A growth model for the mixture of Italian ryegrass and red clover in the dryland of the IX Región

Adrián Catrileo S. 1

A simulation model describing the growth of a short-rotation pasture far the mixture of Italian ryegrass and red clover is presented. The model considers carbon flow and the water-soil balance to describe dry matter accumulation of the pastura. The model is deterministic and dynamic with processes described with time steps of one day. Daily total carbon dioxide assimilation, leaf area index, respiration, growth efficiency, carbohidrates partitioning, temperatura effeet and senescence are the main factors considered to predlct system's behaviour. Actual daily growth is adjusted according to the relationship between actual and potencial transpiration resulting from the availability of water in the soil. Daily data of rainfall, Pan evaporation and mean air temperatura are inputs of the model. Results of the model compared with field experiments over two seasons, show that the model is capable to predict reasonably daily growth rates of the forage mixture, although the degree of prediction is lower in extreme dry conditions.

Keywords: simulation models, photosynthesis, short rotation pasture, water balance.
1 Estación Experimental Carillanca (INlA), Casilla 58-D, Temuco, Chile.