Improving soil structure and reducing soil degradation

31 Pages·2016·4.82 MB·English

Managing soils for profit and restoration

Improving soil structure and
reducing soil degradation
Professor R Jane Rickson

Chair in Soil Erosion and Conservation

Cranfield Soil and AgriFood Institute

January 19th 2016
Outline of the presentation
1. What makes a healthy soil?
2. Soil degradation: cause or effect of ‘poor’
soil health?
3. The importance of soil management for
healthy soils
4. Take home messages
1. What makes a healthy soil?
• Traditional view: soil as inert material

• Modern view – soil as a living organism
– “Physiology” = scientific study of normal function in living
systems
– Soil physiology = interactive, dynamic, process-oriented
study of soils and their ‘functions’

• Soil functions
“Soil sustains, regulates and controls biotic and abiotic
processes [e.g. crop production, water infiltation] through its
interactions with the biosphere, hydrosphere, atmosphere
and lithosphere” (Yaalon, 2000)

• Soils deliver “ecosystem goods and services”
– e.g. crop production, water regulation, carbon storage
– linked to human health and wellbeing, and individual and
national economic status (Daily, 1987)
1. What makes a healthy soil?

1. Soil Quality
“the capacity of soil to function, within natural or managed ecosystem
boundaries, to sustain plant or animal productivity, maintain or enhance
water quality, and support health and human habitation”
Karlen et al., 1997

2. Soil Health
“the soil’s fitness to support crop growth without becoming degraded or
otherwise harming the environment ”
Karlen et al., 1997
1. What makes a healthy soil?
Soil quality and soil health are related to soil
properties:
– Physical (texture, depth, structure, porosity,
ORGANIC
density, water holding capacity, infiltration
MATTER
rate, stability of individual aggregates and
soil mass)
WATER/AIR
BIOTA

– Biological (flora and fauna e.g. seed bank,
micro and macro organisms)

– Chemical (nutrients, carbon, pH) NUTRIENTS STRUCTURE
…and interactions between them: soil as a
complex ‘system’
Soil Health: “The pivotal 5”

(after Professor Karl Ritz, pers.comm)
How can we tell we have a healthy soil?
Concept of Soil Quality Indicators (SQIs)
Example of key soil quality indicators (Minimum data set – MDS)
Selected indicator Rationale for selection
Physical Topsoil-depth Estimate rooting volume for crop production and erosion
SQIs
Aggregation Soil structure, erosion resistance, crop emergence and early indicator of
soil management effect
Texture Retention and transport of water and chemicals, modeling use

Bulk density Plant root penetration, porosity, adjust analyses to volumetric basis

Infiltration Runoff, leaching and erosion potential

Biological Soil respiration Biological activity, process modeling; estimate of biomass activity, early
SQIs warning of management effect on organic matter
Chemical pH Nutrient availability, pesticide absorption and mobility, process models

SQIs
Organic matter Defines soil fertility and soil structure, pesticide and water retention, and
use in process models

Forms of N Availability to crops, leaching potential, mineralization/immobilization
rates, process modeling

Extractable N, P and K Capacity to support plant growth, environmental quality indicator

Suspected pollutants Plant quality, and human and animal health

Electrical conductivity Defines crop growth, soil structure, water infiltration; presently lacking in

most process models
after Arshad and Martin, 2002; Arshad and Coen, 1992; Doran and Parkin, 1994; Gregorich et al., 1994; Larson and Pierce, 1994;
6
Carter et al., 1997; Karlen et al., 1997; Martin et al., 1998
Soil Quality Indicators
e.g. Visual Soil Assessment / Evaluation
– Composite SQI that reflects physical, biological and chemical properties
– Substitute ‘space for time’ analysis of soil conditions

Visual soil
assessment /
evaluation
http://www.landcarere
search.co.nz/publicati
ons/books/visual-soil-
assessment-field-
guide
2. Soil degradation:
cause or effect of ‘poor’ soil health?
As identified in the EU Thematic Strategy for
Soil Protection (2006)

ORGANIC
MATTER

WATER/AIR
BIOTA

NUTRIENTS STRUCTURE

• Estimated 12 million hectares of
agricultural land are lost to soil
degradation every year.
Soil erosion in the UK:
cause or effect of poor soil health?
2. Soil degradation:
cause or effect of ‘poor’ soil health?
Example: Soil erosion in England & Wales

Tillage Co-extraction with root
Wind erosion Water
erosion crops and farm machinery

Typical erosion rate
0.1 – 2.0 0.1 – 10.0 0.1 – 5.0 0.1 – 15.0
range (t ha-1 year-1)

Arable, Arable,
La nd use affected upland, some Arable Arable pasture,
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)