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16 April 2002
The average overall energy use per hectare by New Zealand's dairy farmers
is lower than anywhere reported overseas, despite a doubling in energy use on
our dairy farms over the past twenty years.
The findings come from a MAF Policy-commissioned study "Total Energy Indicators of Agricultural Sustainability: Dairy Farming Case Study"
prepared by the late Dr Colin Wells of the University of Otago.
The study is based on data gathered by Agriculture New Zealand from 150 dairy
farms spread throughout the country, representing about one percent of all
national suppliers. The farms chosen provide a good mix of irrigated and
Dr Wells' report finds that improvements in productivity have kept energy
use on most farms, expressed on the basis of energy use per kilogram of
milk-solids, to an overall increase of about ten percent.
MAF's Director of Policy Information and Regions, Alan Walker, says the
main cause of increased energy use is the growing use of nitrogen fertilisers
and the substantial amount of energy required for their manufacture. "The
high power requirement for spray irrigation is, however, emerging as a potential
sustainability issue," Mr Walker says.
New Zealand's energy consumption in dairy production is measured against
overseas producers by its overall energy ratio. This ratio (OER) is the
all-important ratio of the total primary energy input per kilogram of
milk-solids to the calorific energy output in those milk-solids. New Zealand's
OER is 0.59 compared to an estimated 2.8 in the USA and a range of 0.67 to 2.4
in European countries.
Some individual farms, however, particularly those with pumped irrigation or
high nitrogen application rates, may have higher OERs than those calculated for
some conventional and organic dairy farms in Europe.
The energy use on New Zealand dairy farms is calculated to be about 18
gigajoules (GJ) annually per effective milking hectare. The most significant
contributions to that total energy use on the 'national average' dairy farm
are fertiliser (35 percent), electricity (25 percent) and fossil fuels (20
percent). Estimates of the energy used in running capital equipment and farm
structures add a further 13 percent to the total energy use. On spray irrigated
farms, electricity use jumped to become the most significant energy input at 40
"Interestingly, the report finds that the average production intensity
(kilograms of milk-solids per hectare) and stocking intensity (cows per hectare)
is not significantly different between irrigated and non-irrigated farms,"
says Alan Walker. "Yet the amount of energy used is significantly greater
on the irrigated properties."
The study finds that the use of renewable energy is fairly low at 15 percent-
even on spray irrigated farms. A high proportion of fossil fuel energy is used
in the New Zealand electricity generation mix – during the study period only
57 percent of the total primary input to the generation system was renewable.
Mr Walker says a positive aspect of the report for New Zealand's dairy
farmers is that it identifies significant areas where energy efficiency can be
improved. "Paramount among these is taking opportunities to improve
fertiliser management and in particular, judicious use of urea because of its
high energy content, " he says.
"Where possible, best water management practices on irrigated dairy
farms, and in particular those with high pressure overhead spray systems, could
reduce direct energy use," Mr Walker says. "There is always scope to
make savings in the use of fuels such as diesel through efficient tractor use.
And the insulation of hot water cylinders and milk vats, coupled with greater
use of heat exchanges would reduce direct electricity use in dairy sheds."
Farmers who participated in the energy use study have all received the
results for their individual farm, along with comparisons of where they fit into
the wider district picture and some suggestions on how they can improve their
Mr Walker says with this report, his final publication, Colin Wells has made
a major contribution to the understanding of inputs into dairy farming. "He
has developed a methodology and survey for assessing energy use on farms which
is a world first and will have applications to other farm products. Regrettably,
due to his recent tragic death, we won't have his valuable input into ongoing
work in this area."
For further information, please contact, in the first instance:
Don Bagnall, Senior Policy Analyst and Irrigation Adviser,
MAF Policy Ph. 04 474-4162
Or Alan Walker, Director, Policy Information and Regions
MAF Policy Ph. 04 474-4160
Hard copies of the report are available from the MAF Information Bureau
Ph. 04 474-4186