Agriculture Reference
In-Depth Information
with its nitrogen-fixing algal mutualist, is added to the sys-
tem, fertility is maintained and yields are improved. Similar
results are achieved with the integrated fish and rice systems
of southern China (Guo and Bradshaw, 1993). By allowing
fish to occupy the irrigation channels and flooded rice pad-
dies during the cropping season, nutrients are captured that
might otherwise be lost from the system, especially in sys-
tems where the fish are algae feeders and the algae thrive
on nutrients in the water. Even when part of the rice paddy
is removed from rice production in order to dig ponds that
allow for year-round presence of the fish, the ecological and
economic benefits more than compensate.
Fish can be such an agroecologically and economi-
cally beneficial part of an integrated cropping system that
some systems have developed that combine fish, crops,
and livestock. In parts of Asia, for example, systems exist
that integrate fish, silkworms, mulberries, pigs, sugarcane,
vegetables, and grass in intensively managed wetlands. In
some localities, farmers are adding an aquaculture com-
ponent to an already-integrated crop-livestock system.
Livestock manure is used to stimulate the growth of algae
or plankton, which are consumed by the fish. Waste from
the fish can then serve as a nutrient source for the crops,
and the fish themselves are a marketable product.
Integrated crop-aquaculture systems offer a clear con-
trast to intensive, industrial-scale, single-species aquacul-
ture systems. In many respects, these systems are not
much different from the livestock confinement systems
used for cattle, pigs, and poultry. Feed — different from
what the animals consume in the wild — is often grown
a large distance from the place of animal production,
antibiotics and growth stimulants are often employed, and
waste food and excrement contaminate the water.
Work
energy in plant
biomass made
available as biological
cultural energy
Manure
matter and energy
in standing
biomass converted
to re-usable form
for crops and soil
fauna
Animal
biomass
• inedible biomass
converted to edible
• protein content
concentrated
Plant biomass
(fixed solar energy, nitrogen, carbon,
phosphorus, potassium)
FIGURE 19.9 The transformer role of livestock. Animals
transform plant biomass into useful forms of energy and matter.
itself combine to provide the farmer with an array of
potential on-farm benefits. These benefits are discussed
separately below, in the context of actual farm practices.
The benefits are interrelated and overlapping, but by pull-
ing them apart conceptually it is easier to see how various
forms of integration can be combined to further the overall
goal of establishing mutualistic synergies that improve
agroecosystem structure and function and lessen the
dependence on purchased external inputs. Table 19.1 sum-
marizes many of the benefits of integration by comparing
the conditions of an integrated system to those of a com-
parable nonintegrated crop-based system.
Producing Protein-rich Food and Other Products
Animal biomass is as important as food, both for subsis-
tence and for market. Whether in the form of milk, meat,
or eggs, it contains a much higher proportion of protein
than plant biomass. Moreover, most livestock animals are
able to obtain nutrition from types of plant biomass that
humans can't eat — crop waste, food waste, plant tissues
containing mostly cellulose — and convert it into various
forms of animal biomass that humans can eat.
Animal biomass has many other economically valu-
able uses, of course. Sheep produce wool and waterfowl,
feathers; and at the end of their lives, animals yield bones
and other byproducts that can be used for a variety of
purposes.
B ENEFICIAL R OLES OF A NIMALS ON AN
I NTEGRATED F ARM
As they pursue their ecological role, mimicking the her-
bivores in natural systems, livestock animals transform the
energy and matter contained in plant biomass into three
agroecologically useful streams, as shown in Figure 19.9.
The first stream, animal biomass, has value as food, fiber,
fertilizer, and raw material. The second stream is the bio-
logical cultural energy represented by the ability of live-
stock to do work. Draft animals, which once performed
all the work on farms that humans did not do, are the
obvious workers among the many types of livestock, but
sheep, goats, chickens, ducks, and other animals can also
perform valuable “work” in the form of vegetation and
weed management and pest control. The third stream,
manure, is rich in plant nutrients and provides soil micro-
organisms with a key source of energy for their roles in
the system.
Both the products of animal herbivory — animal bio-
mass, work, and manure — and the process of herbivory
Putting Crop Residue and By-products to Use
Since animals are able to consume much of the biomass
left over after harvest, as well as many of the byproducts
from agricultural processing; using such biomass as ani-
mal feed is an important way to produce harvestable ani-
mal products and convert a potential waste into recyclable
nutrients at the same time. Maize, millet, wheat, oat, and
Search WWH ::




Custom Search