At 23 months, piper had accumulated 222 kg Nitrogen 50 kg, P 686kg , K 225 kg, Ca 75 kg, Mg and 24 kg more than half of the PK Ca and Mg was found in the stem [wood] which is removed from the field and used as firewood when farmers slash the follow . piper biomass [excluding wood] returned about three times more Joe to the soil than imperata ,but differences between total P and S contents were small . For the accumulation of biomass and nutrients, imperata fallows should not exceed 1 year . piper accumulated large amounts of biomass and nutrients, particular K, which is an important nutrient for root crops that dominate the cropping phase in the shifting cultivation systems of the humid lowlands. 2001 Elsevier Science B.V. All rights reserved.