DETERMINATION OF WATER-YIELD RELATIONSHIP OF COMICE PEAR {PYRUS COMMUNISL,) VARIETY IRRIGATED BY THE IRRIGATION AUTOMATION SYSTEM (IAS) BASED ON PROGRAMMABLE LOGIC CONTROLLER (PLC)

摘要

The aims of this study are to determine water- yield relationships of Comice Pear (Pyrus communis L.) variety irrigated by irrigation automation system (IAS) based on Programmable Logic Controller (PLC).Irrigation treatments consisted of five different irrigation levels as 120 (I_(120)), 100 (I_(100)), 80 (I_(80)), 60 (I_(60)) and 40 (I_(40)) of the pan evaporation and were carried out in 3 replications according to the design of random blocks. Irrigations were applied to parcels by IAS based PLC when the total amount of water evaporated from Class A Pan was equal to or greater than 35 mm. Soil moisture was measured by sensor (MAS-1) running with dielectric constant of soil in layers of 30 cm at depth of 90 cm of soil profile.Total evaporation of 1104 mm was measured from the Class A Pan by the IAS during the irrigation season. The IAS irrigated Comice pear variety 27 times during irrigation season. The irrigation interval ranged from 3 to 12 days. The amount of water given to the irrigation treatments of I_(120), I_(100), I_(80), I_(60) and I_(40) in each irrigation were 40-62, 33-52, 26-42, 20-31 and 13-21 mm, respectively. The amounts of evapotranspiration (ET) in irrigation treatments were found to be 1287, 1046, 869, 669 and 527 mm, respectively. Under these conditions, the mean fruit yields from irrigation treatments were 15.3, 12.5, 12.6, 11.3 and 9.8 ton per hectare, respectively. Relationships between fruit yield (ton ha-1) and net irrigation water (Inw, mm) and evapo- transpiration (ET, mm) were found as Fy = 0.0062Inw + 7.0091 (R~2 = 0.91**) and Fy = 0.0065ET + 6.552 (R~2 = 0.92**), respectively. The yield response factor (ky) was 0.60. As the amount of the applied irrigation water decreased, pear yield also decreased but IWUE and WUE increased. However, there was no statistically difference among the yields of the irrigation treatments. Irrigation scheduling based on a 0.4 and 0.6 crop-pan coefficients and their treatments are recommended to the pear producers experiencing water shortage. Under abundant water conditions, I_(120), I_(100) and I_(80) crop-pan coefficients and treatments are also suggested. The pear producers should not consider that the shoot length of Comice Pear take as irrigation timing criteria. In addition, the result of study also showed that IAS could be used to control drip irrigation system, Class A Pan, irrigation scheduling, and to calculated ET and to measure soil moisture.