Make the Most of Manure Fertilizer

Treat your garden to a helping of nutrient-rich, natural manure fertilizer by recycling animal waste.

| March/April 1983

Are you aware that livestock animals in the United States produce as much as two billion tons of manure a year? And did you also know that the fertilizer value, alone, of all this "waste" is close to $10 billion? And that figure doesn't even take into account the worth of the approximately 500 million tons of humus-building organic matter that's also contained in the excrement!

Unfortunately, a lot of the potential agricultural value of manure fertilizer is lost or wasted by either careless handling and storage or inefficient distribution. However, with proper management, it's possible to put back into the soil about 70% of the nitrogen, 75% of the phosphorus, and close to 80% of the potassium found in livestock feed!

A Historical Perspective

Farmers have known about the earth-enriching potential of manure for nearly as long as humanity has known about agriculture. Probably the oldest surviving reference to the use of animal leavings in horticulture is found in Mesopotamian clay tablets dating back to about 2000 B.C. Somewhat later, Marcus Terentius Varro — a Roman scholar and writer of the first century B.C. — noted that he considered thrush leavings to be the most potent of all manures. Later still, in the first century A.D., Lucius Columella concurred with his predecessor about the superior quality of this songbird's droppings. In his book De Re Rustica ("On Farming"), Columella went on to note the excellence of pigeon and chicken manure, as well.

Today, gardening experts generally agree that of all the widely available animal wastes, those of poultry are the richest. But these modern-day commentators often differ about which manure is second best: Some say horse, while others claim cow.

Rich or Poor, Hot or Cold?

Before we take a closer look at which natural fertilizer does rate next after poultry droppings, it's important to understand just what distinguishes a fine "brand" of manure from an ordinary one. Basically, a potent variety will be rich (high in nutrients) and hot (quick to rot). The economic value of a particular kind will depend upon the amount of nitrogen it contains (phosphorus and potassium content are important as well), and upon the fermentation it's undergone.

The nitrogen found in a specific animal's waste will vary with the critter's diet, age, and workload. For example, since seeds are generally high in nitrogen and grasses low, grain-eaters tend to produce richer manure than do hay-munchers. And mature beasts, whose bodies are fully grown and thus require fewer nutrients, excrete more nitrogen than do rapidly growing youngsters. Finally, livestock that's raised for meat will require less nitrogen than will animals reared for milk —so steer dung, for instance, is more potent than droppings from dairy cows.

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