A model to simulate the dynamics of carbohydrate remobilization during rice grain filling

The remobilization of carbon reserves accumulated in stems during vegetative growth is known to significantly contribute to yield formation in many cereals, and to be modulated by water and nitrogen availability during grain filling. However, despite the extensive use of crop models to support irrigation and fertilization plans, current knowledge on carbohydrate remobilization is rarely formalized in the available simulation tools. This paper presents a model to simulate carbohydrate remobilization in rice, based on the balance between source (i.e., the carbon reserves in stems) and sink (i.e., the grains) strength and on the impact of water stress and nitrogen luxury consumption. The new approach was included in the WARM model and evaluated using data from published experiments where two cultivars were grown under two nitrogen fertilization levels and two irrigation strategies. Results highlighted the model effectiveness in reproducing the amount of remobilization under non stressed conditions (R2 = 0.99), as well as the impact of water and nitrogen availability (average R2 = 0.97) for Indica and Japonica rice cultivars. The proposed model can be easily plugged into available rice simulators to increase their adherence to the underlying system.