Abstract:
Impact of land use and land use changes on soil erosion process have received attention and still alarming. Land use
changes mainly affect water, wind and tillage erosion. Soil loss due to crop harvesting (SLCH) which is a soil erosion
process that occurs during the harvest of crops such as cassava, sweet potato, carrot, beetroot, radish, potato, ginger,
onion, yams, green-amaranth, leek and groundnut. Those crops are mostly cultivated in Jaffna peninsula and cassava
is a major food crop for poor farmers or small holder farmers which are cultivated' under low input except the
irrigation. Cassava was cultivated 259 ha in Maha, 159 ha in Yala and average yield was 25MT / ha in Jaffna in 2011. It
is planted as a mono crop or intercrop at early stage and cultivated throughout the year. Easy and un-damageable
uprooting of the cassava plant mainly depends on soil moisture, texture and agronomic practices. This study focused
on the effect of harvesting time after irrigation on.SLCH. Soil moisture had a linear positive relationship R2 = 0.65 with
plant specific SLCH (SLCH spec/p): Soil moisture level decreased from the day after irrigation (from field capacity)
and has lower soil moisture in the evening than morning due to of the day temperature. Similarly estimated crop
specific SLCH crop was slightly lower than morning harvesting because of soil moisture effect. The harvesting time
after irrigation showed weak negative correlation r = 0.75 (p-value 0.07) with soil moisture level. But harvesting time
showed strong negative correlation r = 0.96 (p-value 0.003) with SLCHcrop. Average plant specific SLCH spec/p was
80.7 g / root and crop specific SLCH crop was 6.7 kg / ha / harvest loss in Valliagmam area in Jaffna. From this study
that could be suggested to do harvesting at evening and to avoid harvesting at field capacity level. Soil loss under
cassava justifies the need to conduct further investigations on this process of soil erosion on wide variation in soil and
cassava tuber characteristics.
