mix it into the soil.
In general, it is best to manure your garden in the fall after the year’s growing cycle is done. This way, you can use either fresh or aged manure; the long winter months will compost the manure and condition the soil for spring. However, for this season’s planting, you can use well-aged manure to prepare your garden for spring. Exactly how much manure to use in your garden is a complicated question, one that experts will answer with contradictory information, charts, graphs and advice. A simpler answer is that you should use quite a bit of aged manure and not much of fresh manure. Several inches of properly aged manure or an inch or two of fresh manure is a good rule of thumb.
However, don’t simply dump the manure on the soil; it needs to be worked several inches down into the topsoil. A rototiller can be your best friend for this job, particularly if your soil is hard, but a shovel and some elbow grease works just as well. Invite your grandchildren over for a day and have them get to work; most children love any excuse to get dirty!
While you can buy commercial fertilizer and other expensive chemicals to enhance your soil, nothing quite beats old-fashioned free manure. A visit to your local stable or barn can give you all you need to condition your soil and improve your chances of a bountiful garden this year.