Using tensiometers for precision microirrigation of container-grown roses

The capability to monitor and control moisture tension in container-grown p lants could be enhanced considerably if precise, reliable measurements coul d be made in the plant root zone. Tensiometers and appropriate computer sof tware and hardware have been used with some success in research application s to schedule irrigation. This research focused on the idea of extending th e use of tensiometers from laboratory investigations to greenhouse growing applications using a system available commercially. A Q-COM computer-contro l system along with tensiometers were used to monitor and control moisture tension for potted mini-roses (Rosa hybrida 'Meidanclar' and 'Meirutral') f or the research reported herein. Control capability for low tension (3 to 6 kPa), medium tension (7 to 10 kPa, 9 to 12 kPa), and high tension (15 to 1 8 kPa) treatments were compared under winter conditions using 10 cm pots, s ummer conditions using 15 cm pots, and autumn conditions using 15 cm pots. All experiments were run in a greenhouse with plants randomly placed on sta ndard benches. The results indicated controlling tension within preset limi ts was more successfully achieved under low-radiation, wintertime condition s (in a northern Ohio climate) than under either a summer or an autumn envi ronment, particularly for tensions above 12 kPa. Reliable stable control of moisture tension within 3 to 6 kPa was achieved all three times of the yea r Growers could expect to be successful at controlling low tensions (3 to 6 kPa) with this system. At higher tensions, the reliability of the system d ecreases substantially.