for sustainable agriculture
Martin Wilding
Program for Sustainable Agriculture, AgriSciences,
Stellenbosch University
T
he ever increasing demands on agriculture to
produce higher yields are
mainly achieved by utilization of inorganic manufactured fertilizer and a further exploitation of
natural resources with concomitant
deterioration of soil structure and
fertility. There is however a growing
awareness
amongst
especially
younger educated farmers to
change this and to utilize more organic inputs; especially composted
materials generated from agricultural/forestry waste.
Farmers wishing to make a change
are still hesitant due to lack of reliable and clear information on how to
get started and what materials are
suitable for composting. Other
questions centre on what to add,
how to manage the composted materials, what criteria should be used
to assess the quality of their compost and guidelines on how to apply it; how much and when? Available information is also often contradictory and is lacking in explanations
why
certain
methods/
approaches are used.
Where this “green” route was
adopted, success stories speak for
themselves. Generally farmers going
this route experience a lowered fertilizer input thus reducing costs
with the added advantage of producing better quality produce.
The overall focus should thus be to
find suitable ways to decompose
waste and start a process of humus
formation. By utilizing selected
groups of micro-organisms during
the process of decomposition nitrogen is retained and is converted to
nitrate. Returning such nutrient-rich
humus back into the soil is the basis
of sustainability. Humus contributes
to improve tilth and moisture retention and provides energy, nitrogen
and minerals for a variety of microorganisms; thus enriching soil life.
Reduce, Reuse, Recycle and Repurpose composting
Very few if any material need to
land up in a landfill or a hole on the
farm due to its value it can have as
a supply of organic material for
composting. Materials that can be
composted with success, to name a
few; pine sawdust, grape skins &
stems, citrus fruit wastes,
fruit
waste, olive mill pomace, wheat
straw, alien invasive plant species
(wattle, port Jackson) and difficult
compostable wood like eucalyptus
and citrus. Food wastes, even
though not ideal, can be effectively
composted (fig 1).
Figure 1 show how food waste (left picture) can be turned into humus rich compost.