21 April 2022


The farm-level project in Wales established that remote sensors can provide important information on how grass responds to inputs in greater detail and more rapidly than if farmers manually measured with a rising plate meter.

Tramline trials were established on three Welsh grassland farms for the three-year European Innovation Partnership (EIP) Wales project to allow data to be gathered on how swards responded to different agronomic situations.

A drone, satellite technology and a rising plate meter were used to collect that information and the results compared.

Growth in different grass and clover mixes was monitored and also responses to varying application rates of sulphur fertiliser. The trial also looked at how grass reacted to slurry inputs and other treatments including grass growth promoters and seaweed extract.

Grass yield was measured at regular intervals.

The remote technology uses a system known as spectral reflectance which can estimate crop canopy leaf area. One of the measurements used in the trial was WDRVI (Wide Dynamic Range Vegetation Index), which is an index of plant greenness and canopy size. 

Analysis of the information from this technology showed it could detect significant differences in the agronomic treatments applied on the project farms – data that could not be picked up by the plate meter.

The project also showed important differences in the data available from the two remote sensing methods - the drone could detect the smallest treatment differences at a level two or three times smaller than the satellite used. 

But ADAS consultant Katie Evans, who managed the project, says the results of the trial demonstrate that farmers can be confident in using either technology to estimate grass biomass on their farms and to work out if the agronomic treatments they are using increase grass biomass, and to what extent.

“Access to additional data from satellite and drones could be used to inform precision agronomy and help grassland farmers fine-tune grassland management and improve farm performance,’’ says Ms Evans.

Currently, a rising plate meter is the most common way of measuring grass yield but this is time consuming.

New forage harvester systems can also map grass yield but relatively few farmers have access to this technology, says Ms Evans.

This contrasts to the arable sector where most combine harvesters have yield monitors that produce yield maps to enable growers to understand the effects of different agronomic treatments.

“Grass and forage producers are not able to do this very easily and risk falling behind in terms of rate of productivity improvement,’’ says Ms Evans.

The aim of the EIP project was not to test whether remote sensing can be used to simply measure grass growth - this has been proven already, she points out. 

“This project was about enabling farmers to test the effect of new agronomic practices cheaply and reliably.’’

But there are caveats. Drones require a farmer to have technical expertise to operate and collect data; alternatively a specialised contractor could be used. 

Expertise is also needed to acquire data from satellites and it can only be captured in cloudless conditions.

“Both drone and satellite data require specialist analytical skills to test whether an agronomic treatment has had a statistically significant effect on grass growth,’’ says Ms Evans.


How the costs stack up

Using a drone to detect treatment differences worked out as the most expensive option in this project - it cost around £850 a typical size field.

In comparison, satellite data from the Sentinel-2 satellite was free but to access it required in the region of £200 worth of consultant’s time for each field.

The process of analysing the data to statistically test the effects of agronomic treatments increased the budget further - for the drone it was around £400 a field and for the satellite £250. 

Ms Evans says these costs - which don’t include VAT - are reliant on the farmer being able to provide GPS coordinates and for there being no requirement for additional consultant visits. 

“The trials proved treatment effects of between 150 and 1100 kg dry biomass per ha, so the value will soon stack up when applied over several fields,’’ she says.

The saving from surveying a group of neighbouring fields comes from the likelihood that it is more likely that they can be included in the same satellite image.

Farmers can share the costs by grouping together to carry out these type of on-farm trials, Ms Evans advises - for example three farmers could group together to fund the cost of two trials.



Dairy farmer David Jones has a multi-cut silaging system to make forage for his 200-cow Holstein Friesian herd.

He relies on data gathered from weighing silage trailers to understand how fields at Hardwick Farm, near Abergavenny, are performing but this is only done occasionally.

As one of the three farmers who participated in the EIP project, he wanted to establish if technology could provide a better means of getting that information, with particular emphasis on which grass seed mixes perform best in his system.

He reseeded a field using three variety mixes - red clover and ryegrass, white clover and ryegrass and ryegrass only - and each was managed in the same way. 

Drone and satellite technology and a rising plate meter were used to monitor how those leys grew.

In this trial it was the drone data that gave the greatest level of detail - revealing statistically significant differences in the vegetation indices which are a measurement of forage biomass.

“Having this information, which I would never have captured from weighing silage trailers, will help inform my reseeding decisions,’’ says Mr Jones, who produces milk in a robot milking system.

Although the cost associated with capturing the data is not insignificant, Mr Jones says with soaring input costs he is confident that the financial outlay could be quickly recouped.

“I see it as a very worthwhile process to help us maintain the quality of our grass silage,’’ says Mr Jones, who reseeds approximately 20 hectares of his land annually.

“Also, if we are using different rates of fertiliser we can see what’s working and providing us with value for money. That’s more important now that ever with hyper-inflation.’’

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