Study On Micro-irrigation Technique For Mature Walnut And Simulation The Soil Water Dynamic In Root Zone At Arid Region

According to the backward irrigation technology for fruit trees,low irrigation water use efficiency,and baffling development of fruit industry,this paper was conducted to study the micro-irrigation technique for mature walnut and to simulate the soil water dynamic in root zone.The test studied water consumption characteristics of mature walnut under micro irrigation in arid area,selected the micro irrigation technology,and utilized HYDRUS-2D to simulate soil moisture dynamic of walnut trees at root zone.It formulated the reasonable irrigation system to provide technical support for he development of walnut industry.The main conclusions through the experiment are as follows:(1)Irrigation technology and irrigation quota have important influences on water consuming intensity and total water consumption during the growth period.It suggested that during the whole growing period,the overall performance of the daily water consumption was first increased and then decreased,and both of the daily water consumption and whole water consumption under micro irrigation were less than surface irrigation.Under different irrigation techniques, the average daily water consuming intensity of walnut trees increased from 3.82mm/d to 5.36mm/d,and the total water consumption also had the largest amplitude at 270 mm.The daily water consuming intensity under different irrigation quota was below 5mm/d,and the total water consumption was generally at around 950 mm.However,the daily water consuming intensity and total water consumption under surface irrigation were more than 5mm/d and increased about 150 mm respectively. Micro irrigation for old walnut trees during the whole growth period of crop coefficient(KC) generally showed a single peak curve.In the bud, flowering period, fruit expanding stage, hardcore,oil transformation period,and mature period,Kc were 1.02,1.14,1.18,1.32 and 1.12 respectively.(2)Micro irrigation had different effect on leaf temperature,cell sap concentration and leaf water potential.Micro irrigation could significantly reduce leaf temperature and cell sap concentration,and improved leaf water potential,and they were reduced 0.4%~3%, 7.9%~12.6% and leaf water potential increased 8.2%~30.4% than surface irrigation.Among these treatments,irrigation quota 60 mm of pipe 3 processing had the lowest leaf temperature and cell sap concentration.The leaf water potential was maximum.(3)Micro irrigation improved the photosynthesis of walnut trees.The net photosynthetic rate, stomatal conductance and transpiration rate increased 17.3%~22.8%, 22.2%~35.2%, 22.3%~39.2% than surface irrigation.The intercellular CO2 concentration decreased 8.2%~14.9%. The net photosynthetic rate was positively related to atmosphere temperature,transpiration rate,stomatal conductance and water utilization efficiency, and showed negative correlation to the relative air humidity and the intercellular CO2 concentration.(4)Under different irrigation technology, pipe 3 processing had the highest water use efficiency(0.57kg/m3),and the maximal corresponding output(5393.8kg/hm2).Through the analysis of yield and water use efficiency,the best irrigation treatment was pipe 3 processing which was arranged with a line of three tube.Under different irrigation quota,60 mm had the highest water use efficiency(0.68kg/m3),and the maximal corresponding output(6271.0kg/hm2).(5)The cumulative water consumption and yields for walnut trees showed a quadratic parabola relationship.With the increasing of water consumption,walnut yield increased rapidly.When water consumption increased to a certain degree, it began to show "diminishing returns".When water consumption reached 950-10000 mm, production showed the maximum value,and then with water consumption increased, yield began to decline.(6)Micro irrigation reduced the distribution area of the main roots for walnut trees.Among the horizontal direction at 0~120cm,effective root under micro irrigation and surface irrigation accounted for 90.1% and 86.2% in total root(150cm).In the vertical direction at 0-90 cm,effective root was 90.6% and 56.1% respectively.(7)HYDRUS-2D model was verified according to the measured data,and the dynamic changes of soil moisture in the root zone were simulated by this software.It was optimized the irrigation system for the whole growth period of walnut trees.Walnut irrigation system after optimization was 11 times of the total irrigation(excepting winter irrigation).It reduced 2 times irrigation than the initial test scheme.(8)Based on the above results, it showed that sandy loam soil in the condition of micro irrigation for mature walnut trees is 900~1000mm. In the similar area of Xinjiang tarim basin,the recommended irrigation quota is about 950 mm.The key water requirement during irrigation cycle should be 10 ~ 12 days,and the none-critical water requirement period should be 15-18 days.Mature walnut trees can reach the purpose of water saving and high yield.