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The impact of conservation agriculture on above-belowground interactions

Primary Supervisor: Dr Simon Jeffery, Department of Agriculture and Environment

Secondary supervisor: Dr Joe Roberts

Secondary supervisor: Dr Tom Pope

PhD project title: The impact of conservation agriculture on above-belowground interactions

University of Registration: Harper Adams University

Project outline:

It has become increasingly clear that conventional agricultural production systems negatively impact environmental health. Greater awareness of this issue has led to increased uptake in alternative crop production methods. Conservation agriculture is one such approach that aims to increase agricultural sustainability by treating soil as a living component of an ecosystem and working with soil biota to utilise the ecosystem services that they provide. Interest in this approach to crop production has increased in recent years, though uptake remains significantly behind conventional agriculture in terms of hectarage for UK arable production with < 5 % of arable systems managed in this way. Alongside increased interest in conservation agriculture, there has been an attitude shift regarding the interconnectedness of above-belowground interactions. It is widely accepted that aboveground and belowground interactions cannot be considered in isolation from one another, with changes in either one impacting the wider ecological network. Given that conservation agriculture aims to manipulate belowground interactions, there are likely to be consequences for aboveground interactions using this approach. Increasing our understanding of abode-belowground interactions has the potential to improve the sustainability of agriculture while concurrently minimising its negative impacts on the environment (Orrell and Bennett, 2013).

Arbuscular mycorrhizal (AM) fungi are a key group of soil biota for many arable crops, which act to augment plant health and resilience through increased provision of soil nutrients and water (Ceballos et al., 2013). These organisms are more prolific in conservation agricultural production systems due to its ethos of minimising soil disturbance. While belowground interactions between AM fungi and plants are well understood, their interactions with aboveground plant traits, particularly the fungus-plant-insect nexus, are comparatively understudied. Evidence indicates that belowground organisms such as AM fungi can enhance aboveground herbivore pest control in a range of crops (Schausberger et al., 2012). Pest control by belowground organisms is achieved through several routes: (1) plant defence priming, (2) priority effects and (3) volatile signalling to recruit natural enemies. Belowground organisms also act on other beneficial plant-insect interactions as AM fungi have been shown to enhance pollination by modifying floral traits (e.g., flower number and size) that increase pollinator visitation rates (Gange and Smith, 2005). Although the impact of belowground organisms on aboveground plant traits is well-documented, there has been limited field-scale research carried out in UK arable crops.

This project will quantify plant-AM fungi interactions in an ongoing conservation versus conventional agriculture field experiment and investigate how these belowground interactions influence both positive (e.g., pollination, pest control) and negative (e.g., herbivore feeding) aboveground interactions. Focus will be on determining how AM fungi influence chemically mediated plant-insect interactions.

References:

  1. Ceballos et al., 2013. The in vitro mass-produced model mycorrhizal fungus, Rhizophagus irregularis, significantly increases yields of the globally important food security crop cassava. PLoS One, 8, e70633.
  2. Gange and Smith, 2005. Arbuscular mycorrhizal fungi influence visitation rates of pollinating insects. Ecological Entomology, 30, p.600-606.
  3. Orrell, and Bennett, 2013. How can we exploit above–belowground interactions to assist in addressing the challenges of food security? Frontiers in plant science, 4, p.432.
  4. Schausberger et al. 2012. Mycorrhiza changes plant volatiles to attract spider mite enemies. Functional Ecology, 26, p.441-449.

BBSRC Strategic Research Priority: Sustainable Agriculture and Food: Plant and Crop Science & Understanding the Rules of Life: Plant Science & Soil Science

Techniques that will be undertaken during the project:

  • Investigations of soil health by application of biomarkers and soil physicochemical analysis
  • Staining and microscopy to investigate mycorrhizal fungal root colonisation
  • Air entrainments to collect volatile organic compounds from organic material
  • Gas chromatography-mass spectrometry to identify volatile organic compounds
  • Insect assays to determine behavioural responses to a variety of stimuli

Contact: Dr Simon Jeffery, Harper Adams University