Seasonal changes in durian leaf and soil mineral nutrient element content

The 3-4 year monitoring study showed that fluctuations in durian (Durio zib ethinus Murray) leaf and soil nutrient element levels were closely related to seasonal changes in the crop phenology. The leaf sampling method was sta ndardized taking the 5th and 6th mature green leaf from the shoot tip. The best sampling time was determined to be in November where the coefficient o f variability for most nutrient elements were the lowest at or lower than 2 0%. Tentative standards for durian leaf nutrient elements were set up takin g the 95% confidence interval of the means at this sampling stage. All the leaf macro elements, nitrogen (N), phosphorus (P), potassium(K), sulfur (S) , and the micro elements, zinc (Zn), manganese (Mn), copper (Cu), and iron (Fe) declined or were lower during fruit set and development from September to end of fruit harvest in January. Leaf N was also the lowest in July and leaf P at the tail end of harvest. Soil N, P, and the bases K, Ca, and Mg also exhibited similar trends, lower during fruit development especially in October-November and were lower during active leaf flushing from March to May.