This experiment studied the variation law of soil, air temperature and humidity and crop evapotranspiration in greenhouse under different humid and hot environments in order to reveal the interaction mechanism among them and provide theoretical basis for regulating and controlling the humid and hot environment, preserving moisture and saving water resources in greenhouse cultivation. In this experiment, the greenhouse potted tomatoes were used as study material. Three different kinds of humid and hot environmental treatments were set up, namely normal open greenhouse environment (T1), encapsulated fully enclosed plastic shed environment (T2) and top semi-enclosed plastic shed environment (T3) in greenhouse. The micro-climate change, soil moisture and crop evapotranspiration of the three treatments were measured. The law of change was compared and analyzed. The results were as following: ① In autumn and winter, the change trend of soil moisture was basically the same as that of crop evapotranspiration in the whole growth period, and the change trend of soil temperature and crop evapotranspiration was opposite in the flowering and fruit setting period. ② During the flowering and fruit setting period, air humidity and crop evapotranspiration increased and decreased, while in the mature harvesting period, air humidity changed slightly, and air temperature and humidity changed in the opposite way. ③ During the whole growth period, soil moisture and air humidity showed the same change rule. The change trend and range of soil temperature and air temperature were basically the same during flowering and fruit setting period, but in the later period of harvesting, the change range was obviously different. Air temperature was larger than soil temperature. ④ During the whole growth period, the trend of crop evapotranspiration of the three treatments was basically the same, but the change range of T2 was larger than that of T1 and T3, and was greatly affected by soil and air temperature. The modified P-M simulation value of crop evapotranspiration of T2 treatment was better than the measured value, and R2 was 0.851 4. It can be concluded that the temperature and humidity of air and soil in enclosed greenhouse are more suitable for winter crop growth. The effect of heat preservation and moisture conservation is good, and the water is fully utilized, which saves a certain amount of water resources and provides reference for greenhouse management.

Taking the subsurface drip irrigation schedule for alfalfa fields under different rainfall year types of as the research object and based on the experiments of lower limit control of soil water content under subsurface drip irrigation, through the systematic analysis of the growth, water using and yield indexes of alfalfa in every stubble, the model of hay yield-water consumption-WUE was established, the optimum water consumption of alfalfa in every stubble was deduced, and according to the distribution characteristics of different rainfall years in every stubble of alfalfa production, the irrigation schedule under different rainfall years for Ningxia yellow river irrigation area was established. The results showed that: under different rainfall years, when the soil moisture content of alfalfa field under subsurface drip irrigation was larger than 50% of the field water holding rate, the stubble height showed a two-stage variation process of first increasing and then decreasing. The branch number decreased gradually with the continuation of harvest stubbles, the ratio of stem and leaf increased with the increase of irrigation quota in wet year, and decreased gradually with the continuation of harvest stubbles in plain year. The hay yield of each treatment decreased gradually with the increase of harvest stubbles in different rainfall years, and the yield difference between treatments with the lower limit of soil water content higher than 60% of the field water holding rate was not significant. The irrigation amount of each stubble affected the stem-leaf ratio, the height and branch number of alfalfa by affecting water consumption, and then affected the hay yield. Based on above work, the crop water model between yield, water consumption and water production efficiency was established, the optimal water consumption of alfalfa considering both yield and water production efficiency of each stubble was calculated. According to distribution characteristics of different rainfall years in every stubble of alfalfa production, the subsurface drip irrigation schedule for alfalfa fields in Ningxia Yellow river irrigation area in different rainfall years was put forward as following: irrigation quota 5 000 m³/hm² and 20 times in low-rainfall years, irrigation quota 4 600 m³/hm² and 19 times in normal-rainfall years, irrigation quota 4 132 m³/hm² and 17 times in high-rainfall years.

In order to explore the response of water consumption law of spring highland barley in plateau, the dry matter accumulation and yield to soil moisture variation, the field plot experiments were carried out with the spring highland barley species “Himala 22”. Four lower soil water limits, including 75%~80%θf(CF), 65%~70%θf(QK1), 55%~60%θf(QK2) and 45%~50%θf(QK3), and one control treatment (rain-fed irrigation, CK) were applied in the whole growing stages to analyze the water consumption characteristics, dry matter accumulation and yield change under different lower limits level of soil moisture. The results showed that the water consumption amount and water consumption intensity of spring highland barley increased at first and then decreased, then increased again, and decreased linearly with the decrease of the lower soil water limits. The water consumption intensity basically floated around 5 mm per day. Comparing with CK treatment, the irrigation treatments increased the dry matter accumulation of the spring green by 16.08%. Compared with CF, QK1, QK2 and QK3 reduced the dry matter accumulation and relative growth rate of spring highland barley, and the dry matter accumulation and relative growth rate of late growth decreased with the lower limit of soil water control. The regression analysis showed that the linear relationship was extremely significant between dry matter accumulation and meteorological factors, and the correlation coefficient was 0.980 3. The irrigation treatments increased the yield of spring highland barley, which increased ranged from 11.74% to 53.46%. When the lower water limit decreased to 55%~60% of θf, the yield was 6 237.05 kg/hm2, 28.3% higher than that of CF treatment. In addition, the rainfall in the growth seasons showed a significant positive correlation (r=0.994 5) to the yield of spring highland barley, but the temperature had a significant negative correlation (r=-0.974) with it. Meanwhile, the comprehensive influence coefficient (99.23%) had a significant effect on the yield of spring highland barely. Therefore, the rainfall and temperature were the major meteorological factors to cause the yield of spring highland barley in plateau.

In order to investigate the effect of cut-off ratio, which was suitable for Minqin area of Gansu province, on spring corn growth under border irrigation conditions, a field experiment was conducted on the corn breed Xianyu 335 in 2018. In the furrow irrigation test, there were four treatments, namely Q1(cut-off ratio 0.85), Q2(cut-off ratio 0.90), Q3(cut-off ratio 0.95) and Q4 (combination of two periods of surge irrigation and 0.85 of the cut-off ratio). The results showed that the larger the cut-off ratio, the more uniform the nitrogen distribution. The cut-off ratio affected the growth of corn by affecting the soil water storage and nitrate nitrogen in border irrigation. The uniformity and efficiency of irrigation in treatment Q3 and Q4 were higher. The difference in corn yield among the front, back parts of the border was caused by the change of water content in border irrigation. The smaller the cut-off ratio, the lower the back parts of the border corn yield. The yield and WUE of Q3 were the highest, which were 13 563.6 kg/hm² and 2.7 kg/m³, respectively. The yield of treatment Q3 was 17.9% higher than that of Q1 and 9.7% higher than that of Q2. Based on the comprehensive consideration of soil water storage, nitrate distribution and corn yield, the cut-off ratio of 0.95 can be recommended as irrigation parameter for spring maize border irrigation in Minqin area. If considering the effect of saving water and the yield of corn, the cut-off ratio of 0.85 can be selected by surge irrigation.

In this paper, the relationship between soil structure characteristics and permeability of silty saline-alkali soil in the Yellow River Delta was analyzed by SEM and Mercury intrusion test combined with soil permeability coefficient. The results showed that: the undisturbed saline-alkali soil particles in the Yellow River Delta were closely arranged in a mosaic pattern, the pores were narrow and disconnected, the pores were mainly small pores and micropores, and the pore size was small; through the permeability test on the undisturbed soil, it was obtained that the permeability coefficient of the undisturbed soil was 6.46×10-5 cm/s, and the permeability was weak. After the soil was remodeled, the permeability coefficient of saline-alkali soil decreased to 2.40×10-5 cm/s due to the destruction of flocculants and the high content of silt particles in saline-alkali soil. The silty saline-alkali soil in the Yellow River Delta has a dense structure, narrow pores and no connectivity, which cannot provide sufficient seepage channels for water infiltration, resulting in poor soil permeability in this area. Considering the characteristics of soil structure and permeability in this area, it is suggested to mix sand and gravel to break the original structure and increase the seepage channel.

In order to explore the effects of film mulching and nitrogen application on chlorophyll and photosynthetic characteristics of peanut at the middle growth stage, in this study, the combination treatments of no film covering (B) and film covering (F) with nitrogen application levels (N0, N1, N2, N3, N4, N5) were set, the effects of different combination treatments on chlorophyll and photosynthetic characteristics in the middle growth period of peanut were compared and analyzed. The results showed that: Compared with nitrogen application level N0 treatment, nitrogen application could increase chlorophyll content at the anthesis stage. The chlorophyll content increased with the nitrogen application level under B treatment, and the chlorophyll content increased first and then remained stable with the nitrogen application level under F treatment. Nitrogen application could improve net photosynthetic rate, stomatal conductance and transpiration rate, which reached its peak under N4 treatment. Under same nitrogen application level, the net photosynthetic rate, stomatal conductance, transpiration rate and intercellular carbon dioxide concentration were significantly increased by film mulching. In this period, the effect of nitrogen application was weak, and film mulching played a leading role. In the podding periods, compared with nitrogen application level N0 treatment, nitrogen application could significantly improve chlorophyll, net photosynthetic rate, transpiration rate and stomatal conductance, which reached its peak under N2 treatment, this indicated that within the nitrogen application range of 0~120 kg/hm2, nitrogen application level and chlorophyll,net photosynthetic rate, transpiration rate and stomatal conductance were mutually promoted, beyond this range, the relationship between nitrogen application level and four was inhibited. Intercellular carbon dioxide concentration decreases first and then increases with the increase of nitrogen application level, the change trend of net photosynthetic rate with nitrogen application level was opposite, the net photosynthetic rate, stomatal conductance and transpiration rate were increased with the same nitrogen application level, but the effect was weaker than that of nitrogen, far less than that in the flower needle period. The effect of film mulching was weakened and nitrogen application level played a leading role.

In order to explore the reasonable fertilizer application rate of apple orchard under water storage pit irrigation, and to provide a basis for the selection of influencing factors of apple tree photosynthesis model and a reference for the efficient management of water and fertilizer under water storage pit irrigation, in this experiment, four nitrogen application levels, namely 0, 150, 300 and 600 kg/hm2, were set up, and the photosynthetic rate, stomatal conductivity, chlorophyll a, chlorophyll b content and meteorological parameters were tested by in situ test. The data were analyzed by correlation analysis and path analysis, and the regression prediction equation based on key factors was established. The result shows that: ① the photosynthetic rate and stomatal conductance of leaves under water storage pit irrigation were significantly affected by nitrogen application, and both showed a single peak, with the peak occurring at 300 kg/hm2 nitrogen application. ②stomatal conductance, chlorophyll a, chlorophyll b, fertilizer application, solar radiation intensity and relative humidity were significantly correlated with the photosynthetic rate of apple leaves under water storage pit irrigation conditions, while the correlation between air temperature and photosynthetic rate of apple leaves was relatively low. ③ fertilizer application rate was significantly correlated with photosynthesis rate, stomatal conductance, chlorophyll a and chlorophyll b of apple trees. The photosynthetic rate of leaves was indirectly affected by the influence of chlorophyll b and stomatal conductance, and the through-through coefficient was 0.575 and 0.547, respectively. ④under water storage pit irrigation, the key factors are stomatal conductance, chlorophyll a and chlorophyll b. At the same time, the regression equation of photosynthetic rate based on key factors has a high prediction accuracy.

This paper mainly discusses the effects of different irrigation treatments on soil moisture distribution, physiological and ecological indicators, water consumption characteristics and yield of jujube trees in Hexi inland areas under drip irrigation and small tube outflow conditions. The main conclusions are as following: under the same irrigation method, except for the wet level (W1), the water consumption in the germination stage, flowering fruit setting period and fruit expansion period all increases first and then decreases with the increase of irrigation amount, indicating that moderate water deficit can enhance the anti-aging ability of the plant, delay the senescence time of the plant, and make the jujube leaves still have a strong function in the fruit ripening stage. From the sprouting stage of the red jujube to the stop of the stem growth, the stem growth of the W1F2 treatment is the fastest. The irrigation method has no obvious effect on the increase of transverse diameter of red jujube. The effect of irrigation amount on the transverse and longitudinal diameter growth of jujube is extremely significant, and moderate stress (W2) treatment is most beneficial to the growth and development of jujube grain size. Under the same water condition, the yield of red jujube under drip irrigation is higher than that under tube outflow, and the irrigation method under moderate stress level (W2 treatment) has the greatest impact on the yield of red jujube. At the same irrigation level, the yield of jujube increases first and then decreases with the enhancement of water deficit, and reaches the maximum at moderate stress level (W2 treatment). Considering the growth index, apparent quality and yield of jujube, the yield is higher when the irrigation amount is 55%~60% of the field water holding capacity and the irrigation method is drip irrigation. The irrigation scheme is suitable to be popularized in production.

In order to investigate the effects of different irrigation methods on the growth and water use efficiency of summer maize, this experiment took summer maize as the research object, and set four irrigation methods: traditional continuous irrigation (T), canal irrigation (P), surge irrigation (S) and fixed border surge irrigation (G). The effects of four different irrigation methods on leaf area index (LAI), plant height, dry matter accumulation, and yield and water use efficiency of summer maize were compared and analyzed. The results showed that: ①There was no significant difference in plant height under four different irrigation methods during the growth period of summer maize, which was not affected by irrigation methods. ②During the whole growth period, the LAI of P treatment reached the maximum, and the LAI of different border segments did not change much. The difference between the LAI in the middle part of the bed and that in the end of the bed was large. ③The dry matter accumulation in the above-ground part of P treatment was the highest, and the overall performance was P>S>T>G; ④in terms of summer maize yield, P treatment increased by 7.64% compared with T treatment, and P treatment had the highest water use efficiency. Compared with T treatment, S treatment and G treatment, water use efficiency of P treatment was increased by 17.5%, 9.3% and 11.9%, respectively. Therefore, pipe and canal irrigation can improve water use efficiency, and the use of pipe and canal irrigation for summer maize in Tai 'an, Shandong province can achieve better water saving and yield increasing effects.

In order to explore the light response change law of Xinyang May peach under different soil moisture condition, 3-years-old potted saplings were used as experiments material, four light response models, including right-angle hyperbolic model, non-orthogonal hyperbolic model, exponential model and right-angle hyperbolic correction model, were adopted to fit the light response curves of Xinyang May peach under different soil moisture (SWC was 80%, 60%, 40% and 20%, respectively). The main results were as follows: ①The apparent quantum efficiency value of Xinyang May peach was between 0.02 and 0.05 under different soil moisture conditions, the utilization efficiency of light energy under low light increased with the increase of soil moisture. ②The range of light saturation point of Xinyang May peach was 256~670μmol/(m2·s) under different soil moisture conditions. Adequate soil moisture could alleviate the light inhibition of Xinyang May peach. The light compensation point was reduced and the utilization of weak light was enhanced under higher and lower soil moisture conditions. ③The right-angle hyperbolic correction model had the best effect on Xinyang May peach.

In order to study the relationship between soil water and groundwater under the conditions of wheat and bare land growth in lime concretion black soil, the measured date of the evaporation and infiltration in the wheat field and the bare land in wheat growth period for different groundwater depth at the Wudaogou Hydrological Experimental Station from October to May in 1991-2015 were used to analyze the variation of phreatic evaporation, infiltration replenishment and submersible replenishment under different underlying surface conditions with groundwater depth. The results showed that under the wheat growth condition, the evaporation of phreatic water mainly occurred at 2.5 m, while the evaporation of bare phreatic water mainly occurred at 0.4 m, and both decreased with the increase of groundwater depth. The cumulative infiltration replenishment of bare land was higher than the cumulative infiltration recharge under the condition of planting wheat, which decreased with the increase of groundwater depth. The difference between the infiltration of bare land and wheat field increased first and then decreased with the increase of groundwater depth, and the water storage capacity of wheat field was the highest at 2~3 m.Under the condition of planting wheat, the difference between the dive consumption and the groundwater depth was logarithm, the equilibrium critical depth of soil water and groundwater conversion was 1.62 m. When the groundwater depth was less than 1.62 m, the diving consumption played a leading role, the groundwater converted to soil water, while when the groundwater depth was greater than 1.62 m, the soil water recharged to groundwater. The equilibrium critical depth of soil water and groundwater conversion under bare soil conditions was between 0.2 and 0.5 m. The transformation of soil water and groundwater was affected by crop and equilibrium critical depth.

In order to study the sustainable utilization of water resources in inland arid regions, the system dynamics method was adopted, and three types of human activities, including economic development, urbanization intensification and water conservation, were considered in this study. Five different scenarios were set to predict the water demands of Zhangye basin in the middle reaches of Heihe River. The results showed that the domestic and industrial water demands in Zhangye basin kept increasing while the agricultural and total water demands showed certain volatility. During the prediction period, the agricultural water demands were 2.621, 2.621, 1.951, 2.577 and 1.907 billion m3 in five scenarios, respectively, and the total water demands were 2.880, 3.035, 2.252, 2.831 and 2.209 billion m3, respectively. Different human activities had different impacts on water demands in Zhangye basin in different directions and degrees. Economic development had the largest positive impact on industrial water demand, urbanization had the largest negative impact on agricultural water demand, and water conservation had a low impact on water demands. The sustainable use of water resources in inland arid regions must take into account the impact of various human activities. Only in this way can the water consumption of agricultural production and total water consumption be significantly reduced, thus ensure the sustainable use and development of water resources.

In order to study the main chemical composition and source of farmland groundwater in salinized planting area to achieve rational use of water resources and ensure the safety of residents' water use, this paper selects Wulate irrigation area as the research object, and systematically takes samples and analyzes the groundwater. Comprehensively using descriptive statistical analysis, Kriging space interpolation, piper triangle, comprehensive hazard index evaluation, pearson correlation coefficient method, ion ratio analysis and Gibbs semi-logarithmic coordinates synthetically, the content, distribution, composition, source of groundwater chemical components in Wulate irrigation area were analyzed and water quality was assessed. The results showed that: ①The anion and cation contents in the Wulate irrigation area were Cl->HCO-3>SO2-4, Na+>K+>Ca2+>Mg2+, and the spatial variation of SO2-4, Na+ and Cl- was the most obvious, which was greatly affected by the environment and had higher content, and was the main influencing factor for determining groundwater salinization. ②The groundwater in the study area was weakly alkaline as a whole, and the pH value in some areas was point-like and high. Mainly due to the spatial difference of human activities, TDS was distributed in block shape with large spatial variability. Affected by deep brine water surge in the southwest, TDS value was significantly higher than that in other areas. ③The main hydrochemical type of groundwater in the irrigation area was Na++Mg2++HCO-3+Cl- type, and more than 70% of the groundwater in the study area belongs to the grade 4 water quality evaluated by comprehensive hazard coefficient method. The amount should be appropriate when the groundwater is used for irrigation, otherwise it is easy to lead to soil salinization. The Piper trigram combined with Shukarev classification can effectively make up for its shortcomings, and make the chemical composition types clear while clarifying the ion composition structure. ④The groundwater in irrigated areas was mainly affected by human activities and evaporation. The size of TDS and pH value were important factors that affect the ion concentration. When the pH and TDS in local groundwater meet certain conditions, CaCO3 precipitation and CaMg(CO3)2 precipitation will occur and the ion content will change. When TDS is less than 2 000 mg/L, the content of Na+ will increased due to the hydrolysis, whereas the change was reversed.

In this paper, a water balance model based on Saltmod is developed for groundwater dynamics prediction under water-saving policy in Hetao Irrigation District. The climate information, diversion water, measured water table depth, and total drainage water data from 2000 to 2013 are used to calibrate and validate the model parameters. Then the validated model is used to predict the groundwater dynamics in Hetao Irrigation District in the next 10 years under four different annual water diversion, e.g, 45.1(current condition), 42, 40, 36.4×108 m3, and 4 different precipitation, e.g, 100%, 75%, 50% and 25% of current average precipitation. The results show that the model is accurate to be applied for groundwater dynamics and balance analysis. Under the current water diversion and precipitation condition, the water table depth and drainage water are stable as current. However, the water table depth will increase slightly and the drainage water will decrease obviously as water diversion decreases. The water table depth is impacted by the precipitation greatly. The water table depth will increase 0.02, 0.06, 0.09, 0.12 m under the 100%, 75%, 50% and 25% of the current precipitation with 40×108 m3 water diversion, and the value will be 0.04, 0.08, 0.10, 0.13 m with 36.4×108 m3 water diversion. The drainage will decrease significantly with the decreasing precipitation under the water-saving policy. The drainage water will decrease 1.404, 2.031, 2.590, 3.083×108 m3 under the 100%, 75%, 50% and 25% of the current precipitation with 40×108 m3 water diversion, and the value will be 2.364, 2.918, 3.465, 3.946 with 36.4×108 m3 water diversion. The study results will provide a significant reference for the determination of the water diversion threshold which can maintain the sustainable development of Hetao Irrigation District.

Based on the meteorological data of Nanning station, Beihai station, Yulin station and Longzhou station from 1958 to 2015 and the observation data of cassava growth period from 2014 to 2015, the empirical formula of effective rainfall and Penman-Monteith formula were used to calculate the effective rainfall in the main cassava producing areas and the water demand in each growth period of cassava, respectively.The results showed that over the past 60 years, the available rainfall and water demand of cassava in the whole growing period of cassava in the main cassava producing areas in Guangxi showed a decreasing trend. With the exception of cassava in southern Guangxi (Beihai station) with sufficient rainfall from sowing to seedling stage, water shortage of different degrees occurred in all growth stages of other main producing areas, especially in seedling stage-root formation stage and root formation stage-root expansion stage. The indexes of water shortage and water deficit in cassava growing period in main cassava producing areas in Guangxi are small in the southeast and large in the northwest.

In order to study the relationship between irrigation and nitrate leaching loss under one-dimensional condition, in this study, two irrigation levels (2.25×103 t/hm2 and 4.50×103 t/hm2) and two nitrogen fertilizer levels (450 and 675 kg/hm2) were set up to monitor the changes of soil water and nitrate nitrogen content and accumulation in irrigation silt and lime-calcareous soil, and the leaching solution properties under different treatments were determined. The results showed that: ①different soil types and nitrogen application rates had significant influence on the mass water content of soil profile. ②the nitrate nitrogen content of irrigated soil was higher than that of gray calcareous soil. The nitrate nitrogen content of the soil in each layer treated by T2 was lower than that treated by T1. Compared with the four treatments, the peak value of nitrate nitrogen appeared at 60~80 cm, and the T2N1 treatment of soil nitrate nitrogen content was the lowest while T1N2 treatment was the highest. ③Compared with the accumulation of nitrate nitrogen in T1 and T2 treatment, the surface accumulation in T2 decreased by 33.5% and the deep layer decreased by 17.14%. Compared with the treatment of N1 and N2, the accumulation of N2 increased by 48.72% in the surface layer and 28.8% in the deep layer. ④soil type, irrigation and fertilization had significant effects on nitrate nitrogen and other chemical properties in the leaching solution. Therefore, it can be seen that soil type, irrigation amount and nitrogen application amount all have significant influence on the accumulation and loss of nitrogen in the soil. The order from high to low of the effect degree is nitrogen application amount, irrigation amount and soil type.

In order to reduce the waste of water resources and realize the intelligent control of irrigation, a water-saving irrigation intelligent control system was studied and designed based on MCGS configuration system by using the fuzzy PID algorithm, the two-line communication mode of common line and Modbus communication protocol. The system provides low-voltage DC power supply to several irrigation slave motors through two buses, and carries out two-way communication detection and control. After the error comparison between the actual soil moisture value and the set value, the control quantity is output by the fuzzy PID controller, and the slave machine is controlled by the main machine, and the electric ball valve is opened and closed by the slave machine to realize the intelligent control of irrigation. The experimental results show that the water-saving irrigation system has strong stability and robustness with short response time, small overshoot.

In order to solve the problems of low utilization coefficient of water resources and unsatisfactory irrigation effect caused by backward irrigation technology in traditional facility vegetable planting, an intelligent irrigation control system for facility vegetable based on fuzzy control was designed on LabVIEW platform. Based on the soil water potential, a wireless sensor network was built to acquire soil information, and a wireless monitoring network system constructed by on-site centralized control computer and remote monitoring center was built combining 3G network. The difference between real-time soil water potential and ideal water potential and the change rate of the difference were used as the input of the fuzzy control system, and the optimal irrigation time was obtained according to the fuzzy control algorithm. After testing, the system can complete precise irrigation of crops under unattended condition, and farmers can monitor field data and control irrigation in real time remotely.

Studying the characteristics of water and heat flux on the undersurface of sparse vegetation is of great importance for improving agricultural water management and use efficiency of agricultural climate resources. The distribution characteristics of water and heat flux on the underlying surface of the vineyard at different growth stages and under typical weather conditions and the response of latent heat flux to relevant meteorological factors were analyzed by using the data of vineyard Bowen ratio system and meteorological data in 2018. The BP neural network was used to predict the latent heat flux of vineyard. According to the prediction model, the sensitivity of latent heat flux to environmental factors was analyzed and compared. The results showed that the diurnal variation of water and heat flux presented a single-peak conic curve, which started increasing from about 7∶00 a.m. to about 12∶30 p.m. Sensible heat flux accounted for most of the surface energy in the whole growth period. The latent heat flux was small, and the proportion increased with the growth period, and then decreased after the fruit reached the maximum expansion stage. In rainy days, each component of water-heat flux was smaller than that of sunny days, and latent heat flux was slightly larger than sensible heat flux. The variation range of latent heat flux in overcast days was obviously larger than that in other weather conditions. The latent heat flux simulated by BP neural network according to meteorological factors was highly correlated with the calculated value of Bowen ratio method. Meanwhile, the latent heat flux was most sensitive to the change of net radiation and soil heat flux, but less sensitive to the change of wind speed.

Based on meteorological stations and satellite remote sensing data, statistical methods and Arcgis techniques were used to analyze the temporal and spatial distribution characteristics of meteorological and agricultural droughts. The response coefficient of SPEI index at different time scales to VCI index was analyzed by the maximum correlation coefficient method. The results showed that the drought frequency in spring, summer, autumn and growing season was highest in Longdong, Hexi, Longdong and Hexi, Longdong, respectively. Meteorological drought increased in most areas, while agricultural drought decreased. The frequency of agricultural drought showed high spatial pattern in northwest and east, low in central and south. The correlation between SPEI and VCI indicates that the spatial correlation between SPEI and VCI is the largest in woodland and grassland. In terms of time, the VCI index has the greatest correlation with SPEI-3, that is, agricultural drought is the most sensitive to meteorological drought on a 3-month scale. The results can provide reference for agricultural drought prevention in Gansu province.