Agriculture Reference
In-Depth Information
exacerbate others. For example, reducing
ammonia emissions from manure leads to
greater concentrations of N in manure during
long-term storage and field application, which
can cause greater nitrate leaching losses to
groundwater and greater nitrous oxide forma-
tion and emission to the atmosphere (Rotz
et al
.,
2011c). Simultaneous reduction of all environ-
mental impacts requires comprehensive evalua-
tion and management of all aspects of the farm.
Another important aspect of farm manage-
ment is profitability for the producer. As farm
management or technological changes are made
to improve environmental sustainability of the
farm, this must be done with minimal cost, and
preferably increased benefit, to the producer.
Most animal-producing farms operate with a
relatively tight profit margin, which is unable to
absorb an increased cost of production. If pro-
duction cost is increased by efforts to reduce
losses to the environment, then this cost must be
passed on through an increase in the price of the
product or the producer must receive a govern-
ment subsidy to maintain profit. The ideal situa-
tion is to reduce production costs sufficiently
through improved nutrient use efficiency to
cover any potential cost increases of manage-
ment changes. Although such combinations
can sometimes be found (Ghebremichael
et al
.,
2007), more commonly improvements in envi-
ronmental sustainability come with increased
production costs through new technology or
increased labour and other resource require-
ments (Rotz
et al
., 2006; del Prado
et al
., 2010).
Improving the sustainability of animal pro-
duction systems requires a comprehensive eval-
uation that considers all environmental issues
along with profitability. This type of comprehen-
sive evaluation is best done through process-
level modelling and simulation of farming
systems. Well-developed models can integrate
the many processes involved in farm production,
nutrient management and economics provid-
ing a more holistic evaluation of sustainability.
Considering costs, benefits and tradeoffs
throughout the system provides better informed
decisions on the implications of a set of man-
agement changes than does considering only
individual system components. This type of sys-
tem-wide analysis provides a robust, quantita-
tive basis for decision making and planning of
future production strategies.
Whole-farm Modelling
Many models have been developed and applied
to the evaluation of farming systems. Most of
these have focused on the performance and eco-
nomics of production systems. In the past dec-
ade, a number of farm models have also included
an environmental component, estimating one
or more forms of pollution created by the farm-
ing system. The goal in many evaluations is to
reduce the environmental impact of the produc-
tion system while maintaining or increasing
farm profit.
Modelling techniques
Farm system models can be categorized into
three major types: mathematical optimization,
simulation and life cycle assessment (LCA).
Although they may be used with similar goals,
they are different in structure and function.
Optimization programs work by simultaneously
solving a series of linear or non-linear equations
to obtain an optimum solution. This type of
model has been widely used to determine eco-
nomically optimal strategies for various farm
production systems. A few studies have com-
bined environmental and economic evaluation.
For example, Berentsen and Giesen (1995)
developed a deterministic static linear program-
ming model of a dairy farm, which they used to
analyse institutional and technical change in
dairy farming. Effects of farm management
on N losses were evaluated while optimizing
farm profitability. Annetts and Audsley (2002)
developed a multiple objective linear program
focused on the environmental and economic
planning of farm systems in the UK. The model,
known as the Silsoe Whole Farm Model, focused
on arable crop farming but included a livestock
component.
Simulation-based farm models mimic major
farm processes to represent the production sys-
tem statically or dynamically through time. The
Moorepark Dairy System Model provides an
example of a static simulation model (Shalloo
et al
., 2004). This model has been used to evaluate
greenhouse gas emissions along with the perfor-
mance and economics of Irish dairy production
systems (O'Brien
et al
., 2010). The Sustainable
