New Zealand Journal of Agricultural Research abstracts
Estimation of the in-field variation in fertiliser
application
H. G. Lawrence
I. J. Yule
New Zealand
Centre for Precision Agriculture
Institute
of Technology
and Engineering
Massey
University
Private Bag 11222
Palmerston North 4442, New
Zealand
Abstract Variation in field
application from
a
centrifugal fertiliser spreader has, in the past, been difficult to
assess due
to the intensive field testing required. However, with the application
of
current technologies such as Global Positioning Systems and Geographic
Information Systems, the assessment of field application variation is
now
possible. The aim of this research was to develop a method to assess
field
application variation using basic transverse spread pattern test and
vehicle
tracking data. The information was used to measure and compare the
effect of
spread pattern, driving accuracy, driving method and paddock shape. Two
differently shaped paddocks were used for analysis, one rectangular,
the other
triangular. A simple analysis method was initially used to calculate
which
areas of the paddock received nil, single, or double application. An
advanced assessment
method was also developed to measure application variation within the
paddock
and to calculate field application variation. Transverse spread pattern
data
was averaged at 2 m
increments and linked to GPS tracking data from the
spreading vehicle using ArcGIS 9.1©. The dataset was then analysed
and a field
application map produced. The field coefficient of variation (CV) was
then
calculated from the application map. Three simulations of perfect
driving width
and perfect application pattern were also conducted as a means of
comparison to
the actual field data. Simple analysis results showed, in both
paddocks, the
area receiving the correct application rate was between 70 and 80%,
with 5–15%
of the area receiving nil application. Using the advanced analysis
method, the
calculated field CV was 32.9 and 43.0% for the triangular and
rectangular
paddocks, respectively. However, when simulated “perfect driving”
tracking data
were used, the average field CV was reduced to 24.8 and 23.5%,
respectively.
When both perfect driving and a perfect spread pattern were used field
application variation could be reduced to less than 20% for either
shaped
paddock. The results concluded that there is far greater variation in
field
application of fertiliser than that measured from a single transverse
test,
with the single biggest gain in calculated field CV being from driver
accuracy
and driving method.
New Zealand
Journal of Agricultural Research, 2007, Vol. 50: 25–32
0028–8233/07/5001–0025 © The Royal Society
of New Zealand
2007
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