Conservation farming on steep lands - USAid

13 T. F. SHAXSON
At the western end of the state of Santa Catarina in southern Brazil, there
are sn~all farmcrs growing annual crops in large areas with average slopes
over 20 percent. The conibination of soil types (reddish clays derived Sroni
basalts) and rainfall regime (some rain in most months of the ycar, but
often very erosive) has allowed the development of nlinimum-tillage systems
for annual crops, such as beans. maize, and soya. These systems are characterized
by the maintenance of 100 percent cover practically throughout
ihe year with living and dead niulches of vetches and other low-growing
legumes. Annuals are contour-planted through these mulches either in narrow
furrows or using punch planters. The farmer:; describe the soi!s as
being "fatter" in terms of organic matter content and soil stnlcture, and
they are able to maintain yields with less fertilizer and reduced pesticide
use. In passing, they also mention that runoff and erosion is significantly
less than before.
Across the state border, in P~rana, on somewhat siniilar s~ils but lesser
slopes, excessive use of disk equipinent in growing soya and wheat in rotation
had caused serious problems of compaction at the bottom of the disk layer.
This results in large volumes of runoff and removal of eroded soil and requires
municipal authorities to spend large sums annually on rural road
maintenance, to the detriment of financing other more positive social programs.
Crops often suffered from mid-season moisture stress in dry periods
during the summer rainy seasop because of shallow root systems. Winter
wheat suffered similarly from moisture stress within its restricted root range.
The local rivers and streams were choked with sediment end polluted with
pesticides and fertilizers brought down by !he runoff and erosion. After
extension agents promoted deep tillage to break up the ccmpacted layer
and encouraged farmers not to hurn crop residues, road damage declined
to a startling degree, springs that had dried up early in the dry season started
to flow more strongly and longer, possibilities for fish-<strong>farming</strong> and irrigation
have incr wed, and water quality in streams and rivers is greatly irnproved.
Through programs aimed at improving water n~anagemerlt and making
cropping more secure. conservation of the soil has been achieved as a consequence
of improved land use.
Satisfying land user aims
Because erosion is a consequence of inappropriate land use, conservation
of the soil in situ will be a consequence of appropriate land use. Our
challenge is to devise ways in which the land users' aims can be satisfied
with systems that are also conservation-effective.