Analysingcropyieldandplantqualityinan intercropping system using an eco-physiological model for interplant competition D.T. Baumann a, *,L.Bastiaans b ,J.Goudriaan c ,H.H.van Laar b ,M.J.Kropff b a Swiss Federal Research Station for Fruit-Growing, Viticulture and Horticulture, PO Box 185, CH-8820 Wa ¨denswil, Switzerland b Crop and Weed Ecology Group, Department of Plant Sciences, Wageningen University, PO Box 430, NL-6700 AK Wageningen, The Netherlands c Plant Production Systems Group, Department of Plant Sciences, Wageningen University, PO Box 430, NL-6700 AK Wageningen, The Netherlands Received 20 October 2000; received in revised form 31 January 2001; accepted 17 August 2001 Abstract An eco-physiological model was used to improve understanding of interplant competition based on physiological, morphological and phenological processes. The model was para- meterised based on characteristics of the plants in monocultures and its performance was evaluated for the crop mixtures using experimental data from different growing seasons. A lightinterceptionroutineaccountingforrow-geometrywascomparedtoaroutineassuminga homogeneous horizontal leaf area distribution. The models simulated the light distribution amongthespeciesequallywell.Theproductionofthetwocropsinthemixturewasaccurately simulated using parameter values based on monoculture growth characteristics. Morphologi- cal characteristics of the species such as the relative growth rate of leaf area during early growth and specific leaf area largely determined the competitive strength of the species. Dry matter production of the species, particularly if grown in mixture, was highly sensitive to maximum plant height and radiation use efficiency. Celery was found to be a stronger com- petitorthanleekandclearresponsesofqualitycharacteristicstoplantdensityinmonoculture and mixtures were observed. The model was used to determine ranges of plant densities that enable the intercropping system to meet current quality standards of the component crops. # 2002PublishedbyElsevierScienceLtd. Keywords: Intercropping; Mechanistic model; Interplant competition 0308-521X/02/$ - see front matter # 2002 Published by Elsevier Science Ltd. PII:S0308-521X(01)00084-1 Agricultural Systems 73 (2002) 173–203 www.elsevier.com/locate/agsy * Corresponding author. Tel.: +41-1-7836274; fax: +41-1-7806341. E-mail address: daniel.baumann@faw.admin.ch (D.T. Baumann).