Scientists have found that the microorganisms in healthy, cured compost actually protect plants from soil borne diseases. As Rochelle Eisen (President of Canadian Organic Growers) writes “Common root pathogens that can be ‘managed’ with the addition of compost include:
- wilt caused by various strains of Fusarium oxysporum,
- bacterial wilt of tomato caused by Clavibacter michiganensis subsp. michiganensis,
- damping off caused by Rhizoctonia solani or Pythium ultimum,
- root rot by Phytophthora cinnamomi, Cylindrocladium spathiphylli, or Pythium ultimum.
Pathogenic nematode populations such as Meloidogyne javanica can also be suppressed by quality compost.”
The ingredients used to make compost affect the ability of the finished product to control diseases. Composted hardwood bark is particularly good at suppressing disease but shouldn’t make up more than 15 per cent of a potting mix (by volume).
Regardless of the ingredients in the compost, it is important that the compost is well cured after it has gone through its hot stage. During the curing phase, the compost is colonized with beneficial species. The curing phase can occur in a bin or in the middle of a field, however “moist compost piles on the edge of forests recolonize faster than piles further away.”
Eisen, Rochelle. 2011. Organic Potting Soil Considerations. Organic Agriculture Centre of Canada http://www.organicagcentre.ca/NewspaperArticles/na_potting_soil_re.asp
- Janet Wallace