Our Under Current® RDWC systems are specifically designed to deliver high levels of aeration and circulation. These supercharged conditions allow your plants to uptake water and nutrients easier and more efficiently. With this increased efficiency it is very important to provide the correct amount of nutrients to your plants to ensure consistent growth rates and a successful grow cycle. High nutrient levels are one major factor that can slow down your plants growth rates and hurt your overall yields.
High and Low Nutrient Levels
Most growers use some form of TDS or EC meter to measure nutrient levels. Nutrient concentration in solution is commonly expressed in PPM (parts per million) or EC (electrical conductivity).
High: In a typical grow media based cultivation system it is common to start young plants at around 700ppm or 1.0 EC and allow nutrient levels to spike well over 1750ppm or 2.5 EC.
Low: For the Under Current® RDWC system we typically recommend growers to start plants at around 150ppm or 0.2 EC and peak out at around 900ppm or 1.3 EC.
Nutrient Uptake in Grow Media vs. The Under Current®
Higher nutrient levels are generally acceptable in grow media for two reasons:
- Aeration and dissolved oxygen levels are typically much lower.
- Roots are not directly exposed to the nutrient solution (submerged in).
The grow media acts as a buffer between the minerals and the roots. Plants absorb what they can through ionic exchange and any bound mineral salts remaining in the media can be periodically flushed away by the grower.
The Under Current® water-culture system is a unique cultivation technique where plants roots are fully submerged in highly aerated solution. High levels of aeration and circulation help keep minerals soluble and accelerate the uptake process. Plus, there is no buffer to protect the roots from concentrated mineral salts.
If the same nutrient strength that is normally considered average for other hydroponic applications were applied to the Under Current water-culture system, plants would stall, struggle and possibly show severe signs of stress.
High Nutrient Levels = Lockout
The old adage, “Less is More” definitely applies to growing in a Under Current® RDWC system.
Most hydroponic specific fertilizers including our Cultured Solutions® premium hydroponic plant nutrients are mineral salt based. These mineral salts are solubilized in water and absorbed through plants roots. Though our Cultured Solutions® have low sodium content, too much nutrient can impede the plant’s ability to thrive by slowing down uptake of water and nutrients through the roots. If this happens it can cause a lockout of water and nutrients, slowing the growth rate and hindering plant performance.
The main goal is to accelerate growth rates by preventing lock out entirely. Even a slight increase in nutrient dosage can affect your crop. Your plant may look happy and healthy with white roots but ultimately this excess will decrease your overall yield.
It’s a fine balance between maintaining the proper nutrient dose and maintaining the accelerated growth rates typical in the Under Current® RDWC system.
Deficiencies vs. Excesses
When transitioning from grow media to water culture (DWC / RDWC) based hydroponic cultivation, it is important to keep in mind that with the elimination of grow media you must decrease the nutrient strength significantly. Symptoms of nutrient excess in water culture hydroponics tend to mimic the symptoms of nutrient deficiencies in grow media cultivation.
For example: calcium/magnesium deficiencies in grow media will look just like magnesium excess in water culture.
This is consistent for most macro and micro-nutrients because they can be more easily absorbed in water culture than in grow media.
One more time… Less is More!
If your plants exhibit yellowing tips, dark green leaves or downward curling, reduce overall nutrient strength (EC or PPM) by 25%. This can be achieved by simply adding water to your Under Current® RDWC system or nutrient reservoir.
For top-off reservoirs, the nutrient strength should be maintained around 15-25% higher than the nutrient strength in your system. If your top-off reservoir is maintained lower than your system, your plant will take from the system instead of the top-off.
To prevent high nutrient strength damage, pay close attention to how your plants are consuming nutrient solution and the health of your plants. Always stay within our recommended PPM/EC ranges for each stage of growth (Check out our feeding chart).
If you are faced with these issues and need additional assistance, please call our technical support.