Is having run-off necessary at all in soilless growing?

In this video, I explain the differences between growing with or without run-off. I go through all the reasons why a grower might choose to irrigate with ample run-off and some of the advantages and trade-offs when choosing to run growing operations with zero-runoff.
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[@slay3rjp]

A no run off approach is also difficult to use with a raw water that has sodium and clorides even in low quantities. They get accumulated very fast.

[@ScienceinHydroponics]

Yes, that's a good point!

[@giskio]

5:59 Cat approves! 😂 Thanks for this lesson Prof👍

[@ScienceinHydroponics]

Thanks a lot for commenting! Hahaha, the cat rarely approves!

[@CannabinaTV]

Thansk for all the knowlegde professor, awesome content, coudnt find it anywhere else. I even tried GPT, but here i found all the answers for my grow, thanks. I'm Agronomist thanks.

[@ScienceinHydroponics]

Always glad to hear a fellow scientist finds my content useful!

[@abdullahshereiqi]

You are doing Great job

[@ScienceinHydroponics]

Thank you so much 😀

[@scottmarshall6766]

I've done everything from a full hydro DWC recirc system with water chiller in a climate controlled tent to outdoor in NY pots and homemade wicking boxes. Have clones growing side by side, and have been learning that the plants really need constant attention as their needs vary based on stage of life. lighting, temperature, humidity and plant type. Keeping a runoff around 900 (700 scale) can be too high for some plants in some circumstances, but some plants will love 1250. I try to keep the PH moving between 6.0 and 7.0, trying to average around 6.2 or 6.3, that "opens the window", optimizing uptake on a cyclic basis for all the nutrient. It's looking like shifting EC levels and PH to mimic mother natures changing conditions seems to work the best, and experience in recognizing deficiencies and excesses is really important to maximizing plant health. The nice thing about the cycle method is that if condition aren't ideal, they won't last a very long time, thus not harming the plant long term. You also get to see how the plants respond to the conditions and that helps you learn what plants need what. The more I grow all plants, the more I can tell what moves to make. Right now I'm liking the wicking boxes where I monitor tank PH and only water to overflow (runoff) when the tank PPM gets too high or the PH goes out of bounds. Thanks for your great analysis of the two methods. Subbed!

[@ScienceinHydroponics]

Thanks for writing and sharing your experience!

[@ineedcbsi]

Your videos are great! Thanks 😊

[@ScienceinHydroponics]

Glad you like them! Thanks for commenting!

[@PRAR1966]

Very grateful for this, I was wondering which compounds were likely to build up. I tend to over water and check runoff once every 8~9 days or if there's any plant health issue. As you say there's a lot of testing and filtering/centrifuge work on samples - I love applied sciences ❣

[@ScienceinHydroponics]

Thanks for your comment, I am glad you enjoyed it!

[@Sahity]

First of all thank you a lot for your technical videos. They answered important things that I tried to answer myself googling a lot rsrs. So, I do have a recirculating deep water culture system (RDWC) with water tubs and styroform on top… I am growing ornamental aquatic plants (I am a aquarist and its a market niche for it). I have difficult with nutrient levels management in the system (accumulation, incompatibilities, deficiencies, etc.), so I am thinking in running it with some nutrient in solution and some others (that tend to accumulate as you teached in the videos) like Ca, Mg, S, Fe and micros applied by foliar spray feeding (with some DIY formulation I still researching and testing for). What do you suggest? All the water tubs are connected by the bottom to each other and I will put fish and invertebrates in them to benefit for the unused water body… so I running it at lower TDS 150-250ppm stable.

[@ScienceinHydroponics]

Thanks for commenting. Your problem requires a deeper level of analysis. If you want my help solving your issues please consider booking an hour of consulting through my website (scienceinhydroponics.com/book-now).

[@Runboy7426]

Thank you for another fantastic and informative video @Science in Hydroponics ! Would there be any reason that in a system like this where the plants are watered frequently with solution that you could not provide the full spectrum of micro nutrients as Sulphates and eliminate edta chelates?

[@ScienceinHydroponics]

Thanks for commenting! The media pH can get quite high in a system like this and this will make iron and manganese precipitate as oxides and phosphates. Since managing the pH near the root zone is really hard in a system like this, using only sulfates is often a suboptimal choice.

[@Topsrite]

Good stuff here, thanks! My thing would be it’s unrealistic for 1-2 plants and the complexity of monitoring , designing nutrients and other issues the average home enthusiast will likely have to stay with the drain to waste program. Maybe in time this will change a bit with better technology, will see what happens. Good points and excellent video, again thanks.

[@ScienceinHydroponics]

Great point!

[@radenex854]

I hit really solid numbers on a variety of crops using jacks 321 at a 2.0 ex with 0 run off using blumats

[@a-gradehydroponics6508]

I think it is different per Crop. Growing Chilli/tomato for example RTW (run to waste) isn't necessary, if it is Cannabis then RTW makes sense as the EC requirements are much lower and thus can accumulate much faster, so in short regardless of substrate it depends on the crop.

[@ScienceinHydroponics]

Thanks for commenting! You're right about run to waste not being the best choice depending on your crop. In fact, you absolutely never need to do "run to waste", having a recirculating hydroponic system is always a possibility and a much more efficient use of fertilizer for any yield crop. However, you can certainly grow any crop using a "run to waste" method. The video does not try to cover when it is preferable, just the difference between doing it with or without runoff whenever it is used. Also note, the EC requirements of cannabis can be higher than those of tomatoes, depending on how the plant is grown.

[@speadskater]

Is this assuming organic media (Coco/peat/rice hulls), or is this valid for media like Perlite or Rockwool?

[@ScienceinHydroponics]

Most of the comments here are in general for all soilless media, however, things like nutrient accumulation are significantly more pronounced in media like coco, while media like peat have other issues, such as the decomposition of the peat and the size of the lime buffer included within the substrate. While there might be particular interactions characteristic of each media, the general points should apply for all cases where you have a medium that is watered with a nutrient solution.

[@stefano5080]

In general, what can be considered acceptable EC and pH values of the run-off? For example I have a young lemon plant into the rockwool and starting from ph 6 and EC 2mS/cm the run-off has ph 7 and Ec 2.5mS/cm (I water it every 2 days) . Are these values acceptable? I use osmotic water with 80 ppm of hco3 without adding acids.

[@ScienceinHydroponics]

Thanks for commenting! It depends on the plant you are growing. In your case, the runoff pH should remain in the 6-6.5 region, a 7 runoff is too high and requires correction. The EC at 2.5 mS/cm is ok, provided you can maintain it below 3mS/cm there shouldn't be a problem.

[@stefano5080]

@@ScienceinHydroponics Thanks! To stabilize the pH, would it be better to raise the bicarbonates to 150ppm for example and then lower the final pH with phosphoric acid? Because it seems strange to me to increase bicarbonates and then neutralize them with an acid (even if it has a buffering effect).

[@ScienceinHydroponics]

@@stefano5080 There are multiple options for managing the pH. Increasing bicarbonates is an option, but you should only do this if you account for the nutrient contribution of the acid needed to neutralize them., it is also not very efficient. There are however, better ways to manage this, I will put these in a future video.

[@_hazplants]

I think I have little problem in understanding the uptake of Mn. In every commercially available fertilizer I checked the lables of, Mn is concentrated several hundret times lower than N, K and P, ten times lower than Fe and Zn. So I am having a hard time to explain to myself, how Mn is uptaken actively and easier than P. Does it mean, the plant would take up more Mn than P, if it was fed Mn in that concentration, regardless of its need for Mn?

[@ScienceinHydroponics]

Thanks for commenting. I'll try to explain things better. It doesn't mean it is taken up in a larger amount in absolute terms, but proportionately faster. So while - as a hypothetical example - a plant might take 2 days to uptake 50% of the available P, it might take only 1 day to uptake 50% of the available Mn. In absolute terms the total amount of Mn uptaken will likely be 50-100x less than P, but it was taken proportionately faster, given the initial concentrations. If you fed the plant Mn in the same concentration as P, it would certainly be toxic and kill the plant. The plant won't know to stop taking it up.

[@_hazplants]

@@ScienceinHydroponics Thank you Daniel, for this great explanation. 👍🏻

[@brettmcgilligan5243]

Can you water to much tho if youre getting run off everyday

[@ScienceinHydroponics]

Depends. If you have enough dryback everyday, there is no problem. Runoff doesn't cause the media to become wetter. Once it is saturated it cannot become more wet, so you could do a lot of runoff and the plant will experience a similar condition to just being watered to field capacity.

[@wilsonmatos6734]

So, why equipment is used to test? Gas spectrometry?

[@ScienceinHydroponics]

Depends what you want to test. To test the elemental concentrations of the nutrients in the runoff you would use ICP-AES.

[@djefferson5669]

Run off benefits the nutrient companies selling their gear more then the grower using it.

[@ScienceinHydroponics]

It certainly does!