Precision irrigation with sensors has proven to be effective for water saving in crop production. Internet of things (IoT) system is necessary for monitoring real-time data from sensors and automating irrigation systems. Long-range wide-area network (LoRaWAN) is low-cost and easy to be implemented in IoT systems that can be used for precision crop irrigation. In this study, an IoT-based precision irrigation system with LoRaWAN technology was developed and evaluated as a precision management tool on fresh-market tomato production in an open field. Four irrigation scheduling treatments were designed and tested, including ET (ETc), MP60 (Watermark 200SS-5 soil matric potential sensors, -60 kPa), MP40 (-40 kPa), and GesCoN (decision support system). The treatments were arranged based on a randomized complete block design (RCBD) with four replications. System feasibility, yield, and irrigation water use efficiency (iWUE) were evaluated during the experiment. The results indicated that treatment MP60 and GesCoN had a marketable yield 15.2% and 22.1% higher than ET, respectively. MP40 had a marketable yield 12.5% lower than ET. GesCoN had a significantly higher yield than ET and MP40. However, MP60 did not produce significantly different results from GesCoN and ET but had higher yield than MP40. MP40 received relatively low water via irrigation because of unproper installation and positioning of the soil moisture sensors, which caused a higher incidence of blossom end-rot and thus lower marketable yield. Nevertheless, the LoRaWAN-based IoT system worked well in terms of power consumption, communication, sensors reading and valve control. It can be potentially implemented for precision and automatic irrigation operation in vegetable fields.