Update on the model and its development, June 2007

1. ROOTMAP model of three-dimensional root growth Update on the model and its development, June 2007 Vanessa Dunbabin Tasmanian Institute of Agricultural Research The University of Tasmania Private Bag 54, Hobart TAS 7001 Vanessa.Dunbabin@utas.edu.au

2. ROOTMAP - a 3D root architecture model ROOTMAP - was created by Art Diggle (DAWA - Department of Agriculture Western Australia). Diggle (1988) ROOTMAP - a model in three-dimensional coordinates of the growth and structure of fibrous root systems. Plant Soil 105, 169-178. Art Diggle’s root architecture model can simulate any root architecture and any rooting strategy.

3. ROOTMAP - building a root architecture Root Order 1 Root Order 0 Root Order 2 Branch spacing Change in growth direction determined by deflection and geotropism indices initial root angle A number of basic descriptors/parameters are used to describe a root architecture. Diggle (1988) Plant Soil, 105, 169-178.

4. high low low high geotropism index deflection index growth & branch density low high ROOTMAP - how changing root parameters affects root architecture

5. ROOTMAP has a modular structure ROOTMAP has been developed in C++, so it has a flexible modular structure. It consists of a number of different modules including the water and nutrient modules, the root architecture module and the resource allocation / root response module. All modules communicate with each other to produce a dynamic root simulator. V. Dunbabin et al. (2002) Plant and Soil, 239, pp 19-38

6. leaching, massflow, diffusion, uptake drainage, redistribution, evaporation, uptake the time step is not fixed, all processes run at their own time resolution and events can occur at unique points in time controls local root growth and nutrient uptake on a return on investment basis ROOTMAP has a modular structure stores all plant/soil information through time and 3D space at user specified resolution any number of unique plants can be modelled at one time Dunbabin et al. (2002) Plant & Soil, 239, pp19-38.

7. Putting soil & plant characteristics under the microscope ROOTMAP has been used for investigating root-soil interactions in fine detail. The soil can be divided up into sub-volumes of any size. At any point in space and time, information on local soil properties, such as soil water potential or nutrient concentration, can be output. Root information including the number, length and type of roots each plant has in that local soil area can also be output. The amount of water and nutrient that each plant is taking up from that local part of the soil can also be tracked. Nutrient uptake from fertiliser versus background soil sources can be distinguished. It is this capacity to interrogate the root/soil environment in such detail that makes the ROOTMAP model of root growth a valuable research, extension and teaching tool.

8. Putting soil & plant characteristics under the microscope Soil properties in the local volume Water content Drained upper limit, wilting point Soil water potential Nutrient concentration Temperature pH Etc….. Properties of each plant in the local volume (Plant 1, Plant 2 …) Total root length and root length density Root length and root length density per branch order Growth rate per branch order Nutrient uptake Water uptake Etc…..

9. ROOTMAP - responsive root growth ROOTMAP has been developed from a root architecture model, into a 3D root growth/response model designed to simulate root growth in response to the non-uniform supply of water and nutrients in the soil environment. V. Dunbabin et al. (2002) Plant and Soil, 239, pp 19-38

10. Responsive root growth The ROOTMAP model has been designed to represent the way that grain-crop root systems grow and respond to their soil environment. The model contains a feedback-based module that balances the whole plant demand for water and nutrients, with water and nutrient supply at each root tip. It is this feedback-based approach that allows the model to simulate whole plant responses to water and nutrient status, as well as local responses such as root proliferation in nutrient bands. Dunbabin et al. (2002) Plant & Soil, 239, pp19-38.

11. Drought Control No Nitrogen Whole-Plant Responses Dr Brian Forster et al., Scottish Crop Research Institute, Dundee, Scotland. Drew & Saker (1978) Local Root Responses

12. Field & glasshouse data Field scale Plant scale Using ROOTMAP Theoretical modelling Multiple scenarios Rhizosphere Scale The ROOTMAP model can be used to investigate crop root growth over the range of scales from field-scale to rhizosphere-scale. It can also be used to simulate whole crops growing over a season, or to undertake theoretical analyses of water and nutrient uptake at the crop/root interface.

13. ROOTMAP - a simulation tool for investigating crop root systems • ROOTMAP can be used: • to facilitate interpretation of field and glasshouse data • to assist with experimental planning and design • to assist in identifying important rooting traits for crop production • as a tool for delivery/extension of root/soil research

14. Examples of how ROOTMAP has been used

15. ROOTMAP - modelling root growth responses to the season. Deep, sandy, free-draining soil. Wet Year Dry Year More nitrate (purple colour) lost (leached/deep drainage) below the rooting zone in the wet year Poor subsoil moisture restricts subsoil root growth. Increased root growth in the upper profile as partial compensation. Good subsoil moisture enables root exploration of the subsoil

16. Investigating root architecture & nitrate leaching - Lupins dichotomous theoretical architecture herringbone theoretical architecture L. pilosus L. angustifolius What is the trade-off between rooting depth and root length density for minimising nitrate leaching under lupin crops in free-draining deep sands? increasing root length density decreasing rooting depth

17. 1st order branches only (herringbone) highly branched (dichotomous) increasing rooting density increased nitrate uptake to a point. Beyond this the rooting depth was too shallow to capture nitrate lost to the subsoil so uptake decreased again. The winner: a trade-off root system, optimising both top-soil RLD & rooting depth L. angustifolius Uptake or leaching (kgN ha-1) increasing root length density decreasing rooting depth Dunbabin et al. (2003) Plant, Cell & Environment, 23, 835-844

18. 1st order branches only (herringbone) highly branched (dichotomous) L. angustifolius Uptake or leaching (kgN ha-1) uptake maximised & leaching minimised with a trade-off root system, optimising both top-soil RLD & rooting depth increasing root length density decreasing rooting depth Dunbabin et al. (2003) Plant, Cell & Environment, 23, 835-844

19. Ranking the most important parameters: crop-weed competition • Are the root traits important for water and nutrient uptake in weedy crops the same as for weed-free crops? Annual ryegrass Lolium rigidum

20. Describing root architecture, cropping environment and agronomy Sensitivity analysis approach for screening root traits ROOTMAP was used to run a sensitivity analysis of over 30 root architecture, environmental and agronomic parameters for investigating what factors might be important for crop competition against weeds.

21. Example of some of the parameters included in the sensitivity analysis intensity efficiency deflection index plant density geotropism index Sensitivity analysis approach for screening root traits branch density nutrient uptake kinetics root growth rate soil water and nutrient characteristics rainfall environment

22. Results - separation of traits The results suggest that the root traits important for making a crop a successful competitor against weeds are different to those for successful crop growth in weed-free conditions. Parameters that drive the intensity of root foraging - rapid root growth and occupation of soil space - were important for denying weeds of soil resources and so reducing weed growth. Parameters that drive the efficient distribution of roots through soil and the efficient uptake of water and nutrients at the root surface are important for crop growth in weed-free conditions. Dunbabin (2007) Field Crops Res, In Press

23. ROOTMAP - segregation of important root traits Competition Free = Efficient foragingspatial arrangement of roots through soil & efficient uptake at the root surface, optimising return on investment in roots These results suggest that ROOTMAP could potentially be used as a trait selection tool - matching root systems to cropping environments Root Competition = Intensity of foraging rapid growth and high foraging intensity, occupying space and maximising resource capture Dunbabin (2007) Field Crops Res, In Press

24. Ongoing developments to the ROOTMAP model UT00009, Sustainable Farming Systems

25. Developing ROOTMAP As part of a 3 year (2006-2009) GRDC (Grains Research and Development Corporation) project (UT00009), the ROOTMAP model is currently undergoing a series of developments. Aim - develop ROOTMAP into a software package that researchers, extension officers, lecturers, and teachers can use.

26. Developing ROOTMAP • The soil module will be expanded to represent a wider range of soil types. • The nutrient model currently simulates nitrate & phosphate, and will be expanded to a multi-ion species model. • A library of crop and environmental parameters will be developed. • The data input and output structures, model memory requirements, speed and stability will all be improved. • ROOTMAP will be converted from running on a Macintosh to running on a PC. • The user interface and model graphics will be improved. • A manual will be developed. • The model will be extensively tested using field and glasshouse data sets from around Australia.

27. Convert MAC to PC format Expand soil routine Develop user-interface Incorporate multi-ion nutrient model Developing ROOTMAP Extensive testing Develop parameter library Structural developments Improve graphics Manual & website

28. ROOTMAP publications - journals and books • Dunbabin V (2007) Simulating the role of rooting traits in crop-weed competition. Field Crops Res. In Press. • Dunbabin V, McDermott S, Bengough A.G. (2006) Upscaling from rhizosphere to whole root system: Modelling the effects of phospholipid surfactants on water and nutrient uptake. Plant and Soil, 283, 57-72. • Dunbabin V, Rengel Z, Diggle A. (2004) Simulating form and function of root systems: efficiency of nitrate uptake is dependent on root system architecture and the spatial and temporal variability of nitrate supply. Functional Ecology, 18, 204-211. • Dunbabin V, Diggle A, Rengel Z. (2003) Is there an optimal root architecture for nitrate capture in leaching environments? Plant, Cell and Environment, 26, 835-844. • Dunbabin V, Rengel Z and Diggle A (2003). Root architecture and nutrient capture - the complex riddle of what constitutes optimality of root form and function. In: Innovative Soil-Plant Systems for Sustainable Agricultural Practices, JM Lynch, JS Schepers and I Unver (eds.), pp.2-16. OECD (Organisation for Economic Co-operation and Development), Paris, France. ISBN 92-64-09971-9. • Dunbabin V, Diggle A, Rengel Z, Van Hugten R. (2002) Modelling the interactions between water and nutrient uptake and root growth. Plant and Soil, 239, 19-38. • Dunbabin V, Diggle A, Rengel Z. (2002) Simulation of field data by a three-dimensional model of interactive root growth. Plant and Soil, 239, 39-54. • Dunbabin V, Rengel Z, Diggle A (2001) The root growth response to heterogeneous nitrate supply differs for Lupinus angustifolius and Lupinus pilosus. Australian Journal of Agricultural Research, 52, 495-503. • Dunbabin V, Rengel Z, Diggle A (2001) Lupinus angustifolius has a plastic uptake response to heterogeneously supplied nitrate while Lupinus pilosus does not. Australian Journal of Agricultural Research, 52, 505-512.

29. ROOTMAP publications - conference abstracts & papers • Dunbabin VM (2007) Using root architecture models to bridge the gap between the rhizosphere and the whole root system. Proceedings of RHIZOSPHERE 2 - Second International Rhizosphere Conference, August 2007. • Dunbabin VM (2006) Using the ROOTMAP model of crop root growth to investigate root-soil interactions. Proceedings of the Australian Agronomy Conference, Australian Society of Agronomy. • Dunbabin V, McDermott S, Bengough A.G. (2004) Upscaling from rhizosphere to whole root system: Modelling the effects of phospholipid surfactants on water and nutrient uptake. In: “Rhizosphere 2004 - Perspectives and challenges”, Proceedings of the 1st International Rhizosphere Congress, 12-17 Sept 2004, Munich Germany. • Dunbabin V, Diggle A, Rengel Z, Gill G, Mendham N (2003) Breeding more productive grain crops - could selecting the right rooting traits help? In: "Solutions for a better environment" Proceedings of the 11th Australian Agronomy Conference, 2-6 Feb 2003, Geelong Vic, Australian Society of Agronomy. Published on CDROM. ISBN 0-9750313-0-9. • Dunbabin V, Diggle A, and Rengel Z (2001) Modelling root responses to heterogeneous nutrient supply in three-dimensional space. In Proceedings of the 6th Symposium of the International Society of Root Research, Nagoya, Japan, Nov 2001, pp 98-99.

30. Acknowledgements GRDC, Grains Research and Development Corporation Art Diggle, Department of Agriculture Western Australia Rob van Hugten, University of Tasmania ROOTMAP has been developed as a collaborative partnership between the following parties: The Grains Research and Development Corporation The Department of Food and Agriculture Western Australia The Centre for Legumes in Mediterranean Agriculture The University of Tasmania