CP 3: The Soil-Root-Zone

The accurate quantification of soil-root zone processes for application within yield and efficiency analysis is important to increase crop sustainability while conserving global resources. We address the task of measuring soil-root zones of crops in the field and in controlled environment rhizotron systems with minimally or non-invasive bespoke sensors and robotics. Sensor data will be ground-truthed at sub-millimeter to meter scales, and aligned with above ground sensor and yield component data and analyses in collaboration with CP1 and CP2. The overall aim is to develop technologies and scientific concepts for crop yield predictions and optimize resource inputs on farms in real time.

Hence, in phase I, we concentrate on sensing and predicting predict root performance in the field. Root performance is defined as root architectural development, anchoring, and water and N uptake. If this is successful, later project phases should focus on diagnosis of disturbances in root development. 

Joint experimental platforms in the laboratory and in the field at the rhizotron facility in Selhausen help to achieve these aims. In detail, the following steps are anticipated:

  • Automated single-root sensing to validate single plant root models
  • Establishment of reference plots with and without plants to detect disturbances of field sensing
  • In-situ 4D imaging of root growth and soil properties using use geophysical and spectroscopy sensing devices and compare the results with high-performance tomographic systems in controlled conditions as well as (destructive) automated soil-coring analysis.
  • Mathematical forecasting of sensor signals in the field (deterministic)
  • Surrogate modelling with virtual and real sensor signals to image root growth in field (still underrepresented)

This Core Project thus combines experience from six subprojects

SP1: Does root structure equal function? Assigning function to root structures with minimally invasive phenotyping and modeling:
Novel pheno-physiotyping methods are used to assess and translate root architecture into function, applying automatic coring, magnetic resonance imaging, microscopy and cellular stains and protein analyses for root vitality and N functions.

SP2: Structural and functional field root sensing using tomographic and endoscopic electrical impedance spectroscopy:
Spectral electrical impedance tomography (sEIT) is used as in-situ tool for the structural and functional sensing of root systems in the field; data processing will be optimized and linked with established soil-root electrical relationships to monitor rooting and water uptake depth.

SP3: Imaging spatial and temporal soil water content variations of the soil-plant-root zone using ground penetration radar (GPR):    
GPR monitoring of soil water variability in combination with root-growth data is used to improve modeling of soil-root interaction processes at field plots scale. Full waveform approaches inform on root water uptake, while hydrogeophysical inversion is advanced by the root growth model and soil data (bore-hole gamma).

SP4: Soil-rhizosphere-plant interaction in root system sensing:
For better understanding of root-growth strategies, we use endoscopy in soil pores to quantify soil-root contact areas, combined with stable isotope probing of nutrient uptake and microbial metabolism.

SP5: Soil Dynamics and impacts of potential interventions:
To predict spatial variability of crop biomass and yield in 1D/3D manner, we assimilate observations of below and above-ground processes into a processed-based model, validated by field data.

SP6: Surface flux measurements of reactive nitrogen species for autonomous in-field intervention:
A mobile field system for the online analysis of reactive N gases is developed and applied, relying on threshold values for HONO and NH3 fluxes as main input parameters to minimize N fertilization demands.