Overgrazing leads to changes in pasture composition, erosion and in some cases desertification: It is a global scale problem.

Matching animal numbers feed available is the issue.

Potential animal intake can be estimated from animal size. A 450kg steer eats about 10kg of grass / day and it is safe to eat 20-40% of annual growth. But how much biomass do you have? Availability = area * kg/ha biomass

How to estimate kg/ ha biomass that’s more tricky and time consuming than it seems!

  • (1)Cut quadrats and weight (slow, needs scales & drying oven) few samples
  • (2)Botanal / visual estimates plus cut standards (see 1) plus have to set up regression model.
  • (3)Estimate from photo standards (some people are very good others are hopeless, need a big range of photo standards green dead plus minus trees etc.), need to record.
  • (4)Remote sensing measuring cover not mass (although calibration possible)
  • (5)Capacitance type meters sensitive to moisture content
  • (6)Weighted disk meters – measuring height and relating to biomass – problems in grass with strong stems or very sparse tussocks can be difficult.
  • (7)Modelling, like remote sensing needs calibration (and good inputs like climate data)
  • (8)Lidar (too expensive at the moment)

Pretty much biomass estimated only done by scientists (e.g. in specialist grazing trials) and amount of assessment is quite limited by time and resources.

Proposed solution:

  • Estimate pasture sward density parameters and relate to mass.
  • Measure density and construct density to mass calibration equations and test for generality over various sward types.
  • Mass is concentrated near the bottom of the sward so extra sensing needed here


  • Needs to be a robust gadget that can be used in the field
  • Needs to be inexpensive (< $150 AUD)
  • Should be able to make measurements at the quadrat scale (typically 0.5m*0.5m) for calibration and consistency with established research practice.
  • Should record data and / or upload to a mobile phone
  • Should be upgradable so can integrate with GPS information.
  • Should be able to be carried on a motor bike.
  • Should have one handed operation.

Project Name Grass_stick

Grass_stick V1.1 Aluminium channel

Grass_stick V1.2 25mm PVC

Grass_stick V1.21 bottom end cap too small for encoder use T-piece, use sensor shield on Arduino



Arduino Leonardo

Sensor Shield V4

SD card shield

20 Position Rotatory Encoder with switch

IR distance sensor