Klaus Spohrer, Christof Hübner, Kai Jotter, Tino Wagenknecht, Gaprindashvili, Köller, Karlheinz
Site specifi c drip irrigation with wireless sensor networks in grapevine production Increasing world population and climate change call for improved water use effi ciency in agricultural irrigation practice. Site specifi c drip irrigation has the potential to meet this needs, because water is optimal applied with respect to quantity and location. Since spatial information about the water demand is mandatory, a wireless soil moisture sensor network was developed to identify spatial soil water
more » ... patial soil water content differences. A pressure-driven fl ow valve was designed in order to realize independent irrigation of single dripline sectors. The investigations exemplarily took place in a drip irrigated vineyard. Abstract Landtechnik 66 (2011), no. 1, pp. 22-25, 4 fi gures ■ Drip irrigation plays a key role in optimizing water use and distribution, since water is applied precisely and water losses (evaporation, seepage) are reduced. Site specifi c irrigation (precision irrigation) plays another key role. Site adapted irrigation takes spatial differences in water availability and water holding capacity of the soils into account, which both depend mainly on spatial differences in soil hydraulic properties and topography. Hence, the combination of drip irrigation and site specifi c irrigation is most promising for increasing water use effi ciency. Spatio-temporal information about the soil water balance are mandatory for scheduling site specifi c drip irrigation. In addition, technical solutions are required for its realization. Different irrigation treatments are possible for different dri-plines but not easily practicable along single lines. In the framework of a research project funded by the BLE (Bundesanstalt für Landwirtschaft und Ernährung), a wireless sensor network was developed. It serves for collecting soil moisture data measured with spatially distributed soil moisture sensors as basis for site specifi c irrigation planning. The research took place within a dripline irrigated vineyard. A further research objective aimed on site specifi c drip irrigation and thus on the realization of different irrigation treatments along single driplines. Wireless sensor network Spatio-temporal soil moisture information can be obtained by wireless data transfer from sensors installed in sub-areas to a central station. Subsequently, sampled data of the central station is sent to a web-based data base by mobile radio. The data stored can be read out, displayed and further used for site spe-cifi c irrigation planning (fi gure 1). Soil moisture measurements were realized with dielectric sensors of the Hochschule Mannheim (fi gure 2). The electromagnetic permittivity of a soil depends mostly on its water content and can therefore be used as a measure for calculating soil water content. A sensor consists of a ring oscillator circuit on a fi berglas-strengthened printed board which will be embedded in the soil. Depending on the soil water content, the electrical permittivity is changing and as a consequence the frequency of the ring oscillator is changing as well. This frequency is counted by a micro-controller and transferred in soil water content information in which the infl uence of temperature is accounted for. The calculation algorithm is based either on a soil specifi c calibration or an empirical relation. The output of the sensor can be provided as an analog voltage or current signal or by using digital interfaces (RS485, RS232 or USB). The wireless sensor network was developed in order to transfer the measurement results from the soil moisture sensors to the central station. It consists of wireless nodes operating in the 868 MHz-frequency range. The line of sight propagation range is up to 20 km. Even though the range is distinctly smaller in vineyards due to the attenuation effects of metal supporting wires and vegetation, it is still suffi cient for the described purpose. The data transmission interval from a node to the central station can be adjusted by the user. The current supply