Modelling growth and dry matter partitioning in root crops: a case study with carrot (Daucus carotaL.)

A persistent weakness of root crop models has been reliance on empirical descriptions of dry matter partitioning and leaf area growth. This paper presents an alternative, mechanistic, approach. This hypothesises that leaf growth, leaf senescence, and the partitioning of dry matter above and below ground are controlled by the fraction of light transmitted through the canopy (θtrans). In turn, θtrans depends on leaf area index, forming a feedback loop. A model based on this is developed, fitted, and tested using data from two field experiments with the carrot variety Carson. The model performed well with both fitting and independent datasets. Fitted values of model parameters agreed well with the literature. For yield, root:shoot ratio, and leaf area, the slopes of observed on fitted values were 0.93–1.06, and R2 values were 0.88–0.98. Further development to include nutrient stresses is suggested. Direct experimental testing of predictions made from the partitioning hypothesis is recommended.