Nitrogen leaching is one of the main ways of nitrogen loss， which not only reduces nitrogen use efficiency， but also causes serious water pollution and other negative effects. In the drip irrigation with the Yellow River water， flocculation and sediment are produced when Water Dream adsorbent is used to separate water and sediment. In order to effectively utilize the flocculation and sediment resources， the waste resources can be reused. This paper discussed the effect of flocculated sediment on the hydraulic characteristics， nitrogen leaching loss， pH value and conductivity of moderately salinized soil through the indoor soil column simulation test. Five treatments were set up in the experiment. The proportion of flocculated sediment was 0 （CK）， 20 （T1）， 40 （T2）， 60 （T3） and 80 （T4） g / kg， respectively. Each treatment was repeated for three times. The results show that the application of flocculated sediment can improve the hydraulic characteristics of salinized soil， and the water holding capacity of T1， T2， T3 and T4 increases with the increase of the proportion of flocculated sediment； the flocculated sediment can effectively improve the nitrogen holding capacity of sandy loam， and the nitrogen concentration in the soil leaching solution decreases with the increase of the proportion of flocculated sediment. Compared with CK， the total amount of nitrogen leaching in T1， T2， T3 and T4 leaching solution decreased by 3.4%， 6.18%， 8.06% and 11.27%， respectively； the pH value of salinized soil was not significantly affected by flocculated sediment； when the amount of flocculated sediment was less than 60 g / kg， the soil conductivity value could be reduced， but the effect was not significant. When the amount of flocculated sediment is 40~60 g / kg， it can effectively change the physical and chemical properties of salinized soil， reduce the amount of nitrogen leaching， improve the efficiency of nitrogen utilization， and reduce the risk of non-point source pollution of groundwater.

The study of soil water and solute migration during freezing-thawing process is an important basic content in the fields of prevention and control of freezing damage in civil engineering， soil and water environment protection， land water circulation， soil secondary salinization and so on. In this study， the migration of salt （Cl^-， Ca²⁺ and available P） in four soils with different textures during freezing process in Xiqing District and Jinghai District of Tianjin was studied by laboratory experiments. In this experiment， the laboratory short soil column method was used to freeze the soil samples， and the chemical analysis of salt was carried out by titration and colorimetric method. The results showed that there were great differences in the salt transport among different soils under the same added salt in the process of the soil freezing， and there were great differences in the migration of the salt in the same soil under different added salt in the process of the soil freezing. The salt migration was affected by the interaction between the soil and the salt addition.

In order to improve the water and fertilizer utilization efficiency of integrated water and fertilizer under drip irrigation under film， taking Shihezi surrounding farmland saline soil as the research object， the indoor soil box infiltration test was carried out， the different timing of W， W-N， N-W， W-N-W， W-W-W， W-W-N， N-W-W， N-W-N-W， N-W-W-N， W-N-N-W （W stands for pure water irrigation， N stands for liquid fertilizer irrigation） under the condition of wetting front， the cumulative infiltration and infiltration rate were observed， to analyze the influence of different nitrogen application time sequence on the infiltration characteristic parameters. The results showed that the horizontal migration distance and vertical migration distance of wetted front were significantly affected by nitrogen application sequence in the same time. At the end of the experiment， the horizontal migration distance of wetted front was 21.28%， 13.95%， 21.28%， 9.76%， 22.92%， 17.78%， 26.00 %， -2.78% higher than that of the W treatment under different nitrogen application sequence. The vertical migration distance was 14.67 %， 14.67 %， 28.00 %， 36.00 %， 22.67 %， 28.00 %， 22.67 %， 30.67 %， lower than that of the W treatment， respectively. The wetting ratio of nitrogen treatments was significantly higher than that of the W treatment， and the variance of N-W-W-N was small， namely 0.14； At the end of irrigation， the cumulative infiltration amount under N-W-W-N was 20% higher than that under W-N-W （commonly used in the field at present）， and the cumulative infiltration rate was the highest， which was 17.98 mL /min. In conclusion， the infiltration performance of N-W-W-N time series treatment is better than that of W-N-W time series treatment， and the wetting ratio is stable and the variation degree is small. N-W-W-N should be considered and applied to the field， so as to further compare with W-N-W and lay a foundation for the efficient utilization of water and nitrogen for automatic drip irrigation under film in the field.

With the continuous increase of urban green area， the contradiction between water consumption and water resources shortage is becoming more and more obvious. It is the trend to promote the application of water-saving irrigation technology in cities to solve the problem of water shortage. So， based on the comparison of the technical characteristics of different water-saving irrigation systems， such as sprinkler irrigation， micro sprinkler irrigation， drip irrigation， moistube irrigation and trace irrigation， the water consumption and total investment of five types of water-saving irrigation systems are compared and analyzed based on scenario hypothesis. On this basis， the applicability of the five types of water-saving irrigation systems to reclaimed water is discussed. Finally，the irrigation system suitable for different urban green space forms is put forward. The results show that： compared with drip irrigation system， the annual water consumption per unit area of moistube irrigation system and trace irrigation system is reduced by 39.6% and 42.4%， respectively； the investment per unit area of moistube irrigation and trace irrigation system is the highest， which is 8.09 yuan/m² and 8.02 yuan/m² respectively； The anti-clogging performance of sprinkler irrigation system is the best when reclaimed water is used as water source， followed by micro sprinkler irrigation， moistube irrigation and trace irrigation， and the anti-clogging performance of drip irrigation system is the worst； Considering the technical characteristics， water consumption， total investment and applicability to reclaimed water of different water-saving irrigation systems， it is suggested that the application of micro sprinkler irrigation and moistube irrigation system in urban green space should be promoted. This paper aims to provide reference for the popularization and application of water-saving irrigation technology in the city.

In order to solve the problems of unreasonable specifications of farmland border irrigation， low irrigation efficiency， and waste of water resources， this study used a combination of two field irrigation experiments and WinSRFR 5.1 model analysis to simulate the surface irrigation flow process and irrigation quality. In the first year， soil infiltration parameters （infiltration coefficient and infiltration index α） were determined by field irrigation combined with WSRFR 5.1 model. In the second year， field measured irrigation was used to verify the model， and uncertainty analysis of parameters was carried out according to the irrigation quality contour map simulated by WSRFR 5.1 model. The results show that the uncertainty of irrigation technology is closely related to the parameters of irrigation technology. Border length and flow have a great impact on irrigation efficiency and irrigation uniformity. Irrigation efficiency is more sensitive to uncertainty factors than irrigation uniformity. According to the contour map of irrigation water quality， the combined range of border length and flow rate that meets the requirements of irrigation water quality is obtained. The border length is within 30 m， and the increase of single-width flow has little effect on irrigation quality； The border length is 30~53 m， and the single width flow rate is 2.7~5.7 L/（s·m）； the border length is 50~100 m， and the single width flow rate is ≥3.34 L/（s·m）； the border length is 100~150 m， and the single width flow rate is ≥6 L/（s·m）.

Rhododendron， the king of woody flowers and the city flower of Changsha， is widely used in sponge facilities in Changsha. In order to increase the drought resistance and ornamental of Rhododendron in sponge facilities at a lower cost， the Rhododendron were planted in the soil of original soil， coconut sugar soil （ratio of coconut bran： coarse sand： original soil was 2：4：4）， rice bran soil （ratio of corn bran： coarse sand： original soil was 2：4：4）， sawdust fine sand （ratio of sawdust： fine sand： original soil was 2：4：4）， sawdust coarse sand soil （ratio of sawdust： coarse sand： original soil was 2：4：4）. The growth and drought insistence were determined by physiological indexes and water content in leaf. The results showed that the plants in the original soil died after drought for 30 d， which embodied the decreasing of maximum photosynthetic rate， ETR， qP， Fv/Fm and respiratory rate， but the decreasing of different indexes were different. After treated with drought for 30 d and re-watered for one week， Rhododendron in coconut soil， rice bran soil， sawdust fine sand soil and sawdust coarse sand soil recovered. The changes indicated that the water holding capacities of coconut soil， rice bran soil， sawdust fine sand soil and sawdust coarse sand soil were enhanced， which could enhance the drought resistance ability of Rhododendron. The correlation analysis of indexes showed that leaf water content， maximum photosynthetic rate， light compensation point and respiration rate were significantly correlated with other indexes. Principal component analysis showed that qP， ETR， leaf water content， chlorophyll content， Fv/Fm and light compensation point could better reflect the drought resistance of Rhododendron. Cost analysis showed that the cost of sawdust coarse sand （treatment Ⅲ） was the lowest. The proportion of sawdust and coarse sand for soil improvement in sponge facilities can not only increase the drought resistance of Rhododendron， but also have low cost， which is worthy of promotion.

Investigating the effects of water deficit on the growth and development of green pepper at different growth stages with rainwater harvesting is not only critical to further understanding the physiological mechanism of highly water use efficiency and crop yield in arid areas， but also helpful for making scientific regulated deficit irrigation models. In this study， five modes of regulated deficit irrigation （full irrigation， FI， mild regulated deficit SSMD at seedling stage， severe regulated deficit SSSD at seedling stage， mild regulated deficit FSMD at flowering stage， and severe regulated deficit FSSD at flowering stage） were conducted to examine the effects of water deficit at different growth stages on stomatal traits， growth processes and plant biomass of green peppers （Capsicum annuum var. Zhongjiao 107）. These results showed that： ① The stomatal length and stomatal circumference on the proximal surface could be significantly increased by regulated deficit treatment at the seedling stage of green pepper， but the stomatal density and stomatal width on the distal surface were significantly reduced， and the stomatal length， width and stomatal circumference were significantly increased by water deficit at the flowering stage of green pepper. ② Plant height and leaf area index of green pepper under full irrigation were better， while stem diameter and leaf area index of green pepper under various regulated deficit treatments were significantly higher than that under full irrigation. ③The total biomass of green pepper was the highest under mild regulated deficit irrigation during flowering， and the water content of plant tissues was the highest under mild regulated deficit irrigation during flowering. These results suggested that mild deficit regulation at flowering stage was particularly important for the growth and biomass accumulation of green pepper. The results will provide theoretical basis and data support for the establishment of precise deficit irrigation mode for green pepper planting in the North China Plain.

In order to understand the performance of different soil water sensors， this paper took the frequency-domain reflective （FDR） soil water sensor， which is most widely used in China， as an example. Considering the current new type of tubular probe structure， three domestic mainstream FDR tubular sensors （serial number Q1， Q2 and Q3） were selected to carry out field performance test for 261 days. The results showed that the variation of soil water content curve monitored by the three sensors was consistent， and the peak value occured when there was rainfall， and the fluctuation range of surface soil water content curve was larger than that of deep soil. However， the absolute values of the three species were quite different， and the coefficient of variation of soil water content ranged from 0.20 to 0.58. The observed values of the three sensors were greatly affected by temperature. The variation coefficient of surface （0~20 cm） soil was greater than that of deep soil， with an increase of more than 38%. The coefficient of variation of soil moisture content in summer （June to July） was higher than that in other seasons， with an increase of 16%. Through data fitting of sensor observations and manual observations， the in-situ secondary calibration equations of three kinds of sensor soil moisture were established respectively， which effectively reduced the coefficient of variation between sensors by 53%~66%. Therefore， in farmland applications， the influence of soil temperature and soil type factors on the in-situ secondary calibration of FDR sensors should be considered to eliminate the differences in calibration of different sensor factories.

Based on the measured data of the weighing lysimeter and the soil evaporator, the dynamic changes of the evapotranspiration (T), surface evaporation (E) and total evapotranspiration (ET) of eggplant plants in the greenhouse in autumn were analyzed, and the Pearson correlation analysis method was used to study the relationship between the water consumption of eggplant in the greenhouse and the main meteorological factors, the path analysis principle was used to analyze the direct and indirect effects of each meteorological factor on T, E and ET, and a multiple regression equation was established. The results showed that the ET of the whole growth period of the autumn eggplant in the greenhouse was 254.91mm, of which T and E were 134.97mm and 119.54mm, respectively, accounting for 53% and 47% of the total evapotranspiration. The T, E and ET of eggplants in the autumn in the greenhouse all showed a single-peak curve with the growth period. The surface evaporation of eggplants was dominated by surface evaporation, accounting for 57.13% of the total evapotranspiration. The transpiration of eggplant plants during the flowering and fruit setting and mature periods increased significantly. The ratio of evaporation to total evapotranspiration decreased to 40.99% and 41.61%. Average temperature (T _avg), relative humidity (Rh), saturation difference (VPD) and solar radiation (R_s ) are the main meteorological factors that affect the water consumption of eggplants in the greenhouse. VPD and T _avg are the main and secondary decision-making factors that affect T, Rh is the indirect limiting factor; Rh is the main limiting factor that affects E; VPD plays a major decision-making role in ET, R_s plays a secondary decision-making role. The regression relationship between meteorological factors and ET is ET=0.714+0.786 VPD+0.017 R_s, with a correlation coefficient of 0.77, which can be used to estimate ET. The research can provide scientific basis and decision-making reference for environmental regulation and intelligent irrigation under the efficient production of autumn eggplant in greenhouse.

In order to study the influence of super absorbent polymers on soil water infiltration performance and soil water suction change process, this paper carried out simulation tests on the application depth and dosage of super absorbent polymers in different layers through indoor soil column tests. Four treatments with different application dosage, including non-application of super absorbent polymers (CK), application dosage of 0.1%, application dosage of 0.3% and application dosage of 0.5%, were set and applied to the depth of soil layer 5 cm (W) and 10 cm (S) , respectively. The results showed that super absorbent polymers had an effect on soil water infiltration characteristics. With the increase of the amount of super absorbent polymers, the migration distance of wetting front and the cumulative infiltration amount of soil decreased continuously. The super absorbent polymers had great influence on the migration of wetting front. The soil moisture content of the super absorbent polymers layer was higher than that of the control group. Under the same depth of layer application, the higher the amount of super absorbent polymers layer application, the higher the upper soil moisture content, and the lower soil moisture content. The super absorbent polymers had important effect on soil water suction. With the increase of the content of water-retaining agent, the soil water suction measured in the upper soil in the water release stage of T5 was larger, the soil water suction measured in the water absorption stage of T5 was smaller, and the soil water suction measured in the lower soil in the two stages was larger. Under the same layer application depth, the super absorbent polymers affected the peak value of soil water suction in the upper layer, but did not affect the time to reach the peak value. Both of them had an impact on the water suction in the lower layer. With the increase of water-retaining agent content, the greater the peak value of soil water suction was, the longer the time to reach the peak value was. The results reflect the influence of layer application position and application amount of water retaining agent on soil water suction, which can provide certain theoretical support for irrigation and scientific application of water retaining agent.

In order to clarify the influence of soil moisture on the nutrient absorption and utilization of Chinese kale， based on the conditions of different irrigation upper limits， the influence of soil moisture on the nutrient absorption of Chinese kale plants of nitrogen， phosphorus， potassium， calcium， and magnesium， and the content in various organs were analyzed. The results showed that increasing soil moisture could promote the absorption of various nutrients by Chinese kale plants， and the enhancement was arranged in the order of Ca>P>N≥K>Mg. The N contents in root and basal stem were relatively smaller half than those in basal leaf， bolting leaf， and bolt. The N contents of bolting leaf and basal leaf increased with the increment of soil moisture， moreover， the N content of bolting leaf was always higher than that of the basal leaf. The N content of the bolt showed a relatively decreasing trend with the increase of soil moisture. The P content in the plant organs increased with the increment of soil moisture， and the P content of the bolting leaf increased the most； when the plant was relatively deficient in P， it was more transferred to the bolt. The K content of the basal stem increased greatly when the soil moisture increased， and maintained a relatively stable growth trend in the other four organs， and was arranged in the order of basal leaf > bolt > bolting leaf > root. The Ca content varied greatly among plant organs， with the highest Ca content in basal leaf， more than half in bolting leaf， less in root and basal stem， and very few in the bolt. The Mg content in the basal leaf was the highest， about half higher than those in other organs. The increase in soil moisture will promote the transfer of magnesium to the roots and accumulate in the basal leaves， stalk leaves， and stems. Soil moisture promotes the absorption and utilization of kale nutrients and has a greater impact on the nutrient distribution of the various organs of the kale.

In order to predict the water surface evaporation in arid and semi-arid regions, the measured pan evaporation of 45 weather stations in Northwest China were used as the benchmark, the daily minimum temperature, maximum temperature, relative humidity, wind speed and solar radiation were applied to simulate the pan evaporation using the original classification gradient boosting algorithm model (Catboost), the random forest model (RF) and the Catboost model coupled with bat algorithm (Bat-CB) model respectively. The results indicated that the prediction ability and stability of the Bat-CB model (RMSE: 0.859~2.227 mm/d; MAE: 0.540~1.328 mm/d; NSE: 0.625~0.894; MAPE: 0.162~0.328) were the best. The CatBoost model (RMSE: 0.897~2.754 mm/d; MAE: 0.531~1.77 mm/d; NSE: 0.147~0.869; MAPE: 0.161~0.421) was slightly better than the RF model in predicting water surface evaporation (RMSE: 1.005~3.604 mm/d; MAE: 0.644~2.479 mm/d; NSE: ~1.242~0.894; MAPE: 0.176~0.686). In addition, the Bat-CB model had good adaptability to the seasonal and spatial variability of water surface evaporation, while the random forest model performed the worst in summer water surface evaporation prediction.

In the research of water fertilizer integration device， the peristaltic pump as the power source has the problem of local backflow. In order to improve the accuracy of fertilizer distribution， a performance parameter model was established， and the hydraulic performance test and the analysis of flow rate， pressure and pump pipe temperature were carried out by using different pump head structures with 2， 3 and 4 roller number of peristaltic pump. The results showed that compared with the peristaltic pump with double rollers or three rollers， the flow rate increased by 22% and 7%， the reflux degree decreased by 23% and 8%， the maximum pressure increased by 0.105 MPa and 0.030 MPa， and the maximum temperature of pump tube increased by 13 ℃ and 8 ℃， respectively. Through comparison， it is concluded that the four stick structure of peristaltic pump is the better structure of water and fertilizer integrated power source.

In order to meet the high precision and low cost requirements for water and fertilizer integrated machine in small-scale agricultural production， a kind of simple and light water and fertilizer integrated system was designed. In order to achieve accurate water and fertilizer ratio regulation， the system adjusts fertilizer speed by changing the duty cycle of the pulse width modulation technology until the error requirements are met， where the process is performed according to the standard water and fertilizer ratio input by users and the measured real-time water speed. Furthermore， to reduce the influence of measurement error， the flow rate measured by the sensor and the regulation process of water and fertilizer ratio are modified and optimized to improve the accuracy of water and fertilizer regulation. In addition， two simple control modes， i.e.， touch screen and remote App， are provided， where users only need to input the total irrigation water and fertilizer and the following control process are performed automatically. The results show that the water and fertilizer integrated system can provide high precision of water and fertilizer regulation， stable operation and can realize precise fertilization and irrigation.

To provide references for the design of sprinkler irrigation system on sloping land, a mathematical model of allowable application rate was established according to the water balance principle, and its accuracy was experimentally verified. The model was applied to analyze the effects of soil texture， terrain slope and irrigation quota on allowable application rate. The results showed that the higher the soil clay ratio， the steeper the terrain slope， and the more irrigation quota， the smaller the allowable application rate， and the longer the irrigation time. Considering the operation efficiency and energy consumption of sprinkler irrigation system， it is suggested that the allowable application rate of clay and sand should be controlled within 0.118 mm / min and 0.461 mm / min， respectively. The allowable application rate should be reduced by 11.69% for every 5% increase of slope， and it should be decreased by 50% when the irrigation quota is greater than 30 mm.

In order to analyze the feasibility of high density polyethylene （HDPE） plate lining technology in channel engineering， the modified HDPE raw materials or waste PE drip irrigation tape were used as the channel lining board， and the research was carried out in combination with construction scheme design， hydraulics analysis and numerical simulation of frost heaving. The HDPE plate adopts the construction scheme of hot-melt connection and setting up the extension and shrinkage hole at the connection of the channel segment， which ensures the overall anti-seepage performance. The hydraulics analysis shows that， compared with concrete lining channels， HDPE plate lining with low roughness can reduce half of the channel's flow area and indirectly reduce the project floor area and amount. The frost heave simulation results show that compared with the concrete slab lining channel， the flexible HDPE slab material can greatly release the frost heaving force of the canal foundation soil. The normal and tangential frost heaving forces of the canal slope slab are reduced by 51.15% and 45.49% respectively， and the normal and tangential frost heaving forces of the canal floor are reduced by 84.22% and 85.59% respectively. With the decrease of HDPE plate thickness， the displacement， normal frost heaving force and tangential frost heaving force of channel plate will increase slightly， but no fracture will occur. The comprehensive results show that HDPE plate lining channel has the characteristics of convenient and quick construction， good anti-seepage performance， excellent hydraulic performance， significant anti-frost swelling effect， and in line with the concept of sustainable development， etc. This research can provide reference for the engineering design and construction of trapezoidal channel in cold and drought areas.