Manure is a combination of digested, partially digested, and undigested remains of the food that an animal eats, along with a broad mix of microorganisms.
Manure is part of agriculture, and part of the incredible web of life. Although society considers it a waste product, most farmers and gardeners view manure as a priceless resource.
Like all components of an ecological system, it’s impossible to deal with the subject of manure in isolation. In this book, I’ll try to make some bridges between manure management and crop production, food quality, and human and environmental health. This isn’t an exhaustive reference work, but I hope it will give small farmers and gardeners practical information to help you appreciate and make the most of this wonderful resource.
One note of caution: Throughout this book I’ll make references to average values for various characteristics of manure. The values I refer to here are from reputable sources, mostly various universities, and are often the result of thousands of measurements. It’s good to remember, though, that manure is notoriously variable, and the characteristics of the version you have to work with might be very similar to these averages or quite different. To find out more about the manure on your farm, you can have it tested (I’ll talk more about that in chapter 3).
Wherever living things go about their daily business, manure happens. Physics teaches us that in every ordinary system, matter is neither created nor destroyed. A corollary of this rule is that every living thing produces some by-product of its existence that needs to be accounted for and somehow reused. Broadly speaking, even plants produce “waste” products (oxygen), which illustrates how essential one organism’s waste can be for the very existence of others. Even tiny creatures like nematodes, protozoa, fungi, and bacteria excrete waste products that are very important and beneficial for the life around them.
For the purposes of this book, I’ll use the definition of manure that most people relate to: the dung (feces) and urine, mostly of farm animals, with or without other materials used as bedding. (There is also green manure, which is different: cover crops planted and turned under specifically to fertilize the soil.)
Manure can be a source of fresh organic matter and nutrients that benefit the soil ecosystem and its crop component. It can also contain pathogens that can harm either the plants that grow in the soil or the livestock or people who eat them. Like most components of biological systems, manure has many beneficial traits along with a few we need to be careful of.
Manure is a combination of digested, partially digested, and undigested remains of the food that an animal eats, along with a broad mix of microorganisms.
For thousands of years, manure has been an integral part of agriculture. It is mentioned a number of times in the Bible. Many of the passages refer to human excrement and serve as admonitions or slurs against unholy practices, but at least two examples from the book of Luke refer to manure as a soil amendment. In the 1st century ad, a Roman soldier-turned-farmer and historian, Lucius Junius Moderatus Columella, wrote extensively in 12 books about agricultural practices in De re rustica. The University of Wisconsin Extension publication Management of Wisconsin Soils provides the following quote from Columella:
And by plentiful dunging, which is owing to flocks and herds of cattle, the earth produces her fruit in great abundance.
That statement captures the value and benefits of manure beautifully.
Going back even further, traditional Chinese agriculture relied heavily on manure, not just from livestock, but also from people (more on this topic later in the book). F. H. King, in his classic treatise “Farmers of Forty Centuries,” describes in detail the way early farmers carried out these practices. Cornell University has collected numerous other examples of how ancient peoples used manure as a soil amendment (see Resources).
Wherever people have kept livestock, they have had to deal with the stuff that accumulates behind or underneath them. Early farmers must have noticed that putting manure back on the land not only disposed of it, but also dramatically improved the yield and quality of their crops or pastures. What started out as an exercise in waste disposal transformed into an agronomic practice.
In our modern age, with the advent of chemical-intensive, industrial-scale farming, some farmers seem to have reverted to disposing of manure as a waste product. In some cases, farms even dispose of manure by burning it.
If you’re reading this book, I doubt you look at manure as a liability. For the past decade or two, the demographics of agriculture have been changing in the United States, and the number of small farms has increased dramatically. Many of these smaller operations embrace the concept of sustainability, and most organic farms are small farms, by today’s measures of scale. We recognize the value of animal manure, not only as an economical soil amendment, but as an essential part of the cycle of life.