Agriculture Reference
In-Depth Information
11.6.1 Renewable Inputs
The whole concept of renewable inputs is quite complex. In many real aspects an
example of a renewable input would be carbon dioxide in the atmosphere. It is taken
up by plants and converted to compounds and food that is eaten by animals, including
humans, and eventually returned to the atmosphere as carbon dioxide. A nonrenewable
input would be phosphate mined from deposits that will eventually be totally consumed.
This seems simple, however, it is not. Nitrogen fixed by nitrogen fixing plants
would be seen as a renewable source of nitrogen for crop production because it
results in cycling of nitrogen in the environment much as carbon dioxide is cycled.
However, nitrogen fixed by a chemical process can also be seen as renewable if
the source of energy for the chemical process is renewable. That is, the use of
electricity generated by wind, water, geothermal sources, or from sunlight should be
considered renewable.
This brings up the knotty problem of energy for agriculture. Fossil fuel is a
nonrenewable fuel source. Electricity may be either renewable or nonrenewable depend-
ing on how it is generated. It is often assumed that human or animal power does not
require energy or that the energy is free. Animal or human power requires that the
animal or human consume additional calories to be able to work the land. This means
that additional food must be produced to supply these calories. In this sense animal
and human power, while it may be renewable, is not free. In some sense machines are
more energy efficient because they can be shut down when their power is not needed,
while an animal must be kept “fueled” whether it is working or not.
For farmers recycling of organic matter whether through use of manure, compost,
no-till, or green manure crops will decrease the need for outside inputs and make the
farm more sustainable.
One area of particular importance to sustainability, which cannot be overempha-
sized, is the use of water. Water is either a renewable or nonrenewable resource depend-
ing on how it is used. When water use does not exceed water production, in terms of
rain, for most areas of the world, then it is a renewable resource. Exceptions would
be water from snow or ice. On the other hand, water drawn from an underground
aquifer may be renewed only very slowly. The result is a lowering of the water table
in areas subject to excessive pumping. In all cases considerable margin of error must
always be included in water use if it is to be sustainable.
11.6.2 Organic Agriculture
Organic agriculture, or organic farming, has been defined in many ways. Basically, it
started with the idea of eliminating the use of chemically produced inputs, particularly
insecticides and herbicides. It also excludes the use of chemically produced fertilizers.
This would be nitrogen and phosphate fertilizers. For most organic farmers potassium
fertilizers are acceptable because they can be used as they come from the mine, without
chemical modification. Note that potassium fertilizers are considered suitable for
organic agriculture but are not renewable.
