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Always
use raingauges to check application.
Flood:
almost unheard of in the UK, but can be very cost-effective
way of applying water. However, it needs to be designed
correctly to work and is likely to cause waterlogging effects
and spread disease. If a crop is water logged it uses less
water than it could and therefore produces less yield and
it may well effect quality, depending on crop. But to make
it work you need to monitor 'correctly' - see 'Water
Monitoring' and 'Specific
Crop Watering'.
Sub-surface
Irrigation:
This is only possible with flat areas of land. The idea
is that the fields are laser levelled and then drained in
such a way that in the winter excess water is removed to
the surrounding dykes. In the summer the water level in
the dykes is raised and the water runs back up the drains
and this water will irrigate the crop. Caution: All you
may be doing is drowning some roots that have formed and
hence restricting growth. If a plant needs all it's roots
to grow at maximum speed and you have killed some then the
plant will be under some form of stress. Again, good monitoring
will help you to learn what is really happening - see 'Water
Monitoring' and 'Specific Crop Watering'.
Rain
Guns: The commonest form of irrigation in the UK.
Comparatively cheap and flexible and if used 'correctly'
and with knowledge can produce acceptable results. But as
with all forms of irrigation there are things you need to
know to get these good results and hence you need to monitor
'correctly'. Again, good monitoring will help you to learn
what is really happening - see 'Water Monitoring' and 'Specific
Crop Watering'.
Booms,
Pivots and Linear move irrigators: Assuming they
are well designed and maintained (which many are not - 20
rain gauges can soon see!) all can apply water very evenly
and give excellent results. But: before you start to use,
or worse, buy, any of these you should do your own trials
to see if they can apply water at the 'correct' speed. If
application rate and infiltration rate are not equal, then
large amounts of water can be wasted. On some soils one
finds that a boom may be putting on 25mm in 5 minutes -
many soils cannot cope with that and hence there is a large
amount of run-off, resulting in water use efficiencies of
barely 50%. If you do not know all this then you could be
wasting you a lot of money and losing yield and quality.
It may be possible to improve an existing system, by changing
nozzles and speed of application. Again, good monitoring
will help you to learn what is really happening
Mini
Spinklers: can be a cost-effective way of applying
water, but the more sprinklers you have the more you will
have areas of overlap and this can result in uneven cropping.
Try a little area before you buy large amounts. Also the
more nozzles you have the more scope there is for nozzle
wear and blockages - is your water clean enough? Do you
need to irrigate a 'little and often' as tends to occur
with this system? Often it is not the best way to water.
By applying water a 'little and often' you will be encouraging
disease, so be warned! Again, good monitoring will help
you to learn what is really happening.
Drip
(trickle, seep etc): As the required quality
standards for produce continues to increase this must become
more and more used. It has the advantage of being able to
do what is required when it is required, can be automated,
apply fertiliser and pesticides, requires less labour (when
automated) and is easy to manage.
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