organic fertilizer

Getting What You Want from Animal Manure
Jeannie A. Leggett, Extension Associate, Department of Agricultural and Biological Engineering
Les E. Lanyon, Associate Professor of Soil Fertility, Department of Agronomy
Robert E. Graves, Professor of Agricultural Engineering
Figure 1. The flow of non-fuel energy in animal production operations. Arrows denote a transfer of energy.
body mass
byproducts
and stable
humus
manure
animal products
heat and respiration
heat and respiration
Manure Contains Energy
In a sense, agriculture is all about managing energy flow
(Figure 1). This energy flow begins when solar energy is
captured by growing crops. Farm animals, in turn, use the
energy contained in crops to build body mass and produce
milk or eggs. Some energy is lost through respiration and
heat from the animal’s body. The remaining energy is
excreted in manure. This excreted energy becomes a food
source for microorganisms that live in the manure. Once
the microorganisms deplete the available energy, the
manure can no longer support microbial activity. At this
point, the manure will not decompose further, and is
considered “biologically stable.”
Manure is a biologically active material, alive with
bacteria and other microorganisms that depend on the
energy contained in manure. The use of manure energy
by microorganisms—microbial activity—is a natural
process of decomposition. Except in extreme cases of
cold, pH, or lack of water, biological decomposition is
inevitable. Microbial activity can create a wide range
of byproducts. By storing, handling, or treating
manure in various ways, farmers can control the
byproducts produced by this biological activity. This is
important to a farmer desiring to manage nutrients,
control manure odors, increase ease of manure
handling, or create a marketable product.
G 87
College of Agricultural Sciences
Agricultural and Biological Engineering
Cooperative Extension
An Equal Opportunity University College of Agricultural Sciences, U.S. Department of Agriculture, and Pennsylvania Counties Cooperating