improving soil structure to reduce soil degradation - managing... · non-ssd nslt mpp wt) ssd type...
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Managing soils for profit and restoration
Improving soil structure
to reduce soil degradation
Professor R Jane Rickson
Chair in Soil Erosion and Conservation
Cranfield Soil and AgriFood Institute
February 16th 2016
Outline of the presentation
1. What is soil structure?
2. Soil degradation: cause or effect of ‘poor’
soil structure?
3. The importance of soil management to
improve soil structure
4. Take home messages
1. What is soil structure?
• Soil structure depends on:
– Mineral content (texture: clays, silts and sands) ≈ 45%
• Chemical composition (bonds between particles)
– Air ≈ 25%
– Water ≈ 25%
– Organic matter content ≈ 5%
• Soil flora: roots and leaves
• Soil fauna
– macro-organisms e.g. earthworms
– micro-organisms “microbes”
» bacteria
» fungi
» viruses
• The physical arrangement of soil particles, air space, water content and organic matter = soil structure
– Allows roots to grow
– Allows movement of air, water and soil organisms
– Affects soil strength / loading capacity (resist compaction)
Clays, silts and
sands 45%
Air 25%
Water 25%
Organic Matter
5%
1. What is soil structure?
• Soil aggregate size distribution
• Pore size distribution
– Macropores (easy drainage – a good or bad thing?; poor seed bed; lodging)
– Mesopores (water storage / holding capacity (floods and droughts), water availability
to crops)
– Micropores (water unavailable to crops; more air and water movement)
• The 3 ‘Rs’: Well structured soils can receive, retain and release water
Visual soil
assessment /
evaluation
http://www.landcare
research.co.nz/publi
cations/books/visual
-soil-assessment-
field-guide
1. What is soil structure?
1. What is soil structure?
Soil structure and soil health / soil quality
..but soil structure can be affected by management (good and bad)
ORGANIC MATTER
NUTRIENTS STRUCTURE
WATER/AIR BIOTA
Soil Structure and Soil Health:
“The pivotal 5” (after Professor Karl Ritz, pers.comm)
2. Soil degradation:
cause or effect of ‘poor’ soil
structure?
As identified in the EU Thematic Strategy for Soil Protection (2006)
• Estimated 12 million hectares of
agricultural land are lost to soil
degradation every year.
ORGANIC MATTER
NUTRIENTS STRUCTURE
WATER/AIR BIOTA
Soil degradation in the UK:
cause or effect of poor soil structure?
2. Soil degradation:
cause or effect of ‘poor’ soil structure?
Example: Soil erosion in England & Wales
Wind erosion Tillage
erosion
Co-extraction with root
crops and farm machinery Water
Typical erosion rate
range (t ha-1 year-1) 0.1 – 2.0 0.1 – 10.0 0.1 – 5.0 0.1 – 15.0
Land use affected
Arable,
upland, some
pasture
Arable Arable
Arable,
pasture,
upland
Exported off field Yes No Yes Yes
Comparison of the magnitude of soil loss for different erosion processes (Owens
et al., 2006). N.B. Rate of soil formation ≈ 1 t ha-1 year-1 (Verheijen et al., 2009)
2. Soil degradation:
cause or effect of ‘poor’ soil structure?
• Irreversible loss of a natural resource / asset? e.g. loss of soil depth due to erosion
• Compaction – high bulk density, loss of porosity, flooding?
• Loss of organic matter / carbon (carbon storage and mitigating climate change)
Yield decline (quantity, quality and reliability; e.g. 20 million tonnes of grain per annum)
Costs (e.g. nutrient replacement)
Off-site consequences (water quality)
• True impacts on food production often masked by unsustainable inputs (e.g. irrigation, chemical fertilisers)
Courtesy of Alastair Leake
2. Soil degradation:
cause or effect of ‘poor’ soil structure?
£ million per year
(2010) Ecosystem service
Total
Provision-
ing Regulating
Cultural
Agricultural
production Flooding
Water
quality
Green-
house
gas
emission
s
Other Central
estimate
Erosion 30 - 50 46 - 80 55 - 62 8 - 10 ? ? 165 13%
Compaction 180 - 220 120 - 200 60 - 80 30 - 40 ? ? 481 39%
Loss of organic matter 2 ? ? 360 - 700 ? ? 558 45%
Diffuse contamination ? ? ? ? 25* ? 25 2%
Loss of soil biota ? ? ? ? ? ? ? ?
Soil sealing ? ? ? ? ? ? ? ?
TOTAL 212 - 270 166 - 280 115 - 142 398 - 750 25 ? 1,229
% 20% 19% 11% 49% 2% 100
*cost of regulation to protect soils from
contamination
? Estimates not available at national scale
After Graves, A., Morris, J., Deeks, L.K., Rickson, R.J. , Kibblewhite, M.G., Harris, J.A, and Farewell, T.S. 2011. The
Total Costs of Soils Degradation in England and Wales. SP1606. Final Report to Defra, June 2011.
3. The importance of soil management
to improve soil structure
A. Enhance soil and crop productivity (quantity, quality and reliability of marketable yield)
– Provide physical support to canopy and root development
– Improve uptake of water and nutrients by roots
– Reduce soil borne pests / diseases / weeds
B. Control soil degradation
– Erosion; diffuse pollution; compaction; losses of C, organic matter and habitats; salinisation; acidification
C. Concept of “sustainable intensification”
– Producing more (quantity/ quality/ reliability of marketable yield) with less environmental impact / damage
A + B = C
Aim of soil management: “To maintain a fertile seedbed and root zone,
whilst retaining maximum resistance to soil degradation”
ORGANIC MATTER
BIOTA
NUTRIENTS STRUCTURE
WATER BIOTA
Soil health: the pivotal 5
Soil erosion, Bedfordshire
Soil management practices to
improve soil structure: examples
1. Soil cultivation and tillage – Maintain soil structure
– Prepare a suitable growing medium for a crop (germination, emergence and development)
– Maintain organic matter and soil biology
– Bury/incorporate surface residues/FYM
– Remove local or general soil compaction problems (promote drainage)
– Provide adequate soil strength to support surface traffic
2. Crop agronomy
3. Increasing soil organic matter content
+ 14 minutes rainfall
Soil management practices to
improve soil structure: examples
a) Conventional v conservation tillage
– reduced tillage, minimum till, strip
tillage, zero till, etc.
– The main reasons to use min-till are:
To reduce energy consumption
To reduce labour, fuel and
machinery costs
High work rates
To conserve moisture
To retain plant cover to minimize
erosion
Minimise loss of organic matter
Keep soil structure / less
compaction
+ 14 minutes rainfall
Courtesy of Professor Karl Ritz
Soil management practices to
improve soil structure: examples
a) Conventional v conservation tillage
‘Challenges’ of min-till
• Min-till needs dry ground conditions for
sowing in order to avoid compaction
and smearing in the final seed bed.
• “One of the best tools in your tool box
for min-till is patience”
• Wait until conditions are excellent for
sowing. Avoid sowing in a compacted
or smeared seed bed.
• Residue management
– Slugs
– Machinery
• Weeds and costs of control (economic
and environmental)
+ 14 minutes rainfall
Courtesy of Professor Karl Ritz
Courtesy of Dr Rob Simmons
Soil management practices to
improve soil structure: examples
1. Soil cultivation and tillage
b) Timeliness of operations soil moisture content when trafficking – erosion and compaction risks?
c) Depth of operations plough pan formation?
effects on biota?
Effects on structure?
doubling the working depth, approx. quadruples the drawbar pull force and fuel requirement
d) Direction of operations (up/down on steep, marginal land)
A case study:
Optimising soil disturbance and use of mulches for
erosion and runoff control
Dr. Joanne Niziolomski
Shallow soil disturbance (175 mm), both with and without straw mulch (6 t ha-1).
Winged tine Narrow with two shallow
leading tines Modified para-plough
Field trial treatments
– Modified para-plough with straw most reduced soil loss
– Little significant difference was observed between SSD (different tines) and Non-SSD
– Straw mulch decreased total soil loss as compared with no mulch
Soil disturbance field trial results:
Total soil loss (kg)
0
1
2
3
4
Non-SSD NSLT MPP WT
To
tal s
oil
lo
ss
(k
g)
SSD type
No shallow Narrow tine shallow Modified Winged tine soil disturbance leading tine para-plough
(Niziolomski, 2015)
Soil management practices to
improve soil structure: examples
2. Use of crop agronomy for better soil management
– Rotations
– Cover and companion cropping
– Break crops (deep rooting species)
– Nutrient replenishment (e.g. N fixing legumes)
– Grass waterways (erosion and runoff control)
N.B. Demonstrates Good Agricultural and Environmental condition (GAEC)
Eligible for Basic Payment Scheme under CAP reform and ‘greening’ rules
Crop
Root
Type
Root traits expected to
improve soil structure
Wheat D Fibrous vigorous deep roots
Rye D Deep fibrous roots
Oats D Aggressive deep roots
Italian
ryegrass F
Fibrous root system
Lucerne E Deep and aggressive rooting
Phacelia F Prolific root system but more
confined to surface
Fodder
radish T
Tap root, long and extensive
root hairs on laterals
Chicory T Tap root
Sweet clover E Vigorous and extensive
multi-order lateral branching,
Field bean E Large, strong roots
Lupin E Tap root
Root morphology of cover crops
T D F E T D F E
Radish Mustard
Turnip Rape
Cranfield University PhD study (Agnese Mancini):
Cover crops for soil erosion and runoff control in forage
maize
Case study:
Use of grassed waterways for sediment
control
Case study:
Use of grassed waterways for sediment
control
Soil management practices for
healthy soils
3. Increasing soil organic matter content
– Green manures (cover cropping)
– Composts
– Mulches
– Sewage sludge
– Digestate from AD plants
Increase organic matter content, carbon, soil biota
Improve soils structure and resilience
Effects will be specific to materials used and sites
(weather, soil type, etc)
http://www.biogen.co.uk/The-Biogen-Difference/The-
Closed-Loop
Case study:
Application of organic waste to restore soil
health and productivity of a degraded soil Benedict Unagwu
Increase crop
yield?
Poultry
manure
Mushroom
compost
PAS
compost
(green
waste)
Anaerobic
digestate
Improve Soil Quality
Indicators (SQIs)?
Mean
Mean±SE
CF
CN
F
PM
1F
PM
1NF
PM
2F
PM
2NF
PA
S1F
PA
S1N
F
PA
S2F
PA
S2N
F
SW
1F
SW
1NF
SW
2F
SW
2NF
MC
1F
MC
1NF
MC
2F
MC
2NF
Treatments
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
OM
(%
)
F(17,62) = 16.0899, p = 0.0000Key: C = Control;
PM = Poultry
manure;
PAS = PAS
100:2005 Quality
Protocol compliant
compost;
SW = Anaerobic
digestate solid
waste;
MC = Mushroom
compost;
1 = 10 t ha; 2 = 30
t/ha.
F = with fertiliser;
NF = without
fertiliser
Results: Post-incubation soil analysis
(Organic Matter Content)
Amendment effects on maize height and biomass
27
control
10 t ha-1 PM
At 3 weeks after planting
10 t ha-1 MC
At tasseling (9 weeks after planting)
4. Take home messages
• Soil structure is fundamental to healthy soils
• Soil management can improve soil structure,
increase crop productivity and control degradation
processes
• Cost effectiveness of practices will be site specific
and must fit into current farming practices
– socio-economic context
– infrastructure / machinery
– farmer psychology / behaviour
• Ultimate goal is economically, socially and
environmentally acceptable food production
= “sustainable intensification”
ORGANIC MATTER
BIOTA
NUTRIENTS STRUCTURE
WATER BIOTA
In conclusion…..
“The challenge for global agriculture is to grow more
food, on not much more land, using less water, fertiliser
and pesticides than we have historically done.”
Sir John Beddington
former UK Government Chief Scientific Adviser.
‘The answer is in the soil……’
Thank you for your attention
Professor Jane Rickson [email protected]
+44 1234 750111 ext. 2705