Soil rich in organic matter is most suitable habitat for the isolation of Actinomycetes

Rhizosphere is also a good habitat for plant-associated Actinomycetes.

Red soil is also  a good habitat for actinomycetes isolation. Streptomyces or other rare actinomycetes.

Dear Gillian Lewis,

As stated, soil samples that have rich organic sources are a good sample to start with. You may start with soil that is produced by decomposition of vegetable matter.

Another sample that you can try out with is EARTH WORM Cast. I have seen the soil sample left behind by earthworms are very rich in microflora. If you want to isolate actinobacteria use the recommended media as suggested in literatures.  Please note that never autoclave K2HPo4/KH2PO4 along with medium components. Autoclave it separately, you will get more cfu counts (as autoclaving these with other components generates free radicals that kills the vulnerable bacteria and what you end up with are microbial weeds). Glycerol asperagine medium is one where they sporulates and you tend to get pigmented isolates (diffusible pigment that resembles melanin). 

You can also plate the samples on 100 tiimes diluted Tryptic soy agar and then by simple colony morphology you can pick and purify the actinobacterial isolates.

Another strategy that i have not tried for actinobacteria as suuch. But I have tried with many samples and recorded greater CFU counts compared to others. Whatever sample you are taking, prepare an aq. extract of it, filter it through Whatman No.1 followed by 0.22 um. store this in a refrigerator just before pouring agar plates, add 5 to 10 ml of this filter sterilized extract (brought down to RT) to the cool agar medium.

There are other media as well. If you are trying, go for combination of all these and through trial and error you will isolate many.

Please try out all these combinations, you may definitely end up with novel actinobacterial isolates. Please note Earthwom gut also contains actinobacteria, many of which have PGPR and antimicrobial activities. Isolate those earthworm that are well fed in natural habitats (may be from a pristine forest, if possible, living under the plant compost). If you rear them in lab you will no longer get and isolate the same microbes. 

ALL THE BEST

Pradipta 

Thank you everyone, I appreciate the input and I will look into the areas suggested.