The Use of Simulation Modelling to Explore Interactions Between Root Systems and Environments and Its Implications for Resource Use Efficiency.

Genetic improvement of crop root systems to increase the efficiency of water and nutrient capture requires an understanding of which root traits should be targeted for selection and in which environments those traits are likely to be effective. Within the major cereal species, genetic variation has been reported for several root traits, such as the number of seminal roots, lateral spread of the root system and rate of root extension. It is often unclear, however, what impact this variation has on the growth of the root system as a whole under field conditions and its ability to capture water and mineral nutrients. This paper illustrates how a crop simulation model (SPACSYS) with a root architectural component can provide information to assist in this process. Simulated root growth was compared with field measurements of wheat root length density (RLD) distribution down the soil profile. A sensitivity analysis, in which specific roots traits were varied individually, was then used to identify which traits have the greatest effect on the growth and distribution of the root system down the soil profile. In addition we use a dataset of winter barley to evaluate the ability of the model to predict the dynamics of crop growth and nitrogen uptake over several sites and seasons. Once the validation process is completed, the model will be used to explore the potential effects of modifying the root system on N uptake efficiency under contrasting soil and climatic conditions and husbandry regimes.