Can soil be too sterile?

Soil gets worked hard in organic commercial production and, over time, it can build up with pathogens, pests and diseases. Protected cropping under glass means growers often sterilise soil at the end of the season. But could this practice be leaving the next season’s crops more vulnerable than before? James MacPhail, Commercial Director at Carbon Gold, considers the question…

Sterilisation is a cost effective technique to control some soil-borne pathogens, pests and weeds, which is why it’s become a widespread practice. As the name of the process suggests, sterilising soil will wipe out harmful living organisms but, as the process cannot differentiate between harmful and beneficial microbes, the net result can leave soil more vulnerable to re-infection in the long-term.


Scanning electron microscope image of biochar - copyright Pete Brownsort

Beneficial micro-organisms help to maintain the stability of a growing system by out-competing pests and pathogens; problems most commonly occur when the balance between the pathogens and the biological populations are unequal. By sterilising soil and wiping out soil’s only real defence, you could be allowing for easier re-infection from just the thing you were trying to control!

A traditional solution to this problem would be to rotate crops, plant green manures and add organic matter to ensure the soil is healthy post-sterilisation. Increasing the quantity and effectiveness of the beneficial organisms in a soil can reduce the effects of pathogens, such as nematodes, by feeding on them before they have a negative impact on plant health.

A far more efficient approach would be to stop sterilising all together and boost the populations of beneficial fungi and bacteria in soil to actively control pest issues in the first place. Progressive growers throughout Europe are already adopting this approach, through a product that dramatically improves the recalcitrance of beneficial microbes in soil and substrates: enriched biochar.



Biochar is a purified, highly porous form of charcoal that improves both aeration and the moisture retention of soils and substrates. Over time, the biochar will become colonised by beneficial microbes because its porous quality provides the perfect structure. Enriched biochar products, such as Carbon Gold’s Soil Improver and Enriched Biology Blend, are readily enriched with species of mycorrhizae, seaweed, wormcasts and different strains of trichoderma to speed up this process, creating a naturally healthy living soil - allowing extensive microbial populations to thrive.

Applying enriched biochar to soil instead of sterilising it will naturally increase crop vitality and reduce losses with early flowering and higher yields as proven by extensive professional grower trials in the UK and Europe.

Another benefit of enriched biochar is its moisture retaining qualities, which allow it to absorb up to six times its size in water and work as an effective regulator of soil humidity, meaning that irrigation can be reduced by up to a third.

All of this adds up to healthier growing environments, quicker establishment and root growth at propagation, increased crop vitality and reduced transplant shock.

By keeping soils biologically healthy, growers keep their crop yields high. As growing technology progresses, even the most efficient and widespread practices can be improved upon. By exploring new approaches and embracing R&D, growers can improve their yields, nutrient efficiency and reduce losses. So here’s to building beneficial biology rather than wiping it out altogether.

For more information:
Carbon Gold
sales@carbongold.com


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