Gerbera & Roses growing article August 2005
 

EC and PH;

Dosing the right EC and PH is important for the availability of the different fertilizer elements, if the EC or PH is too high or low it could result in growth reduction and or production loses. Check and calibrate your irrigation unit and hand held EC and PH meter regularly to make sure they give the right EC and PH reading.

Drain water samples;

I strongly advice to send every 2 months (when you re-use the drain water a monthly test is necessary) a drain water sample to a laboratory (www.blgg.nl) to check the drain water to make sure the plant get the right amount of each element. When you use bore or dam water it's also important to check this water to find out which elements are already in the water so you could reduce these elements to get a balanced fertilizer mix.

A drain water sample should be taken after 2 or 3 irrigations are given to the plants and the pot have drained fresh water, take fresh drain water from a few different varieties to get an average mix of each growing stadia. Cover the bottle in a plastic bag and send it as soon as possible to the laboratory.

High salt levels;

When salt levels of bore or dam water are to high you could install a salt removing device, above 0.7 EC in the bore or dam water the plant will suffer from the high salt levels which could reduce the quality and production of the flowers.

Ammonium nitrate;

Too often I see fertilizer mixes with to much ammonium nitrate in the mix, for a basic fertilizer solution a
maximum of 4-6 kg ammonium nitrate is enough. Too much ammonium nitrate in the mix could damage the roots and slow down the growth of the plant.

How to influence the PH;

A high PH in the drip water could be reduced by adding acid in the acid tank and fertilizer tank.

A low PH in the drip water could be lifted with by adding bicarbonate in the Alkaline or fertilizer tank

A high PH in the drain water could be reduced by using some ammonium nitrate and drip with a lower PH (PH 5.3-5.5).

A low PH in the drain water could be lifted when the ammonium nitrate is take out the fertilizer mix and drip with a higher PH (PH 5.7-5.9) don't drip with a PH above 6.0 because this could block you drippers.

** Please note that you have to check the EC and PH of the drain water a few times a week to make changes when the EC & PH gets to high or low.

Trace elements;

Most of the overseas drain water testing companies give advice to use sulphate trace elements, growers in Australia often use chelates trace elements. When you use chelate trace elements you most often have to ad 1-2 times more in the fertilizer tanks!

Make sure that when you order your fertilizer (especially the trace elements and iron) that they give you always the same brand, if it's not the same brand make sure that the new brand have the same percentage of ingredients.

Most of the chelate trace elements are 13-14% but sulphate trace elements are between 20-35%, so you must adjust your fertilizer mix when you use different strength fertilizer.

***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.