Simulation of faba bean (Vicia faba L.) root system development under Mediterranean conditions

Root growth of faba bean genotype ILB 1814 grown under both limited and sufficient moisture supply was studied in 1993-1994 and 1994-1995 at ICARDA's Tel Hadya research station. Crops were sown on two dates in both growing seasons. Root-length density (RLD) and root dry weight were measured at four depths in three locations relative to the crop row. In general, RLD decreased considerably with depth, and by the start of pod-filling, around 60% of the roots were found in the top 15 cm of soil. In the upper 30 cm soil profile, the RLDs of drought-stressed faba beans were significantly lower than those measured beneath well-watered crops. In the deeper soil layers, the RLDs were similar in both moisture supply treatments. An existing root model was employed for the simulation of faba bean root growth. The model estimates the depth of rooting and RLD in each soil layer based on dry matter allocation to the root system, soil layer water contents, genotype-specific rooting characteristics, and soil physical properties. A faba bean growth model provided daily allocation of dry matter to roots as well as soil layer water contents. Overall, with a few modifications, the root model was capable of predicting the RLD of faba bean grown both under limited and sufficient water supply realistically. Limitations of the model and some aspects that need further improvement are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.