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The changes in agricultural production techniques
in industrialised countries over the past few decades
have been dramatic, with economic pressure
favouring the continuous increase of machinery
power, vehicle weight and implement size, write
Kevin McDonnell and Mike O'Flynn
To improve labour efficiency, farm equipment has increased
in size. Tractors, combines, forage harvesters, grain
and forage trailers and manure spreaders have become
progressively bigger. This increase in the size of farm
equipment may cause significant soil compaction that can
negatively affect soil productivity as well as environmental
quality.
Soil compaction is one of the major problems facing modern
agriculture. Overuse of machinery, intensive cropping, short
crop rotations, intensive grazing and inappropriate soil
management lead to compaction. Soil compaction increases
soil strength (bulk density) and decreases soil physical
fertility through decreasing storage and supply of water and
nutrients, which leads to additional fertiliser requirement
and increasing production cost.
A series of trials were undertaken using different tyre widths
and pressures to establish spring barley in a conversional
plough and one-pass system.
One set of trials used a Fendt 716, and the other used a
Massey Ferguson 6280.
The Massey Ferguson was fitted with a range of rear
tyre widths from 520mm to 800mm and operated at the
manufactures recommended tyre pressures. Soil compaction
was measured with a cone penetrometer.
Where the tractor was fitted with a front ballast weight to
counterbalance the one pass the damage done by the
front axle load outweighed any benefits associated with
using a larger rear tyre on the equipment even at low tyre
pressures. The graph opposite shows the significantly
greater compaction done by the weight block via the front
axle compared with when the tractor had the weight block
removed.
This work showed that soil stress is always a function
of the stress at the tyre-soil interface, which is due to a
combination of both tyre inflation pressure and wheel
load, as well as tyre properties and soil conditions. Hence
management of the soil/vehicle interaction is critical for
arable production.
www.irishfarmersmonthly.com
EDUCATION
JANUARY
14
SOIL COMPACTION
STUDIES AT LYONS
ESTATE
Influence of high and low front axle load at low tyre inflation pressure
Soil penetration resistance (MPa)
S
oil p
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tr
at
ion dep
th (
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m
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(a) High front axle load low tyre inflation pressure
(b) Low Front Axle Load low tyre inflation pressure
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