Syahrul Kurniawan works on quantifying the effects of rain forest conversion to jungle rubber, rubber and oil palm plantations on nutrient leaching losses; analysing the sustainability of soil fertility in rubber and oil palm plantations based on partial nutrient balance and soil chemical characteristics; and assessing how management practices in oil palm plantations influence nutrient leaching losses or nutrient retention. Leaching losses are measured in situ by sampling soil drainage water with suction lysimeters, which are permanently installed at 1.5-m depth at 2 subplot locations in all replicate plots of all transformation systems. Temporal sampling scheme is between bi-weekly to monthly sampling. Soil chemical characteristics are measured down to 2-m depth with systematic sampling design in all replicate plots of all transformation systems.