Why and How to Measure Sward Height
Sward height has been shown to be a good practical indicator for use in grazing management which will enable good grass utilisation and livestock performance. Sward height can be converted into the weight of grass in kilograms of dry matter per ha (kg DM/ ha) also known as cover or mass, this enables grass budgets to be calculated.
Why measure sward heights/cover?
Knowing how much grass you have and how it is changing will help you to make management decisions to:
- Set the right stocking density
- Put the right class of stock on to a field
- Gauge how long a piece of grazing should last
- Make the most of fertiliser applications
- Take fields out of grazing rotations and into silage areas
- Identify a potential shortfall in grass before animals/milk yields are affected
- Decide whether supplementary feeding at grass is necessary
Measuring sward height/cover
Walk across a field in a W pattern you should aim to take at least 30 readings in each field. Record them on the app screen as you go and it will work out the average. Avoid gateways, hedgelines and any areas that are not representative of the field in general. If the field has a definite split between wet and dry areas it is a good idea to measure them separately. Measure to the top of the grass leaf with a sward stick or ruler – don’t measure stems and flower heads and don’t measure weeds. Follow manufacturer’s instructions with a rising plate meter- these are less accurate at low sward heights and on steeply sloping ground.
During the peak of growing season sward heights can change fairly rapidly so consider measuring twice a week. The calendar can be used to remind you when to measure again.
Tools to measure sward heights/ cover
Any tool that can measure height in cm can be used, including a sward stick, a rising plate meter, a ruler, walking stick, alkathene pipe or even your boots with a scale drawn up the side. For consistent results the same person should take measurements every time. With plenty of practice you will be able to make rough judgements by eye, but there is no real substitute for walking fields, looking at the sward and measuring sward heights.
By recording sward heights you will be able to improve the use of grass on your farm and optimise animal intakes and reduce grass waste. Grazing at the recommended height/cover will prevent swards becoming stemmy and maintain sward tiller density and quality through the grazing season and produce high levels of livestock performance.
Aftermath swards will respond differently to grazing pressure than normal grazing fields. They must be conditioned by grazing to encourage tillering before sward height/mass guidelines can be applied.
Use the farmGRAZE app to measure sward height and record your grazing wedge. farmGRAZE contains SWARD height guidelines for dairy cows, beef cattle and sheep.