Research Highlights of the CIMMYT Wheat Program 1999-2000

e heavier and more rugged to cut through surface
residues and penetrate the soil to the required
seeding depth. Whereas surface soil in a
conventional system is loose and easy to penetrate
with a light machine, the surface layer in untilled
fields is denser and requires more force for
penetration.
Successful machines for widely spaced crops such
as maize have been developed in several areas,
notably in Brazil. Traditionally these machines have
been heavy, a factor that is not normally a problem
while seeding, but their maneuverability at field
edges is difficult. A new generation of machines
relies more on fulcrum physics than on sheer
weight, and there are now lightweight seeders
available for seeding row crops.
With respect to seeding equipment, the biggest
problem remaining is how to sow small-seeded
crops such as wheat, barley, and many green
manure cover crops. Although single-row seeders
can often sow these crops, the time required for
seeding is high due to the closeness of the rows.
However, advances are being made, and workable
machines, although not perfect, are becoming
available in India, Pakistan, Ethiopia, and Bolivia
(and probably in other countries).
These machines typically seed three to five rows at
a time, and are supported on wheels, at least for
turning at the field margins. Weight continues to be
a problem as the force needed to cut through
residues with a 3-row seeder is three times higher
than with a single-row seeder. However, the time
saved by using these machines is important. In
Bolivia a farmer typically prepares his land twice
with a wooden plow before seeding, broadcasts the
seed, and then incorporates with another pass of
the plow. To plant one hectare, the farmer walks 100
km behind his oxen to prepare the land and cover
the seed, and another 2 km to sow it. In contrast, if
he direct-seeds a hectare with a 3-row seeder (25 cm
between rows), he will walk only a little over 13 km
and will achieve a far better plant stand with the
row-seeded crop than with the broadcast one.
Problems Yet to Be Solved
Alternative uses of crop residues remain a problem
in many areas. However, experience in Bolivia
shows that once farmers see the benefits of surface
residue retention in their fields, they are far more
willing to look for and adopt alternate feed
sources. These include sowing forage crops during
the normally fallow period and planting of live
contour barriers with forage species, which reduce
erosion and slowly form terraces. Increased grain
and straw yields attained with more efficient water
use also allow farmers to use part of the crop
residues for feed and still leave enough residues
for adequate ground cover on the field. However,
one major problem is that according to local
custom, grazing rights after harvest are communal,
which means that an individual farmer is not
allowed to maintain crop residues in his field;
rather, this is a community decision.
Another problem facing development agencies is
harvest methodology. Hand-harvesting small-grain
cereals and then threshing by trampling the crop
outside the field means most of the straw is
removed from the field. Returning the straw for
ground cover is expensive in terms of manpower,
and unattractive to farmers. On flat or gently
sloping land, machine harvesting is the preferred
method, as it is generally cheaper than handharvesting,
reduces the harvest-to-market interval,
results in a cleaner product, and leaves crop
residues on the field. However, development
efforts are required to make machine harvesting
more widely available and to promote small
custom-harvesting enterprises.
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