Sustainable soil management is the Holy Grail for farmers, policy makers and consumers – if we can develop a sustainable system that allows us to grow enough food for the growing population whilst safeguarding our most precious resource then we are achieving our goals.
The FAO have just released a new document entitled Voluntary Guidelines for Sustainable Soil Management, which is designed to be a reference providing general technical and policy recommendations on sustainable soil management for a wide range of stakeholders. Its objectives are:
To present generally accepted, practically proven and scientifically based principles to promote sustainable soil management, and to provide guidance to all stakeholders on how to translate these principles into practice, be it for farming, pastoralism, forestry or more general natural resource management.
For the purposes of this document, Sustainable soil management is defined (as according to the world soil charter) as:
“Soil management is sustainable if the supporting, provisioning, regulating and cultural services provided by soil are maintained or enhanced without significantly impairing either the soil functions that enable those services or biodiversity. The balance between the supporting and provisioning services for plant production and the regulating services the soil provides for water quality and availability and for atmospheric greenhouse gas composition is a particular concern.”
What are the guidelines for sustainable soil management?
1. Minimise soil erosion
The recent State of the World’s Soil Resources report identified soil erosion by water and wind as the most significant threat to global soils and the ecosystem services they provide.
What do they suggest?
Land use changes that cause removal of surface cover and loss of soil carbon should be avoided or carefully planned.
A cover of growing plants or organic and non-organic residues that protects the soil surface from erosion should be maintained
Erosion by water on steep land should be minimised by measures that reduce runoff rates
Where appropriate, buffer strips and cover crops should be used to minimise the risk of soil loss and nutrients downstream.
Wind erosion should be minimised by vegetative or artificial wind breaks.
2. Enhance soil organic matter content
Soil OM plays a central role in maintaining soil functions and preventing soil degradation. Soils contain the largest organic carbon pool on the Earth and play a critical role in regulating climate and mitigating climate change. Soil organic matter is strategic for climate change adaptation and mitigation and global stores of organic matter should be stabilised or increased.
What do they suggest?
Increase biomass production by increasing water availability for plants using methods that maximise water use efficiency and minimise soil erosion and nutrient leaching.
Protect organic carbon rich soils in peatlands, forests, grasslands etc.
Increase organic matter content through practices such as managing crop residues, applying animal or other carbon rich wastes, using compost and providing the soil with a permanent cover.
Make optimum use of all sources of organic inputs
Management practices that ensure that the soil has a sufficient organic cover.
Decreased decomposition rates of soil organic matter by practicing min or no till
Implementing crop rotations
3. Foster soil nutrient balance and cycles
Plant nutrition should be based on crop needs, local soil characteristics and conditions and weather patterns.
Natural soil fertility and natural nutrient cycles should be improved and maintained through the preservation or enhancement of soil organic matter.
Nutrient use efficiency should be optimised by adopting measures such as applying balanced and context adapted soil organic and inorganic amendments.
Plan applications to promote balanced crop nutrient uptake and limit losses.
Soil and plant tissue testing and field assessments should be used
Application of lime is a prerequisite for nutrient use efficiency
4. Prevent, minimise and mitigate soil salinization and alkalinisation
Salinization is the accumulation of water-soluble salts of sodium, magnesium and calcium in the soil. It is the consequence of high evapotranspiration rates, inland sea water intrusion and human induced processes. Salinization reduces crop yields and above certain thresholds completely eliminates crop production.
5. Prevent and minimise soil contamination
Soils may filter, fix and neutralise but also release pollutants when conditions change. Therefore prevention of soil contamination remains the best way to maintain healthy soils and food safety in accordance with the Sustainable Development Goals.
6. Prevent and minimise soil acidification
Human induced acidification of agricultural and forest soils is primarily associated with removal of base cations and loss of soil buffering capacity or increases in nitrogen and sulphur inputs (e.g. legume pastures, fertiliser inputs, atmospheric deposition). Soils with low pH buffering capacity and/or high aluminium content are most prevalent when they have a low content of weatherable minerals.
Monitoring soil acidity and minimising surface and sub-surface soil acidity by using proper amendments
Balanced fertiliser and organic amendment application and
Appropriate use of acidifying fertiliser types
7. Preserve and enhance soil biodiversity
Soils provide one of the largest reservoirs of biodiversity on earth and soil organisms play key roles in the delivery of many ecosystems services. Little is known about the degree of biodiversity required to maintain core soil functions, but new tools for biochemical techniques and DNA analysis suggest significant progress in this area is possible.
Monitor programme for soil biodiversity, including biological indicators
Soil organic matter levels which support soil biodiversity should be maintained or enhanced through the provision of sufficient vegetative cover.
The authorisation and use of pesticides in agricultural systems should be based on recommendations.
The use of nitrogen fixing leguminous species, microbial inoculants, mychorrhizas, earthworms and other beneficial soil organisms should be encouraged where appropriate, with attention to limiting the risk of invasive processes.
Restoring plant biodiversity in ecosystems, thereby favouring soil biodiversity
In-field crop rotation, inter-cropping and preservation of field margins, hedges and biodiversity refuges should be encouraged
8. Minimise soil sealing
Land conversion and subsequent soil sealing for settlements and infrastructure affect all soils, but are of particular concern on productive arable soils because of their importance for food production and food security and nutrition, and circular economy targets. Soil sealing and land conversion causes a largely irreversible loss of some or all soil functions and the ecosystem services they provide.
9. Prevent and mitigate soil compaction
Soil compaction is related to the degradation of soil structure due to imposed stresses by machinery and livestock trampling. Soil compaction (reduced or disrupted pore continuity) reduces soil aeration by destroying soil aggregates and collapsing macropore density, and reduces water drainage and infiltration, generating higher runoff. Compaction limits root growth and seed germination by high mechanical impedance, affecting soil biodiversity and causing surface soil crusting.
Deterioration of soil structure due to inappropriate or excessive tillage should be prevented.
Vehicle traffic should be minimised to the absolutely essential particularly on bare soils.
Machines and vehicles used in the field should be adjusted to soil strength and should be equipped with tyre pressure control systems
Cropping systems should be selected that include crops, pasture plants and where appropriate agroforestry plants able to penetrate and break up compacted soils.
An adequate amount of soil organic matter should be maintained to improve and stabilise soil structure
Macrofauna and microbial activity should be promoted to improve soil porosity for soil aeration, water infiltration, heat transfer and root growth.
In grazing systems, a sufficient cover of growing plants should be maintained to protect the soil from trampling and erosion.
10. Improve soil water management
A sustainably managed soil has rapid water infiltration, optimal soil water storage of plant available water and efficient drainage when saturated. However when these conditions are not met, waterlogging and water scarcity problems arise.
In humid areas where precipitation exceeds evapotranspiration, additional drainage systems are needed to provide aeration for root functions like nutrient uptake.
Surface and sub-surface drainage systems should be installed and maintained to control rising groundwater tables
Increase the efficiency of irrigation water through improved conveyance, distribution and field application methods that reduce evaporation and percolation losses.
In dryland cropping systems measures should be implemented to optimise water use efficiency such as the management of soil cover and water harvesting.
Regularly monitor irrigation water quality for nutrients and potential harmful substances.
To read the full report click here.