HighlightsAn automated irrigation system based on a novel leachate sensor was built to schedule and deliver irrigation to a container nursery.The sensor network was designed to achieve a 0.15 leaching fraction; it maintained an actual average leaching fraction of 0.17.Water use and container effluent were reduced by 60% and 96%, respectively, without reducing crop growth. Abstract.With the aim of reducing irrigation water use, an irrigation and leachate measurement and control system was developed and evaluated to automatically schedule and actuate irrigation in a commercial nursery. Leachate and irrigation sensors were built using a tipping bucket mechanism and used to calculate the daily leaching fraction (LF) = volume leached/volume applied. For the experimental daily irrigation schedule, the previous day’s LF was used to calculate irrigation run time for the current day using a scaled multiplier, where the change in irrigation run time was proportional to the difference between the calculated LF and the target LF, 0.15. The control zone was irrigated for two hours every other day simulating the commercial nursery’s standard schedule. The irrigation control system worked as designed and correctly imposed the irrigation treatments, including correctly delaying in response to rain and actuating based on a programmed minimum runtime, when necessary. Season-long water use was 60% less for the leachate-based irrigation schedule compared to the grower’s standard irrigation schedule (p = 0.0028). The average daily LFs were 0.17 and 0.73 for the LF-based irrigation and control, respectively (p < 0.0001). Compared to the grower’s standard practice the time averaged irrigation application rate was 3.3-fold less and time averaged leaching rate was 12.1-fold less for the LF-based irrigation schedule. Substrate volumetric water content was not correlated with LF and thus was not a good predictor of leaching fraction. Growth metrics were not impacted by irrigation treatment (p = 0.1429), indicating plants received sufficient water in the LF-based irrigation system. This novel system was able to actuate and adjust irrigation run-time based on daily leaching fraction without being influenced by the lag between irrigation and leaching and had an average leaching fraction within 0.02 of the target LF. Reducing water use with this LF-based schedule has the potential to reduce agrichemical-laden nursery effluent and increase nursery irrigation capacity, i.e., their ability to expand production on the current water supply. Keywords: Container effluent, ET-based irrigation, Irrigation schedule, Leachate, Precision irrigation, Sensor-based irrigation.

HighlightsUsing leaching fraction to schedule irrigation is recommended yet no automated measurement system exists.Sensors were developed to automatically measure leachate and irrigation within a sensor network.There was no difference between sensor measured and manually captured volume for sensors deployed in a nursery.After deployment in commercial nurseries, sensors accurately measured leachate and irrigation within 10% margin.Abstract. Nursery crops are often over-irrigated, resulting in wasted water and agrochemical inputs. Irrigating based on leaching fraction is recommended, yet an automated system for measuring and recording nursery container effluent (leachate) does not exist. The objective of this research was to develop and test a sensor-based system for real-time leachate and irrigation measurement in outdoor commercial nurseries. Sensors were developed to automatically measure irrigation and leachate volume in container nurseries that use overhead irrigation with the goal of facilitating the development of an automated leaching fraction-based irrigation system. Sensors were built using readily available components, including tipping bucket mechanisms calibrated to either 4.7 or 8.2 mL per tip, and were designed and constructed to function with commonly used 3.8-, 11.4-, and 14.5-L nursery containers. Sensor networks were developed in order to collect data from the sensors. Sensors were deployed at three commercial nurseries and tested using closed- and open-loop tests. Initially, a closed-loop test was performed on a subset of the sensors to test the integrity of the sensor-container system when subjected to an overhead irrigation delivery system. Following closed-loop tests, sensors were subjected to tests utilizing directed applications of water to compare sensor measurements with the volume of water applied and to compare sensor measurements over time (pre- and post-season). There was no difference between leachate measured by sensors and leachate captured and measured manually in closed-loop tests (p = 0.0570). In directed applications, sensors measured water flow with less than 3% margin at the beginning of the season (p = 0.0485) and less than 10% margin at the end of the season (p = 0.0390) regardless of container size. Pre- and post-season comparisons showed equivalence at the 10% margin for the 4.7-mL tipping bucket size (p = 0.0043) and at 5% for those calibrated to 8.2 mL per tip (p = 0.0198). Sensors deployed in commercial nurseries accurately measured leachate and irrigation within a 10% margin in real-time, on an individual plant scale, making them a viable option for a leaching fraction-based irrigation schedule. Keywords: Container effluent, Container-grown plants, Leaching fraction, Irrigation schedule, Sensor network.