Soil Moisture Monitoring in Grazing Systems

Climate variability is creating challenges for many livestock grazing business. For example, in the last 20 years the Barossa region has experienced reduced annual rainfall, combined with patterns of later autumn ‘breaks’, earlier spring ‘finishes’ and increased summer rainfall. This therefore makes it difficult for graziers to predict seasonal weather conditions and hence pasture production, a key determinant for a property’s stocking rate.

The Barossa Improved Grazing Group (BIGG) has been monitoring soil moisture in grazing systems since 2013, through the establishment of telemetry based weather monitoring stations located in four locally representative pasture paddocks (Flaxman Valley, Keyneton, Koonunga, Moculta). 

Each station comprises a sub-surface capacitance probe measuring moisture to a depth of 85cm, an automatic rain gauge and sensors measuring air temperature, relative humidity, wind speed, wind direction and radiation. These are connected to a solar powered telemetry unit with the data being recorded every 15 minutes and publically available on BIGG’s website. 

The ongoing measurement of soil moisture has allowed the key parameter of plant available water (PAW - a measure of the total amount of moisture that plants can access in the soil profile) to be established for each pasture paddock. Significant differences in PAW have been measured between the four paddocks. 

This information is critical as knowing the PAW, including how full the soil profile is at anyone time and how quickly the moisture is being used, can help graziers make more informed pasture management decisions. For example, if soil moisture levels leading into spring are below average and climate forecasts are predicting on-going dry conditions, spring pasture production (and therefore available paddock feed) will be reduced. This therefore gives graziers an early indicator to critically evaluate and possibly reduce their livestock numbers so to better match the decreased pasture production that is projected. This also has genuine landcare benefits as de-stocking early helps ensure groundcover levels are maintained, therefore reducing the potential for soil erosion and the invasion of broadleaf weeds. 

Graziers in the Barossa region are using information from BIGG’s weather stations to assist with numerous decisions. In 2020, BIGG conducted a survey of its members and found the data is assisting mostly as a:

  • Rainfall check
  • Estimating the length of the growing season (for stock feeding decisions)
  • Suitability of conditions for spraying
  • Stocking rates
  • Timing of nitrogen application

BIGG has also developed several farmer case studies to highlight how the weather station data is being used. This includes Michael Evans of Flaxman Valley who has used it to help make decisions about selling stock early, feed budgeting and in-season nitrogen application.  Read Michael’s case study 

For further resources and information relating to soil moisture monitoring in grazing systems visit BIGG’s website.