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 suf ficient 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 se asons. Root-length density (RLD) and root dry weight were measured at four depths in three locations relative to the crop row. In general, RLD decreas ed 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 prof ile, the RLDs of drought-stressed faba beans were significantly lower than those measured beneath well-watered crops. In the deeper soil layers, the R LDs were similar in both moisture supply treatments. An existing root model was employed for the simulation of faba bean root growth. The model estima tes the depth of rooting and RLD in each soil layer based on dry matter all ocation to the root system, soil layer water contents, genotype-specific ro oting characteristics, and soil physical properties. A faba bean growth mod el provided daily allocation of dry matter to roots as well as soil layer w ater contents. Overall, with a few modifications, the root model was capabl e of predicting the RLD of faba bean grown both under limited and sufficien t water supply realistically. Limitations of the model and some aspects tha t need further improvement are discussed. (C) 1998 Elsevier Science B.V. Al l rights reserved.