Am I using too much nitrogen?

[Errol]

I grow a number of plants (tomatoes, cucumbers, capsicum, strawberries, beans, leeks, beetroot and even carrots) in laundry buckets, in the same recirculating greenhouse hydroponic system. The pre-mixed dry nutrient I use is Peters Professional Hydrosol, containing 6N+36P+18K+3Mg and I've also been adding an equal quantity of calcium nitrate (19.6N+15.5Ca) plus a little Fe. I run with an EC reading of 2.0 which keeps the plants generally happy, although the tomato buckets do get an occasional individual nutrient bonus of 3.0 closer to picking time. The local water supply has a ph of around 7.0 which the plants seem to handle well enough (maybe I should adjust this?). You can probably tell from all this that I'm not an 'exact' hydroponic gardener and that I try to grow a range of plants using a 'median' EC and ph.

I've generally achieved quite acceptable results for some seven years now, but one problem needs fixing - the plants produce too much growth and have large root systems. Strawberries in particular are far too leafy, resulting in aphid, then wasp invasions later in the season.

I'm thinking of cutting back the nitrogen to moderate excessive vegetative growth. Can readers suggest whether I'm on the right track or just heading for trouble? Any advice on plant nutrition would be welcome. Thanks.

[Errol]

Sorry, for Hydrosol read 6N+18P+36K+3Mg

[Luches]

Hi Errol,

I am pretty familiar with these kind of maths and procedures as I used to help out a chap with a similar way of making nutes. As for me, I am actually calculating and mixing my own formulas from scratch (raw materials only).

What you are planning is a bit tricky, as you have to settle for actual NPK, (6N+18P+36K+3Mg aren't actual or elemental, but conventional NPK). And you should preferably use (convert all to) PPM as a common unit for all ingredients. I'll take care of that actually, but you'll have to cope with it
If this isn't done properly, all maths tend to be false, - as you try to mix "apples and pears".

If you agree with this role and confirm, I'll try to get it right for you. I am asking for confirmation because unfortunately, I've had some cases lately when people got overwhelmed by the maths or didn't get back to the topic for some unknown reasons. I did all the writing and work for nothing...

Thanks for the understanding!

Cheers,

Luches

[Errol]

Hi Luches,

Thanks for your response. I'm more than happy for you to do some calcs, but I wouldn't want you to spend a lot of trouble on complex formulae or anything since I'm not over keen to buy and mix my own ingredients. One of the reasons I like Hydrosol is because it's already pre mixed! I had wondered about maybe just reducing the calcium nitrate quantity. I'd be glad to hear what you have to say though.

Cheers.

[Luches]

Hi again!

Originally Posted by Errol

I'm more than happy for you to do some calcs, but I wouldn't want you to spend a lot of trouble on complex formulae or anything since I'm not...

Sounds like an agreement to me

Originally Posted by Errol

I had wondered about maybe just reducing the calcium nitrate quantity. I'd be glad to hear what you have to say though.

Well, I was actually talking about modifying (adjusting) your Hydrosol by adding THE RIGHT (adequate) quantity of calcium nitrate and perhaps talk you nicely into adding one more component.
That is what I was talking about when I narrated about helping out a chap who did the same and wasn't sure what the actual outcome was.

To be sure what you have got, and how much calcium nitrate to add, I need to decompose Hydrosol and put it in my spreadsheet.

You'll have the results tomorrow.

One more question here: have you got 3% of actual Mg in Hydrosol or does it say 3 Mg0? And, I suppose there is no Cl at all, as it is a mono-mix?

Later,
Luches

Edit: are you sure about the N and Ca content of the Calcium Nitrate you use. Commercial fertilizer grade Calcium Nitrate (with a purity of 98-99%) actually has 15.6% of N and 18.5% of Ca. It's not that much of a difference, but we want to get it right, - don't we? ;-)

[Errol]

It comes from relying on a dubious memory after kneeling in a dark shed peering at fertiliser formulae, but you're dead right - the correct calcium nitrate mix is nitrate nitrogen 14.5% + ammonium nitrogen 1.0% for a total N of 15.5%. For the calcium, expressed as elemental it is 19.6% and expressed as CaO it's 27.5%. All this according to the bag label and so cleverly transposed by me in my earlier post!

And you're right about the Mg in the Hydrosol too. The mix is:

nitrate nitrogen 6%
phosphorous pentoxide 18%
potassium oxide 36%
magnesium oxide 3%
Trace elements are B, Cu, Fe, Mn, Mo and Zn. No Cl mentioned though.

Hope this helps and thanks for your assistance. I'm more than happy to add one more component, by the way!

Cheers,

Errol

[Luches]

Nice work!
I wasn't exaggerating when I told you that it was kinda tricky... wasn't I?
You'll see it will get even more odd, before we got it finally nailed

Nothing to worry about though, your part is as good as done until I've figured out the final formula and mix.

Later,

Luches

[Luches]

Here you go Errol!

It may look a bit complicated at the first glance, - but it's simple assuming that you anyway mix 0.Xgr/Liter to get your mix. Have a look at it first and tell me if you need supplementary explanations, perhaps different variations, concentrations or mixes (higher total PPM, higher N-content), etc.



PS: to complement Ca up to 180 PPM standard (only in case your tap water is soft and has little Ca, otherwise it may provide 25-50 or more PPM of Ca already): Calcium Chloride - CaCl (ferilizer grade) gives at 0.1gr/liter 28 PPM of Ca - BUT also 64 PPM chloride (1gr/l = 280/640). To be used moderately anyway - especially if your tap water is already rich in chloridel!

Important: NEVER mix calcium nitrate or calcium chloride (salt or concentrate) with magnesium sulphate or Hydrosol (salt or concentrate)!!! It will lead to a chemical reaction and make the whole batch unusable. In case you want to mix concentrate, make two components: A: calcium nitrate + calcium chloride and B: Hydrosol + Magnesium Sulphate. If sufficiently diluted with water as in the nutrient solution, there is no problem at all.

Cheers,
Luches

[Errol]

Hi Luches, thanks for doing your calcs so quickly. If I'm reading them correctly, it seems that you think the mix could certainly do with some magnesium sulphate - and that the concentration should be 7gms/litre Hydrosol, 7gm/litre calcium nitrate, 4gms/litre MgSO4 and possibly 1 gm/litre of calcium chloride? Am I close or on the wrong tram altogether? Our tap water is soft and not heavily chlorinated, by the way.

Wouldn't that imply that aside from adding a sizeable amount of MgSO4 and a little CaCl2 to my nutrient, I would keep on doing what I am now ie using equal quantities of Hydrosol and calcium nitrate?

This would be at odds with my thinking at the moment ie that the level of N in the 50/50 mix is possibly too high, causing too much vegetative growth.

What are your thoughts on mixes referred to in the following link?

MIXHYDRONUTRIENTS

Many thanks again for your efforts and interest.

Cheers,

Errol

[Luches]

Hi again - you're welcome!

Originally Posted by Errol

If I'm reading them correctly, it seems that you think the mix could certainly do with some magnesium sulphate - and that the concentration should be 7gms/litre Hydrosol, 7gm/litre calcium nitrate, 4gms/litre MgSO4 and possibly 1 gm/litre of calcium chloride? Am I close or on the wrong tram altogether?

Well, I bet you got confused with the decimals. It's 0.7 (zero point seven) gram per liter (litre), 0.7 and 0.4 Mg. (obviously only 0.1g CaCl/liter)
Attention: 7 gram per liter of both would probably kill your plants over night.

Originally Posted by Errol

I would keep on doing what I am now ie using equal quantities of Hydrosol and calcium nitrate?

Indeed equal quantities of both in the present example of a mix.

Originally Posted by Errol

This would be at odds with my thinking at the moment ie that the level of N in the 50/50 mix is possibly too high, causing too much vegetative growth.

But equal quantities only determines the proportion of N vs. P and K, it doesn't say if the N-content is too high or not. It actually depends on how much Calcium Nitrate is used per Liter. I bet you were using more than 0.7 g/l, were you...?

Originally Posted by Errol

What are your thoughts on mixes referred to in the following link?

Well, well.... I haven't read them trough and had no time to check on them in detail, but I've found some things I'd not necessarily agree with straight away. They seem to lean on Dr. Resh a lot and (all due respect) he is going pretty heavy duty (avoiding to say aggressive) on feeding. On the other hand, they are playing "cheap" with Mg and Sulfur. While the standard content of Mg is around 50, and if using Magnesium sulfate, Sulfur should- actually will be around 80 PPM anyway. Which is just fine because most plants require that much of later elements. Dr. Cooper and Hoagland formulas are indeed the basics of all formulas, but also dinosaurs and perhaps a little outdated. But then again it's damn hard to find good and reliable sources for nutrient formulas that are up to date.

If I understood your goal and concept right, you are growing various plants and not mainly leafy vegetables. In that case I recommend a N-content not exceeding 150-170 PPM of N. Lettuce would be happier with some 200-220 PPM, but tomatoes, peppers (as well as cucumbers) and most nightshade wouldn't really like that.

210 PPM of K as an outcome in my example is not really high (not good enough actually), - for tomatoes 280 and plus would be better. But with Hydrosol there are clear limits of increasing K content, without exceeding P limits (50-60 PPM). Well here one could push a little and increase to 0.8-0.9 gram/liter of Hydrosol without doing amy harm. Even somewhat further if more K is badly required (high yield of tomatoes, capsicum).

PS: the problem with Calcium Nitrate is generally that you need to add sufficiently to cover Ca needs (140-180 PPM), and obviously go too high with N. With a small part of CaCl you can cover Calcium needs, without exceeding N-content.

Hope all this is intelligible and helpful.

Cheers,
Luches