Abstract:
Deep ploughing is the one of options to alleviate soil compaction and
upgrade low productive lands for better crop production. However, deep
ploughing should be implemented with the knowledge of land characters.
Field experiments were conducted to evaluate the effect of deep ploughing
on soil water conservation in light soils in the Intermediate climatic zone of
Sri Lanka. Soil compaction of different soil series was evaluated using bulk
density and penetrometer resistance, through which selected the suitable soil
series to evaluate deep ploughing on soil water conservation. Soil water
storage with respect to deep ploughing was monitored during the dry and
rainy seasons using neutron scattering technique. Evaluation of soil physical
properties showed that the range of mean values of bulk density (BD) and
soil penetration resistance (SPR) in the surface soil (0-10 cm depth) of
major soil series in coconut lands was from 1.38 0.02 to 1.57 0.07
g/cm3
and 55 10 to 315 16.4 N/cm2
respectively. The total available
water fraction increased with clay content of soil as a result of high
micropores. However, due to soil compaction, ability of soils to conserve
water and to remain aerated was low for those series. Deep ploughing during
the rainy and dry periods in highly compacted soils (BD >1.5 g/cm3
and
SPR >250 N/cm2
) greatly increased conserved soil water in the profile,
while in less compacted light soils (BD <1.5 g/cm3
and SPR <250 N/cm2
)
conserved water content was adversely affected. Soil water retention in bare
soils of both highly and less compacted light soil series was higher than that
of live grass-covered soil. In addition, deep ploughing even in the effective
root zone with live grass-covered highly compacted soils around coconut
tree was favorable for soil water retention compared to that of live grass
covered less compacted soils.
