The development from kinetic coefficients of a predictive model for the growth of Eichhornia crassipes in the field. II. Testing and refining the model under field conditions

Abstract

Kinetic cocfficicnts derived for Eichhornia crassipes (Mart.) Solms under culture conditions of N and P limitation were used in the Monod model to identify the limiting nutrient and to predict specific growth rates under conditions of varying water nutrient concentration and air temperature. Predicted data were validated by comparison with specific growth rates measured for plants growing in loosely and densely crowded populations at two field sites. The use of culture-derived maximum specific growth rates (Umax) in the model resulted in maccurate predictions of plant growth rates in loosely and densely crowdcd field populations. The use of field-derived Umax values in the model, however, resulted in adequate predictions of plant growth rates in loosely crowded field populations. The incorporation of radiant flux density (diffuse component of the radiant flux) and relative humidity into the model considerably improved its accuracy of prediction. In all cases, specific growth rates were more accurately predicted from the limiting total N or total P concentrations, than from other N or P fractions, in the water.