Theory and development of the hydric balance in PASTMOD

Abstract

In 1996. A pasture simulation model (PASTMOD) was developed to represent a batter understanding of the grass growth and yield, and its interrelationship with soil temperature and soil water PASTMOD used as a basic structure a plant-soil-water system with three basic components: soil temperature, grass growth and water balance. This research describes the background, theory and the development of the water balance component used with PASTMOD. The water balance accounts for soil evaporation, pasture transpiration, percolated  water, and soil water storage. Changes in soil moisture and a possible water stress are passed to the soil temperature and grass growth components, respectively In response, plant transpiration is influenced by changes in leaf area received from the grass growth component