Howeler et al. (1993)observed similarity in the yield of cassava in
NT treatment and tilled treatment on a sandy loam soil of Zaire.
Similar observation were reported byMaurya and Lal (1979)and
Raros (1985). NT significantly decrease yield of cassava in mulch
and unmulched plots of Kimpese, Zaire (Ezumah and Okigbo, 1980)
but an experiment conducted byOhiri and Ezumah (1990)in a
sandy clay loam Ultisol in humid south-east Nigeria showed that
NT and MT had no significant effect on cassava root yield, but
significantly increased top yields in the second year, compared
with conventional tillage (Table 5).Ofori (1973)in Ghana reported
that ploughing increased cassava yield compared with superficial
hoeing, while, Okigbo (1979)at Nsukka, Nigeria found that
ploughing significantly increased yield only in the first one year
out of three years, and that benefits from mulching were
significant in all three years. Findings of these researchers implies
that NT contribute significantly to above ground biomass yield but
the conventional tillage is mostly beneficial in terms of root yield
and this may have resulted from pulverization of soil up to the
subsurface layer, thus, giving room for ease of cassava root
penetration into soil.
Cadavid et al. (1998)on long-term effects of mulch, fertilization
and tillage on cassava in a sandy loam soil confirmed an increase in
top biomass production of cassava by mulching in every cropping
cycle, regardless of tillage and fertilization treatment (Table 6).
They concluded that mulching was beneficial for above ground
biomass production (stem), which serve as planting material for
subsequent cropping season. Mulching is generally known to
reduce soil temperature, improve moisture availability to crop and
improve the organic matter content of the soil.
5. Conclusion
Our study reviewed and investigated soil conservation techniques, i.e. no-till and minimum tillage systems relatively with the
conventional tillage method and soil under compaction, from the
reappraisal of the of the different tillage systems on soil physical
properties (bulk density, total porosity and penetration resistance)
in a field cultivated on cassava. Our research review showed that
the NT treatment is characterized with reduced bulk density
principally at the surface soil, i.e. 0–5 cm and sometimes up to the
Howeler et al. (1993)observed similarity in the yield of cassava inNT treatment and tilled treatment on a sandy loam soil of Zaire.Similar observation were reported byMaurya and Lal (1979)andRaros (1985). NT significantly decrease yield of cassava in mulchand unmulched plots of Kimpese, Zaire (Ezumah and Okigbo, 1980)but an experiment conducted byOhiri and Ezumah (1990)in asandy clay loam Ultisol in humid south-east Nigeria showed thatNT and MT had no significant effect on cassava root yield, butsignificantly increased top yields in the second year, comparedwith conventional tillage (Table 5).Ofori (1973)in Ghana reportedthat ploughing increased cassava yield compared with superficialhoeing, while, Okigbo (1979)at Nsukka, Nigeria found thatploughing significantly increased yield only in the first one yearout of three years, and that benefits from mulching weresignificant in all three years. Findings of these researchers impliesthat NT contribute significantly to above ground biomass yield butthe conventional tillage is mostly beneficial in terms of root yieldand this may have resulted from pulverization of soil up to thesubsurface layer, thus, giving room for ease of cassava rootpenetration into soil.Cadavid et al. (1998)on long-term effects of mulch, fertilizationand tillage on cassava in a sandy loam soil confirmed an increase intop biomass production of cassava by mulching in every croppingcycle, regardless of tillage and fertilization treatment (Table 6).They concluded that mulching was beneficial for above groundbiomass production (stem), which serve as planting material forsubsequent cropping season. Mulching is generally known toreduce soil temperature, improve moisture availability to crop andimprove the organic matter content of the soil.5. ConclusionOur study reviewed and investigated soil conservation techniques, i.e. no-till and minimum tillage systems relatively with theconventional tillage method and soil under compaction, from thereappraisal of the of the different tillage systems on soil physicalproperties (bulk density, total porosity and penetration resistance)in a field cultivated on cassava. Our research review showed thatthe NT treatment is characterized with reduced bulk densityprincipally at the surface soil, i.e. 0–5 cm and sometimes up to the
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