Study Of Regulated Deficit Irrigation On Drip Irrigation Walnut Tree Physiological Ecology And Root System Simulation

Walnut tree planting plays an important role in southern Xinjiang,aiming at the goal of vigorously developing high-efficiency water-saving irrigation of walnuts.In the forest and fruit experiment base of Xinjiang Agricultural University in Hongqipo Farm,Wensu County,Xinjiang,a simulation study on the physiological ecology and root system of walnut trees under drip irrigation conditions was carried out.The experiment used"Wen 185"as the research object,and set two levels of mild（75%ET_c）and moderate（50%ET_c）treatments during the germination stage and the flowering and fruit bearing periods.The combination of the germination stage+the flowering and fruit bearing periods was slightly adjusted.The deficit treatment and the control group were fully irrigated during the whole growth period（ET_c）.The experiment studied the growth and ground temperature of walnut trees under different water deficit treatments,the characteristics of water consumption,yield and water utilization of walnut trees,and Hydrus-2D was used to simulate root water absorption,and the following main conclusions were drawn:（1）After adjusting the deficit and rehydrating in the budding period,the SPAD value showed as mild water deficit>control group>moderate water deficit.Water deficit during the flowering and fruit bearing periods and the continuous water deficit during the germination stage+the flowering and fruit bearing periods.After rewatering,each treatment is always greater than the value of normal irrigation.The fruit volume of each treatment of regulating deficiency was larger than that of the control group.（2）Compared with the control group,the stomatal conductance,transpiration rate and intercellular CO₂concentration of walnut decreased during the flowering and fruit bearing periods,the germination stage+the flowering and fruit bearing periods.The transpiration rate was lower than the control group.The concentration of intercellular CO₂ decreased with the increase of the degree of regulation deficit.The photosynthetic characteristics of different treatments in different growth periods have compensation effects after rewatering during the flowering and fruit setting period and the fruit expansion period.（3）Water is deficient during the flowering and fruit setting period,and the ground temperature rises with the increase in the degree of regulation deficit.Mild water deficit increased by 2.20℃,moderate water deficit increased by 2.53℃.With the increase of soil depth,the fluctuation range of ground temperature gradually decreases,and the larger range of soil temperature change is 5～10 cm below the ground surface.（4）The light and moderate regulated deficit irrigation was applied during the germination period,and the water consumption intensity and total water consumption were reduced by 21.50%,32.35%,2.12%,and2.62%respectively compared with the control group;the flowering and fruit setting period was reduced by21.65%,30.52%and 2.74%,4.06%;continuous mild adjustment loss decreased by 21.88%,23.03%and4.10%.The stage water consumption intensity and stage water consumption of the fat conversion period are the largest.（5）Compared with the control group,all deficit-regulated treatments can increase the yield,water use efficiency and irrigation water use efficiency of walnut trees.Among them,mild water deficit treatment performed the best during the flowering and fruit bearing periods,which were 6751 kg/hm²,0.92 kg/m³ and0.81 kg/m³,respectively;Through the Criteria Importance Though Intercrieria Correlation（CRITIC）evaluation,the highest score is the mild deficit adjustment treatment during the flowering and fruit bearing periods.Therefore,the best irrigation treatment to achieve a win-win situation for walnut tree yield and water use efficiency is the mild deficit-regulation treatment during the flowering and fruit bearing periods.（6）The total root length and root dry weight distribution were different in the treatment of light regulation deficit during flowering and fruit setting period and the treatment of germination stage+light regulation deficit treatment during flowering and fruit setting period.In the horizontal direction,the total root length of the two treatments was the largest at 30～60 cm,accounting for 24.25%and 23.19%of the total root length.In the vertical direction,the total root length of the two treatments was the largest at 40～60 cm and20～40 cm,accounting for 22.64%and 41.30%of the total root length.In the horizontal direction,the root weights of the two treatments were the largest at 0～30 cm,which were 31.58 g and 20.24 g,respectively.In the vertical direction,the root weights of the two treatments were the largest at 20～40 cm,which were 34.08g and 30.28 g,respectively.（7）The results of using the Hydrus-2D model to simulate the root water absorption of the mild deficit treatment during the flowering and fruit bearing periods are better.Therefore,it is reliable to use the Hydrus-2D model to simulate the root water absorption and soil water transport.