Mainly musing about micro organisms
My attitude to personal hygiene is to keep my immune system primed and avoid the use of antibiotics unless they are essential. I think it likely that my very good health is in part due to my lifetime exposure to the open air and the soil.
I only wash my hair if I have a bonfire. Last week Brenda’s hair dresser was ecstatic about my hair’s condition. Perhaps she was being kind! The mixture of natural oils and beneficial bacteria do the cleansing for me.
Considering my attitudes it is not surprising that by normal standards my garden hygiene leaves much to be desired. I have written of my blasé attitudes such as not washing pots, using unsterile soil, my cavalier approach to damping off relying almost entirely on good light and ventilation and, not least, my habit of leaving organic matter scattered on the soil surface.
Don’t get me wrong there are some aspects of garden hygiene where in avoiding garden pest and diseases I am utterly ruthless. If any new plant shows any sign of glasshouse whitefly, scale insect, vine weevil. red spider mite or mealy bug it goes straight in the bin! In consequence none of these afflictions ever concern me!
With modern realization that the biome around us plays an essential part in our own health and survival, and with such startling discoveries that as we walk around we carry far more genes of microorganisms than our own, it is not surprising that the world is starting to reconsider how previously unrecognised beneficial bacteria and fungi and even virus influence plants. Perhaps especially virus considering how frequently in the past they have been responsible for natural gene transfer.
I have recently been reading about the raising of mouthwatering amounts of cash by ‘crowd funding’ to propel agricultural research in this microbial direction. There is hype of worldwide yields of agricultural crops expanding by ten per cent or more.
Such expectations have in some quarters been sceptically received. Not least my own, but wouldn’t it be wonderful if yields were in this way extended.
Or perhaps not if it leads to immoral industry patenting genes and holding farmers and growers to ransom.
Harnessing microorganisms to benefit the garden is not something new. We are all familiar with nitrogen fixing bacteria that live in root nodules and - less significantly in the UK - nitrogen fixing bacteria that live free in the soil.
Mycorrhizal fungi are in popular flavour and are hugely significant. There are already misguided gardeners who buy them in a packet!
All the above embolden me to muse even further than I have previously dared about my own attitude to microorganisms’s significance in gardening!
In an earlier post I have presented the reason why I hardly ever have damping off disease fungus is that I don’t force my seedlings in poor light and I give them plenty of ventilation. Not for me sweaty disease fomenting conditions created by covering seedlings with glass or plastic.
I have not dared float my notion that when gardeners strive for sterility in their water and compost they invariably fail. Their partial success creates a void in populations of previously mutually competing soil micro organisms. In such conditions lack of competition gives notorious and aggressive fungi such as Pythium de baryanum a completely free run through your seed tray felling your plants.
It is not a new concept that an invading micro organism goes through sterile soil like the proverbial ‘dose of salts’. Traditional commercial glasshouse growers steam sterilised their soil principally for the control of soil born pest and diseases. A much appreciated ‘spin off’ was the extra nitrogen released by the elevated populations of the resistant nitrate releasing bacteria that had now no competition. This so called ‘nutrient build up’ was just at planting time when the soil was still warm and the plants needed extra nutrition.
Ken Thompson recently wrote about research in adding sugar to soil to enhance microbial populations and increase their competition to reduce nutrients left available to plants. This could potentially be relevant to reducing fertility for systems where plants might be naturalised in grassland. The technique certainly worked in decreasing fertility and reducing grass growth. Unfortunately it did not seem to lead to extra wild flowers.
|I will be writing about Peter’s restoration project next month|
I recently visited a site of an old slag heap with microbiologist Peter Williams where his research had guided its restoration. Nitrogen fixing bacteria elevated soil nitrogen when wild white clover was sown.
Apparently you can enhance nitrogen fixation by innoculating nitrogen fixers with the right strain of the bacteria called rhizobium. Apparently Peter was able to call upon some of the two hundred strains then held at Rothamsted Research Station. In Peter’s view although the nitrogen fixation worked very well the ‘special strains’ did not seem to make much difference.
Peter, like me, believes that adding mycorrhiza to the garden from a packet is a complete waste of time. Perhaps adding mycorrhizal spores to a fungus-hungry pit heap is one of the few occasions when inoculation is worthwhile? I asked Peter about this. He replied that in those days mycorrhiza were not fashionable. He observed that any self sown plant he had ever found on an unrestored pit heap was awash with native mycorrhiza. Research projects at that time on plants in the process of restoration in colliery slag always showed up abundant mycorrhiza.
No dig and micro organisms
It is not specifically microorganisms but all soil life that is beneficially affected by minimum cultivation. I maintain none diggers and also all those other gardeners who provide good growing conditions have plants less susceptible to pest and disease.
I suggest the balance of soil animals and micro organisms have fundamental benefits to plant health and soil fertility.
Soil life includes nematodes, fungi, bacteria, single celled organisms and invertebrates such as insects, mites and worms. Some might be pests and diseases which damage our plants. Some will be beneficial as already mooted. Many seem to be of little concern to the gardener. All are in dynamic ever changing equilibrium. They are a firmament of aggressive competition, harmony and symbiosis. I suggest the disruptions to a natural soil balance caused by a gardener’s interventions, not least excessive cultivation seem to me to work in favour of pest and disease.
|My on going project planting Cathi’s new border without cultivation. Stirring the soil by cultivation encourages aerobic bacteria that degrade organic matter. It is a common feature of no dig plots that their soil organic matter is naturally high.|
Should gardeners worry about their soil micro organisms?
I have previously written specifically about the significance of soil bacteria and how their populations vary by orders of magnitude caused by such things as temperatures, waterlogged conditions and drought. A gardeners’ activities and the weather have significant effects on soil micro-organisms.
It is unfortunately becoming trendy to attempt to manage gardens by managing the bacteria. It might be very interesting for our United States’ friends to attend a day course at a laboratory offering a course on bacteria but in terms of improving their garden it is a complete waste of time. Suddenly many new ways are being discovered to fleece gardeners of their money.
|Following the sign will do more for your garden than attending a course on bacteria. On the other hand learning about bacteria is absolutely fascinating|
Yes, a gardener’s activities do influence bacteria but usually not in easily predictable ways. Any changes that occur are incidental to good growing techniques practiced for the sake of the plants.
For example you do not look to good drainage for the benefit of the bacteria; you do so for the good of your plants. In improving your drainage there are many reasons why your plants will grow better. One of them might be reduction in numbers of sometimes undesirable anaerobic bacteria
Peter Williams offered me this story about how bacteria colonise a previously sterile material. His early research was on pulverised fuel ash from Yorkshire coal power stations. At that time millions of tons of the stuff was an acute embarrassment and his research involved using it for agricultural production when it was ‘lagooned' as a very thick cover over the ground. Hugely alkaline with a pH more than nine, bacteria will make many improvements. Useful bacteria will ‘fix’ nitrogen, help dissolve otherwise unavailable phosphate, glue particles together and break down fresh organic debris. (In respect of gluing particles in those days we knew nothing about glomalin).
Research from Russia had suggested inoculation of bacteria might be worthwhile. Extensive UK research was done to investigate this theory and found no measurable affect of artificial inoculation.
No inoculation was done in Peter’s project either, just sound management practice. The bacteria came in on their own.
|Temperatures and water has huge effects on the numbers and proportions of soil bacteria|
|Many woodland plants would not be there at all without mycorrhiza|
If in extreme argumentative mood one might observe that in laboratory conditions healthy plants can be grown without the presence of any micro-organisms at all. Most natural changes in your soil micro-life occur on their own and in most cases in practical terms don’t really matter.
I am probably too old to discover whether agriculture is going to go through a biological revolution and whether all those investors get their returns.
Relevant previous postings
My thoughts on not washing pots and damping off disease
My main piece about soil bacteria
Why I think not digging is good for plant health