INTERPRETATION AND ADVISORY APPLICATIONS OF COMPOST AIR-FILLED POROSITY (AFP) MEASUREMENTS

A practical method for rapidly determining the air-filled porosity (AFP) of peat based composts has been developed by ADAS (Agricultural Development and Advisory Service) at the Wolverhampton Centre, U.K. The method as described, has been used successfully in ADAS advisory work to assess the drainage characteristics of commercial compost mixes.

The effect of additives on the AFP of a peat based compost was examined using the method.
Sand was shown to dramatically decrease AFP. This was a result of the sand’s fine particle size and compressive effect on the compost.
The effect of grit was less marked.
Specific size grades of bark, rockwool and perlite were shown to increase compost AFP, and can be regarded as compost ‘openers’. The interactive effects of including sand and grit along with compost ‘openers’ on AFP was also examined.

A classification system relating AFP values to the ease of compost management is presented, based on ADAS advisory experience.

Symposium on Horticultural Substrates and their Analysis

N.C. Bragg, B.J. Chambers

https://doi.org/10.17660/ActaHortic.1988.221.3