In order to solve the problems of poor uniformity of nutrient solution concentration，high labor intensity and excessive fertilization in the traditional irrigation method of integrated water and fertilizer for farmers，a simplified water and fertilizer integrated machine with large fertilizer uptake amount and low cost was designed to match the characteristics of sub-membrane micro-spraying with high irrigation flow.Through the self-designed water and fertilizer integrated performance testing platform， the fertilizer uptake performance of the pump was tested， and the installation position of the suction pump was determined. In order to verify the application effect of the water and fertilizer integrated machine， the uniformity of irrigation nutrient solution concentration under the application of the water and fertilizer integrated machine and the traditional method was tested first， and then a comparative experiment of cucumber cultivation in solar greenhouse was carried out with the total amount of topdressing reduced by 30% compared with the traditional method. The results showed that when the outlet pressure of the water and fertilizer integrated machine was 0.09， 0.11 and 0.13 MPa， the effect of suction pump in front was better than that in the rear. Compared with the traditional irrigation and fertilization method， the spatial uniformity of irrigation nutrient solution concentration under the simplified water and fertilizer integrated machine was not significantly different， but the temporal uniformity was significantly different. The concentration of irrigation nutrient solution under the traditional method decreased continuously over time， while it remained stable under the water and fertilizer integrated machine. In the case of 30% less fertilization，compared with the traditional method， the application of water and fertilizer integrated machine could still increase the yield by 6.18%， 14 hours could be saved per growing season (7 months) for each greenhouse (670 m²)， fertilization could be reduced by 27 kg， and the benefit could be increased by 21 500 yuan/hm². In conclusion， the simplified water and fertilizer integrated machine has broad prospects of promotion and application.

In order to solve the problem of the low water-fertilizer-heat utilization rate of border irrigation maize，the effects of soil water and fertilizer heat coupling on the growth， photosynthesis， and yield of drip irrigation silage maize were studied. By using three factors and three levels orthogonal test， range analysis and variance analysis， the primary and secondary order， significance and optimal combination scheme of water， fertilizer， and heat coupling effect on silage maize were obtained. The results showed that the order of the three factors affecting fresh biomass and grain yield was irrigation quota>topdressing amount>root zone temperature. Irrigation quota and the topdressing amount had a significant effect on fresh biomass yield， irrigation quota and the topdressing amount had an extremely significant effect on grain yield， and the root-zone temperature had no significant effect on fresh biomass yield and grain yield. The plant height，stem diameter， leaf area index， net photosynthetic rate， transpiration rate，fresh biomass，and grain yield of silage maize increased with the increase of irrigation quota，topdressing amount，and the root-zone temperature. Under the condition of rainfall of 148 mm and groundwater depth of 1.66 m during the growth period， the effects of water， fertilizer， and heat coupling on the growth， photosynthesis， and yield of drip irrigation silage maize were comprehensively considered， and the optimal combination of three factors was determined as A₃B₃C₂， i. e.， irrigation quota of 2 520 m³/hm²， topdressing amount of 594 kg/hm² (pure N of 273.24 kg/hm² )， and mulching with ordinary plastic film. The fresh biomass and grain yield were the highest， and the fresh biomass was 96 638 kg/hm²， which was 14.96 % higher than that of CK. The grain yield was 14 927 kg/hm²， 13.25 % higher than CK. This study can provide a theoretical basis for the promotion of soil water， fertilizer and heat regulation system for efficient water-saving irrigation of silage maize in Yellow River irrigation area.

In order to investigate the effects of different water and fertilizer treatment modes on the activities of SOD, POD and CAT, the accumulation of MDA in leaf, yield and WUE of waxy maize under the condition of double ridge and furrow with whole film mulching, and to select the most suitable water and fertilizer management mode, two irrigation levels were set, including I₀ (control the soil moisture content at the appropriate level at four stages, namely 75%~85%, 65%~75%, 70%~80% and 70%~80% of the field water capacity at sowing stage, seedling stage to early jointing stage, late jointing stage to booting stage and booting stage to anthesis stage) and I₁ (control the soil moisture content at an appropriate level for two periods, specifically 75%~85% of the field water capacity at the sowing stage, late jointing stage and booting stage). Also, three fertilizer levels were set, including F₀ (NPK fertilizer as basal), F₁ (combination of basal and topdressing of N/K fertilizer, basal application, jointing stage and trumpet top application ratio is 3∶3∶4, all basal application of P fertilizer) and F₂ (combination of basal and topdressing of N/K fertilizer, base, and huge bellbottom topdressing proportion is 3∶7, all basal application of P fertilizer). The results showed that under different water and fertilizer conditions, the change trend of SOD and CAT in leaves increased first to booting stage and then decreased, and POD and MDA increased gradually in the whole growth period. There was no significant difference in MDA during growth period among different treatments of I₀ level. The sensitivity degree of SOD, POD and CAT to water and fertilizer was POD>SOD>CAT, F₁I₀ and F₂I₀ could significantly increase the 100-grain dry weight of waxy corn, and the grain yield of F₁ and F₂ was higher than that of F₀, and I₀ was higher than that of I₁, with the highest yield increase of 10.9%. Therefore, F₂I₁ was the optimal water and fertilizer measure of this year under the condition of double ridge and furrow with whole film mulching.

The correlation scale error plays a very important role in the improvement of the inversion accuracy of the hydraulic conductivity of the aquifer. Based on numerical experiments， this paper used the successive linear estimation algorithm (SLE) to invert the hydraulic conductivity K. By increasing the number of K measured data to analyze the difference between the estimated value and the real value under the different correlation scale error conditions， and obtained the relationship between the data volume of K measured data and the error of the inversion result. The results show that， when the volume of K measured data is less， changing the correlation scale will cause errors to inversion results. On the basis of the correlation scale errors， with the increase of the measured value of K， the increase in the inversion accuracy of the hydraulic conductivity K becomes slower and slower. It shows that too much K measured data will cause data redundancy. For the numerical experiment set in this paper， the number of K measured value should be less than 30. Therefore， in actual engineering， a more appropriate amount of K measured value data can be selected according to its accuracy requirements.

In order to explore the effects of irrigation amount and pH value on the yield, quality and soil chemical properties of cold vegetables in the south mountainous area of Ningxia, a split-field experiment was conducted. The irrigation amount was the main area with three levels, including W₁ of 3 150 m³/hm², W₂ of 2 700 m³/hm² and W₃ of 2 250 m³/hm². The irrigation pH value was the sub-area with three levels, including B₁ untreated (CK), B₂ treated with pH=6.0 and B₃ treated with pH = 4.0.The results showed that the effect of irrigation amount on soil pH value was not significant. Compared with the control B₁, the soil pH value of B₂ and B₃ decreased by 0.2 and 0.3 on average, respectively, while the soil organic matter, available nitrogen, available phosphorus and available potassium increased first and then decreased with the decrease of irrigation water pH value, and the soil nutrient of B₂ treatment was the highest. The plant height of celery of W₁ treatment was higher than that of W₂ and W₃. The plant height of celery of B₂ treatment was the highest under W₁, W₂ and W₃ treatments. Chlorophyll SPAD value and net photosynthetic rate increased with the increase of irrigation amount. Compared with W₂ and W₃ treatment_, both of them of W₁ treatment was increased by 4.0% and 5.9%, and 6.6% and 11.5% on average, respectively. With the decrease of irrigation water pH, Chlorophyll SPAD value and net photosynthetic rate increased first and then decreased, with the highest values in B₂ treatment. The yield of celery increased with the increase of irrigation water. Compared with W₂ and W₃ treatment, the yield of W₁ treatment was increased by 5.6% and 34.7%, respectively. The yield of B₂ was the highest in all irrigation water pH treatments. The Vc and total sugar contents of celery increased with the increase of irrigation amount, and the Vc and total sugar contents of W₁ increased by 2.3%, 9.6% and 4.9%, 6.3% on average compared with W₂ and W₃ treatments, respectively. With the decrease of irrigation pH value, the contents of Vc and total sugar in celery increased firstly and then increased, both of them increased significantly in B₂ was significantly increased by 9.1%, 15.1% and 6.0%, 13.2% compared with those in B₁ and B₃, respectively. On the contrary, with the increase of irrigation amount, the crude fiber content in W₁ decreased by 7.1% and 13.7% compared with W₂ and W₃, and it decreased firstly and then increased with the decrease of irrigation pH value, the crude fiber content of W1 in B₂ decreased by 25% and 30.2% compared with B₁ and B₃. To sum up, increasing irrigation amount and decreasing irrigation pH value in a certain range can improve soil fertility, and at the same time can promote the growth and physiological characteristics of celery, so as to improve the yield and quality of celery.

In order to explore the safety of the reasonable use of brackish water and recycled water in the area lack of fresh water resources， through pot experiment， four different proportion of reclaimed water and brackish water (5 g/L) mixed irrigation treatments were set， namely reclaimed water irrigation (T1)， brackish water-reclaimed water 1∶2 irrigation (T2)， brackish water-reclaimed water 1∶1 irrigation (T3) and brackish water irrigation (T4)， and clean water irrigation was used as control. The response of crop growth physiological characteristics to mixed irrigation with brackish water and reclaimed water was studied. The results showed that compared with T1， mixed irrigation significantly reduced the aboveground biomass and increased the SOD activity， especially at T2， but had no significant effects on the underground biomass and other physiological indexes. With the increase of the proportion of brackish water in irrigation water， the content of malondialdehyde increased first and then decreased， and the content of soluble protein had no obvious change rule. Considering all factors comprehensively， reclaimed water can be considered as a substitute for clean water and use with brackish water， and the ratio of brackish water to reclaimed water should be 1∶2.

In order to improve the accuracy of precipitation forecasts and reduce economic losses, aiming at the non-linear and non-stationary characteristics of precipitation data series, slope and quantile are introduced to construct the non-equal interval slope gray waveform prediction model on the basis of the existing gray waveform prediction model. Firstly, the slope contour line is used to solve the precipitation data with rising, falling or fluctuating characteristics. Secondly, the quantile is introduced to solve the non-stationary characteristics of the precipitation data. Thirdly, the GM(1,1) model is used to model the contour time sequence that meets the conditions. Finally, the precipitation data of Henan Province from 1990 to 2019 are analyzed by using the method in this paper and traditional methods. The results show that the precipitation prediction results based on the proposed method are more consistent with the measured results, and the prediction error is smaller and the accuracy is higher. The prediction model of slope unequal interval grey waveform proposed in this paper can effectively predict the data series with unequal interval and rising or falling trend.

Under the condition of alternate drip irrigation and the same fertilizer amount， the effects of different soil moisture and fertilization methods on the yield composition， yield， quality and water use of winter-planting potato were investigated through a field experiment to obtain the reasonable water and fertilizer management modes， so as to provide scientific basis for improving the production of winter-planting potato in southern China. Under the same soil moisture treatment， compared to NK_100-0 (full application of nitrogen and potassium fertilizer as basal fertilizer soil)， NK_50-50 (50% nitrogen and potassium fertilizers as basal fertilizer soil， 50% nitrogen and potassium fertilizers as drip irrigation and topdressing) increased potato yield by 17.0%. At NK_50-50， potato yield， potato weight per plant， potato number per plant， potato yield commodity， vitamin C content and starch content in W_A (_{60%~70% θf (field capacity) at the seedling stage， 70%~80% θf at the tuber formation stage， 75%~85% θf at the tuber expansion stage， 50%~60% θf at the starch accumulation stage) were not significantly different from those in WB (50%~60% θf at the seedling stage， 60%~70% θf at the tuber formation stage， 70%~80% θf at the tuber expansion stage， 40%~50% θf at the starch accumulation stage). At NK50-50， compared to WA treatment， WB treatment decreased the reducing sugar content in potato， which was beneficial for potato frying. In addition， at NK50-50， WB treatment increased the water use efficiency of potato by 20.7% compared to WA treatment. Therefore， under the condition of fertilized with N 150 kg/hm²， P2O5 90 kg/hm² and K2O 300 kg/hm²， WBNK50-50 treatment was a rational water and fertilizer mode for the production of southern winter-planting potato.}

In order to solve the problem that the clay particles is not easy to remove in the drip irrigation filtration of yellow river sandy water, through the contrast test method, 4 types of non-full flow soil drainage filtration devices, including vertical buried tube type (V), horizontal buried tube type (L), radiation well tube type (R) and seepage well tube type (S), were set, and the experiments on the filtration performance of yellow river sandy water under unsaturated soil treatment (V2, L2, R2) and saturated soil treatment (V1, L1, R1 and S) were carried out. The results showed that: the average filtration rate of V1, L1 and R1 treatment was 3.73%, 9.52% and 10.56% higher than that of V2, L2 and R2 treatment, respectively, and the average sediment concentration was 2.74%, 3.95% and 1.84% lower, respectively. S treatment had the maximum filtration water amount, while L treatment had the minimum sediment concentration. After each treatment reached stable infiltration, the average sand content of the filtered water was less than 0.3 kg/m³, and the particles greater than 0.1 mm and less than 0.129 mm accounted for only 0.58%.Through the drip irrigation test, the relative flow rate and uniformity coefficient of S, V and L treatments were higher than 75% and 80%, respectively, which met the requirements of drip irrigation. After comprehensive consideration, it is suggested to recommend the seepage well tube type (S) and horizontal buried tube type (L) non-full flow soil seepage filtration device for practical application, which can provide technical support for the filtration of high sediment content water for efficient water-saving irrigation in the Yellow River irrigation area.

In order to explore the influence of fertilizer factors on the hydraulic performance of drip irrigation fertilization system, the effects of different fertilizer types and concentrations on the hydraulic characteristics of emitter flow rate and uniformity were studied by experiments. The results show that the discharge characteristics of drip irrigation are affected by the solubility of fertilizer, and the better the solubility is, the less the influence is. Water-soluble fertilizer is the preferred fertilizer for drip irrigation because it is completely soluble in water and has no effect on the outflow. With the increase of the concentration of compound fertilizer, the Dra and CU of emitter decreased, and the higher the concentration, the greater the decrease of Dra and CU, the higher the blocking rate, and the higher the blocking risk of drip irrigation belt. The concentration threshold of compound fertilizer is different at different temperatures. At 10 ℃, 20 ℃, 30 ℃ and 40 ℃, the concentration threshold is 4.0 g/L, 5.0 g/L, 7.0 g/L and 8.0 g/L, respectively. In the practical application of drip irrigation fertilization system, the corresponding concentration of fertilizer solution can be selected according to the temperature and other environmental conditions to control the blockage risk of the system.

Considering that the Penman-Monteith FAO-56 (PMF-56) model is limited by the requirements of large data sets and the complex calculation process when estimating reference crop evapotranspiration (ET _ref), it is urgent to find an empirical model with simple calculation process and fewer meteorological input variables. In this study, firstly, based on the conventional meteorological observation data of 65 meteorological stations in Anhui province from 2001 to 2014, the simulation performance of 13 typical ET _ref estimation models was systematically evaluated by means of relative root mean square error (RRMSE), mean absolute error (MAE) and Nash-Sutcliffe (NS) coefficient. Then, the data from 2015 to 2019 were employed to verify the performance of 13 empirical models through linear regression model. The results showed that the simulation performance of the empirical model was similar when simulating the ET _ref in different natural regions of Anhui province and the difference was small. Before model calibration, VA3 model performed the best, while PEN, WMO, TRA and JH models had large errors. When the model was calibrated on a monthly scale, the determination coefficient (R ²) between the ET _ref values estimated by the temperature-based, radiation-based and combination models and that calculated by the PMF-56 model all showed the trend of increased first and then decreased, while the mass transfer models showed the opposite trend. Although the performance of the mass transfer models was poor, the simulation results of the mass transfer models in January to March and November to December were good, especially in December, where the fitting R ² value between the ET _ref estimated by the WMO and TRA models and that calculated by the PMF-56 model were both as high as 0.972, which was better than that of VA3 model. After model calibration, the overall simulation effects of the empirical models were satisfied, with only the TRA, MAK and WMO models underestimated the result during April-August. Therefore, if the complete meteorological datasets can be obtained, the VA3 model can be considered as the best alternative to the PMF-56 model. In addition, the temperature-based and radiation-based models as well as the VA1 and VA2 models are recommended for the ET _ref estimation in April to October, while mass transfer models are recommended for other months.

In order to explore the effects of plastic film mulching on the grain filling process and yield of summer maize, a field experiment was carried out in Yangling, Shaanxi province. With no film mulching (CK) as the control. the effects of two mulching methods (i.e., full film mulching (FM) and half film mulching (HM)) on soil temperature, growth indices, grain filling process, yield, and WUE of summer maize were studied. The results showed that compared with CK, FM and HM increased the surface soil temperature, promoted the growth of summer maize, optimized the grain filling process, and finally increased the yield and WUE of summer maize. The yield increased by 15.19% and 8.34%, and WUE increased by 19.75% and 11.80% after applying HM and PM, respectively. The yield increase induced by plastic film mulching was attributed to both increased grain filling rate and extended duration of fast-increase. Compared with CK, the theoretical maximum 100-kernel weight of summer maize at the end filling period under FM and HM was increased by 18.19% and 7.78%, respectively.

Cotton is the main economic crop in southern Xinjiang， but the utilization efficiency of cotton straw is low at present. It is of great significance to study the effects of cotton straw returning on soil water and salt distribution and cotton root architecture in southern Xinjiang to improve the utilization rate of cotton straw and increase cotton yield. In this paper， the effects of different cotton stalk interlayer buried depths on soil water and salt distribution and cotton root architecture were studied by field experiments with four different depths of cotton stalk interlayer embedment： 10 cm (A)， 15 cm (B)， 30 cm (C) and 45 cm (D)， and with no cotton stalk interlayer embedment (CK) as the control. The results showed that the soil water content of treatment A was the highest among all treatments， and compared with CK， B， C and D， the soil water content increased by 21.92%， 69.33%， 62.54% and 28.70%， respectively. The salt movement in the vertical direction was hindered by the cotton stalk interlayer， and the accumulation occurred at the cotton stalk interlayer. The soil conductivity of CK treatment was the lowest among all the treatments， and compared with CK， the soil conductivity of A， B， C and D treatments decreased by 56.22%， 33.27%， 31.01% and 28.76%， respectively. Root indexes such as root weight， root length density， root volume and average root diameter of cotton per plant in C treatment were the best， which were increased by 5.06%， 21.84%， 15.87% and 69.30% compared with CK treatment， respectively. Therefore， it is suggested to adopt the straw returning method with a depth of 30 cm to promote the growth and development of cotton root system and improve cotton yield.

Water right， water market and other economic management programs have been fully applied in some areas at home and abroad and achieved remarkable results. The premise of making feasible economic management plan is to clarify the economic benefits of agricultural water use for different crops. In this paper， based on the meteorological data from 2000 to 2016， CROPWAT model was used to simulate the spatio-temporal variation characteristics of the water demand of main crops at county level in the upstream of Xiong’an New Area. At the same time， crop water demand was used to describe agricultural water consumption. Combined with panel data， the economic benefits of agricultural water consumption of main crops in the upstream of Xiong’an New Area were estimated. Finally， the spatial characteristics of agricultural water economic benefits of different crops were determined by spatial autocorrelation method. The results show that the crop water requirements of wheat， corn， soybean， peanut and cotton are in the range of 355~437， 367~399， 369~401， 407~445 and 465~514 mm. The economic benefits of agricultural water are distributed between 1.40~3.91， 1.56~4.06， 1.43~3.61， 1.67~6.89 and 2.08~5.62 CNY/m3.In terms of spatial characteristics， the economic benefit of agricultural water use in the plain is higher than that in the mountainous area， and there is a lower area around Fuping， Laiyuan and Lingqiu. Relative to crop yield and water consumption， price is the most sensitive factor affecting the economic benefit of agricultural water use.

In order to study the effect of drip irrigation with nitrogen fertigation on tomato nitrogen metabolism and optimal water and nitrogen (N) supply mode, a pot experiment was conducted to investigate the effects of 3 drip irrigation methods (conventional drip irrigation CDI, fixed partial root-zone drip irrigation FDI, alternate partial root-zone drip irrigation ADI) and 3 N fertilization levels on tomato nitrogen metabolism, water and N use. The results showed that: compared to CDI, ADI maintained leaf soluble protein content, NR and GS activity, increased NO₃ ^--N and soluble protein by 16.4% and 16.1% at N₈₀ (applied with N of 0.16 g/kg soil); ADI and FDI maintained tomato water use efficiency (WUE), nitrogen partial productivity and dry mass accumulation at N₈₀. In comparison of the 3 N fertilization levels, under ADI, N₈₀ had the highest NR, GS, WUE, shoot dry mass and total dry mass, while total dry mass had significant correlation with leaf soluble protein, NR and GS activity. Thus ADI-N₈₀ is recommended as suitable water and N supply mode for maintain tomato water use efficiency, nitrogen partial productivity, dry mass accumulation and improving tomato nitrogen metabolism.