Backyard Aquaponics
A place to discuss aquaponics

Since I have started AP I have always planted from seed. One of the things I have observed is, in my setup (using 10mm scoria), plants germinate well but quickly stop growing for a while then all of a sudden they would start to take off. I was often comparing them to the dirt garden plants planted at the same time, the dirt garden would win for a while then the AP would race past it very quickly. I had the same experience with the transplantable pots I was trialing if filled with gravel the growth rate was much lower than if filled with coir.

On experimenting I am starting to conclude that the spaces between the gravel pose a challenge to small plants trying to get a foot hold. Once I started to plant in a small amount of coir, AP growth has raced past the dirt right from germination.

I know that some seedling pots are porous and rely on a process of air pruning. Air pruning happens naturally when roots are exposed to air in the absence of high humidity. The roots are effectively “burned” off, causing the plant to constantly produce new and healthy branching roots. You can find out more about air pruning here
http://depts.washington.edu/propplnt/Ch ... runing.htm

I think you may be right about plants taking longer to develope a root structure in gravel... at least initially...

And the reference to root structure due to "air pruning" is bourne out by the root developement in NFT plants....

I tend to hand water my seed in the gravel beds.... partly because I think they "burn" otherwise with the heat of summer and the gravel...

Then I flood my gravel bed a little higher once the seeds have sprouted for a week or so...

suspect the hand watering and higher flooding for a period perhaps aids the root development due to the raised "humidity"...

I would agree. I tended to hand water the initial start but as I did not see leaf indications of lack of water I would stop. It maybe that the water roots get down to the flood level but the feeders are near the surface and it's not humid enough, using the coir I get capillary effect and it stays wet to the surface. Interestingly I have never seen algae grow on the wet coir. An additional benefit is the coir acts as a perfect surface for bees to collect water. For the last 4-5 years we have never seen a bee in summer, now we have a rich supply of them.

Does the coir stay too wet and rot the plants. What F&D times do you run.

I only use a small amount of coir about a 1/3 of a cup. So far I haven't had a problem with rot.,My GB's are in series, I currently sequence each in about 18min, flood is about 18min drain is five. Once the first bed starts to siphon the second starts filling then the third etc. I only have 2 GB's setup at the moment I intend to have three but with 2 it cycles once every 18min with three it would be about once in 40min.

Having not yet grown from seed I am unqualified to say, but I do notice transplanted (from dirt) seedlings 'brighten up' then pause, with 0 growth for some time before exploding. I had always put it down to shock... but maybe it's similar.

I should be able to let you know more over time but at the moment it seems to me that moving a larger plant which should have feeder roots lower down should have enough humidity, however having said that when I tried transplanting with the porous pots I am trialing I don't seem to have any transplant shock if I plant in coir.

This brings me back the question; should I put a thin layer of peat moss or compost on top of the growbed... It might prove interesting.

Ya might want to test out the peat or compost on one part of a bed or only one bed and see what happens. I found that 100% worm castings stay too wet and will rot most seeds but when I sink a flower pot of compost into one of the grow beds, It makes starting seeds in that pretty easy.

Yes, I like the GBs in series also...I have the 6 Gbs which take ~10 mins to flood (3 min drain), so a cycle is of one hour duration

so when are you gonna add more GBs Novaris

soon, soon
Actually most efforts for the time being will go into the warm water system and the root vegie beds.

so does using coir or peat mossn in the GB help prevent seeds running away with the water??
ITs one of my questions that came up while reading last night

It does but there are many ways to do that i.e. small piece of tissue, I am mainly using it to hold humidity at the root zone. I was looking at it today and although I have not had problems with root rot I have had one or two test spots that kept the seed too wet. I think you would get the required effect by just mixing a small amount with the gravel instead of a patch of coir.

Agreed Novaris... coir just retains water so well... that IMO... in flood and drain it can be problematical... mixed judiciously with vermiculite/perlite or another media and it may be alright

Certainly has a place in "drip feed" applications... .... although drip feed in AP has its own problems, unless the wtaer is filtered to remove solids...