important in the choice of tillage system. The NT system with
residue cover is considered most appropriate in areas where soil
topography is relatively flat (upland areas), where moisture
infiltration is enhanced and excess water drains freely out to
maintain a friable soil condition. In the Democratic republic of
Congo, there was no significant yield difference from CT as
compared with NT plots whenever the field was mulched but
cassava root yield was lowest in unmulched, untilled plots
(Ezumah and Okigbo, 1980). This observation may have been
due to loss of soil organic matter that could protect soil surface
layer from erosion and the decrease in soil organic carbon, which
could improve soil structure and water retention capacity for
enhanced root penetration.
In a related research, Reining (1992)compared conventional
tillage with no tillage and minimum tillage systems where cassava
was planted in an existing grass sod for three growing seasons and
observed no significant difference in root yield of cassava between
NT and CT, while the minimum tillage system yielded less than 30%
of that obtained in the other two systems. The reduced yield under
minimum tillage was thought to have resulted from higher soil
bulk density and quick soil clod formation under dry condition.
Odjugo (2008)in Nigeria observed highest soil moisture within the
0–15 cm soil depth under no tillage system but confirmed higher
yield of up to 46% in the CT compared with NT without mulch. The
implication of his finding as compared with previous researches
was that the NT, like the CT will enhance root yield of cassava only
if the soil superficial layer is mulched with crop residues, while
reducing the cost associated with land preparation and soil
compaction that could arise from the adoption of CT system.
Significant researches have been conducted in recent years on
influence of tillage systems on root crops. Most of the research
findings were concentrated on effects of tillage systems on soil
physical and chemical properties, some of which are discussed
below:
important in the choice of tillage system. The NT system with
residue cover is considered most appropriate in areas where soil
topography is relatively flat (upland areas), where moisture
infiltration is enhanced and excess water drains freely out to
maintain a friable soil condition. In the Democratic republic of
Congo, there was no significant yield difference from CT as
compared with NT plots whenever the field was mulched but
cassava root yield was lowest in unmulched, untilled plots
(Ezumah and Okigbo, 1980). This observation may have been
due to loss of soil organic matter that could protect soil surface
layer from erosion and the decrease in soil organic carbon, which
could improve soil structure and water retention capacity for
enhanced root penetration.
In a related research, Reining (1992)compared conventional
tillage with no tillage and minimum tillage systems where cassava
was planted in an existing grass sod for three growing seasons and
observed no significant difference in root yield of cassava between
NT and CT, while the minimum tillage system yielded less than 30%
of that obtained in the other two systems. The reduced yield under
minimum tillage was thought to have resulted from higher soil
bulk density and quick soil clod formation under dry condition.
Odjugo (2008)in Nigeria observed highest soil moisture within the
0–15 cm soil depth under no tillage system but confirmed higher
yield of up to 46% in the CT compared with NT without mulch. The
implication of his finding as compared with previous researches
was that the NT, like the CT will enhance root yield of cassava only
if the soil superficial layer is mulched with crop residues, while
reducing the cost associated with land preparation and soil
compaction that could arise from the adoption of CT system.
Significant researches have been conducted in recent years on
influence of tillage systems on root crops. Most of the research
findings were concentrated on effects of tillage systems on soil
physical and chemical properties, some of which are discussed
below:
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