Moist soils
are usually highly susceptible to structural damage due to soil–machine
interactions which then result in soil smearing, sinkage and excessive soil
compaction. Although the moist (wet) loose soil would not be recommended for
field work, this condition is however sometimes unavoidable when working tight
schedule or programme. If the water volume that is present in a particular soil
is increased, then the resistance to shear will then be reduced. Therefore,
with a choice of suitable soil moisture content, the risk of soil structural
damage is minimized with corresponding high shear strength which can withstand
both the vertical and horizontal loads of the tractor – implement aggregate.
The best tractive conditions occur off – road on a dry grassland, for example
with cone penetrometer resistance of about 500kpa where tyres obtain a good
grip with no visible sinkage acting on it. Some risk of soil smearing in
seedbed preparation is unavoidable in the use of blades, disc rotary tools and
so on, in most condition, although this can lead to the promoting of clod
reduction.
Using of
conventional plough or other tillage implements in dry season have been hardly
satisfactory due to poor penetration of the soil, slow rate, excessive wear of
discs, accelerated bearing failure and so on. Due to these limitations, highly
rugged harrows or Rome ploughs are used as alternative in the dry season with
suitable matched bulldozer or other prime movers of adequate horse power rating
– thus circumventing the soil structural damage inherent in working on highly
vulnerable wet soils.
The moisture
content of the soil influence on soil–machine interaction, therefore, deserves
a meticulous consideration in soil–machine management for enhancement of crop
production or optimum yield of crop.
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