Fertigation

[Buckowens]

Who is running a fertigation system?
Any input on the injectors? Bule lab Vs dosatron vs dramm vs netafim?
Any hindsight considerations when applying at large scale grows?
Dry vs Liquid ferts?
Best controller for the $$?
I'm getting a prototype Bluelab seven pump injector and a guardian acid injector. was hoping someone would have a little info from their experience to share.

 

[queequeg152]

Ive been building and running fertigation systems for like... 3 years if you count fucking around indoors with HPA.

the key is simplicity. i know this is super hackneyed and shitty disingenuous sounding thing to say, but in this case this suggestion is merited.

you dont actually need fertilizer or acid injection what so ever. you can get by just fine without any of this actually. you just need to periodically refill the reservoire. add a new dose of fertilizers, and ph balance if required.

i refer to this method as batch wise fertigation.

regarding equipment. a simple lawn irrigation controller will work fine. you do not need retardedly overpriced crap from some disgusting hydro oriented marketing company.

you need a proper pump as well. you need something that can produce around 40-60 psi. for anything up to 5-6gpm i HIGHLY reccomend a simple diaphragm pump.

5-6gpm could run thousands of plants if you maximize the duty cycle with a captive air accumulator.

beyond this, a multistage centrifugal or rotary vane will be required.

regarding irrigation emitters. i HIGHLY reccomend netafim. i love their spray stakes... they have been my favorite emitter period. they are however not suited for rockwool slabs... for my slabs i use netafim stake assemblies. .5 and 1gph.

fertigation scales far far far better than any other growing system outside of just plain field agriculture.

 

[queequeg152]

ill elaborate on the above because im tired of studying.

the reason why i always suggest batch wise with manual additions is because the jump from this method, to automated batch wise is a substantial one.

the jump from automated batch wise to a full online fertilizer injection with mixing site is substantial, but not terribly so. not as complicated as the above jump.

automated batch wise is what i am currently invested in... being that it scales well up too single digit hundreds of gallons. no i have not built the automated set up. i simply am too poor to afford the myriad parts ill discuss below.

not only do you need the obvious equipment such as injection pumps, conductivity and ph analyzers, and float switches and sensors.... but you need a substantial amount of ancillary equipment to protect you sensors and recirculation pump. its a substantial systems engineering task we are talking about here.

you want a flow sensor primarily. this ensures that you are not dumping acid or fertilizer concentrate into a system that is not recirculating to the sensors.
a flow switch will work fine, however an actual flow sensor is preferable being that you will able to monitor filter fouling and issues such as scaling and fouling of strainers etc.

i am of the opinion that... for low flow systems, a thermal conductivity flow sensor is ideal here. they are relatively cheap, and very difficult to foul... yea i searched far and wide for a paddle switch that would operate reliably at the low flows that i designed for(sub 5 gpm at 10psi). i am working with a household recirculation pump. a grundfos ups 15-58 with a tamas plastic pump head.

a mag sensor will work even better, however ive yet to see a mag sensor that costs under 500 bucks. gf signet makes a very good mag sensor with/without a digitial back lighted dot matrix read out... if you have the cash, go for it. just be aware that they are sensitive to changes in conductivity, and may require calibrations should you drastically alter your conductivity.

a simple shuttle flow switch will work, so will a paddle switch, provided you maintain them, and keep them free of excess scale.

i also highly highly recommend that a rota meter be involved in your sensor recirculation loop. another rotameter on your non sensor loop is also advisable.

i also suggest that you invest in a back pressure regulator as a means to adjust flow through the sensor loop. ball valves are just not linear what so ever, and very ****y to adjust.
i suppose you could get an indexable v notch ball valve, but such parts are uncommon in my experience, and not available outside of a special order.

you need to provide your conductivity and ph sensor with a constant, relatively bubble free stream of water to ensure good operation. i am of the opinion that your sensor flow assembly should include an air bleed valve. there are a number of such valves available for 20 bucks or so-as replacement parts for pool filter equipment.

i also highly recommend that you buy analyzer equipment with the ability to adjust hysteresis parameters. and maximum injection times. a large system with low flow circulation will require many minutes to equilibration before the analyzers command another injection, where as a small one will see equilibrium very rapidly.

automated batch wise fertigation is my primary focus... but id be happy to discuss various automated online injection methods should any one have questions... they basically fall into one of two groups... pulsed solenoids... or valve actuators on linear or proportional valves. pulsed solenoids tends to be more popular, but often requires a mixing tank.

both methods can operate with dosing pumps, or mazzei injectors... its just a matter of scale. both methods will require most of the equipment noted above, with the flow sensor being necessary and the switch being insufficient. flow rate instrumentation is necessary for metering.