Things I have learnt since starting hybrid systems.

[Kobus Jooste]

The most important thing is to abandon the single pump lay-out if you want to have media beds and rafts / NFT in a compact space.  In the past, I could drain gravel beds into rafts and then to a sump full of netting.  This kept the water in the system clear and the roots in the rafts looking good.  My new lay-out is NFT above and raft at the same height as the media beds, thus the single supply line I have been using is really too dirty for NFT.  Option 1 is in line filters, and option 2 is small secondary pumps for the NFT.  I'm going for the latter.  A high head low wattage pump will be tossed into the sump as soon as I have installed a internal configuration that settles the solids out prior to it getting to the pump.

 

The second issue I am picking up is that hybrid systems tend to have "just enough" gravel rather than surplus, which means that fines and even intermediate solids seem to stay in the system's water.  I picked this up with the sump retro-fit.  I therefore think that if you are going to run a stacked design with raised beds and lots of media-less culture, you need to find ways to settle out fines the way it is done in raft-type systems, but without discarding it.  We are therefore talking in the direction of mineralization / digestion sections in our AP systems, but not yet solids removal.

[Kobus Jooste]

I had a surface spray grid before, but never tried to cut the plant roots back at all.  That bed also got clogged after a year.  In your estimate, how much root volume do you remove at a time?

Harold Sukhbir said:

 Kobus said :"1) No watter what you do for inflow, they will eventually be clogged by root action if you do long-terms crops.  Perhaps the concept of leaving a bed alone foe a prolonged period of time is not a simple as it seems.  Having top inflows over the gravel develop issues.  My internal inflows are clogged after a year of operation.  Either way, water flow, solids build-up and roots seem to get complicated after about a year of operation."

Harold said : I have, in one bed, a drip grid array of pipe covering about 75% of the surface area, which I've cleaned only one time, and i now realize i probably will clean, at this rate, once or twice/yr. This spreads the inflow widely enough to limit clogging. The out pipe is a vertical 3/4" pipe, with many holes along it's one foot length, placed at one end of the bed. When i notice the flow rate from this pipe decreasing at the terminal end( FT ), I push a sharp thin metal blade through the media, along the vertical OD of the pipe, severing any roots in the process. I do this about one/mth, and this takes, all but 30 seconds to accomplish.

This is a constant drip bed, but there is no reason why the drip cannot be used in combination with an F&D bed. It is relatively simple to maintain a siphon with clogging issues.

 

Great point with the vine crop, and even if water supply is not a huge concern, it will require people with smaller systems to "micro manage" AP operations with very time consuming water top ups.(For my first system, daily top ups)

[Kobus Jooste]

nice to be back.  Crazy busy but hopefully it will get better now

Sahib Punjabi said:

Nice to see you back Kobus...looks like came up for air :-)

 

I fortunately have not experienced this issue as yet given my gravel beds are only 7 or 8 months old. I did notice a significant root buildup in one that I had to move recently. If this is true that you need to unclog these gravel beds periodically, this kind of defeats the establishment of a nice natural echo-system. I do like Harolds idea of running "a sharp thin metal blade through the media ...severing any roots". This would leave the nutrients in the system and leave the echo-system largely undisturbed.

 

You are also correct about the continued re-visit to old references. There is so much that went over my mind initially that now makes sense as well as reminds me of what I forgot :-)

 

God bless, 

[Harold Sukhbir]

Kobus said :"I had a surface spray grid before, but never tried to cut the plant roots back at all.  That bed also got clogged after a year.  In your estimate, how much root volume do you remove at a time?"

 

Harold said : With pump in FT the solids are fine( some use gravity from FT and then pump after GB). Slowing down flow rate is also a factor, a bed with 4 gal/min will clog in 6 months as opposed to one at 2 gal/min( In ideal terms). As for removing the roots around the vertical pipe, whatever is severed from around the pipe diameter follows the pipe route to the FT where the fish makes a meal of it. I do this every month to avoid any build up in the out flow, as these are the early roots it's difficult for me to give a root volume figure.

 

To be realistic Kobus, you might want to also consider, as a difference from most other AP, your plant density and ratios, are are very high.

[Kobus Jooste]

I've been wanting to add more to the system in terms of growth space.  I have found that I can achieve great densities, which was the original test aim, but that I cannot sustain these optimally.  not everything stays happy all the time thus in effect, the beds are not used optimally.  What I wanted to know was if the typically African request - how much can you squeeze out of a small system - can be achieved without complication.  After a year, I want to conclude that a heavily stocked, rainwater filled compact system is a difficult beast at best and not the kind of thing that you let loose on an unsuspecting individual.  I'm now looking at doubling the footprint of the system in order to have a more placid unit. I'll keep the original system, but add a large amount of NFT on the flanks while reducing the plant volume in the gravel accordingly.  I need to find a place to work in a second IBR tank to make it all work, but am looking forward to making all the changes over the coming winter.

 

I'm glad that I built this one and that it worked well, but it is not going to be the type of thing that you hand to an aid agency.

Harold Sukhbir said:

Kobus said :"I had a surface spray grid before, but never tried to cut the plant roots back at all.  That bed also got clogged after a year.  In your estimate, how much root volume do you remove at a time?"

 

Harold said : With pump in FT the solids are fine( some use gravity from FT and then pump after GB). Slowing down flow rate is also a factor, a bed with 4 gal/min will clog in 6 months as opposed to one at 2 gal/min( In ideal terms). As for removing the roots around the vertical pipe, whatever is severed from around the pipe diameter follows the pipe route to the FT where the fish makes a meal of it. I do this every month to avoid any build up in the out flow, as these are the early roots it's difficult for me to give a root volume figure.

 

To be realistic Kobus, you might want to also consider, as a difference from most other AP, your plant density and ratios, are are very high.

[Kobus Jooste]

Here is another one from my recent musings (standing and staring at the unit and wondering what can be better).  One of the goals I had setting out with this system was to see how much production can be crammed into a specific space.  To date, that space was dominated by gravel beds.  I have come to the conclusion that trying to do too much here was a design fault.  I think that the gravel beds, playing such an important role in the functioning of the system, should be lightly planted, while high density planting should be reserved for raft, tower or NFT.  I have managed great productive bursts from the gravel, but think that its role as the key bio-filtration, mineralization and nitrification sites in the system need to come first.

[Harold Sukhbir]

Hi Kobus,

I think high plant density in GB's is practical providing the operator is aware beforehand of his need for regular plant rotation.He should not have the idea that he can plant and let it just sit indefinitely.Knowing the constraints of having roots sitting in beds will lead to clogging issues in the long term(example tomatoes) after say 4 months he can replace with new seedlings that are mature enough that it won't be long for them to fruit.In this way it's possible to get higher yields from GB's and still maximize their nitrification capability.

[Kobus Jooste]

Harold: I think we are sying roughly the same thing, but may have some different pictures in our mind of what a heavily stocked GB looks like  

Harold Sukhbir said:

Hi Kobus,

I think high plant density in GB's is practical providing the operator is aware beforehand of his need for regular plant rotation.He should not have the idea that he can plant and let it just sit indefinitely.Knowing the constraints of having roots sitting in beds will lead to clogging issues in the long term(example tomatoes) after say 4 months he can replace with new seedlings that are mature enough that it won't be long for them to fruit.In this way it's possible to get higher yields from GB's and still maximize their nitrification capability.

[Harold Sukhbir]

Hi Kobus,

I know exactly what you mean(just look at your pics!).Nevertheless this is good info for people with newer systems.Initially i had the impression that i would plant it and forget about it but now i realize how important timely rotation is for system balance. I didn't pick this up from my forums so I'm learning from actual experience as i go along.

[Kobus Jooste]

Actual experience is extremely useful!! Sharing it here is even better.  I'm working up the nerve to tackle the next question - productivity.  I've tried before, but people are a little cautious.  I think, looking back at some of the promo stuff I have seen before, that many people in the past set up a system, allowed nutrient levels to build up nicely, and then they planted it so full of stuff that it puts my GB's to shame.  I have often wondered "how does that system look like right now?".  I'm sure it grew like mad and then it was clogged beds and roots all over the place.  Hence the reference to rinsing beds every 6 - 12 months.  This implies ripping everything out on relatively short rotation and then almost starting over again, while the promo says you do almost nothing and the crops just keep coming.  I think the manual for a "balanced" system that does not work on a feast and famine rationale but on sustained production and stable operations is still being written - in forums like these.

[Harold Sukhbir]

Hi Kobus,

Yea, still being written by each one of us! I was also looking at this question of productivity.Back yard AP is basically a mix and match of vegetation, depending on the user preference, which is a great introduction to AP. I think mono-culture(and we might be crossing into Commercial growing) can be used to gather a more accurate picture here. This way we can document all the AP ratios like, nutrient levels,fish densities,plant densities,plant spacing,plant rotation,aeration,filtration, shading,lighting,media and media depth,etc etc. Closer to maximum AP.

[Kobus Jooste]

I have been a little quiet of late.  I have many excuses:

1) It is winter.  I hate winter. 

2) I moved my fish out of the mixed system into the research system, thus the system is roughly running on fumes and nothing is growing really fast

3) I am contemplating many design changes, which requires a lot of tinkering and adjusting on the lay-out of the "mother ship"

4) I'm lazy

 

That said, here are some more ideas:

 

First up, I think, reluctantly, it is time to give up on the idea that I can run my mixed system in its current configuration on just one pump.  I want to have "clean" and "dirty" water, and it is not possible to have both coming out of the same pump line.  I have opted for another 60 Watt pump in the "clean" sump in order to lift the water from there up to the roof of the system.  From there, I will have a few towers and sand beds and NFT and stuff added, because of lesson number two coming up.

 

Lesson number two is that neither UVI or Dr. Lennard's rules seem to comply with my observations on how my mixed design system is behaving.  I had the fish at 20 kg's per 1000 liters, and the gravel beds just about spot on, but still the nutrients in the system remained too high, even with a monster passion fruit in there.  My new approach is going to be to follow my "core" and "periphery" philosophy with an adventurous spirit.  The "core" will be the fish and gravel beds.  I will reduce the fish load slightly and keep the gravel beds as they are, but this season they will be sparsely planted (apart from the one with said passion fruit in it).  Tomatoes may just get banished to the soil garden for a bit.  The "periphery" will constitute the season's quest for answers - basically how many "plant spots" can be added in the form of towers or NFT before the system runs out of nutrients.  I'm still trying to reach my quest of 200 plants.

 

This is what I will be adding.  Picture to follow:

1) Towers over the FT in the compact tower design reported on earlier.  I have strawberries in the trial unit doing well, thus I think the light is good enough over there.  I plan 3 x 10 plant towers for strawberries there.  The towers will drain into the two red beds below.  The duckweed bed will get gravel to make a second "wet" bed for stuff such as cress.

 

2) 4 x newly designed compact towers (8 plants per tower in 50 cm of 110 mm pipe) above the sand bed.  I designed these for a nursery friend as soil based towers with 12 plants in, but with the way the light falls on that section of the greenhouse, there will be a problem lighting the whole tower thus there will be only 8 plants.  These have a core pipe drilled as a pray bar with the outer 110 mm pipe holding the plants.  The idea is to fill the space between the two pipes with something like coir - cheap and light and with enough wicking capacity to keep the plant roots wet for the 30 - 45 minute timer intervals.  The towers will drain into the sand bed currently being tested.

 

This will give me just over 50 new plant spots in the system.  I have pump capacity for more expansion, but am still scratching my head as to how exactly I will be achieving this.  The spare capacity is currently on the "dirty" pump side.  One option is to swap the pumps around, putting the stronger one of the two in the clean water sump and thus creating the redundancy in the clear line.  This will be the cheaper option, as the alternative is to put some of the dirty water through a swirl filter before using it for further nft.  I want to put NFT "wrap arounds" like I did inside the greenhouse on the outside wall as well.  Each line will be 6 meters.  That is a lot of plants.  At this point in time I see the need for bringing the fish capacity up to 20 kg's again, but I'll only do that once all the changes are made.

 

The last lesson for now is in terms of pump capacity.  With our electricity suppliers rabidly pushing up prices, I have been trying tio find the smallest possible pump for the purpose.  That just does not work.  A little (not putting in a pool pump) bit of redundant lift or liters per hour just cannot be done away with.  You can tone down a stronger pump but if the thing is not getting there, there is nothing you can do!

[Sahib Punjabi]

Welcome back from hibernation :-)

Sounds interesting...looking forward to see the pictures.

God bless.

 

Kobus Jooste said:

I have been a little quiet of late.  I have many excuses:

1) It is winter.  I hate winter. 

2) I moved my fish out of the mixed system into the research system, thus the system is roughly running on fumes and nothing is growing really fast

3) I am contemplating many design changes, which requires a lot of tinkering and adjusting on the lay-out of the "mother ship"

4) I'm lazy

 

That said, here are some more ideas:

 

First up, I think, reluctantly, it is time to give up on the idea that I can run my mixed system in its current configuration on just one pump.  I want to have "clean" and "dirty" water, and it is not possible to have both coming out of the same pump line.  I have opted for another 60 Watt pump in the "clean" sump in order to lift the water from there up to the roof of the system.  From there, I will have a few towers and sand beds and NFT and stuff added, because of lesson number two coming up.

 

Lesson number two is that neither UVI or Dr. Lennard's rules seem to comply with my observations on how my mixed design system is behaving.  I had the fish at 20 kg's per 1000 liters, and the gravel beds just about spot on, but still the nutrients in the system remained too high, even with a monster passion fruit in there.  My new approach is going to be to follow my "core" and "periphery" philosophy with an adventurous spirit.  The "core" will be the fish and gravel beds.  I will reduce the fish load slightly and keep the gravel beds as they are, but this season they will be sparsely planted (apart from the one with said passion fruit in it).  Tomatoes may just get banished to the soil garden for a bit.  The "periphery" will constitute the season's quest for answers - basically how many "plant spots" can be added in the form of towers or NFT before the system runs out of nutrients.  I'm still trying to reach my quest of 200 plants.

 

This is what I will be adding.  Picture to follow:

1) Towers over the FT in the compact tower design reported on earlier.  I have strawberries in the trial unit doing well, thus I think the light is good enough over there.  I plan 3 x 10 plant towers for strawberries there.  The towers will drain into the two red beds below.  The duckweed bed will get gravel to make a second "wet" bed for stuff such as cress.

 

2) 4 x newly designed compact towers (8 plants per tower in 50 cm of 110 mm pipe) above the sand bed.  I designed these for a nursery friend as soil based towers with 12 plants in, but with the way the light falls on that section of the greenhouse, there will be a problem lighting the whole tower thus there will be only 8 plants.  These have a core pipe drilled as a pray bar with the outer 110 mm pipe holding the plants.  The idea is to fill the space between the two pipes with something like coir - cheap and light and with enough wicking capacity to keep the plant roots wet for the 30 - 45 minute timer intervals.  The towers will drain into the sand bed currently being tested.

 

This will give me just over 50 new plant spots in the system.  I have pump capacity for more expansion, but am still scratching my head as to how exactly I will be achieving this.  The spare capacity is currently on the "dirty" pump side.  One option is to swap the pumps around, putting the stronger one of the two in the clean water sump and thus creating the redundancy in the clear line.  This will be the cheaper option, as the alternative is to put some of the dirty water through a swirl filter before using it for further nft.  I want to put NFT "wrap arounds" like I did inside the greenhouse on the outside wall as well.  Each line will be 6 meters.  That is a lot of plants.  At this point in time I see the need for bringing the fish capacity up to 20 kg's again, but I'll only do that once all the changes are made.

 

The last lesson for now is in terms of pump capacity.  With our electricity suppliers rabidly pushing up prices, I have been trying tio find the smallest possible pump for the purpose.  That just does not work.  A little (not putting in a pool pump) bit of redundant lift or liters per hour just cannot be done away with.  You can tone down a stronger pump but if the thing is not getting there, there is nothing you can do!