In order to investigate the effect of base fertilizer application and irrigation amount on soil moisture and crop growth， a field experiment of summer maize was carried out. Two basic fertilizer application methods were set up， namely post-tillage fertilization (A mode) and pre-tillage fertilization (B mode). Soil water content， growth factors and yield were measured at three irrigation levels of 45 mm， 60 mm and 75 mm. The results showed that ：①The changes of soil moisture distribution curves were similar in different growth periods with different irrigation amounts. During the whole growth period， soil moisture showed significant changes in three stages， from jointing stage to bell-opening stage.②Both basal fertilizer application method and irrigation amount had effects on soil water content distribution， but the effect of basal fertilizer application method on soil water content was less than that of irrigation amount.③The higher the irrigation amount， the higher the water consumption of maize. The difference of water consumption was mainly due to the soil evaporation in the early stage of maize. The soil water storage in the treatment with higher irrigation amount at harvest time was higher. ④Compared with pre-tillage fertilization， post-tillage fertilization treatment increased the ear length， ear weight， ear diameter and 100 grain weight of maize， but the effect of irrigation on maize yield was greater than that of fertilization method. In conclusion， fertilization method and irrigation amount determine maize yield， and post-tillage fertilization and increasing irrigation amount have the greatest impact on maize yield. The study will provide a model for maize yield improvement.

In order to explore the effects of different deficit-rewatering modes at jointing stage on the growth， physiology and yield of winter wheat， different degrees of soil moisture content and duration of water deficit were set at jointing stage in the experiments. The soil moisture content was set as Y1 treatment of (55%~65%) θ_f， Y2 treatment of (65%~75%) θ_{f and Y3 treatment of (75%~85%) θf (θf is field capacity)， the duration of water deficit was 7 days， and then the soil was rewatered. In addition， CK of (85%~100%) θf with full irrigation during the whole growth period was set as the control treatment. Each treatment was repeated 3 times. Plant height， chlorophyll， net photosynthetic rate， fluorescence parameters， yield and water use efficiency of winter wheat were measured after rewatering for 7 days. The results showed that： the plant height of winter wheat in Y1，Y2 and Y3 treatments was increased by 2.38%，9.52% and 12.70%， and the chlorophyll (SPAD) was increased by 0.67%， 2.51% and 3.85%， respectively， compared with CK after 7 days of water deficit and rewatering. The net photosynthetic rate was increased by 7.04%， 6.61% and 6.44%， Fv/Fm was increased by 16.30%， 16.87% and 16.84%， and Fv/F 0 was increased by 12.20%，11.67% and 11.88%，respectively. It was found that the growth compensation effect was obvious in the winter wheat after deficit-rewatering treatment. Compared with itself at the end of 7 days of water deficit， plant height were increased by 22.86%， 25.96% and 26.87%， chlorophyll (SPAD) were increased by 17.46%， 19.23% and 21.73%， The net photosynthetic rate was increased by 7.04%， 6.61% and 6.44%，Fv/Fm was increased by 16.30%、16.87%、16.84%，and Fv/F 0 was increased by 12.20%，11.67% and 11.88%， respectively. The final yield of Y1，Y2 and Y3 treatment was 18.84%，5.78% and 0.79% lower than that of CK， respectively. The yield of Y3 treatment was 22.24% and 5.08% higher than that of Y1 and Y2 treatment，respectively. The water use efficiency of Y3 treatment was the highest，which was 8.29%，0.55% and 2.77% higher than that of Y1，Y2 and CK，respectively. So Y3 treatment is a suitable water deficit model for water saving and stable yield.}

The accuracy of soil water content sensor measurement values is a prerequisite for its application in precision irrigation to achieve water conservation in agriculture， but the variation of soil temperature has a significant impact on the deviation of soil water content sensor values. The purpose of this study is to analyze the effect of different soil temperatures on the measurement of soil water content sensors， and to further propose an XGBoost (eXtreme Gradient Boosting) based temperature compensation model for soil water content sensors and to verify and compare its prediction accuracy. In this study， 12 sets of gradient wet soil sample benchmarks with soil moisture content of 10%， 15%， 20%， 25%， and 35% were prepared， the sensor readings during the temperature change process from 0 °C to 45 °C in each soil sample were recorded， and the data sets were divided and used for model training and testing. The results showed that： the soil water content sensor readings in the same soil sample benchmark increased with the increase of soil temperature， and the variation of the maximum and minimum sensor readings in each soil sample benchmark category was within [3.6%， 7.9%]， with an average reading variation of 6.25%； the proposed XGBoost soil water content temperature correction model could compensate the influence of the sensor soil moisture temperature. The mean square error (MSE)， mean absolute error (MAE)， root mean square error (RMSE)， and coefficient of determination (R ²) of the test set were 0.013%， 0.825%， 1.165%， and 0.973， respectively； moreover， the comparison results with other tree-based and commonly used machine learning models showed that the XGBoost temperature correction model proposed in the study had the best prediction accuracy.

In order to deal with the threat of water shortage to rice production， since the 1980s， domestic and foreign rice science and technology workers have done a lot of research on rice water-saving irrigation technology or mode， but there is a lack of systematic comparison and evaluation of water-saving effect according to the actual field situation in different regions. By using the method of literature data analysis， this paper summarizes several common rice water-saving irrigation technology modes， and compares the differences， advantages and disadvantages of different technology modes in water-saving and yield increasing effects. The results show that the effect of the "shallow wet sun irrigation" mode is better， but the requirement of field is higher， and it is difficult to determine the irrigation quota. The “intermittent irrigation” mode has better water-saving effect， but it is complex to operate and poor to popularize. The "Controlled irrigation" mode can improve the stress resistance of rice， but there is no unified irrigation index. The water-saving effect of the "suitable rain irrigation" mode is better， but the effect of increasing production is general. The "Drip irrigation" mode can improve the utilization rate of water and fertilizer， but it may reduce the yield. In general， the "drip irrigation" mode and the "controlled irrigation" mode are suitable for popularization in northern rice area， while the "rain storage irrigation" mode has great potential of water-saving and yield increasing， and is suitable for popularization in southern rice area.

In order to provide scientific basis for precise and efficient fertilization management of maize under drip irrigation in aeolian sandy soil area， the field experiment was conducted with corn as the test crop. Under the recommended nitrogen application rate of 300 kg/hm²， five nitrogen fertilizer ratios were set at different stages， including conventional fertilization (F1， the mass ratio of base fertilizer to jointing fertilizer was 1∶2)， taking into account jointing and grain fertilizer (F2， the mass ratio of base fertilizer to jointing fertilizer to grain fertilizer was 1∶1∶1)， uniform fertilization (F3， the mass ratio of base fertilizer to seedling fertilizer to jointing fertilizer to panicle fertilizer to grain fertilizer was 2∶1∶1∶1∶1)， heavy jointing fertilizer (F4， the mass ratio of base fertilizer to jointing fertilizer to ear fertilizer and grain fertilizer was 2∶2∶1∶1)， and attack grain fertilizer (F5， the mass ratio of base fertilizer to jointing fertilizer to ear fertilizer to grain fertilizer was 2∶1∶1∶2). The effects of nitrogen fertilizer ratio on growth index， dry matter quality and yield of maize were analyzed. The results showed that the chlorophyll content of F1 treatment was the highest at growth stage， and the stem， leaf area index and chlorophyll content decreased the most at later growth stage. The growth indexes of F2 treatment were general. The plant height and leaf area index of F3 treatment were the highest， and the leaf area index was the largest. Corn in F4 treatment obtained stronger stem. The plant height and leaf area index of F5 treatment were smaller at early growth stage， and the stem diameter and leaf area index decreased the least at later growth stage； The dry matter of F3 treatment at jointing stage was significantly higher than that of F1， F4 and F5 treatment， and the proportion of dry matter in rachis of F2 treatment at panicle stage was the smallest； At the filling stage， the grain proportions of each treatment were F3， F4， F5， F1 and F2 in descending order； the yield and WUE of F3 treatment were the highest， which were 12.3 t/hm² and 2.16 kg/m³ respectively. Considering the growth， dry matter quality， yield and water use efficiency of maize， it is recommended that uniform fertilization is the best way of nitrogen management under the integrated planting mode of drip irrigation， water and fertilizer for maize in Northwest Liaoning sandy soil area.

In the remote sensing monitoring of inland water quality， no matter which method is used， the model has some limitations. The applicability of the model is different due to the different optical characteristics of the water with different nutritional status. At present， the research scope of most scholars is mainly focused on eutrophication state waters， and there are few studies on intermediate/poor nutrition state waters. In order to establish a remote sensing model suitable for chlorophyll a water quality monitoring in Jingpo Lake， the accuracy of inversion models for different chlorophyll a concentrations in Jingpo Lake was evaluated based on the measured spectral data in September 2015 and July 2018.The results showed that the three-band model had the best effect among the eight models， with the R ² value of 0.79 and the Root Mean Square Error (RMSE) of 0.34 μg/L. Mean Absolute Percentage Error (MAPE) was 20.6%. On this basis， through comparative analysis of the applicability of different models， the following conclusions were drawn： for the chlorophyll a concentration of Jingpo Lake with a smaller span， the modeling accuracy of the semi-empirical and semi-analytical model is better than the traditional empirical model. Compared with the three-band model， in low chlorophyll concentration and low nutrition water， the four-band model with the addition of near-infrared band may also bring some uncertainty， thus reducing the accuracy of inversion.

In order to find out the suitability of the smart fertilizer (pH-responsive coated fertilizer) under alternate wetting and drying irrigation， a pot planting test with three levels of alternate wetting and drying irrigation， including W1 (100% saturated water content as the lowest limit of irrigation)， W2 (90% saturated water content as the lowest limit of irrigation) and W3 (70% saturated water content as the lowest limit of irrigation)， and three fertilizer methods， including smart fertilizer (SF)， common mineral nitrogen fertilizer (MF) and no nitrogen fertilizer (NF)， was carried out. The effects of the treatments on yield and water use efficiency were analyzed. The results showed that the yield of SF×W1 treatment was the highest and reached to 64.84 g/pot， which was 21.8% (W1) and 13.9% (W2) higher than that of normal nitrogen fertilizer. The water use efficiency of SF×W1 treatment was the highest， which was 3.17 kg/m³ and the irrigation water use efficiency of SF×W2 treatment was the highest and reached to 1.20 kg/m³. Combined with moderate alternate wetting and drying irrigation， smart fertilizer could significantly increase rice yield and water use efficiency， which is an effective way to realize water saving and high yield of rice.

In order to find out the methods of flue-cured tobacco seedling raising which are beneficial to reduce water and fertilizer input and reduce nutrient residue， two water-control and fertilizer-saving seedling raising measures， namely water control and fertilizer saving mode I (OM1) and water control and fertilizer saving mode II (OM2)， were set in the flue-cured tobacco seedling raising process with conventional water and fertilizer management (CM) as the control. Water and fertilizer utilization， fertilizer residue and tobacco seedling growth were investigated under different water control and fertilizer saving measures. The results showed that compared with CM， there were no significant differences (P>0.05) in seedling emergence rate， stem height， whole plant biomass and water use efficiency under OM. The nitrogen， phosphorus and potassium nutrient residues at test site 1 and test site 2 were reduced by 52.7% and 58.9%， 47.8% and 60.2%， 45.1% and 61.5%， respectively. Compared with OM1， the water consumption and water use efficiency of OM2 had no significant difference (P>0.05). The residues of N， P and K at test site 1 and test site 2 were reduced by 48.6% and 28.1%， 42.9% and 37.7%， 36.3% and 41.1%， respectively， and the stem circumference of tobacco seedlings was increased by 1.8% and 27.0%， respectively. OM2 (control and maintain water layer depth of 8 cm and initial nitrogen concentration of 50 mg/kg) could reduce the input of nitrogen fertilizer for seedling raising by 47.7% and the residual nitrogen， phosphorus and potassium in the water of the seedling pool under the premise of guaranteeing the transplanting quality of tobacco seedlings. So it is a kind of recommended green and efficient water and fertilizer management measure for seedling breeding.

The precise measurement and regulation of water distribution in the channel is the basis for the total amount and quota management of water in the irrigation area. The integrated measurement and control gate is a device that integrates the function of flow measurement and control， and the corresponding regulation technology is the key to realize the safe water transmission， reasonable water distribution and accurate water use. This paper summarizes the research status of the integrated measurement and control gate and its control technology around gate hydraulic performance， flow estimation， joint control of gate group， etc. Based on the technical difficulties in existing studies， combined with the modern management requirements and development trend of information technology， the future research emphases of integrated measurement and control gate and control technology are prospected， so as to provide reference for the related research of water management in irrigation district.

Canals in irrigation areas are usually lined to improve the canal system water transport efficiency. In order to improve the water utilization efficiency of canal system in irrigation areas，this paper studied the influence of different lining conditions on the anti-seepage effect of canal bed and determined the optimal canal system lining mode in various scenarios within the scope of irrigation areas. Taking Shimen Reservoir irrigation area in Zhongxiang City， Hubei Province， as the research area， through the field survey of canal system distribution， the utilization coefficient of canal water in the study area was calculated by using the calculation software of the utilization coefficient of canal water based on the Kosgakov empirical formula method of channel leakage. According to the possible lining conditions， different lining scenarios were set up and the canal water utilization coefficient of each scenario was calculated. The results show that the water utilization coefficient of the current canal system is 0.713.If no lining measures are taken， the canal system water utilization coefficient will be only 0.604.If all channels are lined with concrete， the canal system water utilization coefficient can be as high as 0.969.The variation range of annual water saving amount per cubic meter of concrete lining in the irrigated area is 70.47~157.40 m3， with an average value of 114.10 m3.The analysis shows that： with the increase of the lining rate， the canal water utilization coefficient and the canal system water utilization coefficient of all levels of canals increase linearly. Under the condition of a certain amount of project or investment， if the partial lining of the canal is carried out， the upstream of the canal should be preferred. If only a certain level of canal lining is selected for the lateral or field canal， the lining of the field canal should be given priority.

It is important to study the correlation between the growth of various organs of crops for regulating the relative growth rate among them， making it develop in the direction of being beneficial to the high yield of crops and improving the efficiency of water and fertilizer utilization. In this study， at the irrigation test base of Tianjin Agricultural University， the drought of winter wheat in different stages was tested， and the correlation between the growth of main organs of wheat under water and nutrient stress was analyzed by using mathematical statistical test method. The results showed as follows： ①The stem leaf ratio of the winter wheat was affected by the water and nutrient stress， the root shoot ratio and the stem grain ratio of the winter wheat were also affected by the water and nutrient stress in the early stage， but less in the later stage after the turning green of the winter wheat； ②The root shoot ratio and the stem leaf ratio and the stem grain ratio of the winter wheat changed significantly with the time under the water stress and the nutrient stress. There was a good correlation between the aboveground and the underground parts， the stem and the grain， the stem and the leaf. There were significant differences between the treatments； ③The root shoot ratio and the stem leaf ratio increased significantly and the stem grain ratio decreased significantly under the water stress and the nutrient stress and the double stress of the water and the nutrient. The quantitative relationship of the growth correlation among the different organs of the winter wheat can be used to improve the crop growth model and enhance the mechanism of crop growth model.

In order to optimize the irrigation and nitrogen fertilizer management in paddy field, field experiments were conducted in five bare farmlands to explore the nitrogen transport under conditions of different irrigation amount and nitrogen fertilizer application rates. NH₄ ⁺-N, NO₃ ^--N and TN concentration in surface water and soil water in each bare farmland were analyzed. The study results showed that the concentration of NH₄ ⁺-N increased rapidly after each application of nitrogen fertilizer and then decreased. NO₃ ^--N concentration increased significantly after the reduction of nitrogen fertilizer application and irrigation amount. Within 3 days after each application of nitrogen fertilizer, the concentration of NO₃ ^--N in surface water was lower than that of NH₄ ⁺-N and the peak generation time of NO₃ ^--N concentration in surface water lagged behind that of NH₄ ⁺-N concentration. Before the field drying, TN and NH₄ ⁺-N concentrations in soil water had similar variations over time, and NH₄ ⁺-N was the main component of TN. After the field drying, TN and NO₃ ^--N concentrations in surface water and soil water varied similarly over time, and NO₃ ^--N was the main component of TN. In the test fields 1~5, the irrigation and nitrogen fertilizer mode of the field 4, with fertilizer rate of 429.3 kg / hm², irrigation amount of 8 587.5 m³/ hm² and topdressing ratio of 6∶4, was more suitable for the local rice growth, which not only saved resources but also reduced environmental pollution. This study results can provide references for water-saving irrigation and non-point source pollution prevention.

Aiming at the farmland soil eco-environmental problems in the arid area of central Ningxia， the effects of different water and nitrogen treatments on potato soil catalase activity， soil urease activity and yield were studied. The results of the study showed that in the 0~20 cm soil layer of potato， both the soil catalase activity and urease activity showed a trend of first increasing and then decreasing with the progress of the potato growth stage； in the vertical direction， with the increase of soil layer depth， soil catalase activity showed a decreasing trend， while soil urease activity showed an increasing trend. Middle water nitrogen (W2N2) was beneficial to increase soil enzyme activity， while low water high nitrogen (W1N3) was not conducive to the improvement of soil enzyme activity； the yield of potatoes and the rate of commercial potatoes treated with intermediate water nitrogen(W2N2) were the highest， which were 53 698.95 kg/hm² and 96.4%， respectively； The soil catalase activity in 0~20 cm soil layer was significantly positively correlated with potato yield， and the soil urease activity of 0~20 cm and 20~40 cm soil layers was significantly positively correlated with potato yield. In conclusion， middle water nitrogen (W2N2) was the best treatment， which was conducive to the increase of potato production， the rate of commercial potatoes， and the improvement of soil ecological environment. Therefore， the W2N2 treatment (irrigation quota of 1 500 m³/hm² and nitrogen application rate of 210 kg/hm²) is recommended as the water and nitrogen management mode for potato planting in the arid regions of central Ningxia.

In this study， by studying the influence of low-pressure operation on hydraulic technical indexes of different types of emitters， the suitable conditions of emitters in low-pressure drip irrigation were determined. The characteristics of emitters of 8 type drip-line with 2 diameters under low pressure were analyzed and compared with those under normal pressure by laboratory test and software fitting of correlation curves. The results showed that： under the low pressure operation condition， the variation coefficient of side wing labyrinth dripper increased with the decrease of pressure， but there was no obvious change in the inlaid emitter and columnar emitter. For the dripper with flow index x >0.5， the flow index increased under low pressure， and for the emitter with flow index x<0.5， the flow index decreased. The influence of low pressure on the flow deviation of drip-line with 12 mm diameter is greater than that with 16 mm diameter. For emitters with flow pattern index x<0.5， the flow deviation under low pressure can be calculated by the pressure flow formula under normal pressure to meet the design requirements. It can be concluded that when the emitter under normal pressure is used as the emitter in the low-pressure drip irrigation system， the selection of the drip-line with large pipe diameter and emitter flow index less than 0.5 can improve the uniformity of the low-pressure drip irrigation system and ensure the irrigation quality requirements.

The Taylor Basin has rich types of groundwater and complex hydro-chemical characteristics. Traditional hydro-chemical methods are not suitable for the objective classification of large amounts of data. The formation of complex characteristics of groundwater lacks a comprehensive understanding. This paper used cluster analysis to divide a large amount of groundwater data during low-water periods into three major groups，ABC，and then subdivided into 10 groups， combined with the lithology of the aquifer to analyze the water chemical characteristics. Through using the Gibbs diagram analysis，it was concluded that the three groups of groundwater were mainly controlled by rocks，but also subjected to different degrees of evaporation. Through using the ion ratio end-member diagram，it was concluded that the three groups of ABC were mainly controlled by leaching silicate，silicate and carbonate，silicate and evaporite. Finally，the mass balance was used to simulate the dissolution of various mineral components in 10 groups of water，and it was found that human activities had a greater impact on the Cl^- content of groundwater. This study deepens the understanding of the complex hydro-chemical characteristics and causes of groundwater in the study area.