 |
|
|
|
|
Summary of full report
A report for the RIRDC/Land & Water Australia/FWPRDC Joint Venture Agroforestry Program
by Peter Carberry, Neil Huth, Perry Poulton and Lisa Brennan
November 2007
RIRDC Publication No 07/192 RIRDC Project No CST-6A
Executive summary
What the report is about
The Agricultural Production
Systems Simulator (APSIM) is a computer modelling tool which simulates
agricultural cropping systems, to help in farm management and assessment
of risk. In this report, APSIM is used to quantify the trade-off between
tree belts and crop productivity on farms in the medium to low rainfall
areas of Australia. The analyses are based on windbreaks and mallee belts
and their interaction with crops at the paddock scale. The report also
details the emergent capability within the APSIM framework to simulate
two-dimensional agroforestry systems; that is, systems which can simulate
many points in a crop or tree area and the interaction between adjacent
crops.
Who the report is targeted
at?
This report is targeted
at researchers and agribusiness advisory services with an interest in quantitatively
assessing the viability of integrated agroforestry and crop production
enterprises. The modelling tool APSIM can also be used to discuss outputs
and agroforestry scenarios with landholders.
Background
The long-term benefits of
retaining or planting trees on farms to rehabilitate land and protect the
soil from erosion or salinity problems have to be traded off against the
impact of tree competition on commercial crops, especially in the medium
to low rainfall regions of Australia. The incentive to plant trees will
be higher where tree competition can be offset by economic returns gained
from farm forestry products and by the beneficial impacts of tree windbreaks
on crop yields and resource sustainability.
APSIM has a well-established capability to simulate cropping systems. It also has process-level modules for tree, crop, soil and atmospheric components and this provides considerable flexibility for specifying interactions between the tree and crop components of an agroforestry system. While several components of APSIM’s capability for simulating agroforestry systems have been previously tested e.g. for tree growth, tree water balance and windbreak impacts, this project was the first to compile and test APSIM’s capability to simulate an integrated agroforestry system. It should be noted, however, that a significant limitation to achieving this objective has been the lack of comprehensive measured data on tree-crop interactions in agroforestry systems in Australia.
Aims/Objectives
The two main objectives
of this project were to:
An additional objective
was to use the new capability to design and implement activities that allow
individual landholders to explore the viability of agroforestry investments
for their own farms.
Methods used
Data on tree-crop interactions
for several sites in southeast Queensland were collected and APSIM was
configured to simulate a conceptual multi-point agroforestry system consisting
of a tree belt along the border of a crop field.
Simulations were conducted for four tree-crop systems around Australia, and the predictions were tested against measured data from the sites. The detailed APSIM-Forest module was used to dynamically calculate effects on a neighbouring crop, on a daily basis – such effects included both windbreak and tree competition impacts (soil, water and nutrients). Case studies for a range of treecrop systems were then assessed over the historic climate record for wood production, crop yield, profitability and deep drainage.
Following the model validation, APSIM agroforestry simulations were used in interactive discussions with a number of landholders and their advisers, to discuss the viability of paddock-scale agroforestry investments.
Results/Key Findings
The achievements of this
project included:
The simulated productivity
of oil mallee hedges was consistent with values reported elsewhere and
suggested that short-duration trees grown within agroforestry systems are
at least as profitable as traditional cropping systems at some locations.
The economic scenario analysis undertaken using APSIM simulations for five sites in northeast Australia (Emerald, St George, Roma, Dalby and Moree) indicated that at the likely prices and costs forecast for timber production in 2003 ($60/m3 and $2025/ha), the economics of E. argophloia windbreaks would be unattractive at all sites. However such agroforestry systems began to equate economically with the current practice of dryland wheat production when establishment costs were significantly reduced and timber prices were increased. Under improved economic scenarios, the most favourable location for the simulated agroforestry system was Emerald in Central Queensland and the least favourable was Moree in northern NSW. For farmers to plant long rotation E. argophloia windbreaks on their dryland wheat paddocks, the balance between timber price and established costs would need to improve significantly, or they would have to value windbreaks in more than economic terms, e.g. for their aesthetic value or for their environmental impacts, such as in reducing drainage or soil erosion. Whole farm benefits beyond the paddock were not simulated.
Interactive discussions with landholders were held to explore their land management interests. This discussion included planting of windbreaks and retention of remnant vegetation on cropping lands.
Almost all scenarios showed inferior economic performance of long rotation agroforestry systems relative to standard cropping systems at the paddock scale. However, these analyses did not account for the environmental and aesthetic benefits highly valued by these landholders, nor did they explore alternative short rotation agroforestry options which may be more viable.
Implications for relevant
stakeholders
Investing in long rotation
commercial agroforestry (e.g. for sawlogs) is risky, especially in the
medium to low rainfall regions of Australia. The tradeoffs involved with
such a changed farming system are difficult to determine and should be
further researched. The ability to combine economic analyses with APSIM’s
simulation capabilities provides a powerful tool for evaluating various
agroforestry options.
This tool can be employed for simulating tree-crop interactions for a range of site, soil, climate, crop or windbreak designs.
While APSIM is available for download from www.apsim.info, its agroforestry simulation capabilities would not be readily useable without access to expert support. One future option is to increase the availability of APSIM for use by individual landholders so that they can quantitatively assess the viability of integrating agroforestry and crop production on their own farms. Current initiatives to use APSIM within established commercial advisory services (www.yieldprophet.com.au) and in public extension activities will potentially facilitate the extension of this new agroforestry capability to landholders around Australia.
Recommendations
There remain significant
barriers to using APSIM as a routine advisory tool on agroforestry options
for landholders. While the APSIM multi-point framework has been developed,
its parameterisation and testing is troublesome given the lack of data
on the growth parameters of suitable tree species and on the interactions
between trees and adjacent crops. An important imperative therefore is
to invest in obtaining such data and in testing APSIM against actual agroforestry
systems and in a greater range of environments. It is the intention of
the Agricultural Production Systems Research Unit (APSRU), a joint venture
between several Queensland agencies including CSIRO, to continue the development,
testing, and application of this new capability.
This model could be used
in the future with new data on tree-crop interactions and environmental
values, to evaluate new farm forestry and agroforestry systems at the paddock
scale.
|