PREDICTING SOIL WATER STATUS, EVAPOTRANSPIRATION, GROWTH AND YIELD OF YOUNG OIL PALM IN A SEASONALLY DRY REGION OF MALAYSIA

摘要

The northern part of Kedah, Malaysia, generally experiences an annual dry season that may extend from two to three and a half months. Nevertheless, there has been increased expansion in the area of oil palm in the region. In this study, the model OPRODS1M (Oil Palm Production Simulator) was used to examine and predict responses to climatic conditions during the first six years after planting, based on daily climatic data, and to predict growth and yield for a further four years. The mechanistic model generally confirmed measured trends in soil water status and crop water use, and effectively simulated annual bunch yields and annual changes in some vegetative parameters. It was least successful in reproducing frond production rate (FPR; mostly overestimated), frond biomass production (FBP; overestimated) and total frond number per palm (TFNP; either over- or underestimated except in the fourth year). Total vegetative standing biomass (TVSB), frond standing biomass (FSB) and trunk standing biomass (TrSB) were simulated well in years three and four but underestimated in the two subsequent years. Trends in root standing biomass were reproduced well. Simulation of trunk biomass production (TrBP) was good, except in year six when it was underestimated. Root biomass production (RBP) was generally underestimated but simulation of total vegetative biomass production (TVBP) was generally satisfactory. Bunch yields were well simulated, with the correspondence between mean measured and modelled yields being improved by lagging yield by two years with respect to the weather data. These results suggest that the model provides a useful first approximation for simulating the effects of climate on yield, dry matter production, water use and soil water balance in a seasonally dry climate. However, improvements are necessary concerning the detailed simulation of vegetative growth.