Using computer models to simulate the interactions between cows, grass, crops and management in a farm system allows us to answer questions that would take a long time and a lot of work in real life.

There are two aims behind farm systems modelling.

• to explore numerous alternatives in a cost-effective way, taking the best alternatives for testing on the ground in farm trials or case study farms.

• to understand the effects of changes in climate, price and management on farm production, profit and environmental footprint.

On-farm experimentation versus farm systems modelling

On-farm experimentation is at the heart of everything we do at DairyNZ. It is through this research that we can understand how the parts of a system influence each other and affect overall farm performance. It is also essential in developing guiding principles for farming in an ever-increasingly regulated environment.

Yet this type of research is resource hungry and expensive to conduct. Such projects must be run over multiple seasons to tease out the effects of environmental factors, to test individual components of the system, and to determine the longer term response to various treatments.

Knowing what to test ahead of applying on-farm research is vital to minimise time and cost. This is where farm systems modelling plays a key role. Once the on-farm experiment has ended, modelling also helps our researchers understand how the different components of a farm system have influenced the outcomes.

A good example of the role of farm systems modelling is Pastoral 21 (P21).

P21 farmlet research spanned 5 seasons in four main dairy regions, with the objective to reduce N leaching while improving profitability. Results from P21 have contributed to our understanding of N leaching on farm and to the development of guidelines for attaining N leaching targets on commercial farms.

Let’s focus on the N leaching research outcomes from P21 and how modelling has helped.

Farmlet data was put into the Whole Farm Model and tested to make sure the model outputs closely matched the results from the farmlets (e.g. modelled N leaching was similar to actual N leaching).

Researchers then used the model to test the effects of changing management strategies to estimate the influence on N leaching. This allowed researchers to understand how each component of the system contributed to the N leaching result. Without modelling capability, more complex and expensive on-farm research would have been required to determine this.

Future farm systems research will have some audacious targets around profitability while maintaining environmental gains.

Researchers are using farm systems modelling in the design phase to help determine what on-farm factors are likely to be the greatest contributors to these targets. These factors can then be tested on-farm.

Farm systems modelling is set to increasingly influence the way we farm. The more data fed into these models, the more accurate they become in estimating actual responses.

It is a fast and effective tool to guide our understanding of implications of changing regulations, climate and consumer demands on how we farm today and in the future.

What other DairyNZ work involves farm systems modelling?

Farm systems modelling is a key component of the Forages for Reduced Nitrate Leaching programme.

An example is using modelling to identify the percentage of the milking platform and support block sown in diverse pastures to optimise production, while reducing N leaching.

“Cow-level” effects also influence N leaching.

For example - what is fed to a cow and what will alter the amount and timing of urinary N deposits?

As the Forages for Reduced Nitrate Leaching programme is cross-sectoral, modelling is also being used to explore the interactions between dairy, and dairy-support/cropping land to ensure that management strategies do not simply result in ‘pollution-swapping’ between sectors.

Such explorations would be extremely difficult to conduct using on-farm experimentation, and so modelling becomes a key tool to build our understanding.

The speed at which various scenarios can be tested makes farm systems modelling a valuable tool for short-term situations requiring timely options for farmers, such as for drought, flooding and milk price volatility.

Finding farm systems offering resilience regardless of milk price is essential for the longer term success of the NZ dairy industry. Current modelling work is investigating farm business performance when following the “Pasture First” principles from 6 to 12 months of the year, and how this influences business profitability at a range of payouts.

Modelling is used to determine the effects of N leaching requirements on water quality and profitability at the farm, catchment and regional scale, informing policy-makers and stakeholders on the effects of water quality targets. This provides robust evidence-based information for an often emotive issue.

Future farm systems to cope with a warming climate cannot be tested on the ground; at least, not until it is actually warmer. Modelling can help us explore today the options that could work for the future, including different pastures, forages and cow traits.  Such information will help plant and animal breeders prepare for the future climate, providing farmers with the means to adapt their system rapidly and effectively as the climate alters. Modelling is also helping identify effective mitigation strategies for reducing agricultural greenhouse gas emissions, enabling the industry to play its part in creating a sustainable future.