A Community and Forum For Aquaponic Gardeners

Timed irrigation and towers

I am experimenting a bit with towers on timed flow. So far (winter) they are happy with 15 minutes on and 45 minutes off. Anyone have experience with towers on timer during hotter weather?

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Permalink Reply by Averan on July 20, 2011 at 10:13am

more accurately, it is probably the ratio of nutrients. i have strawberries in a couple of planter troughs with hydroton that i feed a 16-16-16 seaweed fertilizer and they fruited like crazy. another batch of strawberries in a flood/drain gravel bed in my aquaponics system just grew really big leaves with signs of iron deficiency and are only now just starting to produce flowers/fruit. perhaps you have high levels of N without enough micro nutrients? it is common gardening knowledge that high N fertilizers encourage vegetative growth and fertilizer blends with a a lower ratio of N are used during the flowering and fruiting phase.

perhaps you could try putting your strawberries at the end of the line after other plants have taken up much of the nitrogen, leaving a more balanced ratio of nutrients to encourage fruiting?

Permalink Reply by Kobus Jooste on July 20, 2011 at 10:32am

To make a VERRRRRRRRRY long story short, the system was run in experimentally high fish densities in order to respond to every other local official that wanted to know how many meals you could squeeze out of an AP system. The end result was that the nutrient levels stayed high and there was nowhere in the system that the low nutrient demand plants could be kept happy.

I also ran a rain water experiment at the same time and the end result was a patchy year for the unit. The passion fruit liked the treatment though. I am not going to put as many fish back into it this year and am expanding plant production capacity to get the unit back to a lower density configuration I had previously.

Averan said:

more accurately, it is probably the ratio of nutrients. i have strawberries in a couple of planter troughs with hydroton that i feed a 16-16-16 seaweed fertilizer and they fruited like crazy. another batch of strawberries in a flood/drain gravel bed in my aquaponics system just grew really big leaves with signs of iron deficiency and are only now just starting to produce flowers/fruit. perhaps you have high levels of N without enough micro nutrients? it is common gardening knowledge that high N fertilizers encourage vegetative growth and fertilizer blends with a a lower ratio of N are used during the flowering and fruiting phase.

perhaps you could try putting your strawberries at the end of the line after other plants have taken up much of the nitrogen, leaving a more balanced ratio of nutrients to encourage fruiting?

Permalink Reply by RupertofOZ on July 20, 2011 at 10:53am

Actually Averan... it's probably more a matter of pH and Potassium provision...

Strawberries prefer a pH of about 6.4-6.8.... and when flowering/fruiting a significant Potassium boost... which they got in the system that you were "fertilising"... but obviously not in your flood & drain system, which by the fact that you had signs of iron deficiency.. points to a pH lockout, probably in the range of 7.4-7.8...

Nitrogen is one of the few elements that will be taken up pretty much across the entire pH range...

Permalink Reply by Averan on July 20, 2011 at 11:30am

yes, i know. thanks though! =)

regardless of the original cause, the effect is the same and my point remains, the ratio of nutrients is key. whether that ratio is created by pH lockout or too many fish or something else, the underlying principle holds true.

Permalink Reply by RupertofOZ on July 20, 2011 at 11:42am

Well yes, and no... if for example Potassium is not available at flowering stage, the plant will revert back to vegetative growth and utilise the nitrogen available rather than continuing with flower/fruit set...

pH lockout will thus significantly constrain or alter the plant life cycle... the nutrient ratio becomes somewhat secondary ...

Your fertilisation with 16:16:16, and fruiting results testify to that... if you had used say a 16:16:4 fertiliser... you would no doubt have had significantly more vegetative growth than fruiting... so yes the ratio is important...

But I suspect that the successful plant system was probably within, or at least much closer to optimal pH levels... whereas the flood & drain systems wasn't...

Permalink Reply by Kobus Jooste on July 20, 2011 at 12:02pm

Details! Perhaps Harold should cut and paste these snippets over to the pH and crop discussion too! Thanks guys. I have always been a little lazy on the plant nutrient details - more of a fish, functional and design / components type of person.

Rupert, the stand out thought after looking at your suggestion was the potassium. Because the system naturally had a low but stable pH, I was never upping pH with potassium for a long time. Rain water also had very little of it but I was adding trace elements.

Permalink Reply by RupertofOZ on July 20, 2011 at 12:31pm

Kobus, Potassium wont "up" the pH... but high pH range can result in the availability of Potassium being markedly reduced...

All plants that enter a flowering/seeding/fruiting stage benefit greatly from a Potassium boost...

Permalink Reply by Kobus Jooste on July 20, 2011 at 12:36pm

Rupert, the potassium would have been in the form of potassium hydroxide, not pure potassium - sorry for my short hand

Permalink Reply by RupertofOZ on July 20, 2011 at 12:43pm

Ok... which you were obviously using as a pH buffer...

As such it should have catered for both aspects.. of buffering... and Potassium boosting...

A great reference for Strawberry growing is...

A Technical Guide to the Hydroponic Production of Strawberries – Dr Lynette Morgan - A Suntec NZ Ltd Publication

Permalink Reply by TCLynx on July 20, 2011 at 3:07pm

A note from over in the pH and crop discussion was about the possibility of an over abundance of calcium being able to cause a lock out of potassium so in systems with an excess of calcium (likely due to water coming form limestone aquifers or the exclusive use of calcium carbonate, lime or shells as the buffer material) could cause a lock out of potassium even if there has been supplementation of potassium by the use of things like seaweed extract and it may seem that the pH is locking out the potassium but it could just be the co-incidence of the high calcium that tends to go along with mineral rich alkali water.

Sorry for the Hijack Kobus. (Perhaps we need a whole group for nutrient/pH interactions where the guys with more chemistry can educate those like me who only know that something is going on but dyslexically can't keep any of the letters/numbers straight.)

Will be interesting to see how the strawberry towers do now going forward.

Permalink Reply by RupertofOZ on July 20, 2011 at 3:19pm

That's true TCL... and similarly with phosphorus... but remove the Calcium buffer... the carbonate...which is responsible for the "over-abundance" of the Calcium in the first place... and pH will drop... and the Potassium uptake will probably occur even if a large amount of Calcium is still available...

Permalink Reply by David Waite on July 20, 2011 at 5:30pm

Rubert in my system it is bufferd to a high ph range because of the gravel media. Does it make sense to add the Potassium and phosphorus to help with fruiting or am i wasting my time because of the high ph. ph range is 7.6 to 7.4

RupertofOZ said:

That's true TCL... and similarly with phosphorus... but remove the Calcium buffer... the carbonate...which is responsible for the "over-abundance" of the Calcium in the first place... and pH will drop... and the Potassium uptake will probably occur even if a large amount of Calcium is still available...