Research activities

Studying biology in deep soil layers is challenging and the scientific documentation and understanding of water and nutrient uptake from there is quite limited. Deep Frontier has developed unique research facilities and is developing equipment and methods that allow studying deep roots in these facilities.

Isotope tracers and resource uptake
The project is using minirhizotron methods for measuring roots and 15N isotope labelling for measuring deep root nitrogen activity. In addition, Deep Frontier will develop methods for injecting or placing isotope tracers into the soil in order to obtain realistic data on their uptake and to develop ingrowth core methods. With such methods, we can place soil samples temporarily in soil where roots can grow into the samples, for example take up tracers added to it, and then recollect the soil samples for analysis of roots and nutrient content. Focus will be on uptake of mobile and immobile nutrients as well as uptake of water.

Deep Frontier is testing a range of stable isotope tracers and developing methods in semi-field conditions to study uptake and thereby later use these methods in field conditions. With modern mass spectrometers, one can measure a range of isotopes simultaneously with high precision.

Studying water uptake by use of isotope labelled water pose certain challenges compared to nutrient tracers. Methods to overcome these challenges are under development. Deep Frontier will develop methods based on sampling evaporating water or plant sap water, which can allow very short term non-destructive measurements, or longer term studies by exploiting the fact that oxygen from water is built into plant carbohydrates during the photosynthesis process.

Deep Frontier will analyze the data from root observations, crop development and resource use and their interaction in order to enhance our understanding of their relationship.

Ingrowth cores and root microbiomes
In field conditions the use of ingrowth cores are essential for research in deep soil, hence methods are under development that allow for repeated sampling. Also, protocols for extracting DNA from soil and quantifying plant roots from extracted DNA is a development goal.

Additionally, Deep Frontier is studying microbiology below 2 meters depth. This will improve our understanding of deep root microbiology and colonization strategies in deep soil layers.

Carbon deposition and soil biology
In order to improve our understanding of the processes affecting deposition and decomposition of organic matter and carbon in deep soil layers, to quantify the effect of deep rooted crops on soil carbon stocks below 1 meter depth and to study root interactions with soil (micro)biology, the activities of Deep Frontier in this regard are:

  • Development of methods for measuring deposition and turnover of root derived carbon in deep soil layers, including a simplified model for quantifying soil carbon storage 
  • Quantification of carbon sequestration with deep rooted species 
  • Methods for studying roots and their interactions with soil biological communities and how deep soil and rhizosphere biology are affected by deep rooting crop species.

Deep rooted species and cropping systems
Deep Frontier intend to identify a wide range of deep rooted species with a significant activity between 2 and 4 meters depth in the soil and include these into cropping systems as crops, cover crops or intercrops in mixed stands together with more conventional crop species.

Systems where deep rooted perennial crops are grown in rows and common crops, such as cereals, are grown on the area between the deep rooted rows is compared to cereal crops grown in monoculture. Also, competition and complementarity between deep rooting crops and the companion cereal crops is studied.

Current agricultural systems have a short life span, which is a major limitation in regards to development of deep roots. Using systems where bi-annual crops or cover crops are established much earlier than normal could allow their growing systems to be prolonged. Deep Frontier will study the effects on rooting depth.

Research activities by Post docs and PhD-students

Post docs involved in Deep Frontier research activities:
• Eusun Han at University of Copenhagen is focusing on determining the architecture and function of plant deep-roots that can unlock the hidden soil resources in arable subsoil

PhD-students of the Deep Frontier project:
• Camilla Ruø Rasmussen at University of Copenhagen is working on nutrient and water uptake in deep roots 
 • Zhi Liang at University of Aarhus is working on carbon input and turnover and how this affects the microbial population 
• Leanne Peixoto at University of Aarhus is working on carbon input and retention of different plant species in deep soil layers 
• Annemette Lyhne-Kjærbye at University of Copenhagen is working on the rhizosphere microbiology in deep soil layers