Pasture assessments on Old Man Plains

By Coral Allan

The annual pasture assessments on Old Man Plains Research Station were undertaken by Coral Allan, Chris Materne and Meg Humphrys from the end of May to end of June. The monitoring this year was tough, it was just after a small rainfall event and vegetation response was poor. That rain event made a large portion of the buffel tussocks turn rank which will be reflected in the data analysis. Any greenness found in the occasional tussock had been eaten by cattle and tussocks were pruned accordingly with the dry stalks still standing. Cattle travelled out to the outer boundary of the paddocks, eating grass far away from the watering points which we did not always pick up in our sampling. They had also been utilising top feed (shrubs) which was particularly noticeable in the mulga stands.

Purpose of monitoring

The purpose of this work is to assess if there is enough pasture on the ground to match the stocking rates for each paddock. The figures contribute to the management decisions on stocking into the coming year, which includes destocking if necessary. Eleven paddocks are assessed with each paddock having eight assessment sites located in them except one paddock that has 16 (because it was larger).

This work can be as dry as the season we are experiencing, but needs to be done for the sake of the vegetation, land and livestock. It was a tough year for monitoring with the dry conditions so it really stretched our skills to identify some of the many ‘little tussocks’ struggling to stay upright.

Our transect work

The sites are located 500m, 1km, 3km and 5km from a watering point and are identified by a star picket with a numbered tag attached. These sites are located using a GPS reading or from memory! At the site a landscape photo is taken along the transect which in itself tells a story each visit.

The star picket is the centre of the transect with 20 quadrats assessed either side (1 – 20 and 21 – 40). The pacing between the quadrats is 10m for the 1-5km sites and 5m for the 500m site.

Each quadrat is a metre by a metre square and assessed on total yield, percentage cover, top four species and their yield, percentage rank, buffel present/absent, defoliation, cattle activity, other grazers and grass basal area (yes we can fit that all in a metre by metre square!).

To ensure we are doing a reasonable job of ‘eye ball’ assessments, we calibrate by cutting and measuring vegetation. This sorts out the accuracy of our subjective assessments amongst our team and can be quite competitive at times to see who is calculating best!

What now

This year has been dry with total yields down on the past few years. The numbers have not been crunched yet to give you more detailed notes but the seasons have not been kind to us all!

Ongoing decisions will need to be made about how much livestock we will be able to carry on OMP now and into summer if we do not get rain. This may impact our trial work should we have to reduce numbers but when we live in a variable climate like this we all learn to roll with the punches - all we can hope for is lots of steady summer rainfall events to spark growth events.

Last updated: 28 September 2020

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