Antonio Álvarez, Agrifood journalist

On-site sensor systems as a technological solution to increase yields in horticultural holdings.

One of agriculture’s great present-day challenges is how to produce more with less. According to FAO estimates, in 32 years, that is, in 2050, some 9 billion people will be living on Earth, which will make it necessary to increase the production of certain basic foods such as fruit and vegetables. To achieve this, it seems unquestionable that new technologies will play a fundamental role in how we produce more at a lower cost and through more sustainable practices that respect the environment.

Spain is the second largest fruit and vegetable producer in the European Union and the sixth largest in the world. With an annual production of some 26 million tons and a value exceeding €13 billion, according to data from the Ministry of Agriculture, Fisheries, Food and Environment, the fruit and vegetable sector is one of the most powerful in agriculture.
In total, more than 400,000 people work in the horticultural sector, representing 50% of agricultural employment, according to data from the Spanish Federation of Associations of Fruit and Vegetable Growers/Exporters (FEPEX). All areas of Spain produce fruits and vegetables.

But it is in the Mediterranean arc, which is Andalusia, Extremadura and the Canary Islands, where most of the activity is concentrated. Precisely, areas where agriculture is more conditioned by water scarcity. That is why technology has become a great ally in irrigation efficiency improvements. And here sensor systems play a key role. A tool that is being applied differently, but with a common goal: to achieve precision agriculture that helps producers in decision-making.


An example in Andalusia
This is well known to Karl Vanderlinden, of the Institute for Research and Training in Agriculture and Fisheries (IFAPA) of the Junta de Andalucía. This Belgian who lives in the south of Spain explains when and where sensor systems were applied for the first time. “It was in the eighties in the United States. A sensor designed exclusively in agriculture was developed to measure the apparent electrical conductivity of the soil. We are talking about an electromagnetic induction sensor based on the principle of the current that is generated by a magnetic field”.

There have been many studies since then. First in American universities and, since a few years ago, also in Europe. As Vanderlinden himself does at IFAPA, where he is part of the AGROINNOSENS project that aims to publicise and introduce electromagnetic induction sensors in several crops, including fruit and vegetables, implementing this technology to delimit uniform management areas and estimate productive potential, as well as the soil’s water storage capacity and the 3D spatial distribution of salinity.

They achieve this with a non-invasive sensor system, which gives it a pioneering character, “We have a sensor with four bovine combinations that are at different distances, which allows us to obtain four signals of apparent electrical conductivity”, Vanderlinden explains. A tool they carry in a striking plastic ‘sleigh’ pulled by a quad: “At a speed of five kilometres per hour, we can obtain a map of a two-hectare plot. With this type of precision agriculture, we get to see how irrigation and agricultural work is affected on the plot”, says the IFAPA researcher.
As with doctors after an X-ray, this non-intrusive sensor system provides the producer with greater knowledge when making a decision about how much to fertiliser to use or where there is a greater need for water.

Indeed, for Vanderlinden, the sensor system is fundamental in moving the optimisation of irrigation forward. “For example, to apply patterns in precision irrigation through sensing soil moisture”. A path that his research group started on an olive grove in Écija where, with the ‘sleigh’ of geophysical sensors, they managed to map out 38 hectares of land with the idea of, subsequently, configuring the irrigation system in accordance with each area’s needs. This is what is known as Variable Rate Irrigation: “With pivots or rangers and today’s technology, we can vary the amount of water from each sprinkler. Even modifying the speed with which the machine moves from side to side to vary the pattern of application of water”. However, lack of personnel has, according to Vanderlinden, kept this project inactive.


From Andalusia to Extremadura
Another benchmark in sensor system research in fruit and vegetable holdings is Carlos Campillo, from the Centre of Scientific and Technological Research of Extremadura (CICYTEX). He has been working in this field for more than 20 years to improve decision-making in agricultural practices in order to save inputs. According to Campillo, there is a lot of technology, but the problem is that, generally, it is not applied correctly, either due to budgetary limitations or lack of knowledge.

Thus, with the aim of promoting dissemination of knowledge, the European Union is developing the Fertinnowa knowledge exchange platform, a database where innovative technologies and practices for fertirrigation of horticultural crops can be put to good use. “It is information available for farmers to put into practice on their holdings”, ​​explains Campillo, who is currently working on automating irrigation through information obtained from sensor systems.

He is doing this on a farm of two hectares of plum trees in Villafranco del Guadiana (Badajoz). “Work stemming from a previous project that worked very well on a commercial olive grove where we control four hectares. Using sensors, we manage to save between 10% and 15% of the water”. The reduction in water was accompanied by an increase in production.

However, this expert believes that sensor systems still have a long way to go regarding their use to determine nutritional models in plants. “The problem is that there are no probes which measure continuously. To do this, measurements must be taken in the field. In a tomato farm project, we saw that on certain parts of the plot there was more fertiliser than others, which could have reduced the expenditure”, explains Campillo.

And how are you working in this regard? Through systems which measure electrical conductivity of the soil. “It is a sensor that measures the terrain’s parameters of texture, salinity and humidity. In three or four hours we can measure 60 or 70 hectares to measure soil sampling. The results can be used to make maps of the nitrogen content of the whole plot. Thus, we can help farmers when they fertilise and, consequently, make savings on fertiliser”.


And back to Andalusia
Another example of what the sensor systems of horticultural farms have achieved can be found in Huelva. Spain is the leading producer of strawberries in the European Union, and 95% of this fruit comes from the province of Huelva. Here, farmers in the area have an additional environmental limitation: the Doñana National Park. The marshes of this natural landscape are in danger, so water saving with regard to the surrounding crops is even more crucial.

A group in the Hydraulic Engineering area, from the University of Córdoba, managed to save up to 18% of water used on a farm of almost 1,500 hectares of strawberries, maintaining production and quality. On 1,223 of the 1,401 hectares where they worked, they achieved an average saving of 1,416 cubic meters of water per hectare, which meant a cut in water expenditure of almost 20%.

How did they do it? In three phases. “We started in 2010. In the first stage, we monitored the use of water on several farms working in collaboration with farmers. In the second stage, we analysed the problems and looked for a solution. And finally, we installed the precision system”, explains Manuel Martín, an engineer from the University of Córdoba and one of the members of this project that concluded in 2016. The objective was to determine the timing, frequency and time of irrigation according to the characteristics of the crop, climate and soil.

Therefore, moisture control in the soil profile was one of the pillars of the project. They used humidity probes that allowed them to get to “know the behaviour of the humidity bulbs and determine if the irrigation was excessive or deficient. The normal thing is to use capacitive humidity probes (FDR), installed at three depths: 12, 25 and 40 centimetres and connected to a datalogger that records data every 15 minutes”, as detailed by this group of hydraulic engineers from the University of Córdoba in the project’s conclusions document.

From this work, ‘Irrifresa’, an application for mobile devices, was created by which farmers can make an optimal irrigation schedule for the cultivation of strawberries based on data obtained from the farm’s sensor systems. It is a freely available piece of software, which farmers can use to keep daily control of the cultivation area and schedule its irrigation according to the plants’ needs.

One more step in the development derived from the application of new technologies to agriculture. With ‘Irrifresa’, the producer has all the information provided by the sensors installed in the plot in the palm of his hand. Thus, he can schedule the time of irrigation the plot requires to achieve a good saving in water, which is good not only for his pocket, but also for the future of the planet.