In order to explore the effects of different drip irrigation flows on cotton fiber quality and yield in the process of saline-alkali land improvement, in this paper, cotton was used as the test object, two types of saline-alkaline soils (Xinjiang sandy loam soil, Jiangsu Dongtai silty loam soil) were used to conduct test, and four drip irrigation flows (0.4, 0.8, 1.2, 1.6 L/h) were set. Through combining outdoor rain shelter cultivation and indoor quality analysis, the cotton fiber quality and yield under different water and salt conditions were monitored and analyzed. The optimal evaluation of two kinds of saline-alkali soils and four drip irrigation flows was conducted by data envelopment analysis. The results showed that: ①For the five fiber qualities indexes of cotton (average length, neatness index, fracture specific strength, macron value, elongation), the optimal dripper flow rate under sandy loam planting was 1.2, 0.4, 1.6, 0.4, 1.2, 0.4 L/h, and the optimal drip flow rate under silty loam planting was 0.8, 0.8, 1.2, 0.8, 0.4, and 1.6 L/h. ②For the five yield indexes of cotton (number of bells per plant, quality of single bell, yield of seed cotton, yield of lint cotton, and coating rate), the optimal dripper flow rate under sandy loam planting was 1.6, 0.8, 1.2, 1.6, 1.6, 1.6, and 1.6 L/h under silty loam planting, respectively, and the optimal dripper flow under silty loam planting was 1.6, 1.2, 1.6, 1.6, and 1.6 L/h. ③Within the drip irrigation flow range designed in this study, the comprehensive benefit of cotton quality in sandy loam soil was higher than that in silt loam soil. ④The result of using the data envelopment analysis method to calculate the comprehensive efficiency of cotton quality and yield under different drip irrigation flows indicated that the efficiency of 0.8 L/h dripper flow rate was the highest in sandy soil and silty soil, which was 0.584 and 0.529, respectively. So the moderate drip irrigation flow rate (that is, 0.8 L/h) was more conducive to the comprehensive benefit improvement of cotton quality and yield.

Based on the measured meteorological data of 32 meteorological stations in Shaanxi province from 1971 to 2020, the spatial and temporal characteristics and periodic patterns of drought in different maize growth stages were analyzed by using the rotating orthogonal empirical function method, trend analysis method and wavelet analysis method on account of the standardized precipitation evapotranspiration index (SPEI). On the strength of the data of corn yield from 1990 to 2020 in 9 areas of Shaanxi Province, the meteorological yield of maize was separated by HP filtering method, and the effect of drought on meteorological yield of maize was analyzed by wavelet analysis and linear regression method. The results showed that:①dry characteristics in the study area could be divided into four drought-sensitive centers: Guanzhong, Yanan, Yulin and southwest Shaanxi, the trend of dryness was concentrated in Yanan, Guanzhong and Yulin regions. ②During 1971-2020, Guanzhong, Yulin and Yanan showed dry-wet alternation during the whole growth period, and the drought was severe in most parts of Shaanxi Province in the late 1990s. ③The meteorological yield of maize in Tongchuan, Baoji, Xianyang and Weinan regions was closely related to the dry and wet conditions at the silk stage, and the other regions were most affected by the dry and wet conditions at the whole growth stage. There was a significant positive correlation between maize meteorological yield and drought condition, and there was a resonance period of 1~4 a from 1994 to 2000. ④The meteorological yield of maize in Yulin, Tongchuan and Weinan increased with the increase of SPEI value, while the yield of maize in Yanan, Baoji, Xianyang, Ankang, Hanzhong and Shangluo was slightly or more reduced when the SPEI value was greater than 1.6 or less than -0.4.

In order to investigate the effects of different irrigation levels on leaf indicators of tomato in soilless crops with inorganic matrix, 'Rui fen 882' cultivar was used as experimental material in this study and a closed cropping system with inorganic matrix and recirculation tanks was used. Drip irrigation was used to irrigate the nutrient solution. Six irrigation rates of nutrient solution were used [0.5 L/(strain/d^-1) (T1), 0.8 L/(strain/d^-1) (T2), 1.1 L/(strain/d^-1) (T3), 1.4 L/(strain/d^-1) (T4), 1.7 L/(strain/d^-1) (T5), 2.0 L/(strain/d^-1) (T6)]. The experimental results showed that with the reduction of irrigation amount of nutrient solution compared to T6 treatment, the height of tomato plants in T1, T2, T3 and T4 treatments decreased by 14.23%, 12.77%, 8.76% and 5.84%, respectively, while there was no significant difference in T5 treatment. Compared to T6, yield per plant decreased by 14.91%, 7.37% and 3.28% for T1, T2 and T3 treatments, respectively. Net photosynthetic rate (Pn) and actual photochemical efficiency (F_v /F_m ) of leaves treated with 15d T6 were significantly higher than that of T1 treatment by 89.25% and 6.08%, but leaf water use efficiency (WUE) of T1 treatment was significantly higher than that of T6 treatment by 24.92%. At the same time, leaf thickness, upper and lower epidermis thickness, gate to shark ratio, superoxide dismutase (SOD) and peroxidase (POD) activities showed a trend that first increased and then decreased; malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content first decreased and then increased. With the increase of treatment duration, photosynthetic parameters, fluorescence parameters, leaf structure-related parameters, and leaf enzyme activities decreased, while malondialdehyde and hydrogen peroxide levels increased. The results of this study indicate that a reduction in irrigation amount inhibits plant growth and photosynthesis, decreases tomato yield and light energy conversion efficiency (F_v /F_m ), but increases leaf water use efficiency (WUE). At the same time, moderate reduction of irrigation amount can improve leaf structure indicators and antioxidant enzyme activity, but when it exceeds a certain range, it causes severe damage to tomato leaves.

In order to study the response of available nitrogen in farmland soil to long-term irrigation of dairy wastewater and its reclaimed water, the corn fields irrigated with 5 kinds of water quality at the downstream the Shengle Economic Park of Hohhot City (91.45% of dairy wastewater) were studied. Five treatments were set, namely, the JG irrigation area for 17 consecutive years of well water, the ZG irrigation area for 17 consecutive years of reclaimed water, the HG irrigation area for 17 consecutive years of well and reclaimed water, the W1 irrigation area for sewage (W1) and the W5 irrigation area for 5 consecutive years of sewage (W5). The changes and characteristics of the content of ammonium nitrogen, nitrate nitrogen and hydrolytic organic nitrogen in soil of 0~90 cm in different irrigation areas were studied and the available nitrogen in soil of plow layer (0~50 cm) was evaluated. The results showed that the ammonium nitrogen content in October was lower than that in April. The soil nitrate nitrogen of treatments of sewage, reclaimed water, mixed water irrigation soil are all higher than that of well water treatment. The hydrolytic organic nitrogen content of sewage irrigation in October and April was higher than that of other irrigation methods. It can be concluded that compared with the well water irrigation, irrigation with dairy wastewater has the most obvious increase effect on nitrogen, reclaimed water irrigation has the middle effect, while mixed water irrigation has the least obvious effect.

In order to investigate the effects of alternate brackish and freshwater irrigation on the response of soil salinity stress and yield quality of tomatoes in facilities, three alternate brackish and freshwater irrigation methods, three treatments, including W1 (freshwater-brackish-brackish), W2 (freshwater-brackish-freshwater), and W3(brackish-freshwater-freshwater), were set up, with freshwater irrigation (CK) as the control. One tomato variety, Qinlingshuyue, was chosen as the model vegetable in this study. The results showed that soil salinity accumulated gradually during tomato growth period under alternate brackish and freshwater irrigation, with an overall trend of method W1 > W2 > W3, and the soil salinity surface aggregation was more serious with method W1 and W2, while soil salinity in method W3 had a tendency of downward leaching, resulting in light salt accumulation on soil surface. After alternate irrigation with brackish and freshwater, the soil salinity accumulated to different levels. Tomatoes were thus under salt stress to varying degrees, with malondialdehyde (MDA), proline (PRO), soluble protein (SP), soluble sugar (SS) and superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) contents in tomato leaves found to increase to different degrees. The correlation analysis showed that soil salinity was in highly significant and positive correlation with CAT and PRO of tomato leaves (P< 0.01) and with soluble sugars (SS) of leaves (P< 0.05), indicating that tomato improved its resistance to the salt stress hazard by changing the activities of various protective enzymes and the content of osmotic substances. Comparative analysis showed that the soluble solids, nitrate, Vc and total phenol contents and yield of tomatoes under method W3 were higher than those under the CK, indicating that the appropriate alternate irrigation method of brackish and freshwater can improve the quality and yield of tomatoes.

Low soil organic matter and poor water holding capacity are two major restrictive factors hindering the benign development of the apple industry in the Loess Plateau. In order to solve the above problems, biochar, Super Absorbent Polymers, Bacillus subtilis and Bacillus mucilaginosus were selected as soil amendments for two years field experiment. The results showed that biochar, Super Absorbent Polymers, Bacillus subtilis and Bacillus mucilaginosus addition increased the average total nitrogen content of soil by 88.86%, 49.38%, 30.05% and 25.35% compared with CK, respectively; Compared with CK, the mean of soil nitrate nitrogen was increased by 1.70, 1.50, 1.29 and 1.49 times and soil ammonium nitrogen was increased by 29.01, 8.50, 12.75 and 22.60 times, respectively. Among these soil amendments, biochar has the most significant impact on soil organic carbon storage, with an increase of more than 3.70 time, compared with CK. Through path analysis, soil pH, hydraulic conductivity and nitrate nitrogen directly affect soil organic carbon storage, and soil bulk density, ammonium nitrogen, available potassium and soil aggregates indirectly affect soil organic carbon storage by affecting soil pH and soil hydraulic conductivity. Soil amendments have certain effects on the new height, fruit diameter, root distribution and yield of fruit trees. After the application of biochar, the root density of fruit trees increased by 3.05 time compared with the CK at the depth of 0~20 cm soil layer and the apple yield increased significantly compared with the control (P< 0.05). Through the economic benefit evaluation and analysis, the economic benefit of the improvement after only applying biochar is positive, reaching 1 149.26 yuan·hm^-2. It is suggested that the application of biochar should be an effective way to improve orchard soil and increase apple yield.

Different soil texture directly affects the degree of soil water penetration and crop nutrient absorption, and then affects the yield and quality of crops. In view of the difficulty of efficient and accurate identification of soil texture, this paper uses convolutional neural network random forest (cnn-rf) model algorithm to achieve efficient and accurate identification of soil texture. The soil was ground, screened, and photographed to establish a database of soil texture and images. The color features and texture features in the images were extracted and analyzed by CNN-RF model combined with 3 combination methods (color, texture, color with texture). Mean absolute error (MAE), root mean square error (RMSE) and decision coefficient (R ²) were used to evaluate the regression performance of the model. From the results of model classification using the confusion matrix, it can be found that the predicted MAE, RMSE, and R ² values of sand particles are 3.37, 3.71 and 0.99, respectively. The MAE, RMSE, and R ² values of silt particles are 3.48, 3.79 and 0.98, respectively. The MAE, RMSE, and R ² values of clay particles are 3.38, 3.76, and 0.99, respectively. Compared with RF, KNN, VGG6-RF models, the MAE value and RMSE value obtained by CNN-RF model are smaller. The R ² value is close to 1, and its accuracy is 99.43%. Therefore, the performance is better. This method has the advantages of simplicity, ease of use, rapidity, reliability, and accuracy, and is of great significance to the optimal management and sustainable utilization of cultivated land soil in hilly area of south of the Five Ridges.

Optimizing water and energy resources and adjusting the planting structure of crops is of great significance to ensure food security and ecological security. In this paper, taking Shanxi Province as the research area, the water footprint and energy consumption accounting model are used to analyze the water consumption and energy consumption characteristics of major crops, and a multi-objective planning model is constructed with water resources, energy, and grain as constraints, so as to optimize the planting structure of major crops. The results show that there are big differences in the annual average water footprint and energy consumption of various crops. Soybean belongs to the blue water consumption type with extremely high water consumption and high energy consumption, millet belongs to the high water consumption, extremely high energy consumption and grey water consumption type, and oil crops belong to the high water consumption and high energy consumption grey water blue water consumption type, wheat belongs to medium water consumption and moderate energy consumption blue water consumption type, corn is low water consumption and low energy consumption blue water grey water consumption type, vegetables are extremely low water consumption and extremely low energy consumption grey water blue water consuming crops. In the optimized planting structure plan, the proportion of corn, millet and oilseeds planted area decreased, the proportion of wheat and soybean planted area increased, and the proportion of vegetables did not change much. Due to the difference in water and heat conditions, the planting structure of crops in Shanxi Province has certain spatial differences, corn, millet, soybean and oilseeds are all planted in Shanxi Province. Wheat is mainly grown in the hilly areas of southern and southeastern Shanxi. Vegetables are mainly distributed in basins with relatively superior geographical and hydrothermal conditions. On the basis of the relationship between water-energy-food, the optimized planting structure conforms to the 14th Five-Year Agricultural Modernization Plan of Shanxi Province. The overall plan has the characteristics of low energy consumption, low water consumption and low pollution, which is conducive to improving agricultural sustainable development.

In this paper, two soil conditioners, biochar and attapulgite, were selected, pure soil was used as CK, and three mass ratios of biochar (0%, 2%, 4%) and three mass ratios of attapulgite (0%, 2%, 4%) were set. By measuring soil water characteristic curve and combining with electron microscopy test, the soil equivalent pore distribution, specific water capacity, water constant and soil microstructure changes under different ratios of biochar and attapulgite were analyzed, and the effects of biochar and attapulgite on soil hydraulic characteristics were studied. The results showed that compared with CK, both biochar and attapulgite could enhance soil water holding capacity. When no attapulgite was added, the soil water-holding capacity increased with the addition of biochar; when 2% attapulgite was added, the soil water-holding capacity decreased with the addition of biochar; when 4% attapulgite was added, the soil water-holding capacity enhanced with the addition of biochar. The addition of biochar alone can increase the soil specific water capacity, and the addition of attapulgite alone can reduce the soil specific water capacity. After adding attapulgite, the application of 2% biochar can significantly increase the soil specific water capacity. Compared with CK, the residual water content of soil with biochar and attapulgite increased by 15.6%~103.1%; compared with CK, gravity water decreased by 0%~7.1%. When no attapulgite was added, the micropores increased with the addition of biochar; when 2% attapulgite was added, the micropores decreased with the addition of biochar; when 4% attapulgite was added, the micropores increased with the addition of biochar. The microstructure analysis showed that the biochar and attapulgite would make the soil particles in close contact, resulting in bridging junctions. The study result will provide some theoretical support for the improvement of soil environment in the northwest arid region.

Based on hydrogen-oxygen stable isotope tracing method, the characteristics of stable isotope distribution of soil water, and soil water consumption, photosynthesis and water use in summer maize under conventional irrigation (X) and drip irrigation (D) (X1, D1：15 mm；X2, D2：30 mm；X3 and D3：45 mm), were studied. The results showed that the absorption of water deepened with the advancement of wheat growth period. Soil moisture at 0~20 cm depth was mainly consumed by maize in the jointing stage under different treatments, reaching to over 60%. D1 and D2 treatments mainly used soil moisture at 60~80 cm and 20~40 cm depth, accounting for 21.4% and 23.8%, respectively. By the filling stage, compared with the conventional irrigation, the drip irrigation condition is more conducive to promote the utilization of water below 40cm soil layer, thus reducing the ineffective evaporation of water. With the advancement of growth stage of maize and the increase of irrigation water, the daily water consumption of maize increased significantly, and the water quantity of drip irrigation was lower than that of conventional irrigation. Compared with conventional irrigation, D2 treatment was more conducive to improve the photosynthetic rate, transpiration rate, stomatal conductivity and leaf water utilization efficiency of maize. In addition, drip irrigation treatment significantly increased the maize biomass during the harvest period. Finally, drip irrigation reduced the total water consumption of corn, increasing the yield by 5.3%~21.7% and water use efficiency by 9.2%~26.8% compared with conventional irrigation, the D2 treatment resulted in the highest among different treatments. Related analysis shows that, the water contribution rate of soil water at 20~40 cm depth in the jointing stage and soil water at 60~80 cm depth in the filling state were more conducive to the improvement of the yield of maize, and soil water at 60~80 cm and 80~100 cm depth in the jointing stage was more conducive to improving the water use efficiency maize.

In order to explore the effects of comprehensive evaluation results of different evaluation methods for tomato growth under alternate film drip irrigation under the coupled regulation strategy of water-zeolite, in this paper, principal component analysis, entropy method and optimized analytic hierarchy process were selected to comprehensively evaluate the nine indicators of tomatoes under different treatments, these indicators include plant height(Kh), stem diameter (Kt), root volume(Rv), net photosynthetic rate(Pn), leaf area index(Lai), vitamin C content(VC), soluble solid content(SS), yield(yield) and water use efficiency(WUE), and the comprehensive evaluation score of each treatment was calculated. Using the principal component analysis extracts two principal components, growth quality factor and water efficiency factor, and the variance contribution rate were 74.420% and 17.023%. The comprehensive evaluation scores of each treatment based on the principal components analysis are ranked as follows: Z₆W₁₀₀> Z₉W₁₀₀> Z₀W₁₀₀> Z₃W₁₀₀> Z₆W₇₅> Z₉W₇₅> Z₃W₇₅> Z₀W₇₅> Z₆W₅₀> Z₉W₅₀> Z₃W₅₀> Z₀W₅₀. Using the entropy method, the three indicators with the largest weights are WUE, Kh and Yield. The comprehensive evaluation scores of each treatment based on the entropy method are ranked as follows: Z₆W₁₀₀> Z₆W₇₅> Z₃W₁₀₀> Z₉W₇₅> Z₉W₁₀₀> Z₆W₅₀> Z₃W₇₅> Z₉W₅₀> Z₀W₁₀₀> Z₃W₅₀> Z₀W₇₅> Z₀W₅₀. Using the optimization analytic hierarchy process, the three indicators with the largest weights are Yield, WUE and Rv. The comprehensive evaluation scores of each treatment based on the optimized analytic hierarchy process are ranked as follows: Z₆W₁₀₀> Z₆W₇₅> Z₃W₁₀₀> Z₉W₁₀₀> Z₉W₇₅> Z₆W₅₀> Z₃W₇₅> Z₀W₁₀₀> Z₉W₅₀> Z₃W₅₀> Z₀W₇₅> Z₀W₅₀. It can be concluded that the principal component analysis method can reflect the overall impact of each index on the research objective, but it has the problem of information loss when reducing the data dimension. The entropy value method can comprehensively reflect the influence and function of each index on the research target, but in the process of weight assignment, some indexes with a high degree of importance but a small degree of dispersion are given a low weight. The optimized analytic hierarchy process can take into account the importance and difference of evaluation indicators, overcome the shortcomings of the other two methods, and is the best comprehensive evaluation method. The comprehensive ranking score results based on different evaluation methods are different. However, all of them show that Z₆W₁₀₀ treatment is the optimal control strategy for high quality and high yield of tomato under alternating drip irrigation under mulch, and Z₀W₅₀ treatment is the worst control strategy.

The aim of this study was to investigate the characteristics of maize root morphology and its relationship with yield under local irrigation and nitrogen application. The corn of “Jinxibei 22” was used as the test material for 2 consecutive years under the field condition by ridge planting and furrow irrigation. Different irrigation methods (AI with alternating furrow irrigation， FI with fixed furrow irrigation， CI with conventional furrow irrigation) and nitrogen application methods (AN with alternating nitrogen application， FN with fixed nitrogen application， CN with uniform nitrogen application) were used in the experiment. The root length， mass and surface area of maize plants in each layer of 0~100 cm soil layer (each layer was 20 cm) were monitored at jointing， trumpet， tasselling stage， filling and maturity stages， and the corresponding root density was converted. Grain yield and its composition were measured at harvest time. At tasselling， filling and maturity stages， the total root quantity (total root length， total root dry weight and total root surface area) in 0~100 cm soil layer was as follows： AI>CI>FI under any nitrogen application method (P<0.05). Under any irrigation method， there was no significant difference between AN and CN， but it was significantly higher than FN (P<0.05). The total root amount was the largest in alternating furrow irrigation with uniform nitrogen application (AICN) and alternating furrow irrigation with alternating nitrogen application (AIAN)， while the total root amount was the smallest in fixed furrow irrigation with fixed nitrogen application (FIFN). The grain yield was positively correlated with root length density and root dry mass density in 0~40 cm soil layer at tasselling， filling and maturity stages， and the correlation coefficient reached a highly significant level at filling stage. The number of grains per ear and weight per thousand grains were positively correlated with root length density， root dry mass density and root surface area density. In conclusion， uniform nitrogen application under alternate furrow irrigation and alternate nitrogen application under alternate furrow irrigation could promote the root growth in the 0~100 cm soil layer at tasselling， filling and maturity stages of maize， and increase the root length density， root dry mass density and root surface area density in the 0~40 cm soil layer at filling stages of maize， which was beneficial to obtain higher grain yield.

In recent years, drought events have occurred frequently under the global climate change, which has further led to the sharp loss of forests and aggravated desertification in some areas. Therefore, it is of great significance to quantitatively study the response of forest greenness to drought events. Combining the forest greenness anomaly index which is based on leaf area index and the drought index of standardized precipitation evaporation index, the response of global forest greenness anomalies to drought events is studied, and sensitivity differences of different types of forest greenness anomalies to drought events are explained. The results show that: ①The global forest area increased from 2007 to 2010 and then decreased during the period of 2011-2018. The largest forest area with greenness anomalies appeared in 2008, accounting for 57.15% of the total forest area. ②Under the influence of drought, greenness anomalies occurred in the main forest regions of the world, while the areas without greenness anomalies were mainly occurred in the forest margins and coastal areas. ③There is a positive correlation between forest greenness anomalies and drought events in western United States, South Africa, southwest China and Australia. ④Broad-leaved forest was the most sensitive to drought, followed by mixed forest, coniferous forest and shrubby forest. The results of this study revealed the differential rules of global forest greenness in response to drought events under climate change, and analyzed the attribution of forest greenness changes in various regions, providing personalized scientific basis for global forest ecological protection.

The Qingshui River in the Yongding River basin and the Bai River in the Chaobai River basin are the key basins for Zhangjiakou to build up a water conservation functional area in the capital region. Based on multi-year hydrological data of the Qingshui River Basin (1951-2020) and the Bai River Basin (1970-2020), the trend and abrupt change of runoff and climatic elements (precipitation and temperature) of the Qingshui River Basin and the Bai River Basin were analyzed by using mathematical statistical methods such as ordered cluster analysis and wavelet analysis, the effects of precipitation, temperature and evaporation on runoff changes were also discussed based on Pearson correlation analysis and contribution rate analysis. The results showed that: ①The precipitation in the Qingshui River Basin and the Bai River Basin showed a slight upward trend, with an average decline rate of 0.964 mm/10a and 3.316 mm/10a from 1960 to 2020, and sudden changes occurred in 1965 and 2016; ②The temperature in the Qingshui River Basin and the Bai River Basin showed a significant upward trend, the average temperature rise rate in the Qingshui River Basin was 0.246 ℃/10a, and the average temperature rise rate in Bai River Basin was 0.207 ℃/10a, the temperature suddenly changed in 1988; ③The runoff in the Qingshui River Basin and the Bai River Basin showed a significant downward trend in the last 70 years, both attained a significance test level of 99% and sudden changes occurred in 1979 and 1974; ④The main factor of runoff is precipitation, the annual variation of runoff is mainly affected by precipitation from May to August when precipitation is abundant.

In order to understand the effects of drought stress and rehydration spraying spermidine on the physiological characteristics of T. chinensis var. mairei, in this experiment, the potted water control method was used to simulate different drought environments, and four treatments were set, including normal water supply (CK), mild drought (T1), moderate drought (T2), and severe drought (T3), and three concentrations of exogenous Spermine rehydration treatment (N1, N2, N3) were applied to explore the drought resistance mechanism of T. chinensis var. mairei under different drought conditions, and to compare the optimal rehydration concentration of exogenous spermidine. The results showed that drought stress could significantly increase the total chlorophyll content, SOD activity and soluble protein content of the leaves of T. chinensis var. mairei in the short term, significantly increase the accumulation of malondialdehyde (P<0.05), and with the prolongation of stress time, it showed different fluctuation changes. Under severe drought stress, the changes of various values were larger, and the peak time of SOD activity and soluble protein content came earlier. In the rehydration test, compared with the single rehydration treatment (EGCK), the spraying of spermidine with three concentrations had significant promoting effect (P<0.05), and the combination of 1.0 mmol/L exogenous spermidine (N2) had the best effect on the rehydration of T. chinensis var. mairei at seedling stage, and the drought recovery effect of the three spermidine concentrations on T. chinensis var. mairei was as follows: N2>N3>N1. Comprehensive research shows that moderate drought stress leads to two-way fluctuations in physiological and metabolic activities. Combining drought stress training with spermidine spraying can improve the agronomic characteristics of T. chinensis var. mairei and enhance its stress resistance.

The landscape pattern of source and sink refers to the landscape type or unit which can not only promote the positive evolution of non-point source pollution process, but also prevent/delay the ecological process. In this study, the landscape pattern distribution information of the study area was extracted by Taiyuan high-resolution remote sensing image classification in 2020. Based on “Source-Sink” Theory and Lorentz curve, the influence of landscape spatial distribution on non-point source pollution was analyzed, and the landscape pattern optimization suggestions for non-point source pollution prevention and control were put forward. The results show that the overall risk of non-point source pollution in Taiyuan city is relatively high, and the landscape units dominated by the “source” landscape account for 62.87%. The risk of non-point source pollution in the central part of Taiyuan is higher than that in the eastern and western mountainous areas. The main type of “source” landscape is located in the construction land on both sides of the Fenhe River in the middle of Taiyuan City, which is an extremely high risk area, accounting for 17.69% of the total area, while the pollution risk of the “sink” landscape type (woodland) on the east and west sides of Taiyuan City is relatively small. Based on slope factor and river distance factor, the ratio of “source” and “sink” landscape pollution load is greater than 1. Among the slope factors, “sink” landscape is widely distributed in high slope areas, and the landscape layout is reasonable. Among the river distance factors, the "source" landscape is distributed in the area close to the river, which is easy to lead to non-point source pollution.

In order to understand the migration law of the total iron in the bottom mud of the Yangshapao Reservoir in the western part of Jilin province, through interior simulation experiments, the experimental research on the influencing factors of the total iron migration of the bottom mud under different pH value, water temperature, dissolving oxygen, and water power was performed. The result showed: On the 10th day of the experiment, the total iron concentration with a pH of 9 was 0.120 mg/L, and the total iron concentration with a pH value of 6 was 0.535 mg/L, which was 5.57 times the pH value of 9. On the first day, the total iron concentration at 4 ℃ was 0.024 mg/L, and the total iron concentration at 25 ℃ was 0.037 mg/L, which was 1.54 times at 4 ℃. On the 10th day, the total iron concentration at 4 ℃ was 0.043 mg// L, the total iron concentration at 25 ℃ was 0.153 mg/L, reaching 3.56 times at 4 ℃. In the state of aerobic, the total iron concentration on the first day was 0.037 mg/L, and the total iron concentration on the 10th day was 0.153 mg/L, which was 3.14 times higher than that on the first day. In the state of anaerobic, the total iron concentration on the first day was 0.089 mg/L, and the total iron concentration on the 10th day was 0.447 mg/L, an increase of 4.02 times from the first day. When the oscillating time was 24 h, the total iron concentration of 0 rad/min was 0.037 mg/L, and the total iron concentration under 80 rad/min was 0.249 mg/L, which was 6.73 times in a static state; the total iron concentration under 150 rad/min was 0.513 mg/L, which was 13.86 times in the static state. It can be seen that the alkaline environment has inhibitory effects on the migration of the total iron in the bottom mud. The total iron mobility rate is slow at low temperature conditions. The dissolved oxygen content is negatively related to the migration of the total iron. The disturbance is the main reason for the migration of the total iron in the bottom mud.