Agriculture Reference
In-Depth Information
manure nutrients are removed by environmen-
tal processes. Avoiding manure application dur-
ing periods of high potential for runoff or
drainage is a key aspect of preventing losses of
manure constituents to water (Walter
et al
.,
2001). Timing can also be used to optimize
nutrient delivery; broadcast application imme-
diately prior to a light rain can significantly
translocate manure nutrients into the soil, pro-
viding many of the benefits of the incorporation
techniques described above. However, a variety
of factors prompt farmers to apply at other
times, and these factors must be considered if
manure application timing is to be improved.
The absence of sufficient manure storage is
most often cited as a cause of poor timing. Older,
smaller confinement facilities sometimes lack
the infrastructure to store manure temporarily
and continue to rely upon daily application of
manure, year round (Dou
et al
., 2001). Even
when adequate storage exists, severe weather
conditions (e.g. extreme precipitation associ-
ated with hurricanes) may overwhelm open
storage structures and drive farmers to land-
apply manure when conditions are poor.
Alternatively, site access may push farmers to
land-apply during periods when crops have been
recently harvested, soils are trafficable (water-
logged soils are frozen), or no other fields are
available to receive manure. Ultimately, farming
education, expanded options for land applica-
tion of manure (including off farm export), well
integrated farming systems and accurate, short-
term decision support (e.g. the forecasting tools
described above for site selection) are all key to
ensuring prudent timing of manure application
for crop production.
valuable as animal feed than as plant nutrients.
Utilizing animal manures as feed nutrients has
many benefits including decreases in potential
pollution and feed costs and better utilization of
essential mineral sources. Ruminants are par-
ticularly ideal for the feeding of manures due to
rumen microbiology and their ability to utilize
fibre, non-protein N and nucleic acids. The most
valuable manure for protein supplement in
feedstock is poultry litter, due to the high con-
centration of nutrients. When processed by an
acceptable method, poultry litter is an economi-
cal and safe source of protein, minerals and
energy for beef cattle and swine (Carter and
Poore, 1995; Akinfala and Komolafe, 2011).
The most common methods for processing ani-
mal manures for producing feed are: drying,
composting, ensiling, deep stacking, chemical
treatment and extrusion-pelletizing (Arndt
et al
., 1979; Carter and Poore, 1995). If used as
a feedstock, manures must be collected fre-
quently to reduce losses of valuable N, as NH
3
volatilization from manures and litters happens
quickly after excretion. In addition, the manure
must be treated (composted, ensiled, chemical
or heat treatment) to destroy pathogens and
reduce odours to improve animal acceptability.
It is also important to obtain accurate nutrient
composition of manures if used as an animal
feed as there is great variability in manure
nutrient contents and they may differ signifi-
cantly from published values (Zinn
et al
., 1996).
Manure can also be used in aquaculture
systems, not directly as a feed, but as a fertilizer
to enhance algae and other aquatic plant
growth, which then serves as a feedstock. In
China, animal manures have traditionally been
used as fertilizer for fishponds and integrated
fish farming and livestock production is com-
mon (Edwards, 1980). One of the more common
systems is integrated poultry-fish farming
which combines poultry production with fish
culture where the spilled feed and manure from
the poultry system are inputs into the fish sub-
system (Sinha, 1985). The recycling of nutrients
in the system allows for intensification of pro-
duction and reduction of the environmental
impact of production (Costa-Pierce, 2002).
Despite compelling reasons for recycling
manure as a feedstock in livestock and fish pro-
duction, food safety (e.g. bovine spongiform
encephalopathy) and animal welfare concerns
Manure as a Livestock
Feed Ingredient
As manures contain valuable nutrients and
trace minerals, one option for utilization of
manures (normally collected in dry systems) is
the recycling of nutrients as an animal feed and
as a nutrient source in aquaculture. Smith and
Wheeler (1979) reported that animal excreta
products contain 48% to 73% total digestible
nutrients and 20% to 31% crude protein and
therefore the nutrient content of manure has
been shown to be three to ten times more
