Measuring grass: Why data can help you make better decisions 

Are you truly maximising your grass and forage performance? In farming, challenges now come from all angles and finding an edge can make all the difference. By measuring grass, you can gain on production, profit, and even sustainability, along with the other benefits below. 

What are the benefits of measuring grass? 

This is all about gathering data to optimise your decision-making. And when you have more information, you can really start to benefit from measuring grass: 

• Maximise utilisation: Grow more grazable grass and ensure less is wasted. 

• Drive performance: Feed stock with higher-quality, higher-yielding grass and forage for better milk yields and daily liveweight gains. 

• Improved grazing management: While under-grazing produces stemmy, lower-quality grass, over-grazing harms regrowth. Making data-driven grazing decisions helps you find the balancing point. 

• Input controls: When grass and clover are growing efficiently in swards, you can start reducing artificial nitrogen applications.  

• Reduce bought-in feed: By producing more homegrown feed, you can cut back on more costly bought-in options. 

• Lift profits: With better cost controls and optimal grassland management, you’re in a stronger position to increase profit margins. 

• Make data-driven decisions: Know your farm’s potential and benchmark your fields against your farm’s performance, helping to identify when fields should be reseeded or overseeded to elevate production. 

• Sustainable production: Stronger performance can also support sustainability. Your improved grassland management will enable more strategic use of chemicals and fertilisers. Growing more homegrown feed also means a lower carbon footprint versus buying concentrates. 

These farmers benefit from recording grass data 

Niall Moloney: Dairy, Co. Limerick 

“I have 10 years of information on PastureBase, so I can project forward.” 

Niall maintains a consistent homegrown feed supply by setting and meeting grass targets throughout the year. At peak performance, he has produced 13-15 tonnes of red clover silage per hectare. 

James Henderson: Beef and sheep, Co. Down 

“Grassland management is the crux of our farm business.”  

James consistently measures grass, sharing data with GrassCheck NI. By optimising grass and forage production, he doubled production from 6t DM/ha to 12t DM/ha over nine years and trebled profitability. 

Photo credit: Farmers Weekly

How to measure grass covers? 

You measure grass as kilograms of dry matter per hectare (kg DM/ha), which determines the herbage available for stock to graze. We recommended walking pastures every seven to 10 days to generate the most accurate results. 

During high growth periods, you may need to walk the farm twice in 10 days or even twice in seven days for increased accuracy. You can then quickly adjust your feed plan based on current growth. 

Use a plate meter 

Walk your paddock in a W or X pattern, taking 30 to 50 height measurements, depending on the size. Having multiple measurements will give you a more accurate result for the entire paddock. 

When using a mechanical plate meter, the grass measuring calculation entails subtracting the optimal post-grazing residual height from the paddock height. You then multiply this measurement by 250kg DM/cm. 

How to calculate: 12cm grass height – 4cm residual x 250kg DM/cm = 2,000kg DM/ha available. 

If using a rising plate meter, the ultrasonic sensor measures all the heights for you. Combined with GPS coordinates, all data can be relayed to PastureBase, where your grass covers are calculated automatically. 

Cut and weigh with visual assessment 

Some farmers prefer to visually estimate grass covers, which can be useful if you don’t have a plate meter at hand. To sharpen this skill, it helps to cut and weigh grass so that you know the exact covers while training your eye: 

1. Take a quadrat of 0.5m by 0.5m and place it in a representative area of the field. 

2. If there’s moisture, knock it off before cutting. 

3. Then cut the grass to a height of 3.5-4.0cm. 

4. Weigh the grass. 

5. You can obtain the grass DM% from PastureBase.  

6. Calculate: Multiply grass weight kg x grass DM% x 40,000 = kg DM/ha 

By gaining experience with cut and weigh, many farmers become comfortable with making reasonably accurate visual assessments. However, a rising plate meter paired with PastureBase is extremely accurate and supports long-term data analysis. 

Need advice on forage planning? 

Measuring grass is simple, but choosing the best approach for your grazing system takes careful consideration. Our regional experts are here to guide you.