How to use $ummer Weed Tool

November 25th, 2024

The $ummer Weed Tool uses modelled data to give an estimate of the likelihood of yield, nitrogen and financial benefits of controlling summer weeds. The tool can be used to evaluate a range of scenarios such as the trade-offs associated with delaying summer weed control; the value of returning to control low densities of survivors;  and the likely cost in terms of nitrogen and water loss if summer weeds have already been growing for a length of time before being controlled. The app is designed to work in the absence of a mobile internet connection.

This guide is intended to walk you through using the tool.

Entering your data

To calculate a result for a paddock, the $ummer Weed Tool needs to know….

  • The location, which you can choose from a list of supported regions.
  • The date you are choosing to evaluate. This may be the day you are using the tool, but it may also be, for example, a recent day when you went out and collected the other necessary information.
  • The type of soil in the paddock. You can select the closest type available in the drop-down.
  • Estimated Plant Available Water on the day you are choosing to evaluate.
  • The expected price to be received for wheat per tonne (account for freight and levies etc. for the most complete result).

These optional fields will allow the tool to estimate returns.

  • The expected cost of nitrogen in dollars per tonne of urea ($/tonne urea)
  • The cost of the summer weed control treatment (including application cost) in dollars per hectare ($/ha).

Information on the weeds present in the paddock on the day you chose to evaluate.

Estimation of average weeds per square metre and average number of days since emergence for your chosen date for either

  • deep-rooted weeds. Deep-rooted weeds (e.g. tap-rooted summer weeds) have the potential to extract the most water and nutrients per plant over time.
  • shallow-rooted weeds

The impact of shallow and deep rooted weeds is similar in the model until the deep rooted weeds have been established long enough to grow past the shallow-rooted weed depth. Consequently, you only need to use one of these two weed types, not both.

It should be noted that a significant error in the average number of days since emergence can affect the results.

Once you have filled out all your information, tapping the Calculate button will run the analysis for your chosen inputs.

After the analysis is complete you can review the summary information you entered, by tapping the Your Summary at the top of the page.

To change your information, tap the change button at the top of the page, or the Weed Tool button in the toolbar.

Interpreting your results

The tool is set up to compare your expected profits if you start controlling your weeds at different times, based on modelled data representing the range of possible season types. By default, the tool compares your gains if you start controlling for weeds this week, versus your gains if you start controlling for weeds in ten days.

You may change the second period by tapping the drop-down menu and selecting a different time period. The maximum period available is usually 50 days, and the minimum is 5 days.

The tool compares six values:

Expected increase in yield potential due to water. This shows the difference in potential yield and the additional income generated, based on how much more stored soil water will be available to crops, instead of this water being wasted on growing weeds.

Probability of gaining at least 0.2t/ha due to the increased water availability. This metric shows how likely it is that your yield will increase by at least 0.2 tonnes per hectare, expressed as a percentage. This reflects the distribution of possible outcomes due to uncertainty about the seasonal conditions that will affect the summer weeds and the subsequent crop.

Expected nitrogen benefit. This shows the difference soil nitrogen that will be available for use by crops at the start of the season, instead of used by weeds, saving you the cost of additional nitrogen fertiliser. If you have entered a urea price it will also provide the $ value of that nitrogen.

Probability of at least 10kg/ha nitrogen benefit. This metric shows how likely it is that you will gain at least 10 kilograms per hectare of extra nitrogen that would otherwise be lost to weeds, expressed as a percentage. This reflects the distribution of possible outcomes due to uncertainty about the seasonal conditions that will affect the summer weeds and the subsequent crop.

Probability of at least 10kg/ha nitrogen benefit. This metric shows how likely it is that you will gain at least 10 kilograms per hectare of extra nitrogen that would otherwise be lost to weeds, expressed as a percentage. This reflects the distribution of possible outcomes due to uncertainty about the seasonal conditions that will affect the summer weeds and the subsequent crop.

Probability of gaining at least $20/ha due to extra water and N availability. This metric shows how likely it is that you will gain at least $20 of additional income per hectare (benefit-costs) by controlling your weeds, expressed as a percentage.

Potential return on the summer weed control investment. This metric shows the estimated potential return (benefit-costs) you would receive due to controlling your summer weeds, in dollars per hectare. This is the sum of the of the average stored soil water benefit and the average nitrogen benefit.