Study On Water Requirment And Regulated DeficitIrrigation Patterns Of Pear-Jujube Tree

China is a most lack of water resource country among 13 countries in the world, which also is most lack of water and soil resources for average level in the world. The exploitation of water resource has potential, but it is very difficult. So it is nearly impossible to solve agricultural water requirement depending on building new irrigation engineering only [1]. As a result, it has been trend that developing water saving society and agricultural pattern. Furthermore, it is essential to study more water saving irrigation method. The evapotranspiration and regulated deficit irrigation patterns were studied in this paper. Following conclusions were gained: 1) Compared with the sufficient water treatment, the consuming rate of soil water was decreased in all deficit treatments, and the treatment that non irrigation in fruit maturing stage has the most obvious effect. The soil water content at 0-30 cm layer varied significantly after irrigation. And the vertical variation of soil water content mainly concentrated on 0-80 cm layer, but soil water content at 80-100 cm layer did not change significantly. With the increasing of leaf conductance, the slope of photosynthesis rate and leaf conductance is larger than which of transpiration rate and leaf conductance. With the increasing of leaf conductance, the leaf water use efficiency decreased, the maximum value of leaf water use efficiency was got at the minimum value of leaf conductance. The leaf transpiration rate and photosynthesis rate all were decreased for all water deficit treatments. The leaf water use efficiency was elevated by the treatment that was suffered low water deficit during flower-fruit bearing and serious water deficit during fruit maturing, but which was decreased by the treatment that was suffered moderate water deficit during. 2) In the later flowering-fruit bearing stage (16 July) from 14:00 to 17:00 and in the middle fruit speeding growth stage (7 August) from 14:00 to 16:00, the variation of transpiration lagged with solar radiation. The diurnal variation of transpiration and air relative humidity is similar. The diurnal variation of leaf conductance and sap flux is similar, lower in the morning and night, higher in the noon. The fluctuation of leaf conductance is larger than sap flux in the noon, and which is larger for moderate water deficit than sufficient water treatment. Compared with sufficient water treatment, in the sunny day, the starting time for sap flux is similar, but the decreasing time brought forward, the sap flux was not 0 in the night, which maintained 0.1～0.15 l/h. In the rainy day, the sap flux is similar with sufficient water treatment for lower water deficit treatment in flowering-bearing stage and moderate deficit treatment in fruit speeding growth stage, but which is sill smaller for serious water deficit treatment in fruit maturing stage. The compensation of transpiration only was found recovering irrigation after flowering-bearing stage. The relation of daily sap flux and meteorological factors is obvious. During the water deficit stage for fruit speeding growth and fruit maturing stage, the ratio of daily sap flux of water deficit treatment and the controlled treatment increased with the increasing of relative water available content. 3) In 2004, the shoot of Pear-Jujube tree grew slowly in July. The growth rate of shoot was decreased for the treatment that was suffered low water deficit treatment during flower-fruit bearing stage. The influence to tree diameter for all water deficit treatments is similar. The fruit growth curves all are double "S"curves for all treatments. Compared with the controlled treatment, the evapotranspiration was decreased 10.4%, 11.4% and 13.8% for low water deficit during flower-fruit bearing stage, moderate water deficit during fruit speeding growth stage and the fruit maturing stage respectively. The field experimental results indicated that the yield was biggest for sufficient treatment, which is 17484 kg/hm2. Except treatment3, other treatments all elevated the water use efficiency at the yield level. The water deficit did not elevated all indexes for fruit quality, but the treatment that was suffered serious water deficit during fruit maturing stage decreased average fruit weight, Vc content and soluble protein, but elevated the organic acid and soluble solid mater content, so the fruit quality was elevated by this treatment. 4)The transpiration was calculated with Penman-Monteith equation by using critical surface resistance, the results indicated that the measured daily transpiration and calculated daily transpiration was very relative, the R2 is 0.8171, 0.7986, 0.7421 and 0.7725 for sufficient water treatment, treatment2, treatment3 and treatment4. The maximum absolute error and average absolute error is 0.0997m/d and 0.0579mm/d, 0.0978mm/d and 0.0625mm/d, 0.1346mm/d and 0.0847mm/d, 0.1246mm/d and 0.0873mm/d for sufficient water treatment, treatment2, treatment3 and treatment4.