"Enhancing soil health is key to providing ecosystem services and food security. There are often trade-offs to using a particular practice, or it is not fully understood. This work aimed to identify practices beneficial to soil health, and gaps in our knowledge. We reviewed existing research on agricultural practices and an expert panel assessed their effectiveness. The three most beneficial practices used a mix of organic or inorganic material, cover crops or crop rotations.
This paper which has recently been published in the journal Soil and written by Key et al, aimed to clarify research needs and identify effective actions for enhancing soil health at the farm level.
To read the paper in full please click here.
The benefits of soil management and its relationship with not just farm profitability, but sustainability and environmental resilience are well known. Enhancing soil health is central to delivering food security and ecosystem services. In addition to food production, healthy soils also underpin a wide range of ecosystem services, including the carbon sequestration, flood control and biological control of pests and disease which are crucial to underpinning sustainable development goals.
While many farmers are well versed in how to maintain soil health, they are often not aware of the trade-offs that exist between enhancing certain soil properties and maintaining the functions that underpin them. An example of this uncertainty is the relationship between farming practices and the diversity and functioning of soil microbial communities that help transform nutrients into plant available form.
As well as these trade-offs there are also discussions around the knowledge needs for policy, especially around the need for evidence based environmental policies for sustainable soil management as well as the identification of knowledge needs for researchers and farmers.
The research that this paper describes aimed to identify effective actions that farmers could do that would enhance soil health and see where the gaps were in current research. This was done by looking at a multitude of previous research (718 studies!) around soil management practices that were designed to maintain or enhance elements of soil health. Once the literature had provided a list of practices, an expert panel was then selected (that included soil scientists and practitioners) that assessed the evidence to highlight actions that were beneficial and detrimental to soil health and actions that needed further investigation. The expert assessment was based on four factors:
· How effective was the action at enhancing soil health
· How certain was the expert that the evidence was correct?
· The strength of the potential negative side effects associated with implementing the action
· What soil types or locations did the action cover?
What did it find?
Of the 27 actions that were evaluated, only 3 were considered to be unequivocally beneficial to soil health. These were
- The use of a mix of organic and inorganic soil amendments
- Growing cover crops
- Crop rotation
There were then 4 actions that were considered likely to be beneficial:
· Grow cover crops between the main crop (living mulches) or between crop rows
· Amend the soil with formulated chemical compounds
· Controlled traffic and traffic timing
· Reducing grazing intensity
The only action that fell into the ‘likely to be ineffective or harmful’ category was reducing fertiliser and pesticide use, largely due to the consequent reductions in crop yields.
The majority of the rest of the actions, fell into the trade-offs category, where evidence suggested that the actions were either beneficial in specific circumstance or considered likely to be beneficial but with strong negative side effects. This also suggests that there are a large number of current soil management practices that are based on non-scientific knowledge.
What did it recommend?
The use of both scientists and practitioners helped to identify existing knowledge that should be made more accessible to those who put research into practice and highlighted a wide spectrum of certainty regarding the actions covered in this review.
A key finding of the assessment was that it is not yet clear how effective the majority of the reviewed actions are for enhancing soil health. For actions that are considered to include trade-offs, and where there are clear benefits to implementing, more refinement may be needed to minimise any negative effects.
What was also clear was that there were actions that weren’t included in the review that needed further research, one example being mob grazing.
The other important point to remember is that farming is based on biological systems, that are site specific and as such this specificity shouldn’t be lost. The condition of a site needs to be taken into account when recommending practices, given that the impact of various actions will vary depending on many factors, including soil type, the extent to which the soil is degraded, and local climate. This review could lead to targeted best-fit approaches that would be more beneficial to local soil health.
The review identified that there were some major areas of uncertainty in relation to the effectiveness of certain actions and interventions that, if developed may help to remove the barrier to implementing action at the farm level.
Agricultural intensification is required to improve food security however this needs to be done in a sustainable way if we are to have more resilient agricultural systems in the face of climate change.
To read the paper in full and to look in more detail at the actions that were studied please click here.