Slide 1CORE MODULE II
The Living Soil
S o il
• What are the influences on soil formation?
Parent material
the different proportions of the mineral
particles.
• Clay – very fine particles, sticky feel
• Peat – very dark colour, smooth feel
S o il
• It influences natural fertility and the ease of
management
in turn affects the degree of soil aeration
• Clay particles have particular properties
• Texture cannot be changed
aggregated e.g. crumbly, cloddy, solid!
• Structure is a soil property that can be
changed, sometimes for good and sometimes
for the worse.
• The ideal is an open soil with good ‘crumb’
structure (50% space and 50% solid matter
S o il
• Should we treat soils as living organisms?
• A healthy soil does exhibit some
characteristics of a living organism
Respiration
Excretion
not breathing
open structure BUT
• A balance needs to be struck
S o il
residues and manures
• Contributes to humus building
• Humus in soils: high CEC, high WHC (5 x that of
clays), high surface area
stability and is resistant to decay
• Increases nutrient supply, aeration and depth of
rooting zone
• This is the soil component that many do not consider
• If there are spaces between aggregates they are filled
with either air or water, ideally a balance
• Plant roots need oxygen and they need to get rid of
carbon dioxide
organisms are the same (the bad ones are often
anaerobic)
S o il
• Drainage and run-off issues also important
• Soil analysis is recommended as fertility
requirements for vegetables are different
• If inputs required then apply in advance if possible
• FYM can cover a lot of the requirement but not all
• Lime may or may not be required
S o il
• Macro-nutrients: N, P, K, Mg, Ca, (S)
• Micro-nutrients: trace elements
bacteria, fungi and other soil microbes
• Avoid soil compaction, erosion, structural
damage and maintain appropriate lime
status
fertility as a key part of the system.
• System-oriented practices which benefit biota may
have already be in place for a range of other reasons
including fuel reduction, carbon sequestration and
conservation of above-ground biodiversity, etc.
• Farmers rarely adopt one practice just to improve
soil biota; they are adopted as part of an integrated
policy of soil management
components need energy and nutrients
• Primary energy source is organic matter
• Compost, green manure, crop residues, soil
organisms
not the plant’
S o il
matter inputs;
intensity);
inoculations, etc.
Roger Hitchings
University of Newcastle, to the ORC Producer
Conference 2013
• Much of Liz’s content was based on a Natural England
project: “Managing soil biota to deliver ecosystem
services” (NECR100)
publications.naturalengland.org.uk/publication/2748107
Resources Conservation and Agricultural Resource
Services
Crops suffering in extreme weather”
• “Seeing how the same soil is different under different
management”
• “As an organic farm everything we produce comes from
the soil; an understanding of the soil in each field is
essential to produce high quality livestock / crops”
• “Adopting min till and beginning to see the long-term
effects”
conventional farming wasn't taking advantage of”
S o il
• The importance of biological fertility
• How to increase it
• The soil is home to roughly one quarter of all
living land organisms
as any found on the planet
• It features a wide range of taxa or types
• The range runs from viruses to moles
• All contribute to the benefits but some are
more influential than others
Stabilise soil particles with ‘glues
Vulnerable to cultivations & pH changes
Excellent indicators of soil quality
• Algae
Blue-green algae fix nitrogen
Depend on oxygen
structure
S o il
collects phosphate and trace elements
• Root sheath and mycelium increase surface
area for absorption of nutrients
• Cultivations are bad news
Brassicas – can take 3 years to build up
S o il
that sustain terrestrial life:
Decomposition and recycling of organic matter
Maintenance and improvement of soil structure
Improvement of moisture retention
Moderation of pollution
S o il
• Nitrogen gas is very common but of no use to
plants
nitrogen to nitrate and ammonium, forms that
can be used by plants
• Nitrate is very easily leached from the soil
• Denitrification occurs in poor soils
S o il
• Carbon dioxide is produced during respiration
• CO2 is absorbed during photosynthesis
• Carbon:Nitrogen ratios are important in
controlling the availability of nitrogen and the
rate of decay to humus in the soil
• Additions of C-rich or N-rich inputs will
disrupt these processes
S o il
• The soils on farmed land have generally
simplified ecological systems and soil food webs.
• There can also be significant differences in
biomass, activity and diversity of soil biota in
different agricultural systems
S o il
Bacteria 100 mil. -1
Fungi Several
Nematodes 10-20 10’s – 100’s 100’s
Organisms per square foot
improving the activity, biomass and diversity of soil
biota will benefit agricultural systems
• Methods to support or enhance soil biota include:
Managing the quality and quantity of organic matter
inputs
Diversification of cropping systems
S o il
can be very useful – best to do both
• Be clear about what you want from a soil analysis
before starting
• They can range from the simple ‘ADAS’ P, K, Mg
and pH up to complex assessments giving nutrient
ratios, trace elements, biological activity, CEC, etc.
• Sampling must be consistent and accurate – use
spotless tools and clean bags, mix on clean surface
S o il
• When to carry out?
after
very complex procedures
• Identified deficiencies can be addressed
• Tissue analysis can be more accurate
S o il
Get up close and personal
• Walk your fields and use your feet to give a quick
sense of basic condition
• Look at the grass and the crops – colour and vigour
tell you a lot
• Ditto for the weeds – if they struggle the soil is
probably in poor condition
as is safe.
S o il
Mottles = periodic water logging – position
indicates whether the problem is surface or
ground water
aeration
clods, platy structures, no structures at all
• Feel the soil – you probably know whether its sandy
or silty but it will vary across and between fields
• Look for indicator weeds – rushes speak for
themselves, sorrel = acid, creeping buttercup =
surface compaction
grassland soils
water holding capacity of the soil
• Soil pore sizes influence how much water can
be extracted from the soil
• Excess water will drown roots
• Irrigation should be used carefully – mild
water stress can promote good root systems
• Systems should be chosen carefully
S o il
Soil type
Soil condition
looseness
necessary? Will the structure survive?
Think before trafficking – is it going to
create compaction?
• No but it pays to regard it as such
• Make sure it can ‘breathe’ in oxygen
and ‘excrete’ carbon dioxide
• Think about your role
organic matter so the soil biota can do
its job – it will yield benefits
S o il
S o il
• It is an incredibly complex ecosystem
• It takes time to improve but can be damaged
very quickly
properties
• Observation is a critical tool