Scientists at the Universitat Politècnica de València have combined images provided by European and American remote sensing satellites to diagnose the irrigation status of citrus fields, as well as other crop characteristics such as vegetation cover or plant vigour.
The project is the result of an experiment carried out by the Hydraulic Networks and Pressure Systems research group at the UPV’s Institute of Water and Environmental Engineering (IIAMA) with the goal of improving irrigation planning and the management of plant stress levels.
The new system enables the precise calculation of plant stress levels, analysing real evapotranspiration rates and comparing them to the plants’ optimal hydration needs. This flags up stress levels outside the tolerance threshold due to over or underwatering.
Furthermore, the system is almost entirely automated and enables monitoring on a very large scale, maximising overall production.
Professor Miguel Ángel Jiménez of IIAMA said: “What we do is analyse the thermal imaging data obtained via satellite, which tells us the temperature of the crop and allows us to infer their hydraulic stress. The underlying methodology was developed in Holland and the US, but we took it and adapted it for citrus tree cultivation”.
The system allows irrigation to be scheduled on a weekly basis, adjusting the levels of water delivered to the crops in response to observed stress levels and weather forecasts for the coming days.
“This means that decisions can be made in the moment, diverging from traditional methods where decisions are made based on pre-existing climate data and not on what is expected to happen in the future,” Jiménez said.
“At certain times of the year, in the summer, for example, it is not a bad thing that a citrus plant is around 20 to 30 per cent stressed”, he continued. “All this means is that the amount of water it is being supplied is 20 to 30 per cent less than what has been established as creating optimal conditions of zero stress and does not impact on final yields”.
The irrigation model also strives for an efficient use of water to enable maximum yields with minimum water levels. After three years of scheduling irrigation across various plantations, production has been confirmed as higher than average. A set of recommendations was issued to each citrus farm freeholding, indicating maximum and minimum water thresholds for each group of plants.
The system is currently being applied at local level in the Valencian municipality of Picassent, having already validated the model in collaboration with the Valencian Institute of Agrarian Research (IVIA) in Reva.
Space technology is becoming increasingly important to large-scale agriculture, with innovation driving down the cost of getting a satellite into orbit. E&T reported on this in detail in our feature on farming from space.