EVALUATION OF A CULTIVAR-SENSITIVE SOIL-WATER MODEL FOR THE POTATO CROP

A modified version of the irrigation scheduling model SimISP (Simulati ng Irrigation Scheduling in Potatoes) was evaluated in terms of its ab ility to simulate the potato crop root zone soil water content through the growing season. The model uses daily radiation, temperature, humi dity, windspeed, precipitation and seasonal crop and soil parameter in puts to estimate evaporation, transpiration,canopy expansion and dry m atter accumulation. Recent cultivar-specific characteristics incorpora ted into the model allow for more precise simulations between cultivar s. Simulations were conducted for rainfed, irrigated and artificial sh elter-imposed stress conditions during four growing seasons on two soi l types in Colchester County, Nova Scotia. Generally strong agreement between simulations and field measured (TDR) available soil water cont ent in the top 15 cm of the soil profile was achieved with an average error within +/- 4.7 mm and a relative error within +/- 0.26. Larger e rrors were obtained for the 1.5- to 30-cm soil layer with average erro rs within +/- 7.3 mm and the relative error within +/- 0.52. Differenc es between model simulations and field measurements indicate the need for an improved root growth sub-model that is soil water sensitive and more precise estimates of soil water recharge after rain.