Ausgabe zur AGRITECHNICA 2019

10 Ausg.Nr._20/2019 irrigation T his year, articles dealing with low water reserves for land used for agri- cultural purposes, the high pre- vailing temperatures or climate change in general often carried the title "Drought in Germany". Hand-in-hand with this, the ne- cessity of irrigation is also be- ing discussed with increasing frequency. The consensus is that irrigation is becoming ever more important to safeguard agricul- tural yields. Many climate model calculations are forecasting an increase in temperatures and dry spells for Germany. Recent studies show that irrigation-worthiness, that is the economically justified use of irrigation, is increasing along with these dry spells. It is there- fore to be assumed that, in the medium to long-term, irrigation will also be extended to crops and areas where it has previously been deemed unprofitable. Planning security is decreasing Planning security for farmers, au- thorities and associations is de- cliningalongwiththisextensionof irrigation to new crops and areas. All stakeholders require knowledge regarding future location-specific and crop-dependent irrigation requirements in order to be able to plan and steer irrigation infra- structure in the long-term. Models for forecasting future, small-scale irrigation requirements estimated on the basis of climate projections, such as those developed for Lower Saxony (LBEG, GeoBerichte 20) or Baden-Württemberg (LUBW, Be- ProBW), may prove helpful in ac- complishing this. Efficient use of water is a key trend Farmers in many locations are already finding themselves con- fronted with water shortages. Together with increasing water requirements, efficient use of water is therefore becoming ever more important in irrigation in order to avoid reductions in crop yield and quality. Developments and innovations in irrigation are gearing up to meet this challenge. The fundamental trend towards continuously reducing water con- sumption is clear, for instance. Irrigation efficiency can essen- tially be achieved in two ways: if the potentially possible water ef- ficiency of the irrigation system that is used is not achieved, opti- mised, location-specific irrigation planning can be implemented to move the actual water efficiency closer to its potential. In addi- tion, the potentially possible wa- ter efficiency itself can be further improved through technical and functional modifications or devel- opments. Irrigation planning is becoming simpler Adapted irrigation planning can be undertaken on the basis of soil moisture data. The develop- ment of dielectric measurement approaches in the 1980s laid the foundations for the development of very good and easily operated sensors for measuring soil water content. A wide variety of these sensors are now available on the market at low cost. A few profes- sional matrix potential sensors are also available; these supple- ment the tensiometers, which re- quire maintenance, that measure the tension or suction that plants' roots must exert to extract water from the soil. However, matrix po- tential sensors with good meas- urement quality are still relatively expensive, which is due to their functional principle. As matrix potential sensors are able to de- termine the optimum start of irri- gation very well, the development of inexpensive matrix potential sensors with good measurement quality is highly desirable. An alternative to soil moisture sensors is the climatic water bal- ance, in which the irrigation time and irrigation level are derived frommeasured weather data (pre- cipitation, temperature, humidity, wind velocity and radiation). The climatic weather balance necessi- tates a nearby weather station to measure the required data. Sup- pliers that have access to corre- sponding measurement networks and data, and are therefore able to offer location-specific plan- ning, have become established. Increasing digitalisation and the possibility of networking sensors have led to the development of new options. Individual sensors (for example rain sensors) can be incorporated in the Internet of Things (IoT), for instance, thus enabling optimised water bal- ancing. The measurement den- sity has also improved due to the integration of private weather stations into publicly accessible weather databases. Remote sensing and irrigation planning Data have to be acquired and pro- cessed, and action instructions regarding the irrigation time and level ultimately have to be issued for irrigation planning. Digitisa- tion has made it possible to ac- quire large volumes of data and quickly process measurement data relevant to planning. On the basis of current soil moisture measurements, key soil param- eters (for example field capacity), characteristic plant properties and the weather forecast, modern systems already enable optimum irrigation planning to be imple- mented easily and quickly, out- put on mobile terminals and also controlled and administered with Trends in irrigation technology Klaus Spohrer