Gerbera & Roses growing article January 2007
Recycling drain water;
In most cases, open or run-to-waste
systems are used in the Australian horticulture. In such open systems, the drain
water with the nutrients freely leaches to ground and surface water. Because of
economical motives and environmental concerns, closed soil less systems can be
applied. These closed systems are more efficient with the use of water and
fertilizers, and cause less damage to the environment. For gerberas you have to
sterilise the drain water before you re-use it again, the chance is too big that
you could loose many plants because of the drain water is infected with diseases
as Pythium, Phytophthora or Fusarium.
Test in the Netherlands have proven
using Ultra-violet radiation (or UV) and heat treatment give the best results to
kill all diseases / pathogens in the drain water. UV disinfection; Ultra-violet
radiation (or UV) is a proven process for disinfecting drain water but
pre-filtering through a sand filter of the recirculated water before it goes
through the UV steriliser is highly recommended.
Heat treatment;
When heat treatment is applied, the
drain water is heated for about 30 seconds to a temperature of 95˚C.Advantage of
Advantages recycling drain water;
1 Reduce the use of water up to
30-40%.
2 Reduce the use of fertilizer up to
50-60%
Disadvantage of recycling drain water;
1 Require high quality of water (low
in EC / natrium and chloride).
2 High investments.
3 UV disinfection affects the iron in
the drain water, so extra iron has to be given.
4 Heat treatment increase the water
temperature by +/- 5 degrees and the PH of the drain water has to be below 4.5
before it could go through the heat exchanger.
Especially the last 2 years there are
products on the market in Australia which promise to kill all diseases /
pathogens in the drain water but some of these products have side effects on the
growth of the plants. Be careful with new products; always ask for information
from the supplier, which growers are using. Contact these growers to ask how the
product works and if it has some side effects on the growth of the plants. A few
phone calls could save many troubles!
Note; warm irrigation water (above
27-30 degrees) contains less oxygen; try to keep the water in the storage tanks
during the warm period as cool as possible. It is a good idea to put an extra
pump in the water storage tank to stir around the water in the tank to bring
more oxygen in the water.
Crop maintenance;
Because we now go towards autumn, all
the old leaves should be removed so there is enough circulation around the
plants, which reduce the change of botrytis. After de-leaving it is advised to
spray with a fungicide, this will reduce the spores of botrytis.
Note; if you remove leaves in winter,
be careful not to break the plant, damage young buds and do not take away too
many leaves at once.
Botrytis;
Often botrytis start to develop at the
greenhouse but the botrytis may not be visible at harvest but could develop
further in the cool room causing damage on your flowers. Because most flowers
stay at least 12-24 hours in the cool room, the conditions in the cool room have
to be good. Use the right temperature which is required for your product (Roses
2-4 degrees / Gerberas 7-9 degrees)
- Use a fan in the cool room to circulate
the air; this reduces still standing air with a high humidity around the flower.
- Make sure that the cool room floor is
dry.
- Clean the cool room at least ones a
month with a disinfection product to kill the botrytis spores.
- The cool room is a place where you
store flowers not a place to store other things.
Note; in the greenhouse, fungicides could be
used for control of Botrytis. Always rotate between chemical groupings, using
chemicals twice only before changing to another group.
***Although we trust that this information
could be of considerable help to the success of the crop, we cannot accept any
liability for the results of your crop. All the information in this growing
newsletter is without committing ourselves.
This article is written by Job Roskam of Roskam
Young Plants Pty Ltd. and also published in the Australian flower industry magazine.
