Erosion control in the tropics - Part 8 pptx

Underlying causes of erosion 73
8 Underlying causes of erosion
In the previous chapters we have seen how the chance of erosion can
be lessened by taking certain precautions. However, circumstances are
sometimes such that a farmer cannot adopt another method of produc-
tion that would be less damaging. So we are confronted with the un-
derlying cause of erosion. A simple comparison can be made here with
a farm track (it is sometimes forgotten that roads and paths can be a
serious erosion hazard). Naturally a road is seldom covered with a
protective mulch layer; moreover roads are preferably laid out as
straight as possible, if necessary straight through an erosion prone
area, straight up a hill. This is for the simple reason that roads are laid
out to transport people and products and not to control erosion.
Just as it is for the road in our example, so is it too in agriculture; agri-
culture is primarily for food production or as a money earner. The
choices that are made in agriculture basically have an economic, social
or agronomic background.
Thus it is very important to study these backgrounds carefully when
asking yourself why erosion occurs in a certain area. Not only will the
deeper causes of erosion be found in the socio-economic backgrounds,
but the incentive will be found which motivates the farmer to alterna-
tive land use which would have less disastrous results for the soil.
Crop choice
In Chapter 5, the importance of a good crop choice was pointed out.
However, the choice of crop is not free. Under given circumstances
some crops would dry out, others require tillage for which there are no
machines. Some crops don’t protect the soil well, such as maize or
cassava but they are staple food. People are dependant on these crops
for survival.
Mulch

Farmers in certain areas used to use mulch before, but not any more.
The reason for this is probably the increasing population pressure
which brings with it an increasing need for fuel. The grasses that are

Erosion control in the tropics 74
there and the residues of harvested crops are used as cattle feed or
fuel, so that there is no material for mulching. The cattle manure and
the ash remains are put back.
Growing mulch material on marginal land that is not suitable for agri-
culture is a temporary solution, because the soil may deteriorate and in
turn succumb to erosion. Yet the farmers will have to be offered an
alternative. Maybe crops can be planted which can later be felled for
firewood. If these crops are grown in strips they have a protective
function too.
Cost sharing
A farmer may be convinced of the necessity for taking precautions
against erosion but if there is a question of share cropping, whereby
the farmer is responsible for the cost of erosion control and the yields
are shared with the land owner, of course he will not be inclined to
take precautions, they are too expensive for him!
Lack of security
Also, if the lease duration is shorter (one year for example), the tenant
farmer is not very sure of a prolonged use of the same piece of land.
Understandably the farmer will try to get the most out of his land in
the shortest possible time without bothering too much about maintain-
ing the soil quality.
Being forced to farm steep slopes
In the Andes in South America as in other places, small farmers are
driven from the highlands by large landowners wishing to start large
scale farming there. There remains little choice for the small farmer

than to move to the erosion prone steep slopes and try to go on farm-
ing there. The accepted farming methods are no longer suitable on the
steep slopes and only cause erosion. With the decrease in yields the
farmer slowly slides toward poverty.
Many other examples can be given but we hope that enough has been
said to illustrate that the socio-economic relationship as a driving
force behind land use, is often the deeper cause of erosion taking
place.