Backyard Aquaponics
A place to discuss aquaponics

Wondering if there are any fruit bearing plants that actually grow in high nitrate water. Nitrates are extremely high (+120ppm) and I'm still catching up and planting more leafy greens in my water every day. It'll be a while before I can grow any tomatoes or peppers but are there no fruits I can try?

Tomatoes grow happily in high nitrates. They are supposed to fruit more in lower nitrates, but they'll still grow happily. They also suck up lots of nitrates, so they'll lower them for you.

I'd recommend just trying things out, rather than worrying too much about what will and won't work.

Yeah, a lot of fruiting things will grow happily in high nitrates as long as you also have the other nutrients they require too. Give it a go - the worst that's going to happen is that they use up nitrates for you but don't do much else!

+1 to Colum and Mel, mainly need to make sure they have other trace elements and particularly potassium.
(most likely need to go with sulphate of potash etc). A small amount of blood&bone on the grow bed can help.

Dont put things in the FT water.
Feed direct to bed or foliar feed trace elements and that will help.

In your case you must be **very careful** about how you add the elements - make sure anything you add does not have nitrogen in it. ie. seaweed extract - make sure it does not have any N. (fish emulsion, urea etc).


try few varieties of tomatoes - worse case is they will be nice and bushy and use up your nitrates as Colum & Mel say.

If you have high nitrates and you plant more densely they should by rights bring the levels down anyways.

My systems always ran fairly high nitrates and there wasn't much that didn't do well. Things like corn, tommies, peppers, pumpkin, squash, melons etc that are big heavy duty plants will give the nitrates a nudge.

Yes, I see that but I'm trying to see if there are fruits that DO produce in high nitrates. I don't mean do well, I mean actually produce fruit. Looks like the answer is no

It sounds like you need to add some plants that are heavy feeders to get the system nitrates low - when it becomes a low nitrate system it's a different ballgame. You could also play with the nutrient ratios and that might give you some success even if the nitrate levels are high.

actually the answer is yes - if you pay attention to what the plants need to balance the nitrates and potential lockout. But you cant just expect them to start sprouting fruit without some extra effort addressing things that they need to trigger the flowering and fruiting cycles.

all of the above posts say that (particularly Colum) *but* all have disclaimer that in the worst case is you get leaves and nitrate use. Best case if managed properly is you will get tomatoes as well.
simply that working with really high nitrates is not ideal (<100ppm no problems IMO - I grow at 80ppm)

BTW - there are other things at play here too such as pH, temps, water temp, iron, calcium load etc.

tends to be lots of discussion all over the forum covering many of these - main variables are the combinations of system and system chemistry with the individual being the #1 factor.

As has already been said Toms will do fine with high Nitrate levels,but they will do even better if you can bring it down, which the toms will help you with,as Charlie said plant more densely,then prune to ensure airflow around the plants.If your levels are still high they really will benefit from foliar Potassium around flower and fruit set,as your high nitrate will hinder potassium uptake,the ideal K to N ration is K should be 1.5 times higher than N.
Another draw back with high Nitrates is the fruit will have a lower Brix value,i have this on my computer so copied this extract.

Excessive nitrates burn carbohydrates and reduce brix. In fact, nearly 30% of the energy of photosynthesis is used just to assimilate the nitrates! So to ensure high brix, don’t give the plants more nitrates than they need. Excessive nitrates produce large cells with thin cell walls, making them a target for pests and disease. And since the sugars are burned to produce more top growth, root growth can become restricted and fruit and flower production can be delayed. A brix refractometer can show the signs before it’s too late.

If nitrates are in the adequate zone, but brix is still too low, it may be beneficial to increase the potassium levels. Potassium is a catalyst for carbohydrate metabolism, helping to increase brix. So a grower has three choices for increasing the potassium: nitrate ratio- lower the nitrates, increase the potassium, or do a little of both. Once you find the sweet spot, (no pun intended) the brix should start to improve.