Forage chicory model: Development and evaluation

Chicory has been promoted as an alternative forage crop for livestock farming. It can produce large biomass yields and is highly palatable to animals. However, managing forage chicory in pastoral farms can be challenging because of its growth pattern and low persistence. There is thus a need for modelling tools that can help to understand and manage forage chicory within the farm system. In this work we review the main botanical characteristics of the chicory plant and describe a model developed to simulate the phenology and biomass accumulation of chicory as forage. The model was developed using the Plant Model Framework and it is available for use within the Agricultural Production Systems Simulator. Four experiments with treatments including the use of irrigation, different N fertiliser rates, and defoliation regimes, were used to test the model. We show that the model was able to simulate the biomass accumulation pattern, with R2 values of 0.40-0.54 for standing above-ground biomass and 0.64-0.89 for cumulative harvested material. The performance was weaker when describing plant nitrogen, with R2 of 0.20-0.25 for N content in the above-ground biomass. This indicates that care must be taken when using the model to simulate N balance, and that model refinements are required. For this, more information is needed on the partitioning and mobilisation of N amongst the various organs and on how biomass allocation changes across seasons.