Air Filled Porosity of Coco Coir Grow Bags


When speaking with growers we’re often asked about the various specification metrics used to describe our coco coir grow bags. One of the most important for root health is air filed porosity (AFP). By the end of this article growers will have a working understanding of what AFP is, how it is measured, and its importance in maintaining a thriving, yield-boosting rhizosphere.


What is Air Filled Porosity?

Much like VWC, many legacy cannabis growers are unaware of AFP despite being a commonly referenced metric in commercial agriculture. Air filled porosity describes the amount of air a pot holds when fully saturated. This metric shows the minimum oxygen level a substrate maintains.

How Is AFP Measured?

RIOCOCO uses a standard horticultural research practice to determine the Air Filled Porosity of our coco coir grow bags. Unlike other coco coir suppliers, we publish our AFP numbers. For this calculation we’ll use published specs of the Riococo PCM 1 gallon grow bag, and the WHC calculated in a previous post:

  • Dry Volume = 675 cm3
  • Saturated Volume = 3375 cm3
  • WHC = 1740 mL

To calculate AFP, we’ll use three variables: SV (Saturated Volume), DV (Dry Volume), and WHC:

  • AFP = [SV – (DV + WHC)] / SV
  • AFP = [3375 – (675 + 1740)] / 3375
  • AFP = 960 / 3375
  • AFP = 28.44%

This means that when fully saturated, the media in RIOCOCO 1 Gal PCM grow bags contains 28.4% Air.

The Importance of AFP

I learned about the importance of AFP when researching  the role of media in IPM. According the UC IPM program the threat of pythium can be effectively eliminated by choosing the correct substrate. At ~30% or higher air content soil moisture conditions are not conductive to infection by pythium. 

Choosing an adequately aerated medium is of critical importance when establishing, or optimizing, irrigation practices. While lower-end coco coir brands may advertise an acceptable WHC, they’re not illustrating the full picture. One must examine the full specifications of their chosen coco coir before any implementation can be scaled. Given the value of our crops, and the ever-shrinking margins, momentarily thrifty decisions can have disastrous repercussions down the line.

RIOCOCO builds its business from the success of our clients. We’re here to stay, are you?

Our consistent standards and measurable VWC are just some of the ways RIOCOCO helps growers push their yields. Want to learn more? Click here to contact us!