dc.description.abstract |
The recent decline in farming profits has prompted an urgent need
to increase efficiency, either by increasing outputs or reducing the
cost of inputs. Soil compaction can influence adversely all stages of
crop development, and hence yield, and is expensive to ameliorate
in terms of time taken and power required. Minimum cultivation or
direct drill crop establishment systems can reduce inputs, however,
they are very susceptible to compaction from the previous season.
There is a need to develop a greater understanding of the
compactive nature of soil, and hence trafficability and workability,
in relation to the selection of appropriate machinery to carry out
agricultural operations. A study of research on soil compaction
revealed that the majority of work to date has been carried out
using disturbed soil samples in laboratory situations. The aim of
this project is to develop techniques and models, based on field
data, for assessing the susceptibility of soils to compaction by
agricultural machinery. Work, conducted during this study, was
carried out in the field in a range of soils, crops and climatic
conditions. The study was approached by dividing the project into
two sections:-
(1) Prediction of trafficability and workability on a go/no-go basis.
Soil water suction (h), soil moisture deficit (SMD) and cone
penetration resistance were monitored at six field sites, under grass
and an arable crop, covering a range of agricultural situations
commonly found in central and eastern England.
Strong correlations were found to occur between both h and SMD
and:-
(a) a qualitative assessment of soil condition, and
(b) cone penetration resistance.
These data formed the basis of models for predicting trafficability
and workability at a given site on a particular day, and at any 5km
square in England and Wales as an aid to business planning.
(2) Assessment of the compactive nature of soil during loading.
A methodology was developed which provides a measure of the
susceptibility of soil to damage if land is trafficked when in an
unsuitable condition. It is based on results of plate sinkage tests, in
conjunction with those from confined compression tests, performed
in the field using tractor-mounted equipment. Soil behaviour
during compression was found to be governed by three phases:-
(a) compaction with uniform lateral stress,
(b) compaction with increasing lateral stress, and
(c) displacement of soil laterally.
Mathematical models are presented for predicting, for a given load
and soil, the deformation phase and extent of disturbance likely to
occur.
The prediction models developed during this study provide a new
approach to the selection of, and assessment of damage by,
agricultural machinery. |
en_UK |