Here’s a question that comes up often when discussing growing media that contains composted materials, such as pine bark or peanut hulls. If these composts are so biologically active, what assurance does a grower have that some of that biological activity isn’t plant pathogenic? Growers may remember that in times past mixes containing mineral soil were routinely steam-sterilized to eliminate disease organisms, and the ‘rule of thumb’ was that a moist 160 degrees F for 30 minutes would do the job. So it would appear that we could answer this question if we knew whether compost piles routinely develop such temerature conditions. Truth is, as you may already suspect, it’s actually a little more complicated than that. —Ron Walden
Read More in The Sun Gro’er Issue 3/1 (2005)