Space: the final frontier for measuring grass growth


Innovation Profile Teagasc:Considering that we live in a country known around the world as the Emerald Isle precious little work has been done on the nation’s most important agricultural crop – grass. We tend not to appreciate its importance, not only to the farming sector but to the national economy.

And that importance is quite profound. Ireland’s renowned beef and dairy industries are dependent on their grass-based feeding regimes. The fact that Irish cattle lead largely free range lives and are fed mainly on natural grass is greatly appreciated on export markets and is a key selling point for our beef and dairy products.

But our lack of knowledge and appreciation for the green stuff is about to change. “Grass is Ireland’s most important crop,” says Stuart Green, remote sensing specialist with Teagasc. “But we really don’t know how well it grows despite billions of euro in agricultural output depending on it. We know very precisely the tonnages of wheat and barley we produce every year and how well those crops grow during the year but we have little idea of how well grass grows.”

And knowing how well the grass is growing can be very important. “If a farmer with 100 head of dairy cattle can increase the grazing year by just two weeks that could be worth an additional €2,000 in overall farm income due to reduced winter feed costs and so on,” Green says. “Knowing when the grass is growing well enough to put the cattle back out after winter is very important.”

This vital information should soon be available to individual farmers around the country thanks to Teagasc projects which are utilising satellite technology to monitor and analyse grass growth patterns throughout the country.

“The use of satellites and aircraft to make observations of the Earth below is the science of remote sensing,” Green says. “It allows us to see things we normally can’t, to gain views and insights to the most isolated parts of the country and can help us ensure that Irish agriculture is productive and sustainable. We have been using remote sensing for the past 15 years mainly to produce one-off maps of soil type and vegetation cover.”

Satelite power

But the increased availability of satellites has made it possible to do a lot more than this. “We used to have to pay a lot for satellite images and availability was an issue but the number of satellites has exploded in recent years and we now get the information free from NASA and the European Space Agency.”

The satellite images used by Teagasc many utilise near infra-red (NIR) technology and come from satellites which pass over Ireland every few days. Green vegetation reflects back 10 times as much NIR radiation as it does the red component of light. This makes crops like grass easily observable from space using a NIR sensor.

The amount of NIR that’s detected depends on a number of factors including the amount of plants in a given area, how well they are growing, what species are growing, and how healthy they are.

The satellites used by Teagasc measure the NIR components so precisely that it is possible to calculate the productivity of an individual field as well as the soil type the grass is growing in. They can also tell what crop is growing and its stage of ripening. Other satellites available to Teagasc use radar sensing to “see through” the clouds and fill in any gaps in the NIR images.

Because the technology can tell how well grass is growing in areas as small as 250 square metres it will soon be possible to advise individual farmers on when to put their cattle out after winter. A general notice similar to the potato blight warnings most people will be familiar with could be broadcast on radio to let farmers know that the national growing situation is good but this can be made more precise.

“A mobile phone based alert system for individual farmers might be possible,” Green says. “Farmers might be able to register their land for a service and get an alert when the satellites tell us the grass growth is good enough to put the cattle back out.”

And the applications are a lot wider than herd management. “We are looking at building economic models for what the impact of poor weather conditions is on grass production and on farm income. We will also be able to quantify accurately the number of tonnes of grass produced each year. We can do this to a certain extent already but satellite monitoring offers real time daily monitoring. In five or six years’ time we will be able to produce weekly grass growth forecasts a bit like the five day weather forecasts. These will be tremendously useful to farmers as it will allow them to plan their grassland and herd management throughout the year.”

Farmers have to move cattle into different parts of the farm quite frequently in order to ensure they have sufficient grass to eat and allow other fields to recover. “They have to move the cattle to fields with good grass and there might be only a two-day window for the optimal time to do this,” says Green. “We will be able to assist with that. Also, unlike other crops, grass can have two, three or even four seasons a year. You can use it for grazing, for silage making and maybe grazing again. We need to build this into economic models to assist farmers in future.”


Growth in farm size is also driving the need for agri-informatics of this nature. “In the typical farming model the farmer has to walk the land at least once a week to see what’s happening and make the right decisions. But with farms getting larger this will not be possible. This technology will give them access to the information they need on a computer screen.”

The degree of detail available in the data can be very helpful. “Some of the satellites we use have resolutions down to 50 cm,” says Green. “The can also look at different parts of the electro-magnetic spectrum and we can tweak the images to see growth in individual fields and identify areas which are not performing. This data could in future be fed to farm machinery equipped with GPS tracking so that the underperforming parts of a field receive additional spray treatment.”

The technology can also be used to improve productivity in other food crops. “If you look at the projections for the next 50 years the world is going to have to produce as much food in that period as has been produced in our entire history. It therefore behoves us all to do everything we can to improve productivity. One way we can do this is by using remote sensing technology to assist with disease alerts for crops. For example, we can train the satellites to only look for changes in crop growth which are triggered by disease. We can then alert the farmers concerned to treat the disease before it does too much damage.”