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[Plant-education] Re: (no subject)

David R. Hershey via plant-ed%40net.bio.net (by dh321 from excite.com)
Tue Aug 28 16:08:39 EST 2007

Peter's 20-20-20 is not a good fertilizer for hydroponics. It has too
much ammonium nitrogen, which drives the solution pH down, and lacks
calcium. Your plants probably had a severe calcium deficiency.

Use a half strength Hoagland solution or commercial hydroponic
fertilizer that contains all the essential elements. Peter's Hydro Sol
(5-11-26) is designed for hydroponics and has 100% N as nitrate. It
requires that calcium nitrate be added because Hydro Sol also lacks


You could probably cut the nitrogen to 100 mg/L. A cheap pocket
electrical conductivity (EC) meter can be used to monitor solution

David R. Hershey

On Aug 27, 6:19 pm, "Cote, Gary G" <gc... from RADFORD.EDU> wrote:
> Plant Ed folks,
> Has anyone grown Pistia stratiotes (water lettuce) for research or teaching?  If so could you share any tips?  The papers I've found in the literature mostly say they grow it in Peter's Professional Fertilizer 20:20:20 in the greenhouse in plastic tubs.  I've got them in black plastic tubs in 20 L of water containing 0.325 g Peter's 20:20:20 per L.  I tried 0.5 g per L.  I've been using nanopure water to avoid chlorine and other trace contaminants, although I had expected to switch to tap plus Peter's when they were growing OK.  Temperature is 22 by night, 26 by day, colder earlier because I had problems with the growth chamber temperature.  They get 14 hours light and 10 dark.  Water is changed weekly or every other week (because of travel).  They did poorly at first, and several died.  Then I had one week the survivors started looking really good and produced a lot of offshoots.  Then I went away and they got a cold shock when the power failed (4 C, I'm told).  They don't seem to want to recover.  The leaves are rotting, and the "stem" will just collapse in a froth of bubbles.  I've got one or two originals left and a few surviving offsets.  Any suggestions gratefully received.
> Gary
> Gary G. Coté
> Department of Biology
> Box 6931
> Radford University
> Radford, VA 24142-6931
> (540) 831-5630
> (540) 831-5129 fax
> gc... from radford.edu
> http://gcote.asp.radford.edu

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