Dr Klaus Spohrer, University of Hohenheim, Institute of Agricultural Engineering
Irrigation is the application of additional water onto the plants if the water reserves in the soil and the natural supply of water, through precipitation, are insufficient for crop production. Although this definition may sound simple, the optimum realisation of agricultural irrigation is a complex affair. The need for irrigation is determined by geographically varying soil characteristics, such as water storage capacity or aggregation stability and by the spatiotemporal change in weather. In addition, the plants’ need for water changes over the individual growth phases and varies between different crops. The consequence is a spatiotemporally heterogeneous pattern of irrigation requirements. The objective of irrigation is to determine the best irrigation time for each crop location and to implement the right irrigation level and the ideal irrigation rate.
Some 100 national and international companies from the irrigation industry are currently offering highly suitable solutions for agricultural irrigation. Mature, proven and new technologies are continually being combined, thus improving the offering.
The trend towards increased water and energy consumption efficiency remains unbroken and is more important than ever before against the backdrop of climate change and the related increase in the need for irrigation, while water resources are dwindling at the same time. In this regard, digitalisation is playing an increasingly important role in irrigation.
Digitalisation enables the collection and speedy processing of large volumes of data. Together with fast data transport, this data enables the connection of and communication between various agricultural machines or systems, something that has been dubbed farming 4.0. Accordingly, the concept of digital irrigation can be taken to mean the networking of systems and components with the objective of optimum irrigation for plants. Depending on which irrigation technology is used, this also enables the partial or even complete automation of irrigation. In this process, smartphones are increasingly becoming the central element for users, who are not only able to monitor the current status of irrigation using corresponding apps, but who can also be warned and intervene if problems arise, for instance, or who can also call up real-time information concerning the plants’ irrigation needs.
Digitalisation and the possibility of processing large volumes of data are the prerequisites for using artificial intelligence (AI). AI will play a significant role in irrigation in the future. AI is already being used to evaluate aerial images today. To do this, the underlying algorithm first learns the relationships between the input variables and the target variable on the basis of training data. Later on, the algorithm is able to derive the target variable value from a specific combination of input variable values based on these learned relationships. In the case of aerial images, input variables are usually light reflections of specific wavelengths or wavelength ranges. Target variables can be spatially resolved information concerning various plant characteristics or also the plants’ water status and therefore regarding the plants’ need for irrigation. However, the use of AI is not limited solely to image evaluation. Data from soil moisture sensors, for instance, can be evaluated by means of AI and used to determine absolute soil moisture values. When planning irrigation, AI can evaluate combined measurement data from various areas (soil, plant, weather) and issue irrigation recommendations for specific locations. At present, the use of AI is still primarily the realm of research projects, but the first aerial image-based AI solutions for irrigation are already available on the market. It is to be anticipated that their number will quickly increase when the corresponding research projects are successfully completed and the products are subsequently monetarised.
Increased efficiency in water and energy consumption can only be achieved through optimised irrigation management. Irrigation management combines all of the activities and functions required to undertake optimum irrigation. These include monitoring the farmland to determine the need for irrigation, planning irrigation activities, controlling irrigation, the integration of warning options in the event of system errors and, by no means least, documentation of the irrigation that is performed.
Monitoring the need for irrigation is still often neglected or only undertaken half-heartedly in agricultural practice. Estimating the need for irrigation and the irrigation level using measured climatic variables (climatic water balance) or registering the soil water reserves by means of soil moisture sensors are state of the art. However, neither of these two approaches are suitable for identifying the aforementioned spatiotemporally heterogeneous pattern of irrigation requirements in detail. Image-based approaches using drones or satellites are promising for achieving this. Services that combine a hydrological plant location model with satellite images, for example, and use this to derive precision irrigation recommendations in a 10 m grid are already being offered. The disadvantages of satellite images are the fundamental possibility of disturbances caused by clouds or the relatively low spatial resolution (pixel size) of the images. Due to the low flying altitude, drone-based imaging is able to offer a significantly better resolution and to identify individual plants or leaves. There are already multiple providers of drone-based imaging for agricultural land that use different cameras (particularly spectral, infrared and RGB cameras) depending on the issue involved.
Irrigation planning is carried out based on the monitoring. It determines the irrigation time, level and duration and is implemented on the field by the Irrigation control system. The complexity of irrigation is especially dependent on the size and number of the designated partial areas that are irrigated uniformly. Consequently, stationary irrigation systems have to be set up so that the designated partial areas can be irrigated individually. In mobile irrigation, changes to the irrigation level and irrigation rate must also be possible during travel, something that has already been implemented in the case of circular irrigators.
Cooperation between specialist fields and manufacturers
The trend towards digitalisation and optimised irrigation management means that the spatiotemporally heterogeneous pattern of irrigation requirements is becoming increasingly better and is enabling optimum (precision) irrigation based on this. However, its implementation necessitates perfect cooperation between diverse experts and specialists from the disciplines of drone flying/satellites, image evaluation, data management and irrigation technology. For instance, it has to be ensured that drone-based irrigation planning can actually be implemented on the field. Since it is very difficult for one supplier or manufacturer to cover all of the necessary specialist fields on its own, the individual products must be compatible with one other. Observations show that interfaces to competitors’ or third-party suppliers’ products are being opened up or newly established or that other forms of cooperation such as the establishment of common data standards are taking place in order to simplify and guarantee data exchange between complementary products.
At present, irrigation developments and innovations are clearly focused on digitalisation and optimised irrigation management. Conversely, the focus has shifted away from irrigation technology, where innovations are limited mainly to improving the existing products. Fundamental technical innovations have been few and far between in recent years.
No irrigation is possible without irrigation technology. Hoses enable water to be transported to and on the fields, control systems control the flow of water, and the water is applied onto the fields themselves with sprinklers, spray nozzles or drip irrigation lines using stationary or mobile systems and machines.
The developments and innovations in digitalisation will be followed by developments to adapt the irrigation technology so that the spatially high-resolution information that is now available can be implemented in the form of precision water application. Solutions for locally variable water application, such as the hydraulic telescopic boom presented at Agritechnica for the irrigator for homogeneously irrigating irregular areas, will therefore become increasingly important. The future will also give rise to further innovations aimed at reducing evaporation losses and preventing seepage during irrigation.
Diverse funding programmes are still available for corresponding applied research and development projects, within which companies from the irrigation industry can also develop and realise innovative ideas together with relevant research institutions.