Advice on a seedling potting mix for a frequently flooded seedling system

[Kobus Jooste]

I am converting a small section of my mixed system to house 30 seedlings at a time for new plant establishment.  It will be connected to the existing flood and drain system, which means getting flooded every hour.  I would like to know if there are suggestions out there for a media mix for the seedling pots that will work under these frequent flooding events.  I'm scared of rotting seedlings and was thinking down the line of a mix of sand and coir / coco peat.  Any suggestions? I really want to keep to the pumps I already have going and am trying to avoid putting in another one just for the seedlings.

[Kobus Jooste]

Thanks for sharing Chris.  I like the idea of the gravel as does not give you that many recycling hassles.  Re-use to infinity or until it gets lost.  I like that.  If my mix gets too wet I will discard the cocnut husk and try again with just the gravel.

Chris Smith said:

I use small rock for germination. I have found that small (1/8-1/4)rock will have a wicking capacity. When using a 2"net pot filled with small rock and sitting in 1/8 of water there is usually enough wicking to keep a seed on top moist. I have found this to be a huge benefit because I cannot water log anything. The seed gets all the moisture it needs and when the roots pop they will get all the O2 they need. I get a very good germ rate this way.

In my case I am using small cinder that was washed out of my GB media. I have played with other small rock and it works similar. This technique works so well that I now germ 90% of my seeds this way. I seed net pots that directly in 2x2 foam sheets with 60 spaces. I give them a 3 day germ in the shade then float them in a sprouting table with 1 inch of water.

Here is more details on my technique.

[Ian Hawkins]

Hello Kobus, you could try using the coco husk chippings that are available, as a mix with the gravel or even on their own, i think they are less prone to affecting pH than the gavel is. they are like small bark chippings of coco husk they hold less water and more air so might be good for your frequent flooding method. like the idea. Ian.

[Kobus Jooste]

I have looked around here (my small town) for the coconut chips but I can only get the finely ground stuff.  Our geology down here is relatively stable (mostly sandstone - based gravel), which tend not to mess with the pH too much.  I have had to go with the finely ground coconut husk and gravel mix for now.  At first I thought it was till getting too soggy, but it looks as if I am going to get some germination.  If it is not satisfactory, Ill reduce the coconut component.

 

I have a brother over in the UK (Canterbury / Kent area) who sometimes consider aquaponics (when his job is not murdering him).  Can it be done year-round in a glass house?

Ian Hawkins said:

Hello Kobus, you could try using the coco husk chippings that are available, as a mix with the gravel or even on their own, i think they are less prone to affecting pH than the gavel is. they are like small bark chippings of coco husk they hold less water and more air so might be good for your frequent flooding method. like the idea. Ian.

[Chris Smith]

I have tried the coir/gravel mix and abandoned it due to faster growth in gravel alone. I did side by side test with various medias and mixes. The best preforming by far was the gravel for germination and initial root growth. With the voids in the rocks the roots get far more O2 than with any other coir or mix that I tried.

[Ian Hawkins]

yeas it can certainly be done, although either some form of heating or fish that can handle cold waters will need to be used i guess. im currently setting a small system up in our hydroponic test greenhouse at our retail premises, just deciding whether to use talapia or carp at the minute, our greenhouse is heated year round and we use supplementary lighting in the darker months so either should be fine i think. there is certainly a growing following of aquaponics in the UK the ABLE project in Wakefield have an extensive community led project that is very productive if he fancies having a look, theyre even producing caviar there. 

Kobus Jooste said:

I have looked around here (my small town) for the coconut chips but I can only get the finely ground stuff.  Our geology down here is relatively stable (mostly sandstone - based gravel), which tend not to mess with the pH too much.  I have had to go with the finely ground coconut husk and gravel mix for now.  At first I thought it was till getting too soggy, but it looks as if I am going to get some germination.  If it is not satisfactory, Ill reduce the coconut component.

 

I have a brother over in the UK (Canterbury / Kent area) who sometimes consider aquaponics (when his job is not murdering him).  Can it be done year-round in a glass house?

Ian Hawkins said:

Hello Kobus, you could try using the coco husk chippings that are available, as a mix with the gravel or even on their own, i think they are less prone to affecting pH than the gavel is. they are like small bark chippings of coco husk they hold less water and more air so might be good for your frequent flooding method. like the idea. Ian.

[Kobus Jooste]

Chris, I already had the first mix in when I posted the discussion here.  I will also try the pure gravel as you suggest.  Thanks

Chris Smith said:

I have tried the coir/gravel mix and abandoned it due to faster growth in gravel alone. I did side by side test with various medias and mixes. The best preforming by far was the gravel for germination and initial root growth. With the voids in the rocks the roots get far more O2 than with any other coir or mix that I tried.