GrassGro Release notes

GrassGro Changes

Version 3.4.6, Dec 2023


  1. Includes pasture parameters for Tall Fescue and Cocksfoot as revised by a UTAS project.
  2. Added user option to export components and farm systems as readable XML.


  1. Fleece yield is now displayed with more precision.
  2. Additional maintenance feeding rules now wrap over 1 Jan correctly.
  3. Stocking rates for cattle now increment by 0.01/ha.
  4. Kikuyu parameters have been revised and now it is not a beta species.
  5. Invalid pasture species are now identified before an Acceptability test is run.
  6. Fixed the problem for charting negative values when the Y origin is set to use 0.
  7. Daily weight gain chart in the steer report now works properly for negative values.

Version 3.4.5, Aug 2023


  1. More options on the History list in the Examine Outputs window.
  2. Added a weather file download feature for getting SILO and other weather files.


  1. SILO file wind column properly supported if found in the file. Fillers are also corrected.
  2. Some fixes for spinup and restarting simulations when the pasture is dormant.
  3. When setting the CFA for cows to 12 years it now works properly and gives correct numbers of young.

Version 3.4.4, Apr 2023


  1. Steers can now be sold based on weight change.
  2. New outputs from the model:
    1. Chill index threshold value for each paddock.
    2. Calculated wind speed for each paddock.


  1. The start dates for the Capture window now work properly with the Farm system window.
  2. The grazing rotation window now works properly with Steers. Especially if the weaner mob doesn’t exist.
  3. The Calendar tab on the Farm system window displays age cohorts better. Especially steers and lambs.
  4. The description field on the Replacement dialog is now saved correctly when switching between cohorts.

Version 3.4.3, Jan 2023


  1. The production feeding rules; Drought and Adlib will now allow other rules that are in the same period to run if the pasture status has not triggered them yet. For example, this allows a fixed feeding to run if the drought feeding is not triggered.

Version 3.4.2, Nov 2022


  1. Updated the layout on the examine outputs window.
  2. Fixed the backup files process so it is triggered correctly.
  3. Minor change on saving library files to make it more robust.

Version 3.4.1, June 2022


  1. Steer trading now allows heifer and bull trading.
  2. Steer trading allows more than one cohort of animals in the year.
  3. The application registration can be updated from the main menu.
  4. Release notes can be opened in a browser using a main menu option.


  1. Some issues fixed in the lamb trading enterprise when trading ewe lambs.
  2. Changed the DSE stocking chart in the Acceptability reports and Issue reports to use lines rather than area series that was slightly misleading.
  3. Improved the Farm system Calendar chart in the Farm system window to handle multiple trading cohorts correctly.

Version 3.4.0, Apr 2022


  1. New drought production feeding option to allow moving into a feedlot during a drought period.
  2. Location details now show in decimal degrees with hms also displayed.
  3. Cattle stocking rate is now rounded to 0.05 /ha


  1. Fixed the missing young animals when doing a tactical run that starts on weaning day.
  2. The Pasture rule now loads the irrigated paddocks correctly when the component is opened in an Analysis.
  3. Added the missing intake during lactation curve parameter for sheep. Now the intake matches previous version 3.3.11

Version 3.3.13, Dec 2021



  1. Scaling of the components on a number of dialogs has been fixed for Windows scaling set at 150%.

Version 3.3.12, Sep 2021



  1. Young animals are now sold correctly in leap years for tactical simulations.
  2. GrassGro installer does not use current user locations and now copies examples to public documents. User setup is now doen when the application first runs.

Version 3.3.11, Nov 2020


  1. Includes the BOM 2019 weather data.
  2. GrassGro will backup working libraries at regular intervals as configured in the preferences.


  1. More flexibility with SILO formats.
  2. The tactical Analyses now stores the whole soil profile correctly so that PAW is restored correctly for the tactical run. The soil component will show all the soil layers when they are available.
  3. The tactical Analyses now stores the specific leaf area correctly so that the ground cover is restored correctly for the tactical run.
  4. The adult animals age class weights are configured correctly now for tactical Analyses.
  5. The animal condition scores are restored correctly now for tactical Analyses.
  6. GrassGro will now close correctly when window state cannot be saved correctly.
  7. Fixed small memory leak on Pasture dialog. Added a pasture parameter set version label on the Pasture dialog.
  8. Peak lactaction for dairy cattle has been modified. Higher milk production when no calves at foot. This has required some additional changes to the animal parameters. Old external parameter files will need their structure changed to match the new configuration.
  9. Peak intake parameters during lactation for sheep have been corrected to follow technical spec. This has increased intake when lactating.

Version 3.3.10, Mar 2019

  1. Includes BOM 2018 weather data set.
  2. Added a growth rate (NPP) threshold output variable.
  3. Clear history list option now in popup menu on Examine outputs dialog.


  1. Allow application to close even if the docking file can’t be written.
  2. References to the SILO web site now point to the new site.
  3. Fixed crash when closing the variable selection dialogs.
  4. Irrigation costing now shows in all Gross Margin tables in the reports.
  5. Enhanced the Haycutting dialog error message when trying to cut outside of paddock reservation period.

Version 3.3.9, Feb 2018

  1. Includes the BOM 2017 weather data set.
  2. Irrigation costing is now available. Water application is priced in $/ML.


  1. Weather data preferences now have missing paths highlighted on the weather data tab.

Version 3.3.8, Apr 2017

  1. GrassGro management now supports four production feeding rules.
  2. The Gantt chart on the Grazing dialog now shows all the production feeding rules with tooltips that detail the specifications for the rule.


  1. The Farm system library was malfunctioning when opening another Farm system library file.
  2. The Grazing rotation dialog now saves the grazing stages correctly when switching tabs between animal groups.
  3. Costs for shearing and husbandry; the limits of $10/head have been increased to $20/head.
  4. When haycutting periods are changed on the Grazing dialog, the series on the Gantt chart now redraws correctly.
  5. Added missing Help button on Grazing dialog.
  6. When renaming report section in the treeview on the Report editing dialog, the enter key now doesn’t close the dialog.
  7. Other minor updates of images and icons.

Version 3.3.7, Aug 2016

  1. Farm systems were being lost from the Farm system library in rare circumstances. It was related to moving the library panel by docking it to the other side of the window and then saving any changes. This is now fixed and the libraries work reliably.

Version 3.3.6, Jun 2016

  1. When running the Farm system choice analysis that uses Farm systems as factors, the date ranges were not always working correctly when the two systems did not overlap in their tested date ranges.
  2. Fixed the context sensitive help system for dialogs that had stopped working.
  3. Improve the drawing of highlighted rows and cells in many data grids.

Version 3.3.5, May 2016

  1. Fixed bug which led to cross-bred young incorrectly using parameters of their female parent’s breed.
  2. Fixed the blending of fibre diameter for crossbred lambs.
  3. Sale price scaling of stock now works correctly and the scaled price is now used in sale income calculations.
  4. Corrected inaccurate descriptive label of the “Animal intake” output variable.
  5. Fixed an intermittent divide by zero error in the model. Corrected the calculations for relative intake of the diet components. Will effect the animals intake a small amount.
  6. Other minor bug fixes and stability fixes.

Version 3.3.4, Jun 2015

  1. The Weather component can now handle SILO files with mixed line lengths.
  2. Breed SRW maximum allowed for sheep changed to 110kg for female and 154kg for male.


  1. Fixed a small bug in the random number generating class that may alter some outputs when using the Animal component.
  2. Better error message for loading error when the custom component library is opened at start up.
  3. Encoding for input files fixed so the application works correctly on a Chinese language installation.
  4. Senescence no longer happens in perennials entering winter dormancy. Empty pasture populations stay at the start of the phenological cycle.

Version 3.3.3, Jan 2014

  1. Doing a capture/spinup did not work when there were 10 or more paddocks in the Farm system.
  2. There was a problem with trying to generate charts or tables for compound variables such as Growth limits when the paddock number was greater than 10. The system either gave an access violation or the process hung.
  3. Fixed problem with hovering the mouse over an Invalid Paddock item in the paddock list on the Grazing rotations dialog.
  4. When opening a custom Farm system from the Farm system tree it could not be saved if a Standard (readonly) one had been opened previously.

Version 3.3.2, Nov 2013

  1. When GrassGro was saving or opening large Farm system libraries containing 100 or more Farm systems, out of memory errors were produced. This has been improved but it is still possible to run out of memory with larger libraries.
  2. The save time for the Farm system library has been drastically improved.

Version 3.3.1, Sep 2013

  1. Small enhancement to Seasonal Outlook report. Now includes ground cover percentiles chart.


  1. The Green Area Index is now copied across correctly when doing the initial capture process while running a tactical Analysis. It was causing multiple starting points for GAI and Ground cover when running a tactical Analysis.
  2. Oestrus cycle in cattle is now 21 days.


Version 3.3.0, Mar 2013

  1. All pasture parameter sets have been revised in response to results of Victorian DPI staff showing that the GRAZPLAN pasture model was under-predicting spring growth rates in Victorian (and southern NSW) contexts. Changes were made:
    • to alter the description of the phenology of phalaris so that it is predicted to commence reproductive growth much earlier under Victorian conditions, and to flower somewhat earlier as well;
    • to set radiation use efficiency so that it no longer varies with radiation intensity for C3 species;
    • to shift the temperature responses of phalaris, perennial ryegrass, annual grasses and legumes and capeweed so that growth is more sensitive to low temperatures; and
    • to slow the decay rate of the digestible portion of dead herbage.

    The new parameter set reproduces results from Victorian grazing trials much better than that which was used in version 3.2.6. Validation simulations of several other grazing experiments in WA, Victoria, SA and NSW have been checked to confirm that the GRAZPLAN models still give credible results at those locations.
    Users will find that modelled total above-ground pasture growth increases somewhat from version 3.2.6 to version 3.3.0. In many environments, modelled ME consumption rates by livestock will nonetheless fall slightly (the greater concentration of pasture growth in spring means it is less efficiently utilized). It is also likely that modelled pasture composition will alter for many Farm Systems. We recommend that users repeat the acceptability testing process after importing their custom Farm Systems into version 3.3.0.

    In addition, the relationship between protein degradability of herbage to its dry matter digestibility has been changed, from dg = min(1.00 x DMD + 0.10, 0.99 ) to dg = min( 0.84 x DMD + 0.33, 0.99 ). Wool growth parameters have been altered to compensate for this change, in order to preserve the definition of the reference fleece weight. (These changes are compatible with GrazFeed version 5.0.4.)

  2. Options to irrigate pastures have been added to the Pasture Management component in all Farm Systems. The timing and amount of irrigation events can be determined using a number of criteria.
  3. Fodder conservation has been added as a management option in all Farm Systems that are either ungrazed or have multiple paddocks. Fodder can be conserved as hay or silage and used in place of purchased supplement. The Hay Cutting enterprise type has therefore been combined with the Ungrazed enterprise type.
  4. Hay sale prices can be scaled on a monthly basis.
  5. The Farm system library is now divided into a standard section and a custom user section similar to the other libraries.
  6. The File Open popup menu options for the Component library and the Farm system library have a new Reopen option for opening recent files.
  7. Each GrassGro version stores it’s configuration in a unique directory so that multiple versions can function differently on the same machine.
  8. Many improvements to the layout of Analysis and Acceptability reports. All reports now show up to five paddocks.
  9. The Soil Atlas dialog can now display the custom localities on the map.
  10. Weather localities have been updated to December 2012.


  1. When using flexible stock rotations the withholding period is now obeyed when using a single phase. Previously the paddocks where being checked at the start of every phase regardless.
  2. Minimum target production feeding weight works correctly for various enterprises.
  3. Farm systems cannot be renamed to no name.
  4. Supplement components now can now only be exported with a Feeding component being exported.
  5. When opening a Pasture component any species not listed in the new parameter set will be upgraded automatically and a message shown.
  6. Calculated series in charts now don’t show if they cannot be calculated. This ensures that charts with no data, even containing a calculated series, don’t show.
  7. Cloning Farm systems now copies the Grazing component without losing so many settings. Copying over Grazing components works much better.
  8. Cloned Farm systems are now placed in the same folder as the original one.
  9. Initial fleece fibre diameter for Lambs is now initialised correctly on the Livestock dialog.
  10. The Find tab in the Component library was failing to look in descriptions.
  11. When using the File | Open main menu option, the file type was sometimes getting confused. This was causing Farm systems to be opened in the Component library.
  12. When deleting custom localities it would fail with cannot write to file error and then lose all localities. Temporary files are now in the same directory as the custom locality file.


Version 3.2.6, Apr 2012

  1. Using APSIM SILO files now works reliably.
  2. In the Soil dialog atlas the uniform profiles now show subsoil values correctly when choosing the Northcote number.


  1. Added extra outputs: Property average ground cover, Property gound cover thresholds and Paddock ground cover thresholds.

Version 3.2.5, Aug 2011

  1. There was an Acess Violation error when dropping Farm Systems on to Factor values in an Analysis window. Problem noticed particularly when running on Windows 7.
  2. When closing GrassGro with an unsaved Analysis there was an Access Violation error. Problem noticed particularly when running on Windows 7.
  3. Cast for age selling of Wethers in a Ewe & Wether enterprise now works properly on the dialog.
  4. Fertility scalar for the Paddock component now has a minimum value of 0.35.
  5. Grazing dialog – the start and end date labels for a flexible phase now update when they should.
  6. Fixed a problem with reading SILO files that now have a slightly modified longitude and latitude format.

Version 3.2.4, Feb 2011

  1. Added the optional SCS runoff curve number to the Soil component.
  2. Seasonal Outlook (Tactical) analysis reports now show pasture charts for paddock 2 in a multi paddock system.
  3. Added three new pasture parameter sets: “Poa sieberiana”, “Austrostipa spp.”, “Austrodanthonia spp. (tableland)”
  4. Updated the CO2 response parameters (in particular K(I,6), the specific leaf area response to CO2 concentration


  1. When Management policies with Grazing components are dropped into the Analysis factor tree, the grazed paddocks are now checked and updated. Warning messages are also shown when doing this operation.
  2. When a Management policy with a Grazing component is copied into the Component Library, the Grazing component cannot be edited now. Previously an access violation message was shown.
  3. When hovering the mouse cursor over a boxplot chart on the chart editing dialog, the median value is now shown correctly in the tooltip.
  4. When using Management policies as Analysis factors, the Grazing components were displaying the wrong lambing dates and production feeding dates. Now the local rules are used from the owning Management policy.
  5. When spinning up a multi paddock Farm System the paddocks in the rotation are restored correctly at the end of the spinup process. Fixes the INVALID PADDOCK problem.
  6. When opening another Farm System library a check is now made to ensure all Farm System windows are closed first.
  7. Importing individual Management rules into the Component library now works.
  8. Fixed the problem with some Maintenance feeding rules not working when one of them spanned 1 Jan. Any existing Farm Systems with these types of rules will need to be re-edited and saved.
  9. The chart in a number of reports showing the total supplement fed to young stock has an improved heading. The production summary variable ‘Supplement fed to young stock’, shown in many production summary tables, is now clearly showing that it is for weaners.


Version 3.2.3, Jun 2010

  1. Steer and wether enterprises now have their breed and standard reference weights corrected. The livestock dialog was not saving these values correctly and steer enterprises were showing significantly incorrect results in most cases. Steer enterprises should be reprocessed and the correct results scrutinsed.
  2. The production feeding dialog now stores the animal feeding class correctly for the Ewe & Wether and Beef cow enterprises.

Version 3.2.2, Jun 2010

  1. Yearling female animals now have a grazing rotation (paddock) applied to them. They were being missed when weaning day followed replacement day.
  2. Changes made to fix computation of the number of young stock to leave behind as replacements, in the case where the course of events is sale -> first birthday -> replacement (i.e. replacement stock enter the main flock or herd as yearlings).
  3. Horizontal scrollbar removed from Farm System description memo box

Version 3.2.1, May 2010

  1. Includes the 2009 BOM weather database. Actual solar radiation readings for all stations from 1990 have been added.
  2. Some minor internal changes to assist in supporting other locales.


  1. Localities existing in the Custom set and the Standard set can now be named the same and exist without any conflict in the locality dialogs.
  2. On the Analysis window the choice to use independent Farm system end dates is now saved. Report start and end dates are also stored.

Version 3.2.0, Dec 2009


  1. Rotational grazing can now be governed by moving to the best paddock.
  2. Lamb trading enterprises can now have multiple cohorts of lambs purchased throughout the year.
  3. A new animal enterprise has been added. This is a Ewe and Wether enterprise in which a proportion of male lambs are retained in a wether flock for wool production. Separate stocking rates are used for ewes and wethers.
  4. GrassGro now supports 30 paddocks. New paddock occupation reporting variables have been added.
  5. Growth based selling of young stock. In a Ewe or Beef enterprise the young have an extra sale rule available. They can now be sold if their weight gain over a period drops below a threshold value per day.
  6. Using SILO weather data is now much easier with fewer dialogs to get lost in.
  7. The Management Issues are now contained on a tab behind the Farm Systems tree in the main Library.
  8. The Examine outputs dialog now has a history list of recently chosen reports. Any of these items can be copied into a report.
  9. Monthly price scaling in the prices component can be copied and pasted.


  1. Significant revisions to report layouts.
  2. Purchased sheep now have fleece weights based on the shearing dates set in the Farm System.
  3. A number of other minor bug fixes.
  4. Costs and prices in the standard Farm Systems and library components have been updated.

Version 3.1.3, May 2009

  1. The Livestock component is now above the Mangement Policy in the Farm System tree.
  2. Beef cow acceptability report – production summary table labelling fixed.
  3. Cloning a Farm System in a folder in the Farm System tree now works properly.
  4. Gross Margin value for calves sold at foot in a self replacing beef cow enterprise now reports the correct value.
  5. When the variable ‘Stock traded’ was chosen in a report; fixed the case when some table columns may be hidden.
  6. Fixed gross margin value errors when using Farm System comparison Issue. This occurred when Farm Systems where of different enterprise types.
  7. Ground cover boxplot chart in Acceptability reports now shows values based on minimum for the year rather than by day.
  8. Fixed the problem with pregnant replacements giving birth one day later than the main females and then their offspring were too young for sale with the other weaners.
  9. Large memory leak from the browser component used to display reports is now fixed.
  10. Saving of the report into a web archive .mht format now creates a portable file suitable for emailing.
  11. Custom Issues are now saved correctly after editing in the Tasks list.
  12. The working path set in the Preferences dialog keeps the user’s setting.
  13. Example Analysis and weather are now correctly copied across to the user’s directory if they are not found there.
  14. Includes BOM weather for 2008

Version 3.1.1, Aug 2008

  1. More options on Tasks tab of library window. Right mouse click on Issue allows editing. New button for opening Issues management window.
  2. Component library now contains a custom section. The component library is now divided into two sections; a Standard library that will be updated at each new software update and a Custom library that will remain as configured by the user.
  3. Soils atlas available from soils dialog. Soil texture, Northcote ID and Atlas are all available for choosing a soil type.
  4. Historic supplement costs. Adding historical supplement prices. Prices over time can be viewed on a chart. Uses CPI scaling for constant dollar values. Reports can include a table/chart showing actual supplement costs.
  5. Scaling monthly animal prices. Monthly animal prices can be scaled for all classes of animal sold. Actual sale price can be shown in a report.
  6. Replacement dialog– interactive growth chart. Replacement parameters for the new animal can be compared to an expected range for the type of animal.
  7. Issues contain multiple reports. Issues can have extra reports added to them in the Issues window. Extra reports can be added directly in an open Analysis in the Analysis window. You can specify which report you want to see after processing an Analysis.   Standard Issues now contain an extra brief report.
  8. Report design improvements. Report sections can be inserted or added by right clicking on an item in the sections tree on the Report design dialog. Templates can be used when creating new report sections. Report sections can be cut, copy or pasted in the report section tree. Variables in a report section can now be told to use right or left axis. Computed expressions can be used in reports o do tasks like adding a summary column.
  9. Tactical analysis wizard. When a tactical run is specified in the Analysis window, the initial spinup/capture is done using streamlined ‘wizard’ approach. Farm System component dialogs can now be opened in read only mode for viewing more detail.
  10. Wind speed filler for SILO files. When creating a SILO weather locality, the wind speed value can be obtained from any standard GrassGro locality.
  11. Description text for each output variable. When selecting a variable for a report section or ‘Examine outputs’ chart, the variables now have extended descriptions shown in a new column.
  12. Ewe offspring sale prices specific to gender. Ewe enterprises now have separate sale prices for ewe and wether offspring.
  13. Reports can be emailed easily. The report window has a new button which will allow easy sending of the current report using the standard email client.
  14. Analysis window improved.
  15. Farm System component dialogs can now be opened in read only mode for viewing more detail in the Analysis window.
  16. Added new output variables that can be chosen for reports.
  17. The Component library is now in two sections containing a Standard section and a Custom section. This allows for new items to be installed on the users computer without overwriting custom items.
  18. A new example of a stubble grazing Farm System is included in the Farm System library (or on the CD in the Extra folder for existing users).
  19. A new GrassGro Issue is included to compare feeding management policies at different feed costs.
  20. Reports have had a redesign and include many improvements.
  21. A new Pasture specific report now includes support for multi paddocks. It can be found in the Acceptability reports, the Component library, and in the Stocking rate issue.
  22. Historic Analyses can now have their reporting periods specified. Useful for focusing in on a shorter period of years.
  23. Includes more new Issues in the standard library: Farm System choice, Feeding Management & costs, and Pasture comparison.


  1. Speed improvements during startup.
  2. Many bug fixes.

Version 3.0.8, Apr 2008

  1. Many report sections have improved text in column headings and series legends. Many other improvements to the reports.
  2. The Maintenance feeding dialog now accepts non contiguous extra feeding rules properly.
  3. Better resolution of weather data paths in Farm Systems.
  4. Includes BOM 2007 weather data set.
  5. Many other fixes.

Version 3.0.7, Dec 2007

  1. Library window cannot be undocked now.
  2. Default grazing rotations for stock are now set to no rotation rather than 7 days in each paddock. Fixed problem with yearlings being moved out of main mob by default.
  3. When building an Analysis is cancelled, the Analysis window closes properly.

Version 3.0.7, Dec 2007


  1. Library window cannot be undocked now.
  2. Default grazing rotations for stock are now set to no rotation rather than 7 days in each paddock. Fixed problem with yearlings being moved out of main mob by default.
  3. When building an Analysis is cancelled, the Analysis window closes properly.

Version 3.0.6, Nov 2007

  1. Fix validation bug on the soil dialog for allowable values of field capacity and bulk densityof subsoil.
  2. Eliminated the possible divide by zero error during runoff calculations when certain soils are water logged.
  3. Resetting of perennial grasses fixed.
  4. If the rooting depth is below the depth of the subsoil, an error message is shown.
  5. Allow weight ranges to be set for replacement based on the SRW in the livestock component if available.

Version 3.0.5, Oct 2007

  1. Senescence sub variable of the phenology output was not showing proper value in reports
  2. Preferences dialog now opens quickly.
  3. Closing the Report window while it was loading caused an AV. Now you can only close it after it is loaded.
  4. Unarchiving of weather files fixed. (Was broken in ver 3.0.4)
  5. Paddock numbers formatted better in report chart legends.

Version 3.0.4, Oct 2007

  1. User can select a preference for report windows to be MDI child or topmost in the preferences dialog.
  2. Charts and tables of pasture species-specific outputs are now labelled with the species name (and paddock number).
  3. Simple “profile” graphic added to Soil dialog, to clarify meaning of “cumulative” depth.
  4. SILO weather components now show the path to the data file in their tooltips. Added extra column in station list on the Manage Custom locality set dialog.


  1. Value for stage 1 soil evaporation on Northcote tab of Soil Defaults dialog now displays correctly.
  2. Cattle are now displayed with the correct icon in the spin-up dialog.
  3. Fixed bug with updating of phenology selection combo-box of the Pasture dialog.
  4. The tab key can now be used to navigate within the “fertility” grid of the Costs dialog.
  5. Fixed problem with display of the progress bar during tactical analyses.
  6. Increased maximum allowable SRWs on Stock dialog.
  7. Fixed problem with reporting of production feeding costs.
  8. Costs and prices can be changed, and the new values reflected in newly generated reports, without rerunning an analysis.
  9. Improved the logic used for updating simulation start and end dates when the weather data has been replaced or updated.
  10. Fixed bug in which stopping an analysis could trigger an access violation.
  11. Tooltip added for Pasture component.

Version 3.0.3, Sep 2007

  1. Settable colour backgrounds for the Analysis and Farm System windows.
  2. Added ‘New Farm System’ from main File menu.


  1. The Grazing Rotation component will now always appear in the same place in the Farm System tree. Fixes problem when copying spin-ups from the Capture window.
  2. Maintenance feeding dialog now stores settings properly.
  3. Exporting Issues dialog now uses a default extension for the filename correctly.
  4. When creating a new Issue, the type is now Historical by default.

Version 3.0.2, June 2007

  1. The Farm system window has a new background colour to ensure it doesn’t get confused with the Analysis window.
  2. The Report window is now displayed within the main window, not as a top-most external window.


  1. Updating SILO weather now works more reliably.

Version 3.0.1, June 2007

  1. Totally new user interface designed for solving management issues on grazing systems.

Version 2.5.1, 14 June 2006

  1. Facility added to create custom weather localities based on farm weather records or on data from the SILO weather data project.
  2. In a ewe enterprise: lambs can be retained to 2 years of age and shorn as lambs and as earlings on a separate date to that of ewes in the main flock.
  3. In a beef cow enterprise: heifers and steers can be sold when they reach a nominated live weight as well as by age.
  4. Supplements can be fed to maintain animal body condition or live weight, so that it is now easier to maintain the condition of young, growing stock.
  5. Separate maintenance feeding rules are now available for immature and mature stock in the main flock or herd and for weaned young stock.
  6. Up to 3 production supplements and feeding rules can be specified and simulated concurrently.
  7. “Creep feeding” option added to production feeding rules.
  8. Grazing management: in breeding enterprises, more classes of animal can be moved separately.Key management events (mating, births and weaning) are shown in a calendar when specifying grazing management.
  9. Users can choose to reset pasture populations if they are lost from the sward.
  10. Users can specify that a paddock is “sheltered” by reducing wind speed to a nominated percentage.
  11. 201 weather localities are now available and updated to Dec 2005
  12. In the benchmarking report, production statistics are provided for young and mature stock separately.

Model Changes:

  1. Prediction of wool fibre diameter profiles has been revised.
  2. Significant revision to the parameters of the pasture growth model, resulting in a better-validated model.

Version 2.4.4, 20 Jul 2004

  1. Users must now enter initial fleece weight and fibre diameter for lambs & weaners in the ewe enterprise.
  2. Livestock dialogs now have a “Reset Weights” button that provides default live weight and fleece values.
  3. Separate shearing date implemented for lambs in the ewe enterprise.
  4. The standard reference weight can now be specified for rams in the ewe enterprise or bulls in the beef cow enterpise.
  5. Animal prices can now be given on a per-head basis, with an allowance for the value of unshorn fleece in sheep.
  6. Weather data updated to Dec 2003. 198 localities now available.
  7. Layout of all dialogs modernized.


  1. The lagged daytime temperature (a driving variable) is now explicitly initialised at the beginning of all simulations. Fixes small inconsistencies encountered in the first few days of simulations spun-up to a winter start date.
  2. The effect of shearing on live weight is now taken into account when computing production feeding to a target.
  3. The DMD of supplements now changes to reflect any change made in the M/D ratio (M/D already changes in response to changes in DMD)
  4. Scrolling of annual gross margin values improved.
  5. Valid ranges for various costs and prices hvae been revised in response to the values encountered during the 2002-2003 drought.
  6. An error in calculating the basis of weight limits in price grids (dressed vs live weight) has been corrected.

Model Changes:


  1. Minor change to the temperature response of DMD decline.
  2. Change to the effect of time of year on the efficiency of energy use for weight gain.

Version 2.4.3, 2 Oct 2003

  1. Benchmarking analyses added. A benchmarking analysis summarizes a simulation by providing a set of statistics corresponding to those provided by benchmarking services, and a set of graphs showing key aspects of the enterprise.
  2. Grazing pressure as dry sheep equivalents is provided as an output.
  3. Gross margin analyses can now be copied to the clipboard.
  4. 189 weather locaities are now available, updated to Dec 2002.


  1. Extra validation of conception rates has been added.
  2. Very low weights for weaners in the ewe enterprise are no longer accepted.
  3. The age class to be fed is now retained properly when setting up fixed production feeding rules.
  4. Upper limit of supplement cost increased to $1000/tonne.
  5. Bug in initializing seed pools (introduced in v2.4.2) fixed.
  6. Inconsistencies in RDP content of supplements (introduced in v2.4.2) fixed.

Model Changes:

  1. The effect of pasture legume content on animal intake is now reduced at low herbage availability.

Version 2.4.2, May 2003

  1. Weather localities that use SILO Patched Point and Data Drill weather files can now be used in GrassGro.
  2. Drainage of soil water is provided as an output.
  3. Simulation titles may now be longer than 30 characters.


  1. The detail of the soil moisture profile is now retained if the user changes paddock information with the Paddock dialog but does not alter the initial soil moisture contents. This can be important when a tactical simulation is constructed from a “spun-up” starting point.
  2. Problem fixed with the automatic adjustment of supplement M/D when DMD is altered.
  3. The threshold condition at which weaners are to be fed for maintenance was not being properly retained. This has been fixed.
  4. The weight range allowed for purchased animals has been revised to conform with the new normal weight equation.
  5. On first execution, the dialog for entering the user name and serial number will now appear in fromt of the main program window.

Model Changes:

  1. The fertility scalar now operates to reduce net, not gross, assimilation.
  2. The birth weight assumed for animals entering the simulation is now the same for male & female animals, in line with the foetal growth equations.

Version 2.4.1, 16 Sep 2002

  1. Help is now provided via the HTML help system.
  2. The GRASSRUN.DLL file is no longer required.
  3. Eleven new weather localities have been added.
  4. The user can drag files onto the main window in order to open them in GrassGro.
  5. Multiple files can be selected in the File Open dialog.


  1. In self-replacing beef cattle enterprises, all remaining female heifers are now sold whern the age at sale is greater than one year.
  2. Computations for adlib supplement intake in a feedlot in the beef cow enterprise have been fixed.
  3. The initialisation of conceptus weight has been fixed.
  4. Replacement numbers were not being correctly calculated when a simulation had more than 32767 animals. This has been fixed.
  5. Simulations can now be saved while running without ccausing an “access violation” error.
  6. Costs of replacement beef cows and of supplement fed to lambs are now correctly reported in gross margin results.
  7. All years in gross margin files are now placed on a single line (previously they were organized in blocks of 20 years).
  8. The sire breed is now forced to be the same as the dam breed in self-replacing enterprises.
  9. For simulations with a date range starting on 1 Jan and ending on 31 Dec, a gross margin for Jan-Dec over all years could not be specified. This has been fixed.
  10. Problems selecting pasture species with long names have been fixed.
  11. The “Live shoot & root” graph now displays with a negative Y axis, making the root values visible.
  12. The View as Text window now includes a fixed legume precentage where appropriate.
  13. Occasional problems with date changes in the Graph and Table dialog have been fixed.
  14. Minor problem with entering target cattle weights for production feeding fixed.
  15. The end date for localities ending in 2000 is now visible.

Model Changes:

  1. The normal weight equation has been modified so that skeletal growth under conditions of weight loss. Animals that have had a check in growth will be delayed in reaching mature size.
  2. The animal model used in GrassGro now distinguishes between whole and crushed grains. Incomplete digestion of whole grains is handled.
  3. Time of peak intake during lactation of beef cattle changed from 81 to 62 days.
  4. At the end of lactation, potential intake now returns to its normal level gradually instead of immediately.
  5. Parameterisation of the conception rate model from the user-input conception rates modified.
  6. Pasture parameters have been revised to give higher production in drought years.

Version 2.4, 13 Dec 2001

  1. The following new pasture species and cultivars have been included:
    • Lucerne(Hunter River & winter-active)
    • White clover
    • Bothriochloa macra
    • Annual ryegrass
    • Subterranean clover (Dalkeith)
  2. 154 weather localities are now available, updated to Dec 2000 where possible.
  3. Users have the option to set the pasture legume content by selecting a grass species and specifying a fixed percentage of legume.
  4. In the Management dialog of a steer enterprise, the user may select entire males (i.e. simulate a bull beef enterprise).
  5. Maintenance feeding rules have changed:
    • Each age class in a mob is treated separately.
    • An option to provide maintenance feeding on the basis of the average CS of an age class within a mob has been added. In this case feeding seeks to maintain the average weight of the animals in the age class.
  6. Users may now restrict production feeding to the oldest or youngest age class of animals in a mob.
  7. A “drag and drop” facility makes copying key sections of one simulation to another fast and simple.
  8. Outputs have been added for drainage of soil water, the “chill index”, protein content of pasture and methane production by livestock.
  9. A series of outputs have been added in which attibutes of steers, heifers and weaner sheep are shown classified by age class and gender.
  10. It is possible to produce simulations in which livestock condition falls to dangerously low levels. In such cases the simulation is halted and an error message is displayed.
  11. The “View as Text” window that shows all simulation inputs can now be printed.
  12. A glossary of terms has been included in the Help file.


  1. In a lamb enterprise in version 2.1.1, if the final sale date was past one year of age then lambs less than one year old were not sold, even if they reached the target sale weight. This has been fixed.
  2. In the Livestock dialog for the lamb enterprise, the valid range of initial weights was being calculated incorrectly. This has been fixed.
  3. In the Livestock dialog for the beef cow and ewe enterprises, allowance is now made for the weight of the conceptus when checking whether the initial live weight is valid.
  4. In Livestock dialogs, if the initial live weight provided by the user was too low, then the value was changed without warning the user. This has been rectified.
  5. In the Livestock dialog, if a zero was entered as the initial liveweight the animal weight controls were removed and “No livestock are present on” in red text appeared. A zero value for initial weight is no longer accepted.
  6. In Costs and Prices dialogs, price ranges for wool and livestock have been widened.
  7. In the Costs and Prices dialog for ewe, wether and lamb enterprises, the default value in for “commissions, wool tax etc” is now 5% (was 12.0%).
  8. Topsoil water contents below wilting point may now be entered in the Paddock dialog (allows for soil evaporation).
  9. When “spinning up” a simulation, the weight of any seedling roots was not being included in the root mass presented in the Paddock dialog. This has been fixed.
  10. Problems with dates changing unexpectedly in the Graph and Table dialogs have been fixed.
  11. In the Graph & Table dialogs, the range of years provided in the calendar sub-dialogs has been made consistent with range of the simulation for which outputs are being produced.
  12. Problems with the computation of gross margins in the lamb enterprise have been fixed.
  13. Users can no longer attempt to generate a gross margin for ungrazed enterprises.
  14. In Gross Margin windows, the text in the last column of a gross margin table is now clear and it is now easy to scroll to the bottom rows of the table.
  15. When Simulation windows are copied, the complete soil moisture profile is now copied instead of the average topsoil and subsoil water contents.
  16. In beef simulations using dairy breeds, condition scores were being input on a 0-5 scale but output on a 1-8 scale. All condition and fat scores are now expressed on the 0-5 scale.
  17. Problems with flock/herd structure in v2.1.1 (not v2.0.3b) have been resolved.
  18. Various default initial values have been altered:
    • initial weight of steers 260 -> 220 kg;
    • characteristic fibre diameters now depend on the breed;
    • average fleece weight in the ewe 5.0 -> 4.5 kg.

Model Changes:

  1. New equation introduced to describe the interacting effects of available energy, body condition and stage of lactation on milk production.
  2. New equation for predicting energy and protein content of weight change – takes body condition into account, based on Wright and Russel (1984).
  3. Energy expended by animals in movement is now assumed to decrease when stocking rates are very high.
  4. Energy expended by animals in eating fibrous diets has been reduced.
  5. The default relationship between M/D and digestibility of supplements has been changed to take the ether-extractable content of the feed into account.
  6. The equation for senescence of a pasture species altered to be based on periods during which the soil moisture growth-limiting factor is zero.
  7. The weighting of soil layers in the computation of the water-limiting factor has been changed.
  8. The equations for change in rooting depth have been altered. The rooting front now moves downward at a rate governed by temperature and the soil moisture content of the currently-deepest layer. Each seedling cohort has its own rooting depth. The sub-model for changes in digestibility of live herbage has been completely revised. The pasture model now uses digestibility classes of width 5 units (but aggregates these into 10-unit classes for intake and removal calculations). Leaf and stem are distinguished in all grass species. Seedlings now have variable digestibility.
  9. Respiration above current assimilation now results in loss of digestibility.
  10. The soil evaporation submodel has been further revised:
    • Soil evaporation rate calculations now use a limited value (25 mm) for the maximum soil water depletion
    • Residues are no longer assumed to be horizontal when computing the potential soil evaporation rate

Version 2.2.1a, 28 Aug 2000

  1. 32-bit version of the program implemented. NB it runs only in Windows 95 and higher operating systems.
  2. Most locality files have been updated to 31 August 1999.
  3. The Help file has been updated.
  4. Users can produce a text listing of a .GRW file in a separate window.
  5. There are now two methods of obtaining default soil properties:
    • (a) select topsoil and subsoil texture+BD, much as previously, but with default values based on Australian soils data;
    • (b) select a Northcote Principal Profile Form.
  6. Users may specify rooting depths in the Paddock dialog.
  7. The coefficient of variation of the gross margin is now shown at the bottom of the Gross Margin window.
  8. ME:DM values are automatically updated in the Supplementary Feeding dialog when the DMD values are changed.
  9. The Grazing Management dialog (introduced in v2.1.0) now allows 10 stock movements per rotation phase. A default rotation using all paddocks is generated when the number of paddocks is increased from 1 to more than 1.
  10. If a self-replacing flock has been selected in the Management dialog, the Livestock dialog will have the Ram/Bull Breed selection greyed out. The assumption is made that the male and female breeds are the same in self-replacing stock. This ensures that the standard reference weight of the progeny remains stable.
  11. Beef cows and ewes may now be pregnant when purchased or, in a self-replacing enterprise, be mated before replacement. This mating is only permitted if the replacement animals are old enough on the joining date preceding the replacement date. The usual logic for predicting conception rates is applied.
  12. New output variables have been added:
    • chill index (under Environment outputs)
    • methane production (under Livestock outputs)
    • protein content (under Total Pasture and individual plant species)
  13. Legends for paddock-dependent output variables now include the paddock number.
  14. Passwords and serial numbers now work in the same way as in other GRAZPLAN applications.
  15. The preview graphic in the Print Graph dialog now shows the orientation of the printer (portrait or landscape).
  16. The output (.GRR) file format has changed. Users are therefore required to re-run simulations produced with older versions of GrassGro.
  17. If no changes are made to a dialog then simulation results are not deleted, regardless of whether OK or CANCEL was clicked.
  18. GrassGro will now only permit one instance of itself to run.
  19. Meat-based supplements are no longer permitted. Those used by existing simulations are automatically replaced by a valid supplement (the user is notified).
  20. The program detects unknown pasture species names and prompts the user for an alternative species.
  21. Users can edit the [Locality map] section of INI file manually, if they wish to use their own Map picture.
  22. Users can remove the Splash screen.
  23. Buttons on the Simulation window are now disabled until a location has been selected for a simulation.


  1. Maintenance feeding when pasture DM falls below a threshold level has been fixed.
  2. The Supplementary Feeding dialog was not storing the attributes of the production supplement properly if they were altered from default values. This has been rectified.
  3. A wider range of body weights can now be entered for a given condition score when young replacement animals are being specified in the Management dialogs.
  4. Percentiles of the total of a variable are now computed correctly. N.B. a percentile of a total is a different quantity to a total of a percentile.
  5. The upper limit for wool prices has been extended to 4000c/kg, and prices for stock may now vary from 1-300c/kg.
  6. The CD drive selection in the General Options dialog works more reliably.
  7. In the Graph and Table dialogs, the date controls behave more sensibly when the treatment of the outputs is changed by the user (e.g. from Simple to Percentile).
  8. Outputs for all soil layers are now displayed when there are more than 10 layers.
  9. Tables were occasionally printed on a black background; this has been fixed.
  10. A problem has been fixed with result files overlapping when a simulation file is opened more than once. Now a user can open several simulation windows from the same .GRW file; only the first window is associated with the existing .GRR file.
  11. Temporary simulation results files (grassgro.001 etc) are now unlikely to remain in the working directory after GrassGro is exited, thus saving disk space.
  12. Many Help button links have been fixed.
  13. GrassGro now handles the case where Windows has no printer available.

Model Changes:

  1. “Fleece weight” in the interface (both input and output) now denotes the amount of wool that is shorn, not the total wool weight.
  2. The user is now asked for the average greasy fleece weight rather than the potential fleece weight, and the default values have been scaled back by 10%.
  3. Unweaned lambs and calves are now assumed to eat a proportion of the supplementary feed. The proportion is determined by the previous day’s potential intakes of mother and young. Previously the mothers received all the feed.
  4. The equation describing energy limitation to wool growth has been revised.
  5. The age factor used in the computation of wool fibre diameter has been brought into line with the age factor used in computing wool growth.
  6. The logic for estimating the digestibility of undegraded protein from concentrate supplements has been revised to utilise the acid detergent-insoluble protein fraction of the supplement.
  7. Condition score:body condition relationships for beef cattle have been adjusted.
  8. The logic for estimating initial wool weight of older lambs has been revised.
  9. Changes to pasture parameter sets:
    • Beta-test versions of parameter sets for lucerne (2 cultivars) and white clover added.
    • Phenology of annual grass revised; flowering time parameters for subterranean clover cultivars and capeweed also revised.
    • Germination parameters for annual ryegrass, subterranean clover and capeweed revised.
    • Default rooting depths for capeweed increased.
  10. The logic for net primary productivity has been changed to estimate assimilation and respiration separately.
  11. The logic for the growth-limiting factor for soil moisture has been changed so that the effect of evaporative demand is taken into account as well as soil water availability.
  12. Logic for establishment of seedlings changed; multiple cohorts of seedlings are now followed.
  13. The allocation submodel in forbs has been generalized by introducing a minimum allocation to stem as well as a maximum allocation. The stem:shoot ratio in seedings is set to the minimum stem allocation. Assimilate is now allocated instead of net primary production (see point 2).
  14. Death of seedling roots due to stress or frost was not being properly implemented. This has been fixed.
  15. The soil moisture budget has been revised:
    • Potential transpiration is now reduced when evaporation of free water is non-zero
    • Intercepted water is now computed using results of Leuning et al (1994).
    • Runoff and drainage rates are now computed concurrently rather than one after the other.
    • The soil evaporation submodel has been revised:
    • (a)the computation of the evaporation stage now estimates the depth of the wetting front when computing soil water depletion
    • (b) the equation for the redution of evaporation by residues has been changed based on data of Willis & Bond (1970)
  16. Locality files can use the CERES potential ET estimator. If they do, the Paddock dialog displays a control for the soil albedo. (None of the standard localities use this feature.)

Version 2.1.0k, 21 July 1999

  1. Locality information is no longer kept in separate .loc files.The locations are all stored in one file.
  2. Locations can be selected for a simulation by using a map of Australia and clicking on the point on the map.
  3. The path to and name of the .ini file can be set by using a command line parameter.
  4. The weather files for a locality are now unpacked only when required by the simulation, i.e. when a simulation using that locality is first run.
  5. Added a “history list” (list of recently opened file) to the File menu.
  6. All locality files reviewed and most updated to 1998.


  1. Soil moisture and drainage outputs now extend down the whole profile when there are more than 9 soil layers. The deepest layers are lumped together.
  2. Minor adjustment to the way that times that weaners are present are displayed in the Grazing Management dialog.
  3. Calculation of the Lambs Per Ewe output has been fixed to ensure that it does not double count late weaned lambs (e.g. weaned at 44 weeks) if the next cohort of lambs is in utero.
  4. In tactical runs, any days not simulated are now reported in output tables as n/a (missing data), not zeros.
  5. The upper limit for saturated hydraulic conductivity inputs is now 5000 mm/day.
  6. GrassGro will report an error when a Windows default printer has not been set. It will keep working but not allow printing.
  7. Stack Overflows are less likely to happen.

Model Changes:

  1. The partition of energy between milk production and weight loss in lactating cows has been shifted more towards milk production.
  2. The equation for “relative quality” of pasture has been altered so that a pure legume sward of given DMD has the same relative quality regardless of whether it is in a temperate or tropical pasture.
  3. Effect of age on wool growth altered to reflect maturation of secondary follicles as the key process.
  4. “Winter-dormant” phenostage included in the model (used in Hunter River lucerne).
  5. Relocation of stem material to seed filling introduced (used in annual grasses)

Version 2.1.0h, 10 May 1999

  1. Maintenance feeding logic altered to allow different threshold conditions at different times of the year.
  2. Grazing management logic reworked. In multi-paddock simulations, weaners of either gender can be grazed in separate paddocks to each other and to their dams. New Grazing Management dialog introduced.


  1. Maintenance supplement fed to weaners & their mothers now recorded separately.

Prior to May 1999


  1. All production feeding options available to all enterprises in a separate Production Feeding tab of the Supplements dialog.


  1. Extra tests have been added to deal with errors in Bureau of Meteorology data (e.g. out-of-range values).

Model Changes:

  1. Effect of cold on potential intake is now reduced on rainy days.
  2. Effect of wet conditions on intake is now restricted to pasture intake only (i.e. not supplement intake), and only in level paddocks.
  3. Estimation of saturated soil water content now follows Williams et al. (1992).