Dielectric moisture sensors are particularly suitable to manage irrigation in soil-less greenhouse production. Identifying the practical effects of substrate water content on crop performance is crucial for sensor-based irrigation.
A) Main network control unit (MNCU); B) wireless SDI-12 Host Node (WSHN).
"We have designed and manufactured a cloud-connected system prototype for wireless sensor-based irrigation management and tested it on basil plants cultivated in a perlite-coco (1:1 v/v) soil-less substrate in greenhouse conditions," explained Francesco F. Montesano from CNR-ISPA. The experiments carried out assessed:
- the effects of a progressive decline in substrate water availability corresponding to moisture levels from water holding capacity up to 0.10 m3/m3, on gas exchange parameters and leaf water status;
- the short-term recovery response of plants when re-watered after substrate water content decreased to different levels;
- the effects of different irrigation set-points (0.40, 0.30 and 0.20 m3/m3) and leaching rates (≈8% or ≈18%) on crop performance over a complete growing cycle."
Humidity/ salinity dielectric sensors were used (GS3, Decagon Devices, Pullman - WA, USA).
No physiological stress responses were observed on basil plants when moisture level was higher than approx. 0.20 m3/m3, while plants showed drought symptoms at approx. 0.17 m3/m3, corresponding to a substrate matric potential and hydraulic conductivity of -300 hPa and 0.0005 cm/day, respectively. Nonetheless, photosynthesis and leaf water potential recovered to values similar to non-stress conditions (with moisture level as low as ≈0.10 m3/m3) when irrigation restarted.
Basil growth was similar when plants were grown with irrigation set-points of 0.40, 0.30 or 0.20 m3/ m3 for a complete growing cycle. Fresh weight tended to increase when a higher leaching rate was used, probably because leaching lowered substrate EC. Water use efficiency (basil fresh weight/unit water used) remained unvaried with different irrigation and leaching rate levels.
"Results show that a network of wireless sensors for the real-time sensing of substrate water status, combined with precise information on the effects of water availability levels on plants, is an effective tool for precision irrigation management of soil-less greenhouse basil," states Francesco Montesano.
"Results show that a network of wireless sensors for the real-time sensing of substrate water status, combined with precise information on the effects of water availability levels on plants, is an effective tool for precision irrigation management of soil-less greenhouse basil," states Francesco Montesano.
Source: Montesano Francesco Fabiano, van Iersel Marc W., Boari Francesca, Cantore Vito, D’Amato Giulio, Parente Angelo, 'Sensor-based irrigation management of soilless basil using a new smart irrigation system: Effects of set-point on plant physiological responses and crop performance', 2018, Agricultural Water Management, Vol. 203, pag. 20-29.