Boundary Line Approach in Specifying Durian Nutrient Standards

The boundary line approach was used to improve the diagnostic criteria for durian leaf nutrient standards. The mature `Mon Thong' commercial orchards located in 3 provinces in Eastern Thailand were surveyed during the 1999/2000 growing season. At each location, three to five orchards from each category of low, medium and high-yield orchards were selected. In each orchard, 8-10 uniform and representative trees were chosen for sampling. Second and the third leaves from the terminal of the first flush after harvest were sampled (when leaves were 5-7 months old) at one month intervals from October to December 1999. Eight exposed leaves from the perimeter of each tree were collected to make composite samples for nutrients analysis. The yield of each durian tree was estimated using the equation developed by Koseki et al. (1987)