Integrating trees with high productivity irrigated dairying
Harley Gray
New Zealand Tree
Grower May 2006
Pencarrow is a 207-hectare dairy unit running 730 cows producing
313,000 kg milk solids. The farm is owned by Andy and Tricia
Macfarlane. Andy has his own farm consultancy business, so share
milkers are employed.
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| A traditional two row shelter belt |
The principal operational objectives include environmental, aesthetic
and landscape values with a long term vision. There are financial
imperatives too. The farm is close to Ashburton and there is pressure
to subdivide, so an income goal of $6,000 a hectare has been set.
Tensions between trees and irrigation
The farm illustrates the tensions between the need to provide shelter
and the requirement for as much open space as possible to accommodate
modern mechanical irrigation systems. Irrigation is the life blood of
all farming activity at low altitudes in mid Canterbury, and several
methods are employed on this farm. Centre pivot irrigation is the most
efficient system in terms of water use, border dykes are energy
efficient but labour intensive, and K Line sprinkler systems are even
more so.
Border dykes are also vulnerable to water restrictions which have the
potential to be crippling. Solid set lines are used under trees at
Pencarrow. Some criticise the wasteful use of water of large mechanical
irrigators, but as Andy pointed out, an annual power bill greater than
$100,000 is a strong incentive for carefully planning your water use.
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| One of the border dykes currently
without any water |
Effluent disposal an important issue
Effluent disposal is an important issue. On 45% of the farm, effluent
mixed with fresh water is spread by rotorainer. Cows can be returned to
these paddocks within two days compared to the 20-day delay when
conventional spreading is used.
A range of shelter designs
The nor’wester is the most feared wind in Ashburton, but the cold south
wester is also a major hazard. In general the traditional double row
wind break system used in mid Canterbury is employed. Designs at
Pencarrow reflect an awareness of the need for much denser, impermeable
shelter to protect stock from cold southerly winds, and more porous
shelter to combat the hot, dry nor’wester.
Typical east/west lines are eucalypts, Eucalyptus nitens,
and Leyland
cypress planted at the same time. In the north/south lines, eucalypts
are planted two years later. Radiata pine and flax as well as poplar
and flax are some of the other combinations used. Poplars are used
alongside raceways because their deciduous nature means less winter
shading, allowing faster drying of races and less pugging damage.
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| Poplar with low flax to allow wind to
filter through |
The two-row shelter philosophy
The traditional philosophy with the double row system is to plant the
slow growing trees to windward. These are planned as the main long term
break line. They help to ramp the wind up over the leeward higher
trees, and will provide some strength to the latter’s windward roots.
They will also have been hardened by exposure to the wind rather than
being sheltered by the faster growing trees. At other farms this view
was challenged, particularly where eucalypts deprive the partner
species of nutrients and water. A case will be made in other reviews
below for planting a single definitive row from the beginning.
A parkland setting
This is a beautiful farm with great shelter and world class
productivity, and the owners obviously derive great satisfaction and
pleasure from the environment they have created.
At our first stop there was an impressive array of deciduous midpaddock
shelter trees which were aesthetically pleasing and created a parkland
setting. The sharemilker felt that the stock were happier in this area.
However, there is a clear need for data on the effect of shelter on
productivity. Surprisingly this does not seem to be available. With the
advent of more centre pivot systems it may be possible to
compare dry matter and milk solid production in farms with similar
irrigation profiles and soil types with significant differences in
shelter. Morning tea was provided near a most impressive 50 bale rotary
shed,
surrounded and well-sheltered by native plantings.
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| Scattered deciduous trees, the
preferred grazing environment for cows |
Native plantings enhance and shelter
the milking shed |
(top)
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