Despite the widespread occurrence of Piper aduncum fallows in the humid lowlands of Papua New Guinea,
there is no information available on the amount of biomass and nutrients.
There is also no information available on the effects of Piper aduncum
on the subsequent crop. Therefore, a series of experiments were started in
1996 that investigated these effects. The experiments were conducted in Hobu, near Lae, Papua New Guinea.
Thumbnails (left to right): The experimental site at Hobu; one-year old Piper aduncum trees; fallow experiment with gliricidia, piper and imperata; installation of litterbags in
previous Piper aduncum plots; plots planted with sweet potato
Biomass accumulation in leaves, stems, branches and litter of Piper aduncum during a 23-month growing period in the humid lowlands of Papua New Guinea. Bars indicate standard error of the difference in means. Amount of rain between sampling times in parentheses. Modified after Hartemink (2001).
In the first experiment we planted Piper aduncum plots and also plots with Gliricidia sepium and Imperata cylindrica (see thumbnails). The fallows were slashed after one year and sweet potato was planted. The effects of the fallows on sweet potato yield were investigated including nutrient dynamics, decomposition of the fallow biomass, nutrient uptake and soil chemical and physical changes. In another experiment the nutrient and biomass accumulation of Piper aduncum were followed for two years. Our results have shown that Piper aduncum accumulates large amounts of biomass and nutrients, particularly K, and that is has significant effects on the soil and its productivity.
Thumbnails (left to right): Piper aduncum garden Hobu; experimental site in 1998;
Piper aduncum roots (shallow); farmers' open day at experimental site in Hobu