SOIL MOISTURE-BASED SIMULATION OF FORAGE YIELD

A simulator of seasonal forage yield (SIMFOY) was developed for a 'dry weather-forage crop' insurance plan in Ontario, Canada. Growth is assumed to follow an idealized sigmoidal curve with time. Departures from the potential daily growth increment are determined from an estimate of the soil moisture regime and degree-days above 5°C. The harvestable dry matter at the end of each growth cycle depends on the accumulated daily growth increments. Daily soil moisture is estimated in each of several soil zones using potential evapotranspiration calculated from a modified energy budget approach, and an extraction pattern that depends on soil moisture distribution and root distribution. Validation of SIMFOY is accomplished by comparison of soil moisture and yield estimates with measured values for different soils over a number of years. Results indicate that the model simulated seasonal dry matter production of alfalfa with reasonable accuracy. © 1979.