New Zealand Journal of Agricultural Research abstracts
Developing variable rate application technology: scenario
development and agronomic evaluation
R. I. Murray
I. J. Yule
New Zealand Centre for Precision Agriculture
Massey University
Private Bag 11222
Palmerston North 4442, New Zealand
Abstract Six fertiliser application scenarios
were considered on a hill-country case study farm. The scenarios were
developed for input into a decision tree model and were compared to a
base line scenario that uses the farm’s current blanket application
techniques. A further blanket application was considered along with
several variable rate application scenarios. Throughout this study,
variable rate application technology outperformed the fixed rate
applications in terms of pasture production and fertiliser utilisation.
One scenario, which used full variable rate application and a model
optimised prescription map, produced the highest annual pasture yield
across the 2518 ha Limestone Downs property, North Island, New Zealand,
with 24 789 t DM, some 4854 t DM more than the property is currently
modelled to produce. The blanket application techniques which are
currently employed on this property produced the lowest annual pasture
production with 19 935 t DM yr - 1. Variable rate techniques
were predicted to increase annual production considerably, from 19 935
t DM yr - 1 to between 21 239 and 24 798 t DM yr - 1;
in these cases, an increase in the production variability is also
expected. Increased annual production from targeting additional
fertiliser resources at more productive areas was identified through
the decision tree modelling. Some areas were identified as having poor
response to fertiliser, and fertiliser application to those areas was
considered uneconomic.
Keywords agronomics; decision tree; fertiliser;
GIS modelling; pasture production; topdressing; variable rate
application
A06016; Online publication date 2 March 2007; Received 16
March 2006; accepted 17 October 2006
New Zealand Journal of Agricultural Research, 2007, Vol. 50:
53 - 63
0028 - 8233/07/5001 - 0053 © The Royal Society of New Zealand
2007
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