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Optimal nutrient levels OR how to interpret water test
http://byap.backyardmagazines.com/forum/viewtopic.php?f=3&t=21969		 Page 1 of 2
Author:  chopinwood [ Jun 7th, '14, 03:16 ]
Post subject:  Optimal nutrient levels OR how to interpret water test
Hi all,
I've tried a couple of searches here but couldn't find what I was looking for. Specifically it is how to interpret a water test... or what are optimal nutrient levels? I have sent in soil samples to the local university for testing in the past, and the results provided recommended optimal levels as well as suggested amendments for the soil. I was happy to see they also do water testing for greenhouse applications, however they don't provide an indication of optimal levels. I would have thought this to be a no-brainer, but neither the testing lab nor searching the web has turned up results, so I'm turning to the experts here for help.

Yes, I understand that looking at the plants is a good way to tell, but it seems to me to be as clear as mud, as more than one thing can cause a single symptom (leaf cupping, brown edges, interveinal chlorosis, etc.) and its hard for the untrained eye to read the tea leaves so to speak, to get the message of the nutrient levels.

I will attach a screenshot of the results.

Thank you in advance for any comments or resource links you can provide.
Regards,
Paul

Attachment:
WaterTest-May2014.png
WaterTest-May2014.png [ 18.83 KiB | Viewed 5413 times ]
Author:  smatthew [ Jun 7th, '14, 07:53 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Those numbers look pretty good. Calcium might be a bit high, but might be ok - can anyone else comment on the possibility of nutrient lockout due to high calcium? Phosphorus is definitely too low. Alkalinity should be a little higher.
Author:  chopinwood [ Jun 7th, '14, 10:58 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Thanks for your reply.

When we started seeing wonky plants, my better half was convinced it was a calcium deficiency, so we stopped the 50/50 Ca/K amendments and did straight Ca. (Also started adding DTPA iron) Or maybe it was a Mg deficiency ?

So I thought it better to get a water analysis instead of guessing - but was surprised that the lab didn't have recommendations. Welcome to live-and-learn aquaponics, right ?
Author:  smatthew [ Jun 7th, '14, 11:57 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Yeah, go back to switching up Ca/K, and don't forget to switch the Ca source occasionally to maintain the Mg. right now your biggest problem is Phosphorus.
Author:  Charlie [ Jun 7th, '14, 18:29 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
What feed are you using?
Author:  chopinwood [ Jun 7th, '14, 23:54 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Purina Nutramax Grower 400
Author:  chopinwood [ Jun 9th, '14, 23:16 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Hi smatthew - what do mean by: "switch the Ca source occasionally to maintain the Mg."

I'm currently using Calcium Carbonate as an additive, plus I've mixed in oyster shells in the GB media.
Author:  mattyoga [ Jun 10th, '14, 13:33 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Interesting that this is another water test that suggests phosphorous may be a limiting factor!

As discussed here:
viewtopic.php?f=1&t=21844&start=15

How much feed is going in daily and what sort of plants have you been growing in what growbed area?

Does anyone know how much it costs to get water tests done like that in Perth?
Author:  Stuart Chignell [ Jun 10th, '14, 15:44 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
It would be great to see plant photos to match this water test. :think:
Author:  smatthew [ Jun 10th, '14, 21:43 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
chopinwood wrote:
Hi smatthew - what do mean by: "switch the Ca source occasionally to maintain the Mg."

I'm currently using Calcium Carbonate as an additive, plus I've mixed in oyster shells in the GB media.


Every so often, use dolomite lime instead of oyster shells. It's calcium magnesium carbonate - like oyster shell material, but with some magnesium.
Author:  chopinwood [ Jun 10th, '14, 23:06 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Mattyoga: I'm feeding about 2 cups (10oz, 280g by weight) per day.

Stuart C: We've ripped out a bunch of the plants - the cukes that were thriving in the past produced little. Same with the toms - lots of growth, very little fruit.

Plus we've got a bad whitefly issue at the same time, so that is stunting the younger plants. I'll grab some photos of whats left and post later tonight.

Thanks for everyone's input.
Author:  chopinwood [ Jun 10th, '14, 23:07 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
smatthew wrote:

Every so often, use dolomite lime instead of oyster shells. It's calcium magnesium carbonate - like oyster shell material, but with some magnesium.


Excellent - thank you.!
Author:  mattyoga [ Jun 11th, '14, 09:14 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Wow thats a large feed input - is it a reasonably large system?
Author:  Charlie [ Jun 11th, '14, 09:24 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Yea, I too was surprised by the phosphorus reading (which is why I asked about feed type), It would be good to have test results from a number of other systems for comparison or some insight from someone with a better understanding. Everything I have ever read indicates phosphorus should be abundant in recirc and AP.
Author:  mattyoga [ Jun 11th, '14, 10:40 ]
Post subject:  Re: Optimal nutrient levels OR how to interpret water test
Me too Charlie, though me experience has been different. A few others in the ap world state that phosphorous may be limiting in fruiting systems such as nate storey. There is a push to reduce phosphorus effluent from aq so levels in feed are being reduced where possible. So maybe the issue is a newly formed one.

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