months) requires fertilizer (N-P-K)
equivalent to 0-3-0 or rock phosphate,
while the grafting plot (stage 2, 2-5
months) requires fertilizer equivalent to
20-8-20, and the growth acceleration until
rubber tapping (stage 3) required fertilizer
equivalent to 20-8-20 or 20-10-12, and
after tapped (stage 4) required fertilizer
equivalent to 30-5-18. Hence, the
considered fertilizer formula in this study
was 20-8-20, at the input rate of 5 gm/
tree (Kangpidsadarn, 2007).