increase productivity. Conserva-
tion investments are measured like
other investments: they are under-
taken only if they are profitable.

Soil conservation measures that
produce the most rapid return on
investment are the most favoured.
These include bunds that require
relatively small initial investment,
provide fodder or fuel, and con-
serve moisture on-site (as opposed
to downstream through ground-
water percolation or runoff to a
farm pond). Such opportunities to
combine conservation with quick
increases in productivity are lim-
ited, but they should be exploited
to the extent possible.

Farmers increase the productivity
of SWC by concentrating soil at
appropriate locations, rather than
merely conserving it (Chambers,
1991; Kerr and Sanghi, 1991). This
distinguishes their practices from
recommended ones, which stress
in situ conservation of soil.

There are many examples of farm-
ers' efforts to concentrate soil. In
hilly areas some farmers induce
erosion in the upper end of their
holding in order to concentrate the
soil in the lower part.6

Similarly, in the lowlands, terraces
slowly form behind indigenous field
bunds and waste weirs as soil is
gradually deposited at the lower
end or corer of the protected field.
Farmers must raise their bunds
regularly as the deposited silt ac-
cumulates to the top of the struc-


=~:~- -C---- -
 --- rr-


Figure 4. Silt Harvesting Structure


Panel A depicts an untreated gully. In Panel B, the farmer has placed a
stone check across the boundary and created the small field by trapping
silt. In panel C, the farmer has enlarged the wall to keep pace with the
accumulating silt. Moisture from the gully enables double cropping in
medium to high rainfall areas. Such silt deposition fields are commonly
found in series, with gully plugs on each farm boundary.


ture. Farmers control rills and small gullies in their fields with small stone or boulder checks
across the flow. Silt fills behind the stones until the area is level.


GATEKEEPER SERIES NO. SA34