Estimation of parameters describing morpho-physiological features of MEditerranean rice varieties for modelling purposes

This paper illustrates the estimation of parameters describing some morphological and physiological characteristics of Japonica-type and Indica-type rice varieties to be used in crop modelling simulation. Seasonal variability of the Specific Leaf Area (SLA; m2 kg-1) parameter was calculated from biomass and LAI measurements. Coefficient of light extinction (k; -) was estimated by transmittance measurements recorded by LAI2000 in 2004 experiment. Radiation use efficiency (RUE; g MJ-1) was derived by regressive analysis between different above ground biomass measurements and corresponding cumulative APAR using field experimental data set acquired in different years (2004, 2003, 2002, 1990). Results show that development stage determines more variability in SLA than cultivar typology. K parameter varies during the different plant developing stages in agreement with other published data; however, no significative difference is evident among the varieties, representative of different rice-group, when a mean seasonal value (K=0.53; -) is derived. The analysis highlighted a sensible difference in RUE values between traditional tall Japonica variety (1.83, g MJ-1) and new semi-dwarf Indica variety (3.14, g MJ-1). A method to considered possible thermal limitation that decrease RUE values derived by field experiment is proposed to obtain reasonable figure of maximum potential RUE to be used in crop models. Applying this procedure a maximum RUE for Japonica medium late and Indica Early varieties can be set respectively to 2.69 and 3.25 g MJ-1.