Pasture cuts and estimations
Meat & Livestock Australia April 15, 2024
Tools for pasture cutting
The Quadrat is utilised for measuring the area to cut grass. This is generally 3 sided to allow it to be placed into dense pasture. The internal measurements are either 0.5 m by 0.5 m for more productive areas, or 1 m by 1 m in more arid regions with sparse pastures.
Other tools required include:
- Hand or electric shears – for cutting grass.
- Large paper bags – for collecting quadrat samples.
- Small paper bags – for oven drying.
- Scale – for weighing wet and dry weight of grass.
- Permanent marker – for labelling bags.
Cutting pasture from quadrats
When cutting pasture using the quadrat method a minimum of five cuts should be taken in a representative area. Quadrats should be placed about 10 metres apart by stepping in a straight line while looking ahead at a distant marker, so as not to bias where you place the quadrat. This is called a ‘transect.’ When placing the quadrat frame down it should be placed where your foot lands so the site is chosen objectively. All the pasture attached within the quadrat frame should then be cut with the shears and placed in a paper bag (labelled 1-5).
If a paddock is variable or has different types of pasture; it is beneficial to take more pasture cuts in other transects to better reflect the paddock and give a more accurate estimation of paddock biomass.
Weighing and drying
Once the pasture has been cut, each bag from the transect must be weighed, making sure to tare the weight of the bag first. Once the wet weight of all the bags has been obtained, take a representative handful of each sample and place this in a small paper bag.
Obtain the wet weight of this sample, dry the sample, and then weigh again.
To dry the sample you can use:
- Oven – place the sample in the oven at 80 degrees Celsius for a minimum of 12 hours. Weigh again, place back in the oven for another 2 hours and weigh again. If the weight hasn’t changed, it is ready to calculate the dry matter content
- Microwave oven – please follow the instructions in this article.
This sample can be used to calculate the dry matter percentage of the harvested pasture which can be applied to the individual samples as opposed to drying each one.
Calculating dry matter percentage
Using your wet and dry weights of the combined sample the following formula can be used to calculate the dry matter percentage.
Dry Weight (grams) ÷ Wet Weight (grams) × 100 = Dry Matter %
Calculating Kg of dry matter per hectare
The calculated dry matter percentage can be applied to each individual quadrat wet weight sample to help us obtain the kg DM/Ha. When calculating the kg DM/Ha from several different samples it is important to first take an average dry weight of all the . Once the average has been calculated it can be used in the following equation.
Average Dry Weight (grams) × 40 (if using 0.5 x 0.5m2 quadrat) = (kg DM/Ha)
Remember once this is complete to subtract the unpalatable, detachment and desired residual to obtain the kg DM/Ha available for grazing.