Posted on by Jason G

 Coco watering and moisture dry-back

Recently I have been asked a few questions regarding the frequency of applying a nutrient solution (watering) to coco coir.

It is a great question and I think if you have the spare time to compute and apply the information here it’s worth putting on your future to-do-lists regarding grow room metrics if of course you’re not happy with your current routine/outcomes.

After growing in Coco for about 20 years with phenomenal results I thought I had nailed this aspect of understanding substrate saturation. My 'go-to' approach in this area is Run-To-Waste (RTW) feeding each and every day with maybe an occasional 'no-feed' day here or there throughout the life cycle of the plant.

The 'dry-back' term popped up in conversation recently and I felt like I was missing out on something never hearing of the terminology so I decided to explore it. This tutorial comes from my recent research and discussion with other growers on the topic of feeding frequencies and 'dry-back'.

 

Coco Coir Quick facts:

  • Coco-coir fiber is hydrophilic, meaning it absorbs water.
  • Coco-coir has a high Cation exchange capacity (CEC)
  • Coco coir is made from the natural fiber of the outer shell of a coconut.


Run-To-Waste feeding uses the practice of flooding the coco coir with the same strength solution each day until run-off is achieved which in turn leaves behind a fresh supply of nutrient whilst washing away any unused food from the previous feeding, this ensures our root zone EC doesn’t become too high, and has been a sure fire method to achieve great yields indoors and out.


So, what’s this ‘dry-back’ term all about then?

Dry-back is essentially referring to how dry the coco coir becomes in between feeds (watering). This term defines how much solution is consumed by the plants each feed, the frequency of feeds, the duration between feeds and the duration of each feed.

 

What are the pros and cons of this approach to growing and feeding?

For those who are monocropping (continuously growing the exact same crop over and over again in the same place or conditions), finding the equilibrium of saturated to dry-back coco medium will help standardize results and find the optimal feeds required for the crop.

For those growing different crops each round, finding the optimal feeding and dry-back levels will be tough and require constant monitoring of the crops medium throughout the entire grow.

Heavy feeding plants generally respond well to the higher frequency, light feed scheduling. This can be implemented best by using various forms of irrigation feeding systems on a intermittent timer, feeding small volumes multiple times a day, as the plant requires.

Pros:

  • Save water, by using only the minimum needed.
  • Increased air porosity of media.
  • Save money, by using minimum nutrients.
  • Increased yield with correct feeding balance.
  • Less pests found in drier mediums

 

Cons:

  • Possible root zone damage if incorrectly implemented
  • Higher maintenance; checking fittings, timers & feeding lines each day
  • Best used while monocropping, hard to implement on new crops.

 

I was speaking to a colleague about this topic and he highlighted that even though dry-backs make sense while you’re trying to kick start root growth, we both concluded that although increasing the dry-back encouraged root-growth it can also be detrimental to it at the same time if incorrectly implemented. I believe understanding when to irrigate or water is important knowledge to every grower, knowing when you plant needs more or less water is crucial to making adjustments to your feeding schedule. If you’re doing it right, you are more than likely having to feed 3-5+ times daily with small enough quantities to allow minor dry-backs between feeding.

For more info on coco coir feeding, check out our CEC and EC tutorials