Sustainable Soil Management - Soil Health

What is the definition of soil health?

The capacity of soil to function as a living ecosystem that sustains plants, animals and humans

What is the status of soil degradation in the UK?

· Almost 4 million hectares at risk of compaction

· Intensive agriculture has caused arable soils to lose 40-60% organic carbon

· Soil degradation cost £1.2 billion every year (2010).

What governmental plan is in place to protect soils?

The government's 25 Year Environment Plan states that England's soils must be managed sustainably by 2030 and steps must be taken towards restoring the UK's soils

What are the key ecosystem services provided by soils?

. Regulating water -> soil helps control where rain and irrigation water goes. Water flows over the land or into and through the soil

· Sustaining plant and animal life diversity

· Filtering and buffering potential pollutants -> the minerals and microbes in soil are responsible for filtering, buffering, degrading, immobilising, and detoxifying organic and inorganic materials - including industrial waste and atmospheric deposits

· Cycling nutrients -> carbon, nitrogen, phosphorus, and many other nutrients are stored, transformed, and cycled in the soil

· Providing physical stability and support -> soil structure provides a medium for plant roots. Soils also provide support for buildings.

What are the main principles of soil health?

1) Minimised disturbance

2) Maximised biodiversity

3) Maximised soil cover

4) Maximised living roots

How can you measure soil health?

It cannot be measured directly/in a single measurement

You need to use physical, chemical & biological properties of soils as indicators

- These are easy to measure, accessible to many users & field conditions, and sensitive to variations in climate & management...

What are some examples of physical, chemical & biological soil health indicators?

Physical:

. bulk density

. infiltration

. soil structure

. water holding capacity

Chemical:

. soil nitrate

. soil pH

. extractable phosphorus/potassium

Biological:

. earthworm count

. microbial biomass (C & N)

. particulate organic matter

. soil respiration

What groups of soil organisms are there?

1) bacteria

2) fungi

3) protozoa

4) nematodes

5) arthropods

6) earthworms

How and why can biological action improve soil health?

1) Feed soil regularly (with plants & organic inputs)

- soil OM is a source of energy/food for soil organisms

- decomposition of OM increases nutrient cycling & improves soil structure

- OM application can offset negative effects associated with tillage

2) Reduce tillage as much as possible (previously mentioned benefits)

3) Grow a diverse range of crops

- monocultures build up pest, disease & weed problems

How and why can chemical action improve soil health?

1) Maintain optimum pH

- under pH 5.5, soil biological activity slows down and root growth/function is inhibited

- pH affects other soil properties, e.g. nutrient availability

- soil pH can be raised using lime application

2) Apply nutrients

3) Know soil textures & minerals

- parent material controls the texture and types of minerals in soil

- texture determines ability to hold onto lime or other nutrients.

How and why can physical action improve soil health?

1) Know soil texture and understand limits

- soil texture determines workability & traffic ability limits

- well-structured soils have a better air/water balance, benefitting root growth. Also makes soils more resilient to water logging (allowing increase machinery workdays)

2) Optimise water balance through drainage (if necessary)

- can help wet/slowly permeable soils stay below the plastic limit for longer

3) Minimise compaction and improve soil structure

- tillage disrupts connectivity of pores

- careful management of operations can help a continuous pore network develop

- if soil is in a plastic state, traffic should be minimised.

What are the benefits of better structured soils?

1) Less prone to erosion and surface run-off

2) Increased cultivation window

3) Reduced irrigation costs

4) Reduced tillage costs (in terms of tractor hours)

5) Improved uniformity and yield of crops.