Growing soil carbon
- Tim Ashley
- Oct 19, 2021
- 3 min read
A blog series that looks at various aspects of soil health and dives into the science and tries to pick out the 'take-home messages' - It's more about sharing learning.
This week I watched several YouTube videos which featured Dr Christine Jones, an internationally renowned and highly respected groundcover and soils ecologist. https://www.amazingcarbon.com/
A recent talk she did for a Opico webinar https://youtu.be/GcTBRL0SYq0
What do we hear more than anything from farmers interested in soil health?
How do we increase soil organic matter?
According to the Environment Agency - "Intensive agriculture has caused arable soils to lose about 40 to 60% of their organic carbon" - 'State of our Environment'.
So how do we increase carbon? Organic manures (hot topic this autumn!) Cover crops and direct drilling, chopping straw, stubble digesters, microbe inoculates etc.
Well if you listen to people like Dr Christine Jones and Joel Williams the answer is simple but how do we implement it into a business, a business that is essentially based on monoculture cropping?
So what is the answer according to Dr Christine and Joel; LIVING ROOTS and lots of them. A multi-species vibrant plant community that brings the soil microbiome to life. Their research both scientifically and practically shows:
Actively growing GREEN PLANTS support the MICROBES that CREATE well structured, friable topsoil with high nutrient status and high water holding capacity.
Soils are NOT deficient in minerals they are deficient in microbes.
A diversity of soil microbes is needed, a QUORUM, to function to a higher beneficial level.
Diversity of soil biome comes from DIVERSITY of roots (plants)
Building topsoil/ soil carbon is a BIOLOGICAL process with mycorrhizal fungi as the keystone.
Source: Aberdeen Mycorrhizal Research Group
Roots are quite inefficient on their own but if they are allowed to feed and encourage fungal colonies, this significantly improves their nutrient uptake efficiency. However, fertiliser inhibits mycorrhizal fungi! So where is the economic threshold? Certainly, with nitrogen fertiliser at £580/tonne, this will undoubtedly focus the mind a bit.
8 different plant species (e.g. in a cover crop) provide as much biomass as 2 species PLUS 200kg N/ha/yr. MORE is better. DIVERSITY. source Jena biodiversity experiment.
Wolfgang et al 2017 Biodiversity effects on ecosystem functioning in a 15-year grassland experiment
This species (plant) diversity promotes the idea of Common Mycorrhizal Networks (CMN) - plants share their microbial biome. For example, brassicas naturally do not have a natural mycorrhizal relationship (they use organic acids instead) - they will take nutrients from the CMN if other non-brassica species are growing alongside!
You will ALWAYS lose carbon on bare ground amongst other things like water holding capacity and infiltration and nutrient holding capacity - all well documented
Again according to research, soil biome such as mycorrhizal fungi are inhibited by high analysis inorganic nitrogen and phosphate fertiliser.
Mycorrhizal fungi are 'killed' by excessive disturbance/ cultivation (beware of pot studies!!)
Fungicide treated seed is not a tool that fits into this way of thinking!!!
However, mycorrhizal are stimulated by organic amendments such as manure, compost, compost tea, carbon-based fertiliser.
Two real-life examples of utilising these methods:
Companion cropping which is beautifully demonstrated in a recent tweet from Gareth Culligan @gareth_culligan - 6 species crop and companion cropping. Also, note the interest in the form of questions!
Living mulch - Clive Bailye @TWBfarms direct drilling wheat into 2 species of clover (not quite species diversity that Dr Christine is looking for but it's a practical way forward.
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