THE CLIMATE KELPIE BLOG: GrassGro puts pasture advisors in the know

Posted by BCG on 6th May 2020
Figure 1. GrassGro is a decision support tool developed by CSIRO to assist decision-making in sheep and beef enterprises.

Optimising profitability and sustainability in a grazing business is challenging enough under the best of circumstances, but Australia’s variable climate adds another layer of complexity that can be difficult to manage.

Both day-to-day decisions and long-term strategies need to be balanced with the agility to respond to changing conditions and the seasonal outlook. Such decision making can really benefit from a full analysis of the potential opportunities and risks that may flow as seasonal conditions unfold.

GrassGro is a computer software modelling tool targeted at advisors in temperate Australia. It aims to help them evaluate the impact that variable weather conditions impose on grazing systems and compare potential management options.

The tool has also proven useful for beef and sheep producers and the dairy industry, as well as agricultural research programs and education.


“The tool was developed by CSIRO with support from Meat & Livestock Australia and Australian Wool innovation and is based on decades of field experimentation from across Australia,” says CSIRO software engineer, Neville Herrmann.

“GrassGro predictions have been ground-truthed against data from grazing system experiments at several sites in temperate Australia and by comparing long-term simulations at multiple sites for which there are no experimental data.”

The model uses historical daily weather data to drive models of pasture growth and animal production to help users understand day-to-day changes in soil water content, pasture growth and decay, and responses to grazing.

Figure 2. GrassGro uses daily weather data to drive models of pasture growth and animal production and identify business risks and opportunities.

What it does

GrassGro aims to answer the key questions that livestock managers need to know when planning for the season ahead, such as:

  • What stocking rates are appropriate?
  • When should I start shearing?
  • How can I improve my gross margin?
  • What is the best lambing or calving date for my enterprise?
  • Is an annual or a perennial pasture more profitable at this location?
  • What is the likelihood of needing to feed my pregnant ewes in the next three months?

Outputs include a risk analysis, a summary of the biophysical system, a financial summary including costs and prices, and a comparison of selected options and the impact over several years. GrassGro simulation reports cover a wide number of variables in the farming system, giving valuable insight into the factors driving production outcomes.

The latest version (GrassGro version three) tackles common practical problems that are complex and difficult to analyse objectively over the longer term. Examples include tactical decisions in response to emerging seasonal conditions, variation in stocking rates (with or without different lambing or calving dates), and testing combinations of shearing dates and stock selling dates.

GrassGro uses up-to-date daily weather data from farm records, the Bureau of Meteorology database or the SILO website.

Real-time risk assessment

The ability to assess the risk that variable weather places on the grazing system and the opportunity to test long-term management options under variable climate scenarios is a real strength of the model.

“GrassGro gives people the confidence to manage and recover from dry seasons more quickly or, more importantly, to take advantage of the opportunity to trade stock in better seasons.” said Doug Alcock, of Graz Prophet Consulting.

Mr. Alcock regularly uses GrassGro to help Monaro Farming Systems members evaluate threats and opportunities in their grazing systems and most recently has done the same for producers in the Central Tablelands Local Land Service region during spring 2019.

“GrassGro allows us to plot the current season in real time based on local conditions, such as soil moisture and existing pasture biomass, and then to project the possible future seasonal conditions using past weather data (Figure 3). When compared with the historical baseline this gives us a better understanding of how the season is likely to play out and how this will impact the livestock enterprise.”

Figure 3. GrassGro seasonal projections for available green herbage at Bungarby in spring 2019 show there is little chance of the available green herbage exceeding the long term median (the boundary between the pink and green shading) throughout the spring while by mid-November there is a greater than usual probability of pasture conditions being below the long term 10th percentile (bottom of the pink shading). Projections are based on the published BOM seasonal rainfall outlook; 90th percentile (green line), median (blue line) and 10th percentile (red). Source: Graz Prophet Consulting.

“We can see the impact that a wetter or drier start has on the season’s potential. If we are getting strong seasonal forecast signals from the Bureau of Meteorology, we can adjust the projections to discount unlikely scenarios.”


GrassGro has been available commercially since 1997 and continues to be updated with new features. GrassGro can be purchased for a one-off fee and training is available through CSIRO. It is designed to run on the Windows operating system.

GrassGro is not suitable for summer-active exotic grasses, specialist pasture cultivars such as tetraploid ryegrasses or tropical pasture.

Climate Kelpie has more information about the tool and the brochure and full details are available from CSIRO GrazPlan website or Horizon Agriculture.

More information

Horizon Agriculture, 02 9440 8088,

Doug Alcock, Graz Prophet Consulting, 0411 139 594,

CSIRO GrassGro

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