We are delighted to support a range of investigations by the research work of PhD students. TMAF-supported PhD student Joe Martlew explains the work he is doing to diagnose and treat subsoil compaction in his research ‘Quantifying and alleviating deep-seated compaction in arable soils’.
Why care about subsoil compaction?
“As machinery on farm has increased in size, so has the risk of causing subsoil compaction. Subsoil compaction has been shown to have a negative impact on crop production and soil health. However regular mechanical tillage of the subsoil is not practical and may be damaging in the long-term.
A well-functioning soil is essential for crop production, has a critical role in natural processes such as the water cycle and flood protection, and can mitigate aspects of climate change. However, these soil functions are negatively impacted by compaction. My undergraduate degree was BSc. (Hons) Biology at the University of Portsmouth and I then studied for an MPhil degree at Harper Adams University entitled ‘Traffic and tillage management for row crops in Sub Saharan Africa’. I have also worked as a BASIS and FACTS qualified agronomist in the south of England.
Through my experience I have observed how small changes in management practice can have a large impact on crop performance and the stewardship of our farmed environment. Using plant roots as tillage tools may represent a step change in our approach to crop production and the chance to study this area, with the experience of NIAB TAG of putting academic research into practice on farm, was an exciting opportunity.
Digging up the evidence
Through a combination of laboratory studies and NIAB TAG field experiments, my research aims to better understand the impact of subsoil compaction and to assess whether deep-rooted cover crops may have potential to alleviate subsoil compaction.
I am based at Cranfield University. The project is sponsored by the Felix Thornley Cobbold Trust and the Chadacre Agricultural Trust as well as TMAF, and I work closely with NIAB TAG. I split my time between laboratory experiments based at Cranfield University and the NIAB TAG STAR (Sustainability Trial in Arable Rotations) field experiment in Suffolk, UK. TMAF is contributing £24,750 over 3 years towards the NIAB STAR trial.
Subsoil, as obvious as it sounds, is deep in the soil profile and has required a huge amount of physical effort from volunteers and has tested some of our sampling equipment to the limit in order to access it.
On the surface, with the seasonal challenges of topsoil and crop management on farm, it is easy to forget the subsoil. However, subsoil is an amazingly diverse system and is the location where our management of farmland interacts, largely undisturbed by tillage, with soil biology and the underlying geology of a given local region. Unearthing previously unseen subsoil profiles during field experimental work has been fascinating.
The story so far
The laboratory and NIAB TAG STAR field experiments have given us an indication that long-term approach to tillage and deep-rooted cover cropping may have an impact on subsoil physical characteristics and crop performance. However, it is difficult from these observations to attribute whether these results are likely to be detrimental to crop production and/or the farmed environment. To address this, I am currently conducting laboratory analyses on 80 cm deep undisturbed soil cores taken from the NIAB TAG STAR site to better understand what the field observations mean. Using a combination of traditional laboratory methods and cutting-edge technology, such as X-Ray computed tomography, I am attempting to characterise any change in soil structure as a result of the rotation and tillage treatments. This will allow me to better understand the implications change may have on crop performance, the farmed environment and the wider environment.
Seeking sustainable solutions to subsoil compaction
Improving our understanding of how to manage subsoil compaction and exploring alternatives to mechanical tillage, such as deep-rooted cover crops, will play an important role in increasing the sustainability of our soil management.
I am currently in my second year of work with two experiments now underway. Experiments 1 and 2 are the NIAB field experiment plus related lab work and the polytunnel laboratory experiment respectively
The third experiment is planned to begin in August 2019. This will be a laboratory experiment that will focus on taking steps to improve the characterisation of subsoil compaction using commonly-available field measurement techniques, employing results generated from experiments 1 and 2. I hope that I will be able to write up and share a final report in Spring 2021.”