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 j.rickson@cranfield.ac.uk

+44 1234 750111 ext. 2705