Analisi comparativa di sonde FDR in perlite

In floriculture and horticulture it is necessary to identify precisely the best time to perform the intervention and the volume of water to supply, to get a quality product, but also to safeguard the environment by avoiding unnecessary waste of water and fertilizer and the resulting pollution of aquifers by nitrates. The need for sustainable production processes and a market more exacting, necessarily bring about to develop methodologies to enable a proper and precise irrigation management. The precision required by these methods and the volume of business involved in the production process and in the market justifying investments in well-advanced technology. Automation systems entrusted to timers, to monitoring of environmental parameters such as those based on climate models, or the reading of water potential by tensiometers however, seem to provide answers often inaccurate or related to culture conditions in which they are. The use of sensors able to monitor directly the volumetric water content in the substrate seems to respond appropriately to requirements relating to irrigation management, particularly in hydroponic technology. This category includes impedance probes as the TDR (Time Domain Reflectometry) and FDR (Frequency Domain Reflecotmetry). Although designed for hydrological studies, these probes have found employment in the management of green areas, but only in recent years are beginning to be studied for application in automated irrigation in agriculture, mostly for horticulture and nursery. Several years of experimentation at the CRA-FSO of Sanremo, allowed to evaluate and validate the reliability and efficiency of some type of FDR sensors, then used successfully in some productions on the national territory. The use of such sensors still facing some resistance; this is also due, in addition to general distrust towards investment in new technologies, to the considerable cost of such probes. However, the market began to be present for a wide range of these sensors, which can also be used for growing pots, and in the substrate in bed cultivation, raceways, bags or open field, with very competitive prices. Therefore it seemed appropriate to check the reliability of the cheaper probes compared with that one which higher technological level sensors. It was then prepared an experimental laboratory comparison between the probe ML2x of Delta-T Devices, already widely used in previous tests at the CRA-FSO Sanremo, with two cheaper probes: the 10HS probe by Decagon and the VG400 probe by Vegetronix, in agriperlite with water content at container capacity. In our experience the probe ML2x was, as expected, the most reliable. Nevertheless, the response given by the other two probes was not so bad. From this preliminary analysis it is possible to affirm that the use of sensors of lower economic bracket, characterized by relatively simple technologies and limited and economic material, could be the right compromise between agricultural applications of innovative technology and sustainability of investment costs. With attention in the set-point regulation of the controller or the software used to manage the automation irrigation system, and the possible use of multiple sensors, it is then possible to propose the use of this low-cost technology for the automated management of irrigation (and fertilization) both to flower and vegetable farms that nurseries, as well as possible broader applications in the context of crops