2017 ASHS Annual Conference

Cyclic irrigation is an established basis for nursery crops irrigation scheduling that can improve efficiency and reduce water use and leachate volume, while increasing plant growth. Daily water use is a newer scheduling basis that replaces the volume of water used in evapotranspiration in the previous 24 hours. The objectives of this experiment were to develop a tri-daily water use (TDWU) schedule and evaluate the differences between the TDWU system and a nursery’s cyclic irrigation program on C. kousa var. chinensis ‘Milky Way’ and C. florida‘Cherokee Princess’ trees. The sensor-based, TDWU irrigation schedule compares the current moisture level to container capacity three times per day, each time irrigating with the volume needed to return the container to container capacity. The TDWU zone for ‘Milky Way’ was programmed to compare VWC and irrigate accordingly at 1:15am, 10:00am, and 2:05pm. The TDWU zone for ‘Cherokee Princess’ was programmed to compare and irrigate at 1:45am, 10:30am, and 2:25pm. The cyclic zones for ‘Milky Way’ and ‘Cherokee Princess’ were irrigated approximately 1 hour after the nursery’s overall program, which begins operating at 2:10am, 11:00am, and 5:45pm. Container volumetric water content (VWC), daily and cumulative water use, and plant height, caliper, and quality were measured on ‘Milky Way’ and ‘Cherokee Princess’ dogwood trees produced in zones to which either the experimental TDWU or the nursery’s standard cyclic irrigation (3 cycles/day) were applied. On September 16, 2016, ‘Milky Way’ height was 148.1 cm and 128.4 cm for the TDWU and cyclic, respectively and 91.2 cm and 114.5 cm for ‘Cherokee Princess’ in TDWU and cyclic, respectively. ‘Milky Way’ caliper was 13.6 mm and 13.0 mm, respectively, and 10.4 mm and 14.4 mm for ‘Cherokee Princess’ in TDWU and cyclic, respectively. From August 1-29, 2016 the ‘Milky Way’ and ‘Cherokee Princess’ cyclic irrigation zones used 14,274 gallons while the TDWU ‘Milky Way’ zone used 11,065 gallons, 23% less and were of a comparable quality. ‘Cherokee Princess’ TDWU zone used 7,510 gallons, 47% reduction in water use, but trees were not of an acceptable quality. Daily minimum VWC for ‘Milky Way’ was 27% and 24% for TDWU and cyclic, respectively, and for ‘Cherokee Princess’ was 29% and 27% for TDWU and cyclic, respectively. Later potting date, extreme and prolonged summer heat, and a brief period of low VWC while establishing the system may have contributed to reduced growth and quality of ‘Cherokee Princess’.