Air Filled Porosity of Coco Coir Grow Bags

Cultivation professionals are asking the RIOCOCO team about the various 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 fruit, vegetable, and flower 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,  AFP is a common referenced metric in commercial agriculture. Air filled porosity describes the amount of air a given volume of substrate 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 the published specs of a RIOCOCO 250 gallon grow bag, and the WHC calculated in a previous post:

  • Dry Volume (DV) = 4176 cm3
  • Saturated Volume (SV) = 18000 cm3
  • WHC = 9.553 l

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

  • AFP = [SV – (DV + WHC)] / SV
  • AFP = [18000 – (4176 + 9553)] / 18000
  • AFP = 960 / 3375
  • AFP = 23.73%

Therefore, when fully saturated, the media in RIOCOCO 250 grow bags contains 23.73% Air.

The Importance of AFP

An acceptable AFP is an integral factor of successful IPM procedures. Choosing the correct substrate effectively eliminates the threat of Pythium. According the UC IPM program, 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. Unfortunately, while some coco coir grow bag manufacturers purport to have an acceptable WHC, they’re not illustrating the full picture. As they scale, successful growers are implementing media with precise specifications.  Given the thin margins greenhouse growers face, the wrong decision can have disastrous repercussions down the line.

RIOCOCO has built its business alongside the success of our clients for the past two decades. Our consistent standards and measurable AFP are just some of the ways RIOCOCO helps growers push their yields. Want to learn more? Click here to contact us!