How to Measure Grass on Irish Cattle Farms Using the DJI Mavic 3 Multispectral

Accurate grass measurement is the cornerstone of efficient grazing on Irish cattle farms. Whether you’re managing beef or dairy herds, knowing exactly how much grass is available helps reduce feed costs, improve animal performance, and optimise pasture rotations.

Traditionally, farmers rely on plate meters, visual scoring, or cut-and-weigh methods. While effective, these are time-consuming and can vary depending on who’s measuring. That’s where drones – and especially the DJI Mavic 3 Multispectral (M3M) – come in.

What is the Mavic 3 Multispectral?

The Mavic 3M is a compact drone equipped with a multispectral camera system that captures data in red, green, red edge, and near-infrared bands. This allows it to create detailed maps showing plant health, biomass density, and pasture performance.

With this drone, you can measure the grass across your whole farm in minutes.

Why Use It on a Cattle Farm?

• Get weekly grass growth data without walking paddocks

• Detect poor-performing or stressed fields early

• Plan rotational grazing with accurate DM/ha estimates

• Cut silage and spread slurry at the right time and place

• Build a long-term record of field performance

Step-by-Step: How It Works

1. Plan Your Flight

Use the DJI Pilot 2 app to set up a mission:

• Fly at ~100–120 m altitude

• Set 70% overlap

• Map individual paddocks or multiple fields in one go

2. Fly the Drone

The M3M flies automatically over the area and captures multispectral images.

3. Process the Data

Import the images into:

• DJI SmartFarm Web, or

• Pix4Dfields

These tools generate a colour-coded NDVI map, showing areas of lush growth vs. poor performance.

4. Convert NDVI to Grass Measurement

NDVI values correlate with Dry Matter per hectare (DM/ha). Here’s an example:

You can calibrate these values using a plate meter for your farm and then apply them consistently across all fields.

5. Use the Results

• Identify which paddock to graze next

• Delay grazing on weaker paddocks

• Apply fertiliser only where needed

• Plan silage cuts based on growth, not guesswork

Real-World Example

A dairy farmer in Meath flies his Mavic 3M every Monday morning. NDVI maps reveal two paddocks aren’t recovering well. He skips grazing there and spreads slurry only in those spots. By doing so, he avoids overgrazing and boosts regrowth – with less fertiliser used.