The grapesim model: a model to better understand the complex interactions between carbon and nitrogen cycles in grapevines

Abstract

Context and purpose of the study – Nitrogen fertilization is an important practice to guarantee vineyards sustainability and performance over years, while ensuring berry quality. However, achieving a precise nitrogen fertilization to meet specific objectives of production is difficult. There is a lack of knowledge on the impact of nitrogen fertilizers (soil/foliar; organic/mineral) and different levels of fertilization on the interactions between carbon and nitrogen cycles within the vine. Crop models may be useful in that purpose because they can provide new insights of the effects of fertilization in carbon and nitrogen storage. The objective of this study is to build a model to simulate grapevine carbon and nitrogen content in vines to evaluate the impact of different fertilization strategies in vine growth and yield.

Material and methods – The model GrapeSim has been designed to simulate dynamics of carbon and nitrogen content in organs over multiple years. The model runs at a daily time-step and it decomposes the plant in several compartments; Leaf, Berry, Shoot (annual), Perennial organs (trunk and roots) and Storage. Carbon production is based on the radiation use efficiency approach and carbon is allocated to organs according to their growth demand. When carbon production surpasses organ demand, the remaining carbon is stored in the storage compartment, otherwise, carbon is remobilized from the storage to satisfy organs demand. Nitrogen fluxes are simulated analogously to carbon fluxes by considering a nitrogen demand to reach a specific concentration in each organ. GrapeSim has been calibrated using organ growth trajectories obtained from a pot experiment using ‘Sauvignon Blanc’ grafted onto ‘SO4’.

Results – GrapeSim provided an estimation of the carbon and nitrogen content in storage and their response to nitrogen fertilization, which is quite difficult to measure under field conditions. Several types and amounts of nitrogen were applied to evaluate the effect of nitrogen availability on plant growth, photosynthesis and yield and to validate specific outputs of the model. This work is an example of the relevance of combining field research with crop modelling to have a better understanding of vine responses to horticultural practices such as nitrogen fertilization.
Within the “NV2” project (that brings together 4 private companies, 1 technical institute and 3 public institutes), the next step will be to understand how nitrogen deficiency can affect subsequent reproductive development (bloom return and fruit set) using GrapeSim.