Soil Biology

Wet on Top — Dry Underneath – Guest Post by Niels Corfield

Wet on Top — Dry Underneath – Guest Post by Niels Corfield 1500 843 Soilmentor

This is a guest post by Niels Corfield, Independent Farming Advisor and Educator. Learn about his courses here.

The winter of 2019/20 was challenging for farmers to say the least. Incessant rain meaning fields were not accessible, and winter crops were not sowed, large areas of flat or low lying country flooded (sometimes repeatedly) and otherwise generally redefining the concept of mud.

By springtime, what was the ground like out there? Wet, soft, or already hardening-up? Chances are it was the latter. So how can this be, after the wettest winter in living memory? When the ground across the farm (and the country), it seems, was saturated.

What if I said, that it’s the same root cause that produces both drought and flooding? That your farm, whether it be cropping or grazing, organic or conventional can be reworked to be both drought-proof and immune to extreme rain events. Sound too good to be true? Well read on.

If it’s not there when it’s wet, it’s not there when it’s dry

First we better rewind a few steps and show so how it is that a single causal factor is responsible for droughts and flooding.

This single causal factor means that on the one hand (in 2018) we were feeding-out first-cut silage and achieving little or no grain-fill and this winter we ended-up with maize harvests that looked like the battle of the Somme (reparable but not good optics).

Management Dictates Infiltration

Time to Infiltrate 1″ of Water: 7 seconds (field margin, at left) — 20+mins (reseeded pasture)

Above we see two spade samples of the same soil type on the same day, margin on the left and grazed pasture on the right, recently reseeded.

Simply put, the causal factor is a lack of infiltration (or low infiltration rates) in all but the lightest or stoniest of soils — and a lack of water retention in these soils. The water that falls as rain has only one of two places to go – either into (and through) the soil OR away as runoff.

If your soil is very light or naturally free draining that water will go straight through, and in heavier soils that water will run-off. In both cases that water has left and has not been retained within the soil profile.

But our soils were clearly saturated this winter, I hear you say! How can you be suggesting there’s a lack of infiltration?
Well, the experience is, that it’s the surface of these soils that was at capacity, the bulk soil was dry, often very dry. See soil pictured below for an illustration.

Soil Sample: well hydrated in top 2″, dry below. Standing water and loamy soils.

You’ve got one chance, and one chance only, to get the water into your soil and that’s when it rains, as infiltration.

Without infiltration that water will run off. It’s a simple choice – where would we prefer to have our rainfall: in the soil where it can grow crops and forage, or in the valleys where it fills up like a bathtub: damaging property, and causing travel disruption and economic impact?

It seems counter-intuitive to say we want more water in our soils, given the experiences of winter we’ve just had. Surely, all that mud and saturation wants to be mitigated, by drainage or other means?

Well, no, in a word.

What we are looking for is deep penetration into – and through the soil profile.

Structure

So what does this mean? What is this indicative of?

Simply that these soils lack pore space. They often are blocky and consolidated and largely just structured in their “native”, mineral state (where all the soil particles are bonded to each other, in a tight crystalline state). These bonds are strong, but brittle, so when they fail, they may well “cleave” along fault lines, revealing: cracks, jagged edges and angular shapes.

At the landscape scale what features do we associate with these terms (and shapes)?

Generally: cliffs, rock faces, and mountains. And what is the study of these materials and these types of features? It’s geology.
Simply put, if your soil looks and behaves like geology: it shatters, cracks or cleaves, has the appearance of rocks or stone, it is geology.

Which makes sense because the sand, silt and clay is basically just ground up rock. However, when we refer to soil that’s just sand, silt and clay, it’s subsoil (in old money). Fundamentally, the difference between subsoil and topsoil is that topsoil is subsoil that has been acted upon by biology.

And what is biology’s influence on the soil structure? Primarily the creation of pore space. Converting the soil from its native, homogeneous state where the soil particles “pack” readily, into to a heterogeneous state, binding together disparate soil particles into crumbs or “aggregates” with a network of internal voids running between them.

Just as a biscuit maker converts base ingredients, flour and sugar, into crumbs with the addition of a binding agent, like butter. Where the flour and sugar particles are effectively the same size as one another, but once the binding agent is added those crumbs that result now have a large variation in size, from something like a bowling ball down to a golf ball.

In the case of the soil, our sugar is analogous to sand (coarse, granular), while the clay is analogous to flour (since if you purchase dried clay it comes bagged, as a powder). In soil, the aggregates are bound together by sticky substances like polysaccharides (carbohydrates) that are secreted by organisms like bacteria. In the same way that if you’ve ever got slug trail on your clothing it goes on sticky, cannot easily be washed off and sets hard, in other words these compounds are glue-like in nature.

So, we can say that soil aggregates are literally glued together by the secretions of biology.

This is what gives soil it’s friable crumbly and easily workable texture.

Fundamentally it’s this crumb structure and the pore space that facilitates infiltration. Over and above what the native soil does alone.

Moreover, with light soils these crumbs increase the surface area and with-it water holding capacity making them more moisture retentive. Since these surfaces of the aggregates are places where water films form. And it’s these billions of tiny water films throughout the soil volume that gives it its water holding capacity.
In heavy soils the opposite is the case, it serves to make the soil more free-draining. By opening up the dense structure and introducing pore spaces. Spaces that are interconnected, through which rainfall can easily percolate whilst also collecting around the aggregates as water films.
In both cases this forms a water reserve that can be drawn upon by crops and forages in the sunny, warm periods that are optimal for growth and grain fill.

So, with the exception of a small number of self-aggregating soils, crumb structure is entirely a product of biological activity and an expression of the carbon cycle in action, as these are carbon-based compounds, derived from plants, often root exudates (sugars).

It’s these processes at play in the above example comparing margin with reseeded pasture

Management Determines Infiltration Rates

So, what can you do, how can you achieve this friable structure without necessarily going to grass? Simply put, apply the soil health principles at every stage of your cropping and management practices.

Pasture vs Covered Arable vs Bare Arable (Photo: LSU AgCenter)

Simply put here in the UK we are not victims of either too much or too little rainfall, just inadequate infiltration or retention. In a cropping situation it’s not only the lack of pore space but also surface capping (from rainsplash etc)

As Yoda might say:
“Hmm, not how much it rains that matters, how much we retain, it does.”

So in one fell swoop by fixing infiltration we not only do ourselves a favour: eliminating muddy conditions and poor field access options early and late season, we also optimise production through seasons like 2018.

Learn all about soil health and regenerative farming! Upcoming courses and workshops by Niels Corfield: Specialist Training courses for farmers, growers & land managers.

Courses focus on soil health and include specific courses for pasture, arable and horticulture. As well as regenerative grazing and whole farm planning.

All courses are now online.
Find out more HERE

Soilmentor makes it easy to monitor infiltration rates over time – discover how well your land is soaking up water now, and see how changes in management impact/improve infiltration rates (and other metrics!).

Beneficial insect focus: Spiders – Ben Harrington, Edaphos

Beneficial insect focus: Spiders – Ben Harrington, Edaphos 591 340 Soilmentor

Edaphos offers agronomy services on all types of farms in all situations. Their philosophy is to improve soil and plant health, whilst harnessing the soils stored resources to their full potential to achieve a healthy, well balanced system.

Increasing biocontrol on farms by raising awareness of the beneficial insect community could lead to reduced pesticide use, costs and better support our own environment. In this blog we will be focusing on Spiders (which are arachnids and not an insect but certainly a most valued beneficial predator) through conservation biocontrol!

Before going into Spiders in detail, it is important to understand that to enable conservation biocontrol it is a direct focus on increasing the numbers and diversity of naturally occurring beneficial insects that are already within the area. To create a successful biocontrol through conservation alongside farming, predators and parasitoids need to thrive more so than in smaller production systems due to the fact that fields are subject to a whole host of management from us through mainly pesticide use, tillage, baling, mowing of margins and the management of field borders. Because a lot of fields are subject to the above, they don’t provide enough shelter, forage and overwintering habitat for many of our beneficial insects that would provide us with the wonderful benefits of pest control in crop and as a knock on effect, this also has an impact on other wildlife, pollinators and birds that are in a declining population.

The focus of conservation biocontrol is to focus on creating the necessary food and shelter and any other needs that has been proven to increasing numbers of beneficial insects. Once these are in place the biocontrol system will continue to develop and persist year on year as natures cycle of life and natural balance take place.

Back onto the Spiders! Hopefully over the winter and into the spring, many of you will have experienced spiders while walking crops, alongside margins or noticed a glint of an expanse of webs across the crop that is most noticeable at dawn and dusk which is a great sign and start to creating your biocontrol community.

Spiders are often the most abundant predator in agriculture although they play good and bad roles towards our purpose. Spiders are generalist predators which may feed indiscriminately on other insects and as you might expect for certain species their webs can cause chaos to any insects that fly.

Spider life cycles vary a lot between Arachne species, from species that have one generation per year and live for 2-3 years to those that are very short lived and have multiple generations per year. Spiders may lay eggs within silken nests in the soil, grass clumps, plant debris, under bark or inside hollow stalks of vegetation which these are the areas the adults also overwinter in as well.

For web-spinning species, vegetation as crops and weeds or a soil surface with adequate trash to create a diverse architecture provides a suitable habitat and hunting ground to spin webs. Leaving trash on a more cloddy surface with straw still standing helps retain web-spinning spiders in the autumn and the presence of the diverse architecture from the crop and arable weeds provides a suitable hunting ground in the spring and summer. Some web spinning spiders are capable of producing a long thread in which they can disperse themselves over long distances in a process called ballooning where they are carried in the wind. Web Spinning Spiders can offer us the first and one of the most effective controls against aphids in the autumn by covering whole fields in their threads from ballooning into and across the field. When they are present, you can easily see how and why they are so effective at aphid control and not many pests would get through their hunting grounds.

Wolf Spider (Wildlife Trusts, 2020)

For the hunting spiders such as Wolf Spiders and Jumping Spiders, they don’t rely on creating a hunting ground with their webs and will persist generally along field margins, hedgerows and plant foliage to hunt on the ground and will travel 50 metres into the field from these areas.

It is important to know that the more mobile species of Spider will only settle in locations with sufficient levels of prey and as such will show responses to prey densities. If you do not have the diversity or insect populations spiders will not be abundant.

To encourage the establishment of spiders you will want to integrate field margins as hedgerows, grass and pollinator strips into the field. Splitting fields with beetle banks or wildflower strips can help massively to improve coverage of these species into the field. Leaving crop residue and trash on the surface and leaving clods within the field will also give the spiders a diversity to their habitat and enable them to hunt effectively. Cover crops can also help to provide an ideal autumn habitat as a hunting ground and nesting site.

Flower rich margin

If you are interested in integrating Mid-Tier schemes for helping to promote Spiders and their necessary habitats and food sources the following would be useful to look into and integrate into the farm: Nectar Flower Mix (AB1 – £511/ha), Beetle Banks (AB3 – 573/ha), Flower Rich Margin and Plots (AB8 – £539/ha), Unharvested Cereal Headland (AB10 – £640/ha), Two Year Sown Legume Fallow (AB15 – £522), Autumn Sown Bumblebird Mix (AB16 – £550/ha), 4-6m Buffer Strips on cultivated land (SW1 – £353), In-field Grass Strips (SW3 – £557/ha), Winter Cover Crops (SW6 – £114/ha) and Woodland Edges on Arable Land (WD3 – £323/ha).

Spiders are highly vulnerable to pyrethroid insecticides and through good practice and management such as not spraying all fields with insecticide in one year and leaving some untreated, adhering to spray buffer zones and not spraying insecticides close to margins we should be able to minimise the risk to our populations of beneficials.

The value of biodiversity in agriculture

The value of biodiversity in agriculture 1024 512 Soilmentor

Farmland across the world has potential to host a fantastically complex network of plants and animals, and this complexity provides many ecosystem services that we humans rely on: decomposing our waste, cleaning our water, and purifying our air – not small concerns! Invertebrates such as hoverflies, bees, moths and butterflies pollinate our crops, and others such as beetles, spiders, harvestmen, wasps and nematodes provide natural pest control.  

To put it in financial terms: insect pollination is estimated to be worth £400 million to the UK economy, and predatory insects providing natural pest control is estimated to be worth $13.6 billion to the US economy! Biodiversity is also linked to productivity: increased farmland biodiversity is linked to increased plant growth above and below ground, suggesting higher productivity. 

Despite all of these advantages, farmland biodiversity is suffering huge decline – new European data suggests 76% of species and 70% of habitats related to agriculture now have poor conservation status. 

 

How to build biodiversity on your farm

Generally speaking, the best way to farm in tune with biodiversity is to imagine a mosaic of habitats across your farm – the more you variation you can create, the more you are mimicking nature’s natural state. This might mean field margins, wildflower borders, hedgerows, cover crops, multi-species herbal leys, woodland and grassland! Field margins and hedges are more appealing to wildlife when left a bit messy – if you can bear it, let your grasses become tussocky over summer and try to avoid cutting back your hedges more than once every three years to allow wildlife to establish itself amongst the branches. Land managed with varied pockets like this means your farm can become a wildlife corridor; a network of linking habitats for animals to migrate across as they move across the country!

Watching wildlife in a biodiverse field border at Eastbrook Farm

 As an example – farmland is home to over three quarters of British butterfly species – and many of these species have suffered real decline in recent years. Butterflies and moths have a complex life cycle, involving different life stages: from egg, to caterpillar, to pupa, to adult. Each of these stages require slightly different environments, and different species of butterfly and moth have different preferences on where to lay their eggs or feed on pollen. It’s easy to imagine how a monoculture doesn’t appeal to butterflies – they just don’t have the environment they need to get through their different life stages in these systems. So, the best way to reverse this is to create (where you can) a mosaic-esque range of habitats for the species on your farm.

In terms of management, your use of pesticides, insecticides and soil cultivation will also affect your farm’s biodiversity. We know that the use of insecticides and pesticides reduce plant and invertebrate biodiversity, which then has a knock on effect to the birds and mammals that rely on these species. Where there is low invertebrate diversity, there is limited potential for a natural buffer of beneficial insects to control pests, increasing reliance on a chemical system, and so it goes on… Reducing (or eliminating) usage of these chemicals can feel like a bit of a leap of faith, but building a resilient, biodiverse system is likely to reward you in the long term. If you currently spray insecticides across your whole cropping area, you can start by limiting usage to targeted areas, or choose to stop spraying during spring and summer, when beneficial invertebrates are most likely to be affected.

Plenty of homes for wildlife at this agroforestry site at Eastbrook!


This quote from John Kempf’s blog on our human-centric view of what defines a pest perfectly explains our sentiment on this:

If we are to be stewards of these ecosystems, we must acknowledge that it is our management of the environment that determines whether these organisms express themselves as a benign participant or as a pest…

Neither the wolf nor the rabbit is a pest. They are symbionts in the environment and are dependent on the greater ecosystems they are a part of to sustain themselves…

If we desire them to not be present to the point of causing economic damage, we only need to manage the ecosystem differently.

It is possible to manage pest problems by healing the ecosystem to all it’s resilient glory – and all this depends on biodiversity. (Read the full John Kempf blog here.)

Minimising cultivation of your soil will protect species living below the ground, who are also incredibly important members of your farm’s food web (see our Earthworm Engineers series for more info on this!) The standing crop residue left in no-till systems is an important habitat for farmland mammals, birds and insects – keeping permanent cover in this way (and with over winter cover crops) greatly benefits your farm’s biodiversity, as well as your soil health.

How the soil web links together! (Source: USDA Conservation Service)

We hope that our using our new Soilmentor biodiversity tool can empower you to think about how best to boost your biodiversity! Getting into the swing of monitoring which species are present on your farm is an important step in realising what might be missing, and what you might need to improve. Read how to use the tool on the biodiversity protocol page and get started recording on your farm now! 

 

 

Information Sources

After the rain — How to get more forage from your pasture – Guest post by Niels Corfield

After the rain — How to get more forage from your pasture – Guest post by Niels Corfield 2592 1936 Soilmentor

This is a guest post by Niels Corfield, soil health, agroforestry and whole farm planning advisor, researcher and advocate.

What can we do to capitalise on rain when it comes; so we can get more forage and improve the health of our pasture and animals? I’m going to present some observations from pastures around the UK. Along with what I feel are the key opportunities available to graziers (in the West at least).

Key Observations
Below are 2 pics of the same spot in a permanent pasture. What is a fairly typical situation. What can we glean from them?

Firstly, and most importantly, there are clear bare patches. There could be as much as 50% bare soil, in this case.

These images are following a grazing event (in this case rotational grazing). This type of situation may well be similar to what is revealed after a hay cut, although in this case a low “sward density” maybe a more representative way to quantify the amount of bare soil, since much of the soil after a hay cut will be covered with residues (which is good but is only short term) and otherwise covered by leaves, though still open at the base — leaving space (bare soil) between the plants.

Bare patches in the pasture (as in all soils) are a weakness since it’s a place where water and carbon are lost, and soil health is declining. But they may also be an opportunity.

Ideally, there is no bare soil in pasture, it being covered by living plants, a tight/dense sward, with a closed canopy.

See here for details on recording bare soil in pasture.

Ideally these areas are covered with residues (litter or mulch). In a grazing situation, this would be the product of high stock density grazing management, where low utilisation rates leave residuals that are trampled on to the soil surface, see brief discussion on this topic in earlier article here.

A more ideal solution to this is to have a dense sward with leaves and turf tight enough that it forms a closed canopy that covers the soil surface.

We’ll focus on this second approach and see about turning this problem into a solution.

Selecting Options

Establishing seed into existing leys or pasture is notoriously tricky. In this piece I will not focus on the nuance of this process. Except to say that when selecting methods available to you, whether through contract work or doing it your selves, those options that score higher on the soil health principles should be preferred, see above. With obviously the plough down reseeding scoring pretty low.

A few of the standard methods are outlined below:

Ensuring Good Establishment

Broadcast Overseeding
In this case, where we have a high degree of bare soil, broadcasting is an option that is highly indicated. Basically, spinning-on a mixture of seed. Though slot seeding is still a good option, see below. Where considering broadcasting, there are a few things to bear in mind to get a good take:

1.Improve seed-to-soil contact by rolling or trampling
Cambridge rollers, cultipackers etc are suitable for this purpose as well as, grazing livestock at high stock densities — 100,000+kg live weight/ha, for a day or less (aka mob grazing) after broadcasting. Both these practices could be combined with mulching, or bale grazing, see below.

2.Retain soil moisture by covering soil
Even when there has been a lot of rain, it’s still a good idea to maintain that soil moisture, to improve the take.
Do this by spreading loose materials like straw, woodchip etc. To mulch the soil and keep the soil surface damp.
See pics below for illustration. And further discussion in mob grazing section at foot of earlier piece here.

3.Offer fodders in the field (while still moving the animals)
There’s a few different ways to cut this. But basically keeping the animals in the field and keeping them moving, ideally in tight groups, will aid the process of seed establishment. Different options include: bale grazing and green hay strewing.

Both methods mean being able to keep the animals in the field (when there’s insufficient forage left) and, particularly when combined with high stock density grazing they are ways to:

– tread-in seed — see point 1, above
– dung and urine densely — seeds will grow under pats
– provide some residues to cover seeds and retain moisture
– introduce perennial pasture seeds back into the pasture

In fact these solutions provide most of the functions required to achieve good take: seed contact, covered soil, seeds.
While also keeping animals out in the field, removing the need for muck handling in the yard. And providing better conditions for animals, than indoors.

Legume seedlings germinating in manure pile

Slot Seeding
Another option for establishing seed into pasture, perhaps where bare soil is less prevalent, and the appropriate kit is available, is slot seeding.
Drilling, rather than broadcasting means the seed will have the better seed-to-soil contact. It will also be placed below the surface where the soil moisture will be higher, at least nominally.
It is certainly more frugal with seed.
Perhaps the main drawback with this option, is that in these very dry conditions it may be difficult to penetrate the soil surface.
Either way, where the kit is available, this method is perhaps the most robust and economic — when it comes to seed, at least.

What Seeds to Sow

Making Initial Selections
We’ve talked about establishment options. So what’s the best seed to actually sow in the pasture? Given that we have run out of forage (due to a lack of regrowth) and we have a degree of dormancy in our pastures.
What might our selection criteria be for selecting plant species:

  1. Fast growth — forage available this season
  2. Bulk — lot’s of dry matter to make up for the short-fall
  3. Nutritious — ensuring sufficient animal performance

So, what type of plants meet these criteria?
Annuals, diverse mixes of them.

Why Annuals, What’s Wrong with Pasture Grasses etc?
Well in a word growth rate — annuals need to complete their lifecycle in a year or less (so it’s a sprint race for them), in that time they can grow tall and produce a lot of bulk and their seed is cheap. You might even have some in the shed right now.
In this case particularly, as a way to get an early bite, and to beat the season, they are highly indicated.
Coupled with that the option to use warm season species (those adapted for hot dry conditions) they’re doubly indicated.

How to get the best return on investment? Sow mixes of annuals.

Compared to this pasture species are perennials, they are: generally slower growing, slower to establish and typically much smaller plants (adapted for multiple grazing events in one season). This is all related to their life cycle of multiple year.
It’s not to say that they can’t be included in a seed mix for sowing now, but with annuals. There’s also the small consideration of seed cost. And grass seeds are on the upper end, needing to be purchased from specialists seed merchants. Another indication for hay strewing or bale grazing.

Principles of Diversity & Soil Health
One of the most important of the soil health principles is diversity. The key insight being that a diversity of plants feeds a diversity of organisms. This diversity is regarded as the key to soil organic matter formation and to a balanced diet for plants, as each organism has it’s own nutrient mineralising specialisms. Ensuring a better diet for animals.
Diversity is also correlated with increased yield.
This is where cover crops and pasture species, being mixes, really excel, compared to crops which have their own restrictions, tending to monocrops.
Once you add-in annuals into the mix, alongside perennials, you really can push the diversity lever up to 11!
Experience has also shown pasture cropping examples, like this, that have resulted in step-changes in soil aggregation, with all those extra living roots pumping-out exudates into the pasture.

Diversity in Action
When it comes to diversity, how much is enough? And what should you choose? Given there’s so much choice.
Thankfully there’s some simple rules, we have been offered from US practitioners, that we can follow:

  1. 8x species (or more) is a sweet spot, for soil health benefits, from
  2. 3 out of 4 functional groups

Functional Groups
What are these functional groups, and why are they important?
Well they give us some pointers as well as narrowing-down the options somewhat. They are:

  • Warm season grasses
  • Cool season grasses
  • Warm season broadleaves
  • Cool season broadleaves

Perhaps this seems like an odd list. And why choose warm season plants for instance?
Well, the first reason is they can actually grow really fast. Due to the fact they photosynthesise using different frequencies of light, more prevalent in strong sun situations. This is why maize is such a high yielding crop, growing to 7′ in a season. These plants are also known as C4 plants.
The other reason we’d select them, in this particular case is due to the fact that we are actually in a warm season, right now. And our pastures (which are all cool season species) have gone dormant or “burned off” because of the extended dry spell. Warm season plants are adapted for these conditions, and have the ability to grow through the “summer slump”. Though establishment is certainly still an issue.

The Specifics
Below is a table of the main species of cover crops.
Remember select 8 or more species from 3 or more of the functional groups.

There’s nothing to stop you using farm-saved seed: peas, oats, wheats etc.
The other option is to source bird seed mixes and feed cereals locally/in bulk. This will certainly bring down the cost, compared to a seed merchant.
In fact there’s a real advantage to doing this as it will allow you to up the seeding rate. If there’s one golden rule with cover crop establishment it’s:

Don’t skimp on seed, too little is as bad as no seed at all.

Putting It All Together

So what might a successful oversowing of annual-based forage mixes look like?
Some examples below. And a few new bits of jargon, all of which are relevant to this situation. Although the text mostly refers to a cropping situation, they are equally suited to pasture, when due diligence is followed around establishment. It’s clear to see that these mixes have the potential to produce large volumes of diverse (quality) forage in a short space of time.
Pasture stitching is the name given to drilling forage crops into pasture.

Final Thoughts

I hope that this piece offers some practical suggestions of what to do in droughted, burnt-off pasture or more generally in tired pasture, when you want to get a forage boost, or provide forage in the off-season, while improving soil health, and with it animal health — through better quality (diverse) forage.

Take Home Messages

  1. Use the soil health principles to inform your decisions and to direct your observations in pasture
  2. Cover bare soil by litter and living plants
  3. Choose rapid growing annual species for instant results
  4. Diverse plantings are preferred, where planting date is appropriate
  5. Keep costs down by: using your own seed/creative sourcing
  6. Experiment, try some different: mixes, seed rates, establishment methods

And for those that want to find out more, or discuss this in more detail please get in touch or consider joining me on one of my soils courses. If you have any thoughts or questions, get in touch: info@nielscorfield.com

Soil health courses & info
https://www.facebook.com/pg/nielscorfieldland/events/

Further Reading
Part 2 — Realising the Promise of Soil Health in Organic Horticulture
https://medium.com/@nielscorfield_90202/no-till-for-growers-realising-the-promise-of-soil-health-in-organic-horticulture-646fd553257

How to store water in your soil and prevent erosion

How to store water in your soil and prevent erosion 4032 3024 Soilmentor

As the weather in the Northern Hemisphere gets rainier going into the Autumn months, the question of our soils’ relationship with water springs to mind. We know that healthy soils absorb much more water than unhealthy soils, and that healthy soil is less likely to degrade into runoff, but what’s the science behind this?

We’ve done some reading around the literature on this subject, to learn how to keep our soils in top shape with regenerative agriculture, and to build a greater resilience to climate extremes like flooding and droughts. 

First, leaving soils uncultivated has been shown to increase the structure of macroaggregates within the soil – many studies show an improved macroaggregate stability in soils under no-till compared with ploughed soil (1,2). This is because the net of undisturbed roots and mycorrhizal hyphae entangle smaller aggregates together, reducing the likelihood of soil runoff during heavy rain, and increasing porosity. You can easily assess the macroaggregate stability of your soil with the VESS test or the Slake test (and the results can then be recorded within our Soilmentor app!). Hopefully, having an awareness of how your soil scores on these tests will help you to understand how to improve your soil health! 

A long-term study found that conservation agriculture plots retained ⅓ more water under both wind and water erosion compared with conventionally tilled plots (3). Reducing wind and water runoff is significant – we know for example that the devastating US ‘Dust Bowl’ in the 1930s was caused by intensive cultivation, and hugely impacted food security at the time – it’s estimated that 300 million tonnes of topsoil was swept up by the wind, destroying crops and killing livestock (4). With extreme weather events increasing due to climate change, building soil resilience is of utmost importance.

In the same vein, agricultural runoff causes massive ecological damage, and is a major source of nonpoint source pollution in water systems – with runoff likely containing fertilisers, pesticides, nutrients and topsoil. A study comparing four streams with catchments from land under different management, found streams feeding from land under conservation agriculture had a higher diversity of invertebrates and more ‘clean water’ species than streams under tilled land, which was attributed to improved soil structure reducing agricultural runoff (5). The reduced topsoil runoff into nearby rivers and streams also reduces sedimentation, which increases the river’s capacity, as well as the clarity of the water – allowing sunlight to benefit the wildlife and photosynthesis in aquatic plants. Rivers with high sedimentation also absorb more heat from the sun, causing local warming which potentially causes further damage (6). 

Soil erosion in the UK is clearly visible from space. Credit: NEODAAS/University of Dundee

We loved seeing the rainfall simulator at Groundswell this year – it really helped us to visualise the ability of healthy soil to absorb rain! You can watch a video of a rainfall simulator in action here.

Rainfall simulator in action at the 2019 Groundswell show – the bottles on the ground show the water that filtered through the soil in each plot, while the hanging bottles show the ‘runoff’ water.

So, to wrap up, healthy soils absorb and hold more water than degraded soils, which helps to reduce flooding, aquatic pollution, and resistance to drought conditions and wind erosion! Keeping your soil optimally protected involves minimal disturbance, continuous cover with mulch and living roots, and root diversity (from crop diversity) allows for increased microbial populations which help to aggregate soil. All of these come under the soil health principles.

We developed Soilmentor as a simple solution to help farmers monitor their soil health progression – seeing your soil health improve over time helps you to understand which farming methods are working for you, and hopefully give you an incentive to stay on a regenerative journey!

Learn more about making your soil rain-ready here, and learn about monitoring the impacts of water run-off here

Paper references:

  1. Congreves, K.A., Hayes, A., Verhallen, E.A., Van Erd, L.L. 2015. Long-term impact of tillage and crop rotation on soil health at four temperate agroecosystems. Soil and Tillage Research. 152: 17–28.
  2.  Parihar, C.M. Yadav, M.R., Jat, S.L., Singh, A.K., Kumar, B., Pradhan, S., Chakraborty, D., Jat, M.L., Jat, R.K., Saharawat, Y.S., Yadav, O.P. 2016. Long term effect of conservation agriculture in maize rotations on total organic carbon, physical and biological properties of a sandy loam soil in north-western Indo-Gangetic Plains. Soil and Tillage Research. 161: 116–128 
  3. Van Pelt, R.S., Hushmurodov, S.X., Baumhardt, R.L., Chappell, A., Nearing, M.A., Polyakov, V.O., Strack, J. 2017. The reduction of partitioned wind and water erosion by conservation agriculture. CATENA. 148: 160–167
  4. Baveye, P.C., Rangel, D., Jacobsen, A. R., Laba, M., Darnault, C., Otten, W., Radulowich, R., Camargo, F.A.O. 2011. From dust bowl to dust bowl: soils still a frontier of science. Soil Science Society of America Journal. 75: 6
  5. Barton, D.R., Farmer, M.E.D. 1997. The effects of conservation tillage practices on benthic invertebrate communities in headwater streams in southwestern Ontario, Canada. Environmental Pollution. 96: 207-215
  6.  Lal, R., Reicosky, D.C. & Hanson, J.D. 2007. Evolution of the plow over 10,000 years and the rationale for no-till farming. Soil and Tillage Research. 93:1–12

What is soil health and why should farmers and growers care about it? Guest post by Niels Corfield

What is soil health and why should farmers and growers care about it? Guest post by Niels Corfield 2379 1770 Soilmentor

This is a guest post by Niels Corfield, soil health, agroforestry and whole farm planning advisor, researcher and advocate.

In this article I’d like to lay out the main tenets of soil health, but before that I want to present what I feel are the main motivations for “going to all that effort”!

Why bother about soil health?

First of all, in this climate change acceptance world, all forms of agriculture, and land use must wipe their face in terms of carbon. Being at least carbon neutral, if not carbon negative (or positive, whichever way you prefer it phrased).

All land, and all production must sequester carbon and it can, it’s been done, one example has raised their soil organic matter (SOM) from 2.4% to 8–11% in 6 years. 0.5–1% per year increases are regularly achieved.

Every single cropping cycle is a growth cycle and therefore should be net cumulative, in terms of carbon — through the process of root exudation. Simply put, all plants have the potential to improve soil (fertility), it’s the simply the management and composition of those plants (in space & in the rotation) that determine this fact. However, this is very hard to achieve when regularly cultivating, for example.

If you’re serious about climate change, business as usual is not an option. The good news is if you rigorously apply the same health principles production can be carbon negative.

What’s in it for us?

Apart from saving the planet, are there any other arguments for adopting novel practices? Is it just about doing good while our livelihoods suffer? Not at all!

Adopting the soil health principles wholeheartedly is one framework that can both address global issues and bring production benefits — showing that cropping (and farming) doesn’t have to be a zero sum game.

How would these benefits manifest? Everyone knows how well their crops look when the land is in good heart. And that that translates to fewer crop failures, less drought-stress, better infiltration and more yield. Moon on a stick? All of these are correlated with better soil health.

Another benefit of better crumb structure will equate to fewer passes to raise a seed bed, where cultivation is practised. That’s less diesel and better windows for field access (a window that’s fast becoming undependable). Either way there’s wins to be had once we harness the latent potential of plants.

Grass & fertility

Perhaps one of the few things that farmers (and growers) can agree on is that the land is “in best heart” the first year out of grass. So, is there something magic about grass, compared to other plants? Does it have unique “healing powers”?

Basically no, but to be clear, what is it we can say about the conditions under grass?

A living root, covered soil, undisturbed, diverse (ideally), some animal impact (potentially) and few if any chemicals.

Cropland (at left) — Grass margin (at right)

Soil fertility (health) can and should be built within the cropping phase of our operations, and can be achieved without going to grass. Not that grassing-down and fallowing aren’t efficacious practices, just that we have more tools available to us that are perhaps more appropriate in a cropping situation. We just need to closely mimic those conditions we find under grass, and that’s where the soil health principles come in — 7 ways to help you select management practices, and to make decisions on your operation that build soil: cropping or fallow, spring or fall.

One key insight — microbes matter

Perhaps the most important single insight that underpins, most, if not all of us or health principles is the understanding that microbes matter. And they matter to us the growers. But, why do they matter? What’s so good about them? And, what do they do for us? There are three parts to the answer:

Firstly they create crumb structure. Their actions bind together disparate soil particles into crumbs or “aggregates”.

Secondly, they feed plants. They digest elements out of the soil mineral matrix (as well as organic matter) and transform them into plant available nutrients. They literally eat rocks. Hitherto known as decomposition but since the process is done enzymatically it’s much more akin to digestion.

This is what’s known as the “microbial bridge”. Simply put, plants (and healthy plants in particular) are nourished by nutrients provided by organisms.

Thirdly microbes protect plants. Through a number of different mechanisms they either out compete or shield plants from disease-causing organisms and often pests as well. Perhaps the poster child of this final point is mycorrhizal fungi that snare root feeding nematodes which when caught are then digested and past up to the host plant.

So the plants are getting a pretty good deal here! They’re getting a nice loose structure to push their roots through easily, room service and their own live-in healthcare service. Are they getting all that for free? Emphatically no, this is where the soil health principles come in, read on..

The Soil Health Principles

Weed roots, rhizosheath forming (at upper left)

1 The Living Root — maintain a living roots in the soil for as long as possible and as often as possible

This is number one on the list because perhaps it is the most important. Because, simply put, roots make soil and they do this by producing root exudates, — carbon secretions that feed (and recruit) soil organisms, which in return deliver plant available compounds, right in the “root zone”.

Gothelney Farm: Rhizosheaths on oat cover crop (Photo: Fred Price)

If you want to see the effect of the living root on soil structure examine the soil around the roots of the healthiest plants on your farm (often a weed!). So the next time you’re out in the field, take a moment to carefully lift one or two plants and examine those roots. You will typically notice finally grained soil that has excellent crumb structure, potentially some of which may be actually stuck to the roots themselves, in what’s called a “rhizosheath”, this is a phenomenon seen where microbes are active and producing the glue like substances that bind together soil particles into aggregates. Where you see rhizosheaths you can infer from that that root exudation is taking place, as, without this carbon (energy) source these organisms would be inactive.

What you are seeing is soil building in action — where you are seeing crumb structure around roots and rhizosheaths. Without roots and root exudates, organisms become inactive, microbial populations become simplified and ultimately aggregates become consumed by those same organisms, since they have nothing else to eat, as these, glue-like substances, are all organic (carbon based) for example polysaccharides, hence are comestible. Literally the structure of aggregates is edible, Think Hansel and Gretel.

2 Covered Soil — protect soil, from wind, rain and sun, with leaves or residues

Maintaining a soil cover is essential. This is a fact that “nature intrinsically understands”, which is why bare soil is such a magnet for weeds, because without a cover, soil degrades quite rapidly, nutrients are lost, soil caps and water runs off. Ultimately that porous structure crumb structure that we all value is sacrificed. We should be taking steps to reduce the frequency of bare soil as well as the length of those periods.

Bare soil is the enemy of soil health. Don’t farm naked as some say.

3 Minimise Disturbance and Compaction — reduce tillage severity and frequency

No dig and no till are perhaps the foster children of the soil health movement but certainly it shouldn’t be reduced to this one single measure. Simply shifting to no-till and making no other changes will not bring the kind of results that we are really looking for. It will not bring health back to the soil on its own, it must be coupled with the other principles and particularly diversity. That said it’s worth expanding on the rationale for not tilling, by laying out the issues with tillage itself.

The first and most important point to make is that tillage destroys soil structure. This seems counter-intuitive because one of the primary reasons for tillage is to improve structure, or to get a tilth. While certainly there is a loosening effect post tillage, this is a short lived phenomenon, however, the structure of the soil is soon lost and it will then settle back into it’s more native, mineral-structured state, more akin to the subsoil. If all conditions are right then the crop can be established in this short phase, but this window is getting more unreliable by the day.

The reason that tillage destroys soil structure is because when we are talking about crumb structure we are talking about aggregates ultimately, and aggregates are made of small soil particles bound together with glue-like substances that have been secreted by organisms. When you till you break open these aggregates, splitting apart these crumbs, exposing them to oxygen at which point “R-strategist” organisms invade the space and rapidly decompose or digest (literally eat) the binding agents that glue together these crumbs. The process of aggregation is directly analogous to that of making biscuits in that the homogeneous flour (and sugar) particles are bound together by the butter or fat into larger non-uniform (heterogeneous) clumps or crumbs. In this analogy the sugar is analogous to sand and the flour is analogous to clay. And the fat is analogous to those binding agents, those polysaccharides that are biologically derived in the same way that a fat is.

Generally speaking if you want retain good crumb structure then reduce tillage — reduce the depth-, the frequency and minimise inversion.

That said, is there a place for tillage as a force for good? That depends much on the starting point. But there does seem to be a small number of clear cases where tillage (or mechanical interventions in general) can help to rectify the situations related to past management.

If your starting point is tired old pasture (But I thought you just said that pasture ticks all the soil health principles? Well yes it does, but management is always superior).See photo below: Old pasture (especially horse) may well be heavily consolidated and there’s only so much that your crop roots and even cover crop roots can do to undo this situation. In horticulture operation the Real Food Garden, they good results with ploughing the existing pasture and then a year of cover cropping before conversion to no dig.

Horse pasture (at right) — Fence line (at left)

4 Diversity — increase diversity in your plantings and rotations

Diversity above ground feeds diversity below ground. If you want your plant to have a balanced diet it needs to associate with a diversity of organisms that mineralize a diversity of nutrients.

It’s been shown that so that the formation of humic substances and stable aggregates is closely correlated with below ground diversity.

Below ground diversity requires a diversity of foods, from a diversity of root exudates etc.

This is one realm where cover crops can really excel. We can bring in so much diversity. And so long as we’re destroying without tilling, we can retain a significant portion of that beneficial structure. This diversity can be so much more, it can include C4 plants, which are rare and general in the UK cropping situations. Plants like maize, millet, sorghum, quinoa, amaranth, and the more common sunflower and buckwheat.

Trill Farm: High diversity (at left) — Low diversity (at right)

All these fancy seeds in a mix sounds expensive don’t they? Well it doesn’t have to be, just source your seeds from the feed merchant, rather than the seed merchant. Bird seed mixes are a great starting point and most of them already have the 8 species or more, recommended: broadleaves and grasses, warm season and cool season. And when the costs are low you can start sowing at proper seed rates which maybe 2 times or 3 times the standard advice. This overcomes the main pitfall people have when experimenting with cover crops: too little seed.

Schumacher College: Amaranth crop

That said, diversity isn’t limited to cover cropping. We can introduce diversity into our cash cropping operations. This is potentially where some of the biggest wins are actually to be had. Given that increasing species diversity from 1 to 2 represents a doubling in diversity that’s a big win. And going from 2 to 3 represents another 50% increase. So, include: catch crops, intercrops and relay crops whether practical.

There should be gains to be had in this case, so long as we doing our due diligence with the other soil health principles — especially around bare soil and the living root. Again we don’t want massive space between the plants being unfilled with roots and uncovered. This is where intercropping and catch cropping can really pay dividends.

5 Feed Soils — hungry organisms need food to stay active and healthy

This is definitely one area where the organic crew got it right. But what do we mean by this? What eats stuff in soil? Well organisms, life, life eats stuff. Not the “soil” per se, as this is simply a matrix of geological degradants.

What actually eats stuff in the soil is soil organisms: the soil food web members. So the question is then, what do these soil organisms like to eat? Really we’re talking about fungi and bacteria in this case, as they make up the vase majority of soil biomass. So, what’s their preferred food? Well in this case it’s root exudates. Simple to utilise (metabolise) foods such as carbohydrates, often as straightforward as glucose. But that is what’s being supplied by the roots, no? So, that’s covered under principal number one — the living root, right?

Well yes. Except we are in a cropping situation which means there may be a break in cropping. Where there’s a break in cropping, the organisms that are present in the soil, those active communities of bacteria for example that have built up, through your good management of cropping (and potentially diverse cropping) will all go dormant, but before they do, that they will consume the most readily available food source present. And what is that in this case? It will be the binding agents that hold the aggregates together. They will literally eat their own homes because there’s nothing else to eat. Evoking that famous phrase “burning the furniture” — when you’re snowed in and it’s freezing outside and you run out of firewood, you’re only alternative to keep warm is to burn the furniture but once you’ve done that where are you going to sit?

So what are we to conclude from this observation? Simply, where a break in cropping exists, provide a subsistence ration. This would typically be over winter. But either way, this is the prime time to apply bulky organic matter. And if all goes well, when you come to plant your next crop you will have a nice surface tilth and an active population of organisms ready to immediately associate with your plants.

The last two soil health principles are perhaps the least relevant to an organic growing situation. However I include them for the purposes of being thorough.

6 Incorporate Animals

Diversify your straight cropping operation by rotating animals or integrating livestock into your system.

So what’s good about animals? What benefits can they bring to a cropping system? Firstly, their manure contains inoculants that are rare, even in good compost and they can carry out the work of distributing (or applying) that manure through their own natural behaviour.

That said the key rationale behind this particular principle is that all ecosystems contain animals as part of the web, and they add a whole new dimension of diversity to the system so perhaps they should come under principal number 4, but in this case the desire is to be explicit.

Ian Boyd’s farm Whittington Lodge

7 Minimise Use of Chemicals

Simply put, the use of chemicals and synthetics undoes all of your good work further up the list.

Firstly, use of synthetic fertiliser or soluble nutrients in general discourage, the production of root exudates. Basically root exudation is a quid-pro-quo for plants. They’re effectively paying for nutrients in a form that they can absorb with energy (or sugars) the only currency plants hold. So, when a plant is artificially nourished through soluble fertiliser applications it’s need to offer exudates is removed, though this is fine in the short term, however, the removal of foods from our friendly minions (the soil microbes) means they will at best go dormant and at worst start chowing down on the aggregates themselves because there’s nothing else to eat and then go dormant.

Fertilisers in salt form, and in very high concentrations, actually force their way into the plant structure. So the plant almost becomes over nourished or certainly has no control over the quantities and types of nutrients that enter the cell structure.

Further to this and perhaps, more obviously is the use of pesticides etc which basically have all sorts of impacts on non-target species. But it goes without saying that applications of fungicides for example have detrimental effects on mycorrhizal fungi, though that said, so does tillage.

Putting it all together

Ultimately the strengths in this approach, this framework, is that the principles can be applied individually or in consort. But ultimately the real wins are to be had where all of the soil health principles are applied both in the cropping phase and fallow periods.

I like to think of the soil health principles as different levers maybe like you might picture in an old signal box, or a graphic equaliser. With each lever representing a different principle. Ultimately, over time want to be able to push all of the levers up to full, bring all of the benefits to bare.

Furthermore, for each principle there’s obviously a range. Similar to gears on a gearbox. Ultimately where limited by equipment or tools, it’s like being unable to change up from 3rd gear for instance. There’s nothing worse than being stuck in 3rd gear on the motorway. If we can gradually increase the upper maximum we can achieve each year we will gradually be able to leverage more of the latent power of nature to grow better crops.

Conclusion

So in conclusion, the soil health principles are another iteration of nature mimicry, offered, in this case to farmers and growers as a tool for decision-making on-farm.

Simply put, where two options are considered for a particular situation, that which scores highest, in terms of the soil health principles, should be preferred, where practical, or when it becomes practical.

I hope that you will use these principles in your day-to-day practice and in your longer-term rotation planning.

And for those that want to find out more, or discuss this in more detail please get in touch or consider joining me on one of my soils courses this autumn. If you have any thoughts or questions, get in touch: info@nielscorfield.com

Soil health courses & info
https://www.facebook.com/pg/nielscorfieldland/events/

Further Reading
Part 2 — Realising the Promise of Soil Health in Organic Horticulture
https://medium.com/@nielscorfield_90202/no-till-for-growers-realising-the-promise-of-soil-health-in-organic-horticulture-646fd553257

Soil Science Latest: How Can We Sequester More Carbon and Build Soil Health?

Soil Science Latest: How Can We Sequester More Carbon and Build Soil Health? 3024 2257 Soilmentor

A few weeks ago we presented at Wageningen Soils Conference with Elizabeth Stockdale, Head of Farming, NIAB. We shared about the work we had done together converting the AHDB soils scorecard into an interactive Soil Quality UK Dashboard, with the main focus being “How can we get farmers talking about their soil health, based on soil health tests?”. We had lots of brilliant feedback about the dashboard we built and everyone at the conference was very positive as we talked about the benefits of a very different, more thoughtful, type of user research.

Whilst we were there we also listened to many brilliant talks sharing the latest soil science, some of which were incredibly relevant to the farming community, so we want to share the insights with you.

Building short-term vs long-term Carbon – it’s all down to the microorganisms!

We have all heard of words like humus, humic acid etc in terms of soils and carbon stored in soils. Well it turns out in the words of Johannes Lehman, soil scientist at Cornell University “humus is dead”.

He was very clear that it’s false to think there is such a thing as a long term carbon store that is locked up forever.

The idea that stored organic carbon can be neatly separated into 3 different types (Rapid, labile, stable), which has been the model for many years, is not reflected in the research any longer.

We shouldn’t worry about the idea of building long term carbon vs short term carbon, essentially all carbon that is sucked into the soil via photosynthesis or decaying organisms has the potential to become long-term carbon. What actually matters is which microorganisms are present and what they do with it.

There is no clear silver-bullet pathway to locking up carbon for good, instead we can think of soil organic carbon as an ongoing cycle of carbon gains and losses which we need to constantly manage. To many farmers this may not come as a surprise – that is exactly what we have seen happening in the field. As we practice more regenerative approaches (living roots in the soil, ensuring plenty of plant residues etc) we are quickly seeing the advantages of healthier soils which is so often synonymous with higher soil organic carbon and a more alive soil system (i.e more microorganisms).

Read more in this paper: Microbial models with minimal mineral protection can explain long-term soil organic carbon persistence
Dominic Woolf & Johannes Lehmann  Scientific Reports volume 9, Article number: 6522 (2019)

Johannes showed that soil management techniques on farm to improve food security can have large beneficial effects on soil organic carbon. He drew from an example of changing agricultural practices in Ethiopia where they have been implementing agroforestry, diversified cropping systems, terracing, and many other agroecological practices — first and foremost as a measure to decrease poverty and prevent future drought scenarios. The project was undertaken on 600,000 Ha and had many benefits to the community, food security as well as environmental rehabilitation. However Johannes pointed out that it also had an unintended positive effect of sequestering significant amounts of carbon helping Ethiopia to meet their climate targets.

Read more in this paper: Land restoration in food security programmes: synergies with climate change mitigation
, & Climate Policy Journal Pages 1260-1270 | Received 24 May 2017, Accepted 05 Jan 2018, Published online: 26 Jan 2018

Carbon Current Account and Interest Rates

We discussed these findings with Elizabeth Stockdale, Head of Farming at NIAB, and she gave the analogy that this implies we need to think of our soils like a current account – you are constantly making deposits and withdrawals of carbon, and that will be reflected in your carbon balance. From a farming perspective, what I wanted to know is what is the interest rate on this current account? That essentially would reflect how effective we will be in the long run at sequestering carbon in soils and building up our SOC. The banking analogy also makes a lot of sense, as it reflects the fragility of soil carbon in the face of larger scale disasters and fluxes in the market, as everything can be ‘lost’ at any time.

In summary Johannes Lehmann’s work showed that the focus of building soil organic carbon should be on farm ‘short-term’ carbon cycling interventions (e.g cover cropping, leaving plant residues, agroforestry, composting applications, rotational grazing) and the microorganisms will do the work to build longer term carbon deposits from there! Unfortunately this new understanding of soil organic carbon and the value of microorganisms has not been incorporated into IPCC models yet, so the value of these practices aren’t fully taken into account in global carbon targets…but Johannes said it will all change quickly.

Johannes also posited that the traditional models for understanding soil, based on adsorption and aggregation, although helpful in their way, are not necessary to explain soil organic matter and soil functioning. His work has shown that soil organic carbon and soil function can all be explained by the makeup of microorganisms and the action of microorganisms in the soil. It’s early days for fully understanding this as we still only understand around 5% of all the microorganisms in our soils!

 

The Soil Microbial Carbon Pump – how do microorganisms affect carbon storage in soils?

One model put forward for understanding the effect of microorganisms in sequestering carbon in soils was the Microbial Carbon Pump, explained by Chao Liang from the Chinese Academy of Sciences. The Soil Microbial Carbon Pump is a model for understanding how microbes are an active player in soil carbon storage. Chao showed how it could be applied at many different scales from the rhizosphere (plant root-soil interactions) to the field and landscape scale, which could have implications for understanding the responses of ecosystem carbon processes to global environmental changes.

My interpretation of what he was saying is that there are two types of carbon sequestration pathways through soil microorganisms:

  1. Biomass: The living biomass of the soil i.e living microorganisms taking carbohydrates being offered by plant roots and using it for food, excreting it in the form of slimes, building fungal hyphae etc. This is what Dr Christine Jones refers to as the liquid carbon pathway. (Catabolic pathway)
  2. Necromass: All the dead material, whether plant residues or compost materials etc being broken down and processed by microorganisms. Increasingly scientists are recognising the important role this plays in building soil organic matter. (Anabolic pathway)

Read more in this paper: The Importance of Anabolism in Microbial Control over Carbon Storage
Chao Liang, Joshua P. Schimel, Julie D. Jastrow Nature Microbiology volume2, Article number: 17105 (2017)

Chao showed how this model allowed them to investigate the effects of plant covers on microbial communities and what that meant in terms of the magnitude and composition of the soil carbon pool. He outlined that once the Microbial Carbon Pump processes carbon, it will either be released back to the atmosphere as CO2 – known as the priming effect (i.e decreasing the storage life of the carbon) or further increase the storage life of the carbon – known as the entombing effect. Their results showed that as the fungal proportion in the microorganism community increases the amount of carbon that goes through the entombing effect and becomes longer term carbon significantly increases after a certain time and then remains constantly high, whilst the priming effect although initially peaks, it then decreases and falls significantly below the entombing effect (you can see this in the photos below, where the high fungal content soil sample is the middle graph, highlighted in red)

Essentially what that means is that in soils with a higher proportion of fungi, the carbon is more likely to be turned into longer-life carbon deposits.

What does this mean for farmers?

The scientists are saying that yes it’s all about building microbial communities if you want to increase soil organic carbon.

There is no silver bullet, but it will take new management strategies based on careful monitoring of carbon gains and losses and making sure you are building more carbon on a field than you are taking away.

We can very much see ourselves as key actors when it comes to reducing greenhouse gas emissions and sequestering carbon at a global scale and that employing methodologies that improve soil health and soil microbial communities are the best way to do this. Of course, we already know this is what regenerative agriculture, conservation agriculture, permaculture and so many other farmer-led practices are all about! But it’s good to know the scientists are behind it all, and we hope this will enter the minds of the policy makers sooner rather than later!

We learned a lot from the conference and you will see some changes to Soilmentor in the coming months as we reflect some of our learnings to bring you some new tools to help you understand what your soil monitoring results mean.

Earthworm Engineers #4 – Manure & Earthworm Populations

Earthworm Engineers #4 – Manure & Earthworm Populations 1600 1067 Soilmentor

Welcome to the fourth and final post in our Earthworm Engineers series, where you can learn from some of the best science about the value of these amazing creatures. We’re so excited that Professor Jenni Dungait is now the editor of the European Journal of Soil Science – and she’s made some important earthworm papers open access for a month. We’ve picked our favourite four and summarised them in this blog series.

Access the earthworm archives in the European Journal of Soil Science, to learn more about the science behind on-farm worms!


#4: Quantifying dung carbon incorporation by earthworms in pasture soils

This study looks at the effect of different earthworm communities on the amount of soil carbon (within dung applications) shifted into the soil. They tracked this process by labelling the carbon with isotope tracing, which is a clever technique that gives a really specific picture of where exactly the carbon is moving to. The three main earthworm types were tested in different treatments: surface-dwelling worms (epigeic), deep-burrowing worms (anecic), and network-creating worms (endogeic).

First, the researchers found that with increasing inputs of dung, the abundance of earthworms tested also increased, presumably because the worms had a more consistent food source in these pots and could flourish!

Most of the tracked carbon was found in the soils top layer (0-75mm), although when the earthworm population included deep burrowing (anecic) earthworms, carbon from dung was often found at depths of up to 300mm, which shows just how effective these worms are at burrowing materials from the soil surface into its lower levels. The most successful treatments (with the greatest flow of dung shifted into soil organic carbon (SOC)) were those with all three types of earthworms present (epigeic, anecic and endogeic). So, a diverse population of worms is necessary for optimal dung break down into soils!

In pasture soils, dung left by livestock can therefore contribute to increased earthworm populations, as well as increasing soil organic carbon. This is important for the soils nutrient supply, and also helps to reduce CO2 levels in the atmosphere, which has potential to reduce the effects of climate change. In conventionally grazed systems, the quantity of dung deposited per hectare are less than the amounts used in this study, but it’s interesting to think about how this research adds to the evidence supporting mob-grazing systems, where livestock graze fields more intensively, and more manure is deposited per hectare as the stock moves through!


Earthworms are one of the best indicators of soil health – find out how to monitor earthworms on your farm.

Earthworm Engineers #3 – Organic vs Conventional Systems

Earthworm Engineers #3 – Organic vs Conventional Systems 5184 3456 Soilmentor

Welcome to the third instalment in our Earthworm Engineers series where you can learn from some of the best science about the value of these amazing creatures. We’re so excited that Professor Jenni Dungait is now the editor of the European Journal of Soil Science – and she’s made some important earthworm papers open access for a month. We’ve picked our favourite four and summarised them in this blog series.

Access the earthworm archives in the European Journal of Soil Science, to learn more about the science behind on-farm worms!


#3: The impact of soil carbon management on soil macropore structure: a comparison of two apple orchard systems in New Zealand

This study compares two sites of the same soil type under apple orchards on one farm. One site had been under organic treatment, with regular compost application and grass cover, while the other was under ‘conventional’ treatment, with regular irrigation, fertilisation and herbicide applications.

When testing for earthworm populations, the researchers consistently found more earthworms in the organic soil compared with the conventional soil. They also reconstructed the 3D ‘macroporosity’ structure of both soils using X-rays, and again found greater macroporosity within the organic soil compared to the conventional soil. This isn’t a coincidence! Macroporosity is defined as the network of pores with a diameter of over 0.3 mm in the soil, and earthworms are known to create these kinds of channels.

This increased macroporosity is important for several reasons. First, it is known to increase the rate that CO2 in the atmosphere is locked up as soil organic carbon (SOC), which both increases soil fertility and also has potential to reduce the rate of climate change. As expected, this study then found that the organic orchard had a 32% greater SOC content than the conventional soils! Increased macroporosity also improves the soil structure, as the stability of soil aggregates is increased, which allows more microbes to live in the soil.  

Denitrification rates are known to increase in anoxic, water-logged soils, which leads to increased emissions of N20, a gas that contributes to climate change. As a result, increased macroporosity reduces denitrification in the soil, by allowing oxygen to penetrate into the topsoil, and reducing the chances of water logging.

It’s amazing to see evidence of how organic techniques allow our earthworm friends to flourish, and how positive their presence is in orchard soils!

Read the fourth and final instalment of our Earthworm Engineers series here!


Earthworms are one of the best indicators of soil health – find out how to monitor earthworms on your farm.

Earthworm Engineers #2 – Arable Farming & Earthworm Populations

Earthworm Engineers #2 – Arable Farming & Earthworm Populations 5184 3456 Soilmentor

Welcome to the second in our Earthworm Engineers series where you can learn from some of the best science about the value of these amazing creatures. We’re so excited that Professor Jenni Dungait is now the editor of the European Journal of Soil Science – and she’s made some important earthworm papers open access for a short time. We’ve picked our favourite four and summarised them in this blog series.

Access the earthworm archives in the European Journal of Soil Science, to learn more about the science behind on-farm worms!


#2: Effects of different methods of cultivation and direct drilling, and disposal of straw residues, on populations of earthworms

This paper was written in 1979, and uses some pretty intense soil sampling methods (dousing the sample sites with formaldehyde to isolate worms) – we think they probably could have done with Soilmentor to count earthworm populations at each site!

The paper makes some interesting conclusions about the effects of cultivation on earthworms in topsoil. They tested the number of earthworms over four years on direct-drilled fields that were sprayed with herbicide before planting, and ploughed fields (of varying soil types). They found earthworm populations were consistently greater in the direct-drilled soils compared with ploughed soils, although deep-burrowing species were affected similarly in both treatments.

They also test the effect of spreading mulch on the fields compared to burning straw residue, and find (unsurprisingly) that earthworm populations were greater in fields where straw residue was spread rather than burned, particularly in surface feeding species. This surface debris becomes an important food source for the worms, and makes their diet more stable.

The paper also suggests that the extra earthworm channels created under no-till soils may help to reduce any compaction in the soil, as well as distributing organic matter and increasing drainage. The presence of worm channels may also allow plant roots to penetrate more deeply, which can also reduce compaction.

It’s nice to know that regenerative farming approaches have such a positive influence on the earthworm community. We’re really excited to speak at Groundswell this year on how to become a soil expert on your farm, and to learn more about the benefits of no-till systems.

Ready for to learn even more about the wonder of worms? Read part 3 of Earthworm Engineers here.


Earthworms are one of the best indicators of soil health – find out how to monitor earthworms on your farm.