Inspiration Day: Happy with sensors in the field

Gepubliceerd op
17 augustus 2017

Van Hall Larenstein University of applied sciences has organized the grassland symposium about grassland sensors on the 2nd of May. The current status of the application of sensors in grass management has been illustrated by researchers, advisors and people with practical experiences. This afternoon was all about the questions: "What do we know, what do we measure and what can we advise?" With around 75 visitors, we can conclude it was a successful symposium.

Lector Herd Management and Smart Dairy Farming at Van Hall Larenstein University of applied sciences, Kees Lokhorst, led the afternoon. After the opening, the afternoon started off with a short video message from Arjan Hulsman, currently working and living in New Zealand. The video was an introduction about his passion for grass and how he sees the future of sensors in grassland management.

What do we know?

Idse Hoving and Bert Philipsen, both researchers at Wageningen Livestock Research, told us something about the subjects within the current grassland management studies such as; growth height, growth forecast and reflectivity measurements. The dream of Bert Philipsen is to develop a "Grass information system", comparable to Dairy Herd Information records. In their presentation, they illustrated the path from research to practical implementation through innovation. They showed research results and it became clear that there still quite some different indexes used and that proper calibration based on available calibration lines is needed. The WVDI index shows to be most promising today something on the amount of biomass (kg DM/ha) of grass. 

What do we measure?

Gerbert Roerink, working at Wageningen Environmental Research (Alterra) has been shown us the world of remote sensing using satellites. He has demonstrated, among other things, what images we can get from this and what we can actually assess here; The growth index and the grassland intensity. Open information can be seen at or A practical advice is that currently a resolution for grass observation between 5 and 8 m will be sufficient. He also told us to start learning using new indexes. When Celsius started also nobody could interpret it as we are used now. Work on quantification of grass.

Christel Thijssen of Loonbedrijf Thijssen has made everyone acquainted with the Ebee (drone) and the Veris Scan (soilsensor). Both sensors have the aim to improve the quality of the grasses and the soil. His expectation is that we can save between 10 to 35% on fertilser and getting better quality food for the cows.  A practical tip is that the pH for grassland soils should be above 5. A qoute from Thijssen was  ‘Droneworkers are the Agricultural Contractors for tomorrow’.

Piet Jan Thibaudier is a farmer that uses summer feeding and together with Arjan Hulsman he is importer of the Pasture Reader. The Pasture Reader is a sensor which measures the height and the density of the grasses with ultrasound. By using the Pasture Reader you can for example measure the grass yield. For good grassland management at least pH, drainage and fertilisation should be ok to produce 15 tDM/ha/year. A basic rule is that 1kg N/ha brings 30 kgDM/ha. Thibaudier also stresses the importance of good and regular calibration. He sees much room for improvement. According to him only 1% of the Dutch Dairy farmers are using simple plate meters, and there is also a lack of good management software.   

What can we advise?

According to Gerard Abbink, working at GroeiKracht, your own senses will remain the most important sensors. When sensors will be used reliability will be an important issue. Farmers have to learn to look at the grass and learn from themselves. In this sense his quote ‘I spend much easier 1000 € in a tool, then changing my habits’ is very important. Understanding the complex dynamics in soil-grass interactions and the way the weather, humans, machines and cows influence this is not an easy job, but the way to go. A simple rule from Gerard  is that you might need 1 t/ha/year of lime to keep the pH on a sufficient level. For the growth of maize a pH above 5.5 is needed. So if you have not used lime for a couple of years then you should be alarmed.  

The application of sensors in grass management is still developing according to Theo Courtz, working at Yara, the sensors are still out of place due to the associated costs and the fact that sensors around grassland are still in their infancy. He also stresses the importance of having local and dedicated calibration, especially if you are selling your sensors all around the world. According to Courtz the biggest challenge is how to involve humans in the management process of observing, analyzing and taking appropriate actions. The farmer has a very important role to play, and he wants it very simple. Education should be aware to train the present and the future farmers.

Aaldrik Venhuizen of Agrifirm Plant  indicates that the advice of precision agriculture depends on the quality and timeliness of the input. Rye culture with more precision largely depend on the maximum utilization of animal manures. Sensors are simply a tool for measuring and monitoring more data. Because measuring is knowing. He also sees that the number of dairy farmers with interest in precision grassland management is still limited. There are also limited experience with different fertilizing strategies for variable rate applications within grassland parcels. He introduces two concepts. The ‘Robin Hood’ model and the ‘King John’ model. In the coming years we have to experiment with farmers and these kind of concepts what fits to Dutch and European grassland management.  Work together with advisors and farmers.

The meeting ended with a short group discussion. It became clear that sensing of grass will be needed in the future, but that we have to learn quite a lot how to involve farmers, students, contractors and advisors in these developments. Will farmers take up the task themselves or will they prefer contractors to do the job. The answer is not needed , but we should be aware of these potential roadmaps. An interesting journey that has started.  

Click here for an impression about the Inspiration Day