Do I top off res with water or nutes during flowering phase for hydroponics?

D

Delps8

Well-Known Member
Unless you are doing tissue analysis and adding specific chemicals to keep the levels in the leaf tissue at a certain range, the safer course of action is to top off with RO/plain water and swap the res when you've had a certain % drop in EC or when you've added back a certain amount of plain/RO water.

If you're not doing tissue analysis and if you add nutrient mix, you run the risk of creating nutrient imbalances.

The reason for this is that the different chemicals in a res are taken up at different rates. N, P, K, and Mg are taken up in a matter of hours so if you add nutes the next day, for example, you're adding in more and more of the chemicals that the plant has already taken up.

The plant can't not take up those nutrients because about 50% of nutrients absorbed by a plant are taken up via transpiration. The only way to avoid creating an imbalance is to swap the res. If you're OK doing that, fine but by adding back just RO, you don't have to swap the res as often and you will reduce the chances of having nutrient issues.

If you do want to add back nutes, you can avoid nutrient issues by replace the entire res frequently but, overall, the safest approach is to use RO and replace the res when the EC has dropped by about 25%. Another approach is to swap the res when the volume you've added back is equal to the volume of the res.

When I first started growing, I topped up with nutrients but the "mass balance" concept made a lot of sense. I now start with a res at EC 0.6, do a new res at 1.0 in late veg, and do a new res at about 1.6 in flower. I haven't had nutrient issues in years. The bottle of CalMag I bought is used as a door stop.

I've attached a couple of papers that discuss the issue.

You may want to review this video and this video.
 

Attachments

C

Cosmonaut Ry

Member
Delps8 said:
Unless you are doing tissue analysis and adding specific chemicals to keep the levels in the leaf tissue at a certain range, the safer course of action is to top off with RO/plain water and swap the res when you've had a certain % drop in EC or when you've added back a certain amount of plain/RO water.

If you're not doing tissue analysis and if you add nutrient mix, you run the risk of creating nutrient imbalances.

The reason for this is that the different chemicals in a res are taken up at different rates. N, P, K, and Mg are taken up in a matter of hours so if you add nutes the next day, for example, you're adding in more and more of the chemicals that the plant has already taken up.

The plant can't not take up those nutrients because about 50% of nutrients absorbed by a plant are taken up via transpiration. The only way to avoid creating an imbalance is to swap the res. If you're OK doing that, fine but by adding back just RO, you don't have to swap the res as often and you will reduce the chances of having nutrient issues.

If you do want to add back nutes, you can avoid nutrient issues by replace the entire res frequently but, overall, the safest approach is to use RO and replace the res when the EC has dropped by about 25%. Another approach is to swap the res when the volume you've added back is equal to the volume of the res.

When I first started growing, I topped up with nutrients but the "mass balance" concept made a lot of sense. I now start with a res at EC 0.6, do a new res at 1.0 in late veg, and do a new res at about 1.6 in flower. I haven't had nutrient issues in years. The bottle of CalMag I bought is used as a door stop.

I've attached a couple of papers that discuss the issue.

You may want to review this video and this video.
Click to expand...
Thank you for info and the notes! I will read up on them asap!
 
You must log in or register to reply here.
Top