Hartemink, A.E.

English

Wageningen Yield 

  
Fallow  Compartment C N P K Ca Mg 
Piper  Stems 2.7 23 7.4 92 10 5 
aduncum   Branches 0.6 11 4.5 58 10 6 
 Leaves 1.7 67 8.2 125 78 23 
 Litter 0.7 19 1.7 23 59 11 
 Total vegetation 5.8 120 21.8 299 157 45 
 Soil (0-0.15 m) 80.3 8081 5.9 377 4981 879 
 Total 
 
86.1 8201 27.7 675 5138 924 
Gliricidia  Stems 6.9 164 24.2 159 90 23 
sepium Leaves  2.4 145 8.6 81 127 24 
 Litter 1.1 47 3.0 8 95 17 
 Total vegetation 10.4 356 35.9 248 312 64 
 Soil (0-0.15 m) 86.2 8059 4.7 327 4600 868 
 Total 
 
96.6 8415 40.6 575 4912 932 
Imperata  Whole plant 6.7 76 11.9 89 56 29 
cylindrica Soil (0-0.15 m) 85.7 8311 5.2 508 5329 871 
 Total 92.4 8387 17.1 597 5385 900 
 
 
Carbon (Mg ha–1) and nutrient content (kg ha–1) of the topsoil and above ground 
biomass of one-year old Piper aduncum, Gliricidia sepium and Imperata cylindrica 
Nutrient stocks (soil, vegetation, litter) of one-
year old fallows with Piper aduncum, Gliricidia 
sepium and Imperata cylindrica were assessed in 
the humid lowlands of Papua New Guinea. The 
experimental site was a high base status soil 
(Typic Eutropepts) and in Papua New Guinea 
such soils are most intensively used for 
agriculture.  
Nutrient stocks and nutrient cycling of fallows 
in the humid lowlands of Papua New Guinea 
 Alfred E. Hartemink 
International Soil Reference and Information Centre (ISRIC), PO Box 353, 6700 AJ Wageningen, The 
Netherlands Hartemink@isric.nl  
Results 
Gliricidia had accumulated the largest amounts of all 
major nutrients except for K, which was highest in 
the above ground piper biomass. Imperata biomass 
contained the lowest amount of nutrients. The largest 
stocks of C, N, Ca and Mg were found in the soil, 
whereas the majority of P is found in the above 
ground biomass and litter. Almost half of the total K 
stock of piper and gliricidia is found in the biomass.  
When the fallows were slashed imperata returned 
more C than piper and gliricidia that have more than 
half of the C removed with the wood. Soil organic C 
significantly increased under gliricidia fallow 
whereas no net changes occurred in piper and 
imperata fallows. 
 
0
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piper gliricidia imperata
Ca
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piper gliricidia imperata
Mg
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piper gliricidia imperata
K
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piper gliricidia imperata
P
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piper gliricidia imperata
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returned to the soil
kg
 h
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piper gliricidia imperata
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removed with the wood
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 h
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Conclusions 
The study has shown large differences in biomass
and nutrient stocks between the two woody fallows 
(piper, gliricidia) and between the woody fallows and 
the non-woody fallow (imperata). There is a higher 
potential for woody fallows compared to grass 
(imperata) fallows in the humid lowlands of Papua 
New Guinea. 
 


Nutrient stocks and nutrient cycling of fallows in the humid lowlands of Papua New Guinea

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