How to measure the quantity and quality of grass in the field

Technology can help you manage grass supply better, but it doesn't completely replace a trip to the field. The best solution is often a combination of in-house measurements and digital tools.

By Linda Rosager Duve

Disclaimer: This article has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, errors or inaccuracies may occur, and some content (such as images, videos, PDF-files, etc.) has not been translated.

Managing grasslands requires knowledge of how much grass there is and how the quality is. Traditionally this has been based on experience and judgement, but today there are several techniques that can support decisions - both simple and more advanced.

Measuring the amount of grass - the plate lifter is still the most accurate

The amount of grass (biomass) is most accurately measured with a disc lifter. An electronic plate lifter converts grass height to biomass and gives a good overview of the grass supply in the grazing fields. However, it requires regular walks across the fields.

Advantages of biomass measurements with a plate lifter:

The most accurate method in practice.
Measures grass height and converts it to kg dry matter per hectare.
GPS versions can store data and provide an overview per field.
The downside is that it takes time and requires walking through the fields.

Read more about grass height measurement with an electronic plate lifter in the article:

Measuring grass height enhances grazing

Satellite-based grass height measurements can provide an overview

Drones and satellite data should be relatively easy to use for estimating biomass in grass, as it is the entire biomass that is determined rather than, for example, grain crops where the grain yield is only a fraction of the biomass. Nevertheless, it has proven difficult in most studies to use satellite data for frequent accurate absolute and not just relative estimates of grass biomass. This is due to a need for calibration and a high sensitivity to cloud cover.

Satellite-based systems, such as Farmmote and Ruumi with the ability to calibrate satellite data with local measurements, are likely to become more widely used for monitoring grass supply in the future.

Benefits of satellite-based solutions:

Uses satellite imagery to show grass quantity and growth.
Provides an overview of all fields at once.
Suitable for planning and prioritisation.
Accuracy is best if the system is calibrated with your own measurements (e.g. plate lifter).

Limitations of satellite-based solutions:

Clouds can interfere with measurements.
Often shows relative differences rather than exact kg dry matter.

Drones can provide very detailed images, but are only suitable for small areas or specific problem fields. It is therefore most relevant to use drones for specialised tasks and not daily grassland management.

Measuring grass quality - what can be done?

Grass quality (e.g. protein and sugar content) is more difficult to measure directly than grass quantity.

There are currently no commercial solutions calibrated for measuring quality traits in clover grass in Denmark.

Multispectral data can in some cases measure crude protein content. The results are promising, but not yet fully developed for Danish clover grass fields.

Sugar content in grass is highly dependent on solar radiation and temperature and is therefore better suited for modelling than direct measurements.