In order to explore the soil ammonia volatilization law under different topdressing application periods under water storage pit irrigation and the factors affecting ammonia volatilization，field experiments were conducted from April to September 2018． There were 4 treatments: top dressing at late flowering stage ( T1) ，top dressing during fruit expansion stage ( T2) ，average top dressing at late flowering stage and fruit expansion stage ( T3) and not topdressing treatment ( T4) ．The correlation between soil ammonia volatilization rate and surface soil ammonium nitrogen，pH and temperature was analyzed． The results showed that topdressing fertilizer significantly increased the ammonia volatilization rate and accumulation amount of soil，and the ammonia volatilization loss rate of orchard soil was 0．80% ～ 1．45% under water storage pit irrigation． The relationship of ammonia volatilization rate among different treatments was shown as follows: T1 ＞ T2 ＞ T3． Soil ammonia volatilization rate had significant or extremely significant positive correlation with surface soil ammonium nitrogen and soil pH，and it had no significant correlation with soil temperature at the late flowering stage，but had significant positive correlation at fruit expansion stage． Rainfall also had some influence on soil ammonia volatilization． To sum up，T3 treatment had the least ammonia volatilization loss，so reducing single fertilizer application and sub－fertilizer application under the condition of water storage pit irrigation could reduce the ammonia volatilization loss of orchard soil．

Rapid and accurate acquisition of soil moisture content in the root region of winter wheat is of great significance for the realization of precise irrigation． In this study，winter wheat at jointing stage with different moisture treatment was taken as the study object，the canopy spectral reflectance was obtained by using a unmanned aerial vehicle ( UAV) equipped with a six －band multispectral camera，and soil moisture content at 5 different depths ( 10，20，30，40 and 60 cm) were simultaneously collected． The multiple regression models between soil moisture and the reflectance of different bands were established by stepwise regression，partial least squares and ridge regression． The results showed that the three regression models had high monitoring accuracy for soil moisture content at 10 and 20 cm depth，which could better predict the soil moisture content of crop roots; the stepwise regression model had the best prediction ability ( modeling R2 were 0．815 and 0．747，validation R2 were 0．774 and 0．717，RPD were 2．007 and 1．862) ; however，the three regression models of 30，40 and 60 cm had low monitoring accuracy for the soil moisture content． The results of this study have certain reference value for guiding precision irrigation．

In order to establish an efficient non－destructive method for monitoring water content of winter wheat plant，which can be used to reflect crop water status and guide precise irrigation，in this study，taking winter wheat in Daxing，Beijing as the research object，the spectral reflectance model and spectral vegetation index model of winter wheat were constructed by using the multi－spectral camera carried by UAV to collect the spectral information of five bands of winter wheat，and the interpretation model of water content of winter wheat plants in typical areas was screened． The results showed that the water content of winter wheat plant was significantly correlated with the reflectance spectrum at the 0． 05 level; the prediction accuracy of the two models was higher，the relative error was less than 10%，and the determination coefficient was greater than 0．75; considering the complexity and physical meaning of the models，the optimal model for estimating the water content of winter wheat plant was a spectral index model based on stepwise regression method，and the calibration and validation of the two models were determined; the constant coefficients were 0．78 and 0．83，the root mean square errors were 6．79% and 5．47%，and the relative errors were 9．73% and 6．91%． This study provides an effective method for the rapid and efficient monitoring of crop moisture using UAV multi－spectral remote sensing technology．

In order to study the application effect of“Geng－nong Drought－Resistant Bao”in agricultural production in Qinghai Province， with wheat，rape and potato as test material，three treatments，including 22．5 kg /hm2 ( A1) ，30 kg /hm2 ( A2) and 0 kg /hm2 ( CK) ，were set to study its effects on bulk density，soil moisture content in tillage layer，morphological characteristics of different growth stages and yield． The field test was carried out in Haidong Agroecology Test Station of Huangshui River in Qinghai Province． The results show that: “Geng－ nong Drought－Resistant Bao”has certain beneficial effects on bulk density，water content，crop growth characteristics，yield components and yield; it can reduce soil bulk density and improve soil pore structure; it can improve soil water retention and water storage capacity; the application amount under the optimal water retention capacity varies with different crops; the plant height of wheat and potato is the highest when the application amount is 22．5 kg /hm2 ，and the plant height of rape is the highest when the application amount is 30 kg /hm2 ; the diameter of rape plant is the largest when no“Geng－nong Drought－Resistant Bao”is applied; when the application amount is 30 kg /hm2 ， the highest yields of wheat and rape are 7 761．08 and 3 763．88 kg /hm2 ，which is increased by 20．6% and 11．4% than that of control group; when the． application rates is 30 kg /hm2 ，the highest yield of potato is 52 859．78 kg /hm2 ，which is increased by 9．3% than that of control group． Considering comprehensively，the appropriate amount of“Geng－nong Drought－Resistant Bao”can be popularized and applied in Qinghai agriculture．

In order to explore the distribution rules of soil water and salt in tomato root zone，the changes of soil water and soil salt in tomato root zone were studied under the conditions of three substrates，two different irrigation amounts and three substrates，two different irrigation amounts and two fertilizer amounts were studied experimentally． The results showed that the soil moisture and soil salinity increased with the passage of time under the conditions of seedling box and pot planting; the soil water content and soil salinity of each soil layer were higher under high irrigation water content than under low irrigation water content; after irrigation，the bottom soil moisture and soil salinity were slightly higher than the surface; in the seedling stage，the soil moisture and soil salt in S1 substrate were evenly distributed in the vertical direction，while the soil moisture in S2 and S3 substrate was evenly distributed in the vertical direction，but the soil salt was not evenly distributed; at the same time，the soil salt accumulation in S1 and S3 substrate in the pot planting stage was higher and the leaching risk was higher，and S3 substrate had a good water storage effect．

In order to study the effects of furrow irrigation on the water and salt in the ridges and furrows of the saline soil in Gansu. On the basis of unified ridges, three gradients of furrow irrigation quota were set: 6600 m3/hm2 (T1), 7200 m3/hm2 (T2), 7800 m3/hm2 (T3). The effects of different irrigation quota on the soil moisture, salinity and salt ions of saline soil were studied in field experiment. The test results show that the furrow irrigation can help to accumulate water in the furrow, and control the soil salinity in surface soil layer to a lower level. The soil moisture in the furrow is 19.6% higher than on the ridge average, and the soil salinity in the furrow is 21.8% lower than on the ridge average in 0-60 cm soil layer. The soil salinity decreased significantly with the irrigation quota. The yield of oil sunflower was the highest under T3 treatment (2.51 t/hm2), but the highest water productivity of oil sunflower under T2 treatment (16.22 kg/m3). The plot is located in arid areas so water resource is limited. What’s more, excessive irrigation not only waste water resource but also increases the risk of secondary salinization. Therefore, furrow irrigation and the irrigation quota is 7200 m3/hm2 which is suitable for improving the saline soil in this area.

To study the effects of subsurface irrigation on the growth, yield and water use efficiency of jujube trees in arid areas under different irrigation quotas, taking 5 years old jujube trees as the research object, we conduct a 2 factors 3 levels field experiment with different irrigation quotas (828, 1248, 1668 m3/hm2) and different irrigation methods (subsurface infiltrate irrigation, underground drip irrigation, pipe irrigation). The results showed that the subsurface infiltrate irrigation could promote the growth of the diameter of shoot, jujube length and fruit rate of jujube compared with the underground drip irrigation and pipe irrigation, when the irrigation quota was the same. At the same time, the yield of jujube was increased by 2.84%~25.70%, and the water use efficiency was increased by 8.02% ~ 18.96%. Under the condition of subsurface infiltrate irrigation, the yield and water use efficiency of jujube were reduced by 2.47% and 8.84% respectively when the irrigation quota increased from 1249 m3/hm2 to1668 m3/hm2. Therefore, subsurface infiltrate irrigation is more suitable for jujube growth when the irrigation quota is 1248 m3/hm2, which has the highest yield (9418.85 kg/hm2) and the highest water use efficiency (3.84 kg/m3), which can provide a theoretical basis for the popularization of subsurface infiltrate irrigation technology in arid areas.

Field experiments of different supplementary irrigation techniques of potato were carried out in Dingxi area of Gansu province to study the effects of different supplementary irrigation methods on soil moisture，water consumption characteristics of farmland，rainfall utilization rate and water utilization efficiency of potato． The results showed that the yield of furrow irrigation was higher than that of drip irrigation under the same soil moisture level，and the yield of furrow irrigation potato decreased significantly． The water use efficiency of drip irrigation was 87． 69% higher than that of ditch irrigation，but it was not conducive to rainfall utilization． Under the condition of water resources permitting，the supplementary irrigation method of furrow irrigation should be adopted to ensure potato yield． In the case of water resource shortage or in potato facility breeding industry，submembrane drip irrigation has important popularization and application value．

In order to obtain the influencing factors of the soil water characteristic curve of the low－suction stage of the aeolian soil in the alluvial plain，based on the measurement of soil water characteristic curves of three typical water－bearing soil profiles in Fenhe Irrigation District，this paper explored the influence mechanism of texture and structure ( including bulk density and water－stable aggregate content greater than 0．025 mm) and organic matter content on soil moisture characteristic curve in low suction stage． The results show that: ① soil texture，structure and organic matter content have significant effects on soil water characteristic curve; ② the size，distribution and connectivity of pores in the soil are the fundamental causes for determining the difference in soil water characteristic curves; ③ the influence of soil level on the internal pores of the soil cannot be ignored，and reasonable gradation can greatly improve the water retention performance of the soil． The research results have certain significance for the fine study of soil water characteristic curve and provide theoretical support for scientific and rational irrigation．

In order to explore the effects of the combined regulation of two chemical agents，SAP and fulvic acid，on the growth and water use efficiency of greenhouse tomato plants，5 treatments were set according to the different combinations of SAP and FA and irrigation quota， including S，F，SF，SFL and CK． The results showed that: SAP and FA could significantly promote tomato growth，increase soil moisture content，yield and water use efficiency; under the same irrigation condition，the soil moisture content of SF treatment in the whole growth period was the highest，with an average increase of 5．0%，10．6% and 17．0% compared with that of S，F and CK treatment; the soil moisture content of S and F treatment were 13．0% and 4．0% higher than that of CK treatment，respectively; the maximum yield of SF treatment was 111．8 t /hm2 ，which increased by 8．6%，6．8% and 14．1% compared with S，F and CK treatment; compared with other treatments，SFL treatment used less irrigation water，resulting in a yield of 110．6 t /hm2 and an increase of 12．9%，with the highest water use efficiency ( 50．3 kg /m3 ) and a 23．1% increase compared with CK treatment． The combined regulation of SAP and FA can control water conservation and increase yield effectively．

Taking the subsurface drip irrigation schedule for growth season alfalfa fields as the research object，this experiment adopts completely random design to carry out the soil water content lower limit control test under subsurface drip irrigation． Based on the comprehensive analysis of growth，water use and production indexes of each stubble alfalfa，the subordinate function method is adopted to carry out the quantitative evaluation to determine the suitable lower limit of soil water index of each stubble alfalfa and then set up the subsurface drip irrigation schedule for growth season alfalfa fields in wet year in Ningxia yellow river irrigation area． The results show that: under different lower limits of soil moisture content，the hay yield of each treatment decreases gradually with the increase of stubbles，but the yield difference between different treatments can not reach a significant level when the lower limit of soil moisture content is higher than 60% of field moisture holding rate; the correlation between hay yield and branch number，stem－leaf ratio，fresh yield and water consumption is very significant，and the correlation with height is significant; the effect of branch number and stem－leaf ratio on yield is greater than that of plant height; plant height in all harvested stubble shows a two－stage change process of first increasing and then decreasing，branch number decreases gradually with the continuation of harvested stubble，stem and leaf ratio decreases gradually with the decline of irrigation quota; the irrigation amount of each stubble affects the stem and leaf ratio of alfalfa by affecting the water consumption，and then affects the plant height and branch number to affect the hay yield． The irrigation schedule of subsurface drip irrigation for growth season alfalfa fields in wet year in Ningxia yellow river irrigation area is: irrigation quota 3 410．95 m3 /hm2 ，irrigation 17 times，the first stubble irrigation quota 230．5 m3 / hm2 ，irrigation 4 times，irrigation cycle 7d，irrigation water amount 922 m3 /hm2 ; the second stubble irrigation quota 276． 5 m3 /hm2 ， irrigation 3 times，irrigation cycle 7 d，irrigation water amount 829．5 m3 /hm2 ; the third stubble irrigation quota 138．3 m3 /hm2 ，irrigation 8 times，irrigation cycle 4d，irrigation water amount 1 106．4 m3 /hm2 ; the fourth stubble irrigation quota 276．5 m3 /hm2 ，irrigation 2 times， irrigation water amount 553 m3 /hm2 ; the suitable lower limit of soil moisture content for each crop was 70%，60%，80% and 60% of field moisture holding rate respectively．

Based on the theory of water transport in saturated-unsaturated zone, simulating the movement process, infiltration range and water demand of soil moisture under different irrigation modes in Saixi Irrigation District, analyzing the state of water movement under different irrigation conditions, and evaluating the effect and economy of water-saving irrigation. The results show that under the same irrigation effect, the water consumption of water-saving irrigation is significantly less than that of free flooding. According to the water requirement of wheat growth cycle, putting forward a value of water-saving irrigation flux is 0.375 cm3/h and a depth range of underground piping with the tube layout distance of 100 cm under this flux value is 50-60 cm, and water-saving irrigation has great economic performance. The simulation results of moisture diffusion can provide theoretical basis for water-saving irrigation in irrigation area.

This paper constructed a comprehensive evaluation index system of eco － compensation，which covered three levels，including social and economic development，pollution discharge and monitoring，and pollution treatment aspects，and established a combination weigh model based on analytic hierarchy and entropy methods for comprehensive eco － compensation effect considering subjective and objective evaluation． Taking Xiaohong river basin as an example，the compensation effect of four counties in the basin before and after the implementation of ecological compensation policy from 2008 to 2015 was comprehensively evaluated． The results showed that the comprehensive indicators in the basin showed an upward trend and the difference of water environment quality among four counties had been narrowed，which indicated that the eco－compensation of the basin had achieved certain results． The research results can provide scientific reference and technical support for eco－compensation effect evaluation．

Scientific and effective water quality assessment method is the premise of analyzing the causes of river pollution and formulating pollution control measures. Taking the lower reaches of Luanhe River in Haihe River Basin and the coastal rivers in eastern Hebei Province as examples, the monthly water quality of 17 monitoring sections in the study area was evaluated by five representative methods, and the differences of different evaluation methods were compared and analyzed. The results show that: ①all monitoring sections are inferior to Class V water quality, with serious pollution in Yinmahe River, Tanghe River and other sections, and NH3-N as the main pollutant; ②Different water quality analysis methods have their own advantages. The method of combining single factor evaluation with principal component analysis is simple and can meet the requirements of identifying water quality categories, major pollutants and exceeding standard multiples, which is more suitable for water quality assessment in this area.

The development and utilization of reclaimed water is one of the important ways to alleviate the shortage of water resources in China. In order to scientifically and accurately identify the influencing factors of China's reclaimed water utilization, this paper uses the data of 6 years in each province from 2012 to 2017 to comprehensively consider the influencing factors of economic investment, sewage treatment and water use level, and uses Spearman rank correlation analysis. Sensitive indicators affecting the use of recycled water. The results show that the correlation between the utilization of reclaimed water and the indicators of sewage treatment is relatively large, and the correlation with the four indexes of reclaimed water production capacity, reclaimed water pipeline length, drainage facility investment and per capita water resources is significant. Reclaimed water use has a close relationship with production and operation water and public service water. This study can lay a foundation for establishing a scientific and effective evaluation index system and potential prediction of reclaimed water utilization potential, and provide a reliable, effective and universally applicable reference for the selection of research indicators for the development and utilization of reclaimed water.

In order to improve the yield，quality and efficiency of vegetables under drip irrigation of reclaimed water，three different irrigation standard levels ( 2 290，3 235，4 180 m3 /hm2 ) of reclaimed water treatment and contrast treatment ( tap water) were set to conduct comparative experimental studies on the effects of reclaimed water treatment and contrast treatment ( tap water) on tomato yield，quality， photosynthesis and chlorophyll． The results showed that the yield of tomato increased by 6．7%，5．9% and 6．7%，respectively，compared with that of the contrast group; compared with the contrast group，the regenerated water treatment had a certain impact on tomato quality，reducing the content of vitamin C and increasing the content of total acid，soluble solid，lycopene and soluble sugar; reclaimed water compared with contrast treatment had promoting effect to the tomato photosynthesis and chlorophyll，the irrigation quota of three levels of net photosynthetic rate increased 2． 9%，2． 9% and 2． 2% respectively，transpiration rate increased 8． 8%，5． 5% and 7． 4% respectively，and stomatal conductance increased 16． 7%，52% and 48． 5% respectively，intercellular CO2 concentration increased 11． 4%，9． 2% and 16． 7% respectively，the chlorophyll increased 2．5%，3．0% and 2．0% respectively; in the horizontal irrigation quota of reclaimed water，tomato yield，photosynthesis，chlorophyll and lycopene were the highest，vitamin C，soluble sugar，total acid and soluble solid were moderate，and the quality indexes met the limit indexes of“quality standard of pollution－free tomato ( DB510422T018－2010) ”． Therefore，the equal－level irrigation quota of reclaimed water is 3 235 m3 /hm2 ，and the corresponding irrigation quota is 135 m3 /hm2 with 22 irrigation times，which is a suitable drip irrigation system in the local area．

Complete outdoor randomized trials are used to study their removal rate model of green myriophyllum verticillatum under the influence of ammonia nitrogen, nitrate nitrogen and total phosphorus. The result shows: green myriophyllum verticillatum's water purification ability is varied to three factors, especially to total phosphorus and ammonia nitrogen. Influential factors show that total phosphorus> ammonia nitrogen> nitrate nitrogen, and first two of them can change purification ability much. The removal rate model of three factors is negative index model, and differs from concentration. And the same to a and b in the model. The first 0～12d is critical purification period when removal ability is the best, removal rate is the fast, and removal contaminant is the most after building the green myriophyllum verticillatum ecosystem，the removal rates of ammonia nitrogen, nitrate nitrogen and total phosphorus were 60.4~78.1%, 40.20~49.88% and 78.6~82.94% respectively. This paper can provide reference to know pollutant concentration in time, and also can provide guidance to make purification better by using myriophyllum verticillatum.

By studying the influence of parameter changes in VG model on output results，not only the efficiency of calibration model parameters can be improved，but also a more reliable and stable mathematical model can be obtained． In this study，the forest field test in the yellow irrigation area of the central Ningxia plain in 2017 was taken as a verification example，and 11 parameters of VG model were selected for global sensitivity analysis． The global sensitivity of each parameter is quantitatively calculated and graded according to the sensitivity． The results show that: when taking Se as the output variable，the performance of parameters，θsa，αa and na，is extremely sensitive，while αb， θra，nb and θsb are relatively sensitive，but the performance of Ksa，Ksb and l is generally sensitive or insensitive; when the output variable is K( Se) ，the parameter θsa is the most sensitive，while αa，na and Ksa are relatively sensitive，but other parameters are relatively weak． The more sensitive parameters are modified and applied to VG model，and good results have been achieved． Moreover，the global sensitivity analysis method can effectively improve the efficiency of parameter calibration of VG model，and the field universality is strong．

In order to explore the soil salt inversion under thecondition of vegetation cover，the Jiefangzha sub－district of the Hetao Irrigation District was used as the research area，and the GF－1 image was used as the data source． The salt index ( SI2，S2，S3) ，the enhanced vegetation index ( EVI) and the near Infrared band were used as input factors． The soil salinity inversion model at 0 ～ 60 cm depth was established by multivariable linear regression，quantile regression and back propagation neural network respectively． The results showed that both the MLR model and the QR model had high precision and could better invert the soil salinity during vegetation coverage; among them， the QR model had the highest verification accuracy，and the coefficient of determination ( R2 ) of modeling and verification were 0．627 and 0．636，the root mean square error ( RMSE) was 0．249，and the mean absolute error ( MAE) was 0．235，which was the optimal model for soil salinity estimation; the BP model had a relatively poor effect，the modeling and verification R2 were 0．605 and 0．558; the QR model was used to invert the soil salinity in the study area，and the salt trend of the model inversion was found to be in line with the actual situation; the irrigation area mainly distributed non － salt soil and mild salinized soil; the southern part of the irrigation area had a low degree of soil salinization，which accounts for about 32%; the area with higher salinization accounted for about 19% of the total area of the irrigation． This paper provides an idea for exploring soil salinity inversion during vegetation cover