Soil health, organic matter and crop yieldsmartagriplatform.com/resources/Chamen et al - Soil...Soil...
Transcript of Soil health, organic matter and crop yieldsmartagriplatform.com/resources/Chamen et al - Soil...Soil...
Soil health, organic matter and crop yield
A compilation based on talks given by: Tom Sizmur, Chris Watts, Simon Jeffery,
Karl Ritz, Matthew Shepherd Presented by Tim Chamen, SWMC
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/
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.htm Further dedicated reading! http://soilandhealth.org/wp-content/uploads/01aglibrary/010120albrecht.usdayrbk/lsom.html
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
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
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
Arndt and Rose, 1966
• “Excessive traffic necessitates excessive tillage”
– or
• The more you run over it, the more you have to cultivate it
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, S
oil
org
anic
Carb
on, g/g
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Yie
ld, M
g/h
a
0
1
2
3
4
5
6
7
S, S
pecific
dra
ught, k
Pa
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 + roots associated with increased mineral N & FYM
Watts
Crop management & Plough Draught (Mineral Fertilizer)
Treatment
N0 N1 N2 N3 N4 N6 FYM
SO
C, S
oil
org
anic
Carb
on, g/g
0.0
0.5
1.0
1.5
2.0
2.5
3.0
S, S
pecific
dra
ught, k
Pa
72
74
76
78
80
82
84
86
88
90
Yie
ld, M
g/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 is mostly generated by soil life, which relies on OM as a food source. – soil life recycles nutrients and increases crop yield and
quality.
• Structure effects practically all soil processes.
• Rooting from high yielding crops helps generate structure and increase OM content.
• High OM content and earthworm populations reduce soil strength and increase its resilience.