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A.R.?GravesEmail author P.J.?Burgess F.?Liagre J.-P.?Terreaux C.?Dupraz 《Agroforestry Systems》2005,65(1):53-65
A review of existing computer models of silvoarable1 economics was undertaken for a project, entitled Silvoarable Agroforestry for Europe (SAFE), which aims to reduce uncertainty
regarding the introduction and management of silvoarable systems in Europe. Because the published literature describing and
comparing such models is sparse, a framework was developed and then used to characterise five computer models: POPMOD, ARBUSTRA,
the Agroforestry Estate Model, WaNuLCAS, and the Agroforestry Calculator. Key characteristics described for each model were
the background, systems modelled, objective of the economic analysis, economic viewpoint, spatial and temporal scales, generation
and use of biophysical data, model platform and interface, and input requirements and outputs. Each of the models could produce
a partial budget of the profitability of a silvoarable, arable, or forestry system at a one-hectare level using discounted
cost–benefit analysis. Whilst the research models undertook the analysis from a viewpoint of a generic farmer, models developed
for decision-support also included appraisals from the perspectives of tenants, share-croppers, and participants in a joint-venture.
The two farm-scale models, ARBUSTRA and the Agroforestry Estate Model, could also be used to examine the feasibility of silvoarable
systems on an existing business, and to determine the effects of heterogeneous land types and phased planting. The framework
allows users to identify the pertinent issues for selecting or developing a particular model.
The word ‘silvoarable’ is synonymous with the word ‘agrisilviculture’ described by Nair (An Introduction to Agroforestry,
Kluwer Academic, 1983) and describes the same type of production system.
An erratum to this article is available at . 相似文献
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Improved fallow is a technology that can help to raise agricultural productivity in systems of poor soil fertility and low
financial capital. Models, once calibrated, can be used to investigate a range of improved fallow systems relatively quickly
and at relatively low cost, helping to direct experimental research towards promising areas of interest. Six fallow crop rotations
were simulated using the WaNuLCAS model in a bimodal rainfall setting in Kenya over a 10 year period: (A) alternating fallow
and crop seasons, (B) one season fallow followed by three seasons crop, (C) one season fallow followed by four seasons crop,
(D–F) 1–3 seasons fallow periods followed by 3–5 seasons crop. The strategies were tested using a number of fallow growth
rates, soil clay contents, and rainfall amounts to determine the interaction of fallow rotation and biophysical variables
on maize (Zea mays (L.)) yield and sustainability (organic matter, N2 fixation, leaching). The best simulated fallow strategies doubled maize yield compared to continuous maize over a 10 year
period. Across all biophysical treatments strategy A and B of no more than three consecutive cropping seasons and of one consecutive
fallow season yielded the most maize. This was because fallow benefits were largely due to the immediate fallow soil fertility
benefit (IFB) rather than the cumulative benefit (CFB). The difference in yield between the two strategies was through a balance
between (1) their interaction with the biophysical variables affecting accumulation of organic matter, hence increasing soil
fertility and (2) the extra intrinsic soil fertility used for maize productivity by the inclusion of more cropping seasons
within the rotation. We propose the following conceptual framework to manage fallows for maximum maize yield: when environmental
factors are strongly limiting to fallow and crop growth then fallow strategy A would be the best strategy to employ (less
risk but more labour) and when factors are less limiting then strategy B would be the best to employ. 相似文献
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