Abstract
ABSTRACT Traditional shifting cultivation is only sustainable with long fallow periods. In many upland areas of Southeast Asia, fallow lengths have shortened to a point where the objective of the fallow, to restore soil fertility, is not being met, and shifting cultivation is no longer sustainable, either economically or environmentally. On steeply sloping land, soil erosion is substantial, especially as soil fertility declines. ‘Improved’ fallows can hasten the process of soil fertility recovery, and provide alternative products for market. A bioeconomic analysis of one such improved fallow—namely a fallow involving a Gliricidia plantation on Imperata grassland—is reported here. A Gliricidia fallow system is not commonly practiced by smallholders. It is modelled here to assess its potential as an alternative to traditional shifting cultivation systems on steeply sloping land. The analysis is undertaken using a computer model, which is an amalgamation of an existing biophysical, agroforestry model (SCUAF version 4), and an associated economic spreadsheet model. The model predicted that a Gliricidia fallow can increase soil nutrient concentrations (carbon, nitrogen, and phosphorus) and reduce soil erosion. This contrasts with the negative effects of an Imperata fallow. As well as enhancing maize production by maintaining higher soil fertility, Gliricidia fallows offer revenue from other products, such as firewood. Although the Gliricidia fallow system does require significantly more labour to operate than the Imperata system, this is compensated by the higher level of productivity and revenue from other products. Overall, the Gliricidia fallow system is potentially more profitable and more productive than the Imperata fallow system, especially where there is a reasonable market for firewood. The time taken to establish the Gliricidia fallow system in the first instance is an important factor in adoption by smallholders. During the conversion period, smallholders will incur a loss in the first year, and it will take approximately four years for smallholders to begin making a profit above that which is achievable with the Imperata fallow system. The approach to evaluation reported in this paper has merit in being relatively inexpensive, yet powerful. However, the time frame and cost of this analysis are minute in comparison to what would be involved in field experiments.
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Claims 9
Claim · model-written summary
The model predicted that a Gliricidia fallow increases soil carbon, nitrogen and phosphorus concentrations, in contrast to an Imperata fallow.
- Taxon
- Gliricidia
Gliricidiae0 - Treatment
- Gliricidia fallowe0
- Outcome
- soil nutrient concentrations (carbon, nitrogen, and phosphorus)e0
- Direction
- increasee0
- Comparator
- Imperata fallowe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The model predicted that a Gliricidia fallow can increase soil nutrient concentrations (carbon, nitrogen, and phosphorus) and reduce soil erosion”
e1“This contrasts with the negative effects of an Imperata fallow”
Claim · model-written summary
The model predicted that a Gliricidia fallow reduces soil erosion, in contrast to an Imperata fallow.
- Taxon
- GliricidiaGliricidiae0
- Treatment
- Gliricidia fallowe0
- Outcome
- soil erosione0
- Direction
- reducee0
- Comparator
- Imperata fallowe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The model predicted that a Gliricidia fallow can increase soil nutrient concentrations (carbon, nitrogen, and phosphorus) and reduce soil erosion”
e1“This contrasts with the negative effects of an Imperata fallow”
Claim · model-written summary
Gliricidia fallows enhance maize production by maintaining higher soil fertility.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhancing maize production by maintaining higher soil fertility, Gliricidia fallows”
Claim · model-written summary
Gliricidia fallows offer revenue from other products such as firewood.
- Taxon
- GliricidiaGliricidiae0
- Outcome
- revenue from other productse0
- Qualifier
- such as firewoode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Gliricidia fallows offer revenue from other products, such as firewood”
Claim · model-written summary
The Gliricidia fallow system requires significantly more labour to operate than the Imperata system.
- Taxon
- GliricidiaGliricidiae0
- Treatment
- Gliricidia fallow systeme0
- Outcome
- laboure0
- Direction
- moree0
- Comparator
- Imperata systeme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Gliricidia fallow system does require significantly more labour to operate than the Imperata system”
Claim · model-written summary
The Gliricidia fallow system is potentially more profitable and more productive than the Imperata fallow system.
- Taxon
- GliricidiaGliricidiae0
- Treatment
- Gliricidia fallow systeme0
- Outcome
- profitable and more productivee0
- Direction
- moree0
- Comparator
- Imperata fallow systeme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Gliricidia fallow system is potentially more profitable and more productive than the Imperata fallow system”
Claim · model-written summary
During conversion to the Gliricidia fallow system, smallholders will incur a loss in the first year.
- Taxon
- GliricidiaGliricidiae0
- Outcome
- a loss in the first yeare1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“to establish the Gliricidia fallow system”
e1“smallholders will incur a loss in the first year”
Claim · model-written summary
It will take approximately four years for smallholders to begin making a profit above that achievable with the Imperata fallow system.
- Taxon
- GliricidiaGliricidiae0
- Outcome
- begin making a profite1
- Value
- approximately four yearse1
- Comparator
- Imperata fallow systeme1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“to establish the Gliricidia fallow system”
e1“it will take approximately four years for smallholders to begin making a profit above that which is achievable with the Imperata fallow system”
Claim · model-written summary
The authors state that the model-based evaluation approach is relatively inexpensive yet powerful, with time and cost minute compared with field experiments.
Verbatim
e0“The approach to evaluation reported in this paper has merit in being relatively inexpensive, yet powerful”
e1“the time frame and cost of this analysis are minute in comparison to what would be involved in field experiments”
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