soil health, organic matter and crop · pdf filewhat is the difference between organic matter...
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Soil health, organic matterand crop yield
A compilation of talks given by:Tom Sizmur, Chris Watts, Simon Jeffery,
Karl Ritz, Matthew ShepherdPresented by Tim Chamen, SWMC
Ritz
Jeffery
Shepherd
Ritz
Ritz
Shepherd
Shepherd
Shepherd
Sizmur
What is the difference between Organic Matter and Soil Organic Matter
• OM is considered to have become SOM when its original form is no longer recognisable
• SOM is considered to have become humus when it is stable and resists further decomposition
Further reading:http://www.extension.umn.edu/agriculture/tillage/soil-management/soil-management-series/organic-matter-management/
Sizmur
Ritz
Sizmur
Sizmur
Organic matter equilibrium
• For every soil in every climatic region there is a dynamic equilibrium soil organic matter content:
SOM = input - oxidation from soil biota
• our activities act positively or negatively to disturb this equilibrium
Further reading:http://www.fao.org/docrep/009/a0100e/a0100e06.htmFurther dedicated reading!http://soilandhealth.org/wp-content/uploads/01aglibrary/010120albrecht.usdayrbk/lsom.html
Jeffery
Importance of Soil Structure
• Soil structure is the arrangement of soil particles and aggregates and of the pore spaces between them.
• Several different mechanisms and processes within the soil are involved in controlling structure: soil type, physical chemistry, organic matter
• Likewise, the structure influences the processes
Watts
Importance of Soil Structure
Soil structure has a significant influence on virtually all processes that occur within the soil. Some examples:
• Water infiltration – hence the amount of water that is stored in the soil, available to plants, runoff, erosion.
• Aeration – needed for root growth and other biological activity – organic matter turnover.
• Strength and stability – strong soils can impede root growth and are difficult to cultivate.
• Physical pore structure defines habitats for a range of biota.
Watts
Soil stability & resilience
There is little advantage to having a soil with an ideal geometrical structure if it does not persist
• Soil structural stability: Ability of structure to resist imposed stresses without change in its structural form.
• Examples of imposed stresses include: rapid wetting, contact with free water, raindrop impact, wheel traffic
• Cultivations are often designed to modify soil structure.
• Resilience is the ability of soil structure to recover once stress has been removed.
Watts
Jeffery
Importance of soil organic carbon on aggregate stability
Aggregates (1.0 > 2.0 mm) collected from the upper 2 cm, air-dried and then
subjected to 50 mm of simulated rain and finally allowed to dry
SOM has the equivalent of around 58% SOC
Watts
Effect of SOC on soil stabilityWatts
Watts
>
Shepherd
Shepherd
Ways of maintaining SOM in arable cropping
1. Ley-arable farming – i.e. intermittent pasture
2. Add crop residues
3. Add manures or other organic “wastes”
4. Break or cover crops …………………………………………………..
5. Minimise tillage• small effect, mainly redistribution
• but useful to concentrate SOM near surface
• other benefits
6. Grow plants with larger roots (breeding)
7. Grow larger crops by using fertilizers (small effect)
Watts
0.00
0.50
1.00
1.50
2.00
2.50
0 4.5 9 18
% C
in
to
ps
oil
, 0
-23
cm
Rate of straw applied t/ha/yr
7 years
11 years
22 years
Effect of 22 years of straw incorporation on soil %C
(Rothamsted, 25% clay – 3 rates of straw)
Very small SOC increase at “normal”
straw application rate
Watts
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0 4.5 9 18
% C
in
to
ps
oi,
0-2
3 c
m
Rate of straw applied t/ha/yr
11 years 22 years
Effect of 22 years of straw incorporation on soil %C (note C in sandy soil is only 50% of that in silty clay loam)
(Woburn, 9% clay – 3 rates of straw)
Watts
Watts
Watts
Sizmur
Sizmur
Sizmur
Sizmur
Sizmur
Sizmur
Shepherd
Shepherd
Shepherd
Sizmur
Shepherd
Shepherd
In traffic lane – practically zero infiltration
In non-trafficked bed – modest infiltration
In non-trafficked bed with surface crust broken – rapid infiltration
Clay dispersed due to heavy rainfall
Crop management & Plough Draught (Mineral Fertilizer)
Treatment
N0 N1 N2 N3 N4 N6 FYM
SO
C,
Soil
org
anic
Carb
on,
g/g
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Yie
ld,
Mg/h
a
0
1
2
3
4
5
6
7
S,
Specific
dra
ught,
kP
a
0
10
20
30
40
50
60
70
80
90
100
Kg N/ha 0 48 96 144 192 288 (35 t FYM)
Much larger crops + rootsassociated with increased mineral N &FYM
Watts
Crop management & Plough Draught (Mineral Fertilizer)
Treatment
N0 N1 N2 N3 N4 N6 FYM
SO
C,
Soil
org
anic
Carb
on,
g/g
0.0
0.5
1.0
1.5
2.0
2.5
3.0
S,
Specific
dra
ught,
kP
a
72
74
76
78
80
82
84
86
88
90
Yie
ld,
Mg/h
a
0
1
2
3
4
5
6
7
Bigger crops result in lower soil strength; as a result of better soil structure?Biological tillage so sustainable intensification
Kg N/ha 0 48 96 144 192 288 (35 t FYM)
Watts
Summary
• Adding OM is the key means of improving soil structure.
• Structure effects practically all soil processes.
• Rooting from high yielding crops helps generate structure and increase OM content.
• Structure is mostly generated by soil life, which relies on OM as a food source.– soil life recycles nutrients and increases crop yield and
quality.
• High OM content and earthworm populations reduce soil strength and increase its resilience.
With thanks to:
• Karl Ritz, Nottingham University
• Tom Sizmur, University of Reading
• Matthew Shepherd, Natural England
• Simon Jeffery, Harper Adams University
• Chris Watts, Rothamsted Research