Digital NPK meter for hydroponics system

[kiakotkotkot]

I can't find an NPK sensor/meter on the internet.

Does anyone know if there is a DIY NPK meter or just N, P or K sensor/meter?

We're about to do a project that could lessen the nutrients from the lake using a hydroponics system

and once the measured NPK decreased from its initial state, then the remaining water from the container will pumped back into the lake.

 

[cowboybob]

Don't know of one. Not likely there is one. Trying to pick out the three elements with a single sensor would be enormously difficult (short of using a spectrum analyzer).

I've used the pH of algal blooms to get a relative level of NPK. I can explain in more detail if you like.

Just out of curiosity, how are you planning on reducing the NPK levels?

 

[kiakotkotkot]

That would be great. Thank you cowboybob.

Actually, what we're trying to do is to have a denitrification process with the use of hydroponics sytem. The plants would automatically absorb the nutrients cming from the lake.

 

[cowboybob]

Maybe not a solution for you, perhaps, but back when (mid-90s) we were growing shrimp (commercially) in large, outdoor saltwater ponds, we had to pay very close attention to alga blooms (due to their huge effect on DO). We also would have liked an NPK monitoring device, but no economical, in-situ solution existed. And, of course, the problem was aggravated as the shrimp grew larger.

So, to do this, we closely monitored pond water pH since the nutrient loads (from excess food and shrimp waste) made the algae very happy and they predictably "bloomed" vigorously. We wanted some, of course, since they were daylight DO producers (and pushed the pH up). But too much was disastrous (because at night they were voracious DO users and pushed the pH down).

Over time, it worked well enough that we could reasonably predict, from the pH levels (plus time of day), a pending bloom "crash" and crank up extra aeration (and water exchange to a limited degree) in anticipation of them. Of course, we could also simply look at the pond water color and color density. But the blooms could, literally, explode overnight and we needed to know beforehand.

My point is that the state and efficacy of the nutrient uptake by the algae (judging by the pH and intermittent chemical analysis as proof) gave us an idea of the relative reduction of NPK levels in the water.

It was a crude system, largely predicated on empirical data, very large nutrient loads, hyper shrimp concentrations (300/m[SUP]2[/SUP]) and essentially fixed water exchange rates (15%/day).

Presumably yours is a freshwater system. This ought not make that big a difference. Scale may be an issue as well: our pond's surface areas were no less than 2, and up to 7, acres.

But pH is an excellent predictive water condition (and hence, biological processes) value if the processes going on can overcome the normal buffering capabilities of the water in which these processes are happening.

 

[JL Anacleto]

Hello. Is there a relative relation between pH level to determine the level of N P K? We are doing some research to lessen overuse of fertilizers. Thank u

 

[cowboybob]

Welcome to ETO, JL!

As a relative indication, yes. See: https://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar10f_ph.html

In essence, high algal production = high pH levels = assumed high NPK levels. All of which is extremely dynamic. The obverse (low pH = low NPK levels) is not reliable since you're merely observing an effect of the algal activity.

You'd have to cross reference actual instantaneous NPK levels (by chemical tests) vs. correlated pH levels observed, all of which will be influenced by algal growth levels and somewhat augmented by DO levels. And a cloudy day would throw it off track.

Not the most precise method, but the resulting water chemistry data trends worked well enough for our commercial scale shrimp production situations.

 

[Tony Stewart]

https://www.atlas-scientific.com/kits.html