We examined the effects of different combined soil amendments on the quality of saline-alkali soil and on the growth, yield, and quality of watermelon in a field experiment. There were four treatments, including 75 kg·hm-2 sulfur fertilizer+600 kg·hm-2 bio-organic fertilizer (T1), 75 kg·hm-2 sulfur fertilizer+300 kg·hm-2 soil conditioner (T2), 600 kg·hm-2 bio-organic fertilizer+300 kg·hm-2 soil conditioner (T3), and 75 kg·hm-2 sulfur fertilizer+600 kg·hm-2 bio-organic fertilizer+300 kg·hm-2 soil conditioner (T4), with no amendment application as the control (CK). We analyzed the effects of different treatments on soil pH, soil salt content in the 0-100 cm soil profile, as well as photosynthetic characteristics, growth, yield, and fruit quality of watermelon. The results showed that all amendment treatments reduced soil pH and salt content to different extents. The decrease in soil pH was mainly concentrated in the 0-60 cm soil layer. The treatments of T3 and T4 showed more obvious effects on reducing soil pH in the 20-40 cm soil layer. The T2 treatment had a more prominent effect on reducing soil salt content, with a reduction of 13.8% and 29.5% in the 0-20 cm and 20-40 cm soil layers, respectively. The T2 and T3 treatments significantly increased net photosynthetic rate, transpiration rate and stomatal conductance of watermelon. The T2 treatment mainly promoted leaf area expansion and main vine elongation. The T3 treatment mainly promoted main vine elongation and stem thickening. The T1, T2, T3, and T4 treatments increased watermelon yield by 8.9%, 12.4%, 12.3%, and 11.0%, respectively. The T3 treatment significantly increased fruit hardness, while the T2 and T4 treatments significantly increased soluble solids, vitamin C content, and sugar-acid ratio. Based on the multi-criteria decision-making model, the comprehensive ranking of different treatments on watermelon was T2>T3>T4>T1>CK. Overall, the combined application of 75 kg·hm-2 sulfur fertilizer and 300 kg·hm-2 soil conditioner was the optimal treatment for improving saline-alkali soil, promoting watermelon growth, increasing yield and improving fruit quality.

【Objective】Optimal drip irrigation parameters using brackish water is important for crops grown in gravel-sand mulched fields but is currently lacking, limiting the rational use of brackish water resources. This paper presents the results of a field experiment that investigated the effects of emitting rate and irrigation amount on soil water-salt distribution, as well as growth, fruit yield and quality of watermelon in such soils. 【Method】The experiment was conducted in a watermelon field. It involves three emitting rates: 2.0, 3.0 and 4.0 L/h, and three irrigation amounts: 112, 224 and 336 m3/hm2. During the experiment, we measured the spatiotemporal distribution of soil water and salt, growth indexes, yield and fruit quality of the watermelon.【Result】①Soil water content in the 0-100 cm soil profile increased with irrigation amount. When the irrigation amount was the same, soil water content in the 0-40 cm soil profile decreased as emitting rate increased. ②Within 0-30 cm horizontally from the emitter and 0-100 cm soil depth, soil electrical conductivity increased with increasing emitting rate, while decreasing with increasing irrigation amount. ③At the end of first growing season, most treatments resulted in soil desalination in the 0-100 cm soil layer, except the combinations of 336 m3/hm2 + 3.0 L/h emitting rate and 336 m3/hm2 + 4.0 L/h emitting rate, which that led to a salt accumulation in the 0-100 cm soil. ④Combinations of 224 m3/hm2 irrigation amount + 3.0 L/h emitting rate and 336 m3/hm2 + 3.0 L/h emitting rate improved growth and fruit yield of the watermelon by 74.7% and 72.1%, respectively, compared to that in the 112 m3/hm2 + 2.0 L/h treatment; it also improved fruit quality and irrigation water use efficiency. ⑤Structural equation analysis showed that the drip irrigation parameters indirectly affected growth, yield and fruit quality of watermelon, through directly regulating soil water and salt redistribution in the soil profile. 【Conclusion】Considering soil water-salt distribution, soil salt balance, growth, yield and fruit quality of the watermelon, the optimal parameters for drip irrigation using brackish water in gravel-sand mulched fields are an irrigation amount of 224 m3/hm2 combined with an emitting rate of 3.0 L/h.

Soil gravel–sand mulching—an ancient farming method in arid areas—is used to cope with drought by conserving water and improving soil temperature, the latter being a key factor affecting agricultural production. The objective of this study is to ascertain the influence of soil water content and meteorological elements on soil temperature under gravel–sand mulching conditions. Field experiments, analysis of variance, Pearson correlation analysis, and other statistical methods were used to study the effects of varying soil moisture content on soil temperature at 0–25 cm depth under gravel–sand mulching conditions, and to analyze the relationships between meteorological factors and soil temperature during the temperature measurement period. In the 0–20 cm soil layer, the soil accumulated temperature decreased with an increase in soil moisture content, while the change rate of temperature increased. In the test range, the temperature conductivity of 10–15 cm soil increased with the increase in soil water content in the 20–40 cm layer. Under gravel–sand mulching conditions, soil temperature was not only related to air temperature but also positively related to water vapor pressure. When the soil moisture content was high, the soil temperature decreased with an increase in atmospheric evaporation capacity. When the soil moisture conditions were poor, the meteorological factors had an effect of increasing the soil temperature. Under gravel–sand mulching conditions, soil moisture content exhibits a significant negative correlation with both soil temperature and accumulated temperature. Higher soil moisture enhances vertical heat conduction, facilitating heat transfer from the surface to deeper layers. The 10–15 cm soil layer acts as a thermal buffer zone, regulating temperature fluctuations and mitigating extreme heat variations. However, higher air temperature leads to greater heat accumulation, while, in wetter soils, enhanced heat conduction and evaporative cooling lower soil temperature.

[Objective]The objective of this study was to explore the effects of continuous reduction of chemical fertilizer on supply of soil nitrogen,phosphorus and potassium,and grain yield of spring wheat in Yellow River Irrigation Area of Ningxia(NYRIA),and to analyze the factors affecting yield stability,and then to provide a theoretical basis for rational fertilizer reduction and high yield and stable yield of spring wheat.[Method]The field positioning experiment of chemical fertilizer reduction application was carried out for four consecutive years from 2019 to 2022,with Ningchun 4 of spring wheat cultivar as the test crop.The field treatments included conventional fertilization(CF with N 270 kg·hm-2,P2O5 150 kg·hm-2,K2O 75 kg·hm-2),the lower limit of reduced fertilization(RF1)with N180 kg·hm-2,P2O5 45 kg·hm-2,and K2O 30 kg·hm-2(which reduced N,P2O5,and K2O by 33.3%,70.0%,and 60.0%,respectively,compared with conventional fertilization),the upper limit of fertilization reduction(RF2)with N 225 kg·hm-2,P2O5 75 kg·hm-2,K2O 45 kg·hm-2(which reduced N,P2O5,K2O by 17.0%,50.0%,40.0%,respectively,compared with traditional fertilization),and no fertilization(CK).The climatic factors during the growth period of spring wheat,soil moisture content before sowing and harvest of spring wheat,soil mineral nitrogen,available phosphorus and available potassium content,dry matter accumulation in shoot,grain yield and yield components of spring wheat at harvest were analyzed,and correlations among them were also discussed.[Result]The soil moisture content before sowing were inter-annual differences in 2019-2022,among which the average was only 19.5%in 2022;the soil moisture content before sowing was significantly affected by fertilization treatment in 2020,there was no significant difference of soil moisture content before sowing between fertilization treatments in other years.The content of mineral nitrogen,available potassium and available phosphorus in the soil before sowing and harvesting were higher under conventional fertilization CF treatment,followed by RF2 treatment;there was no significant difference between them,while which of the RF1 treatment tended to decrease.In 2019,the CF treatment had the highest accumulation of dry matter in shoot and grain yield,which was 23 261.7 kg·hm-2 and 9 449.0 kg·hm-2,respectively,and had an increase of 2.8%-4.5%and 3.2%-16.0%compared with the RF2 treatment.However,from 2020 to 2022,the RF2 treatment had the highest accumulation of dry matter in shoot and grain yield,and there was no significant difference between the RF2 treatment and the CF treatment,but the yield of RF2 treatment performed the most stable at 4 years.From the perspective of inter-annual changes,the number of ears,1000 grain weights and yields of hectares for all treatments showed a downward trend year by year,so the fertilization rate was not the main reason for the inter-annual difference in grain yield,but which was closely related to soil moisture before sowing,precipitation,temperature,humidity and wind speed.The decrease in yield in 2022 was accompanied by a lower soil moisture before sowing,hot dry air phenomenon during the filling period and a change in the nitrogen fertilizer base ratio.[Conclusion]In NYRIA,continuous and appropriate reduced application of chemical fertilizer with N 225 kg·hm-2,P2O5 75 kg·hm-2,K2O 45 kg·hm-2 would not significantly reduce the supply capacity of soil nitrogen,phosphorus and potassium,and increase the number of ears,ear grains and 1000 grain weights in the hectares of spring wheat,and promote the transfer and accumulation of dry matter in shoot to grains to a certain extent,then tend to increase the grain yield of spring wheat.However,there were interannual differences in spring wheat yield due to climate factors,such as rainfall,wind speed,and humidity,as well as soil moisture,continuous cropping obstacles,and nitrogen fertilizer application ratios.Among them,temperature,relative humidity,and wind speed were the main factors affecting interannual variation of wheat yield,and their impact on fertilization effects needed further research.

In arid areas, droughts caused by climate change seriously impact wheat production. Therefore, research on spatial and temporal variability of dry and hot wind events and drought risk under different development patterns of future climate can provide a reference for wheat cultivation planning in the study area. Based on meteorological data under three scenarios of the CMIP6 (Sixth International Coupled Model Comparison Program) shared socio-economic path (SSP), we introduced wheat dry hot wind discrimination criteria and calculated the Standardized Precipitation–Evapotranspiration Index (SPEI). Future temperature changes within the Ningxia Province were consistent, increasing at a rate of 0.037, 0.15 and 0.45 °C·(10 a−1) under SSP126, 245 and 585 scenarios, respectively. Simultaneously, average annual precipitation would increase by 17.77, 38.73 and 32.12 mm, respectively. Dry hot wind frequency differed spatially, being higher in northern Ningxia and western Ningxia, and lower in southern Ningxia and eastern Ningxia. During the wheat growing period, there is an obvious increasing drought risk trend under the SSP585 model in May, and the possibility of drought risk in the middle period was highest under the SSP126 model. In June, SPEI was generally higher than in May, and the risk of alternating drought and flood was greater under the SSP585 model, while near-medium drought risk was lower under the SSP126 and SSP245 models. The influence of DHW (dry and hot wind) on wheat yield will increase with the increase of warming level. However, when DHW occurs, effective irrigation can mitigate the harm. Irrigation water can be sourced from various channels, including rainfall, diversion, and groundwater. These results provide scientific reference for sustainable agricultural production, drought risk and wheat meteorological disaster forecast in inland arid areas affected by climate change.

It is crucial to understand and forecast future climate change and its impact on regional crop yield. This study employed the optimized World Food Studies (WOFOST) model and Coupled Model Intercomparison Project Phase 6 (CMIP6) data to assess the effects of climate change in different emission scenarios [e.g., ssp126 [sustainable development with low greenhouse gas (GHG) emissions], ssp245 (balanced development with medium GHG emissions), and ssp585 (conventional development with high GHG emissions)] on the spring wheat yield and growth period in Northwest China. Lasso regression, Support Vector Machine (SVM), Recurrent Neural Networks (RNN), Random Forests (RF), and RNN showed superior optimization performance for radiation amount surface downwelling shortwave radiation flux (RSDS), maximum temperature (Tmax), minimum temperature (Tmin), wind speed (sfcWind), and precipitation (PR). These optimizations decreased the root mean square error (RMSE) of RSDS, Tmax, Tmin, sfcWind, and PR by 1.0285, 2.6396, 2.7839, 2.3763, and 0.3020, respectively, compared to the original data. Long-term annual PR will increase by 415 mm in the ssp126 scenario, whereas the increases were estimated to be 257 mm and 249 mm under the ssp245 and ssp585 scenarios, respectively. Regarding temperature, Tmax and Tmin are expected to rise by 0.97 °C and 1.08 °C, respectively, under the ssp126 scenario. These values are also projected to be 2.29 °C/1.70 °C and 1.81 °C/3.36 °C for Tmax/Tmin under the ssp245 and ssp585 scenarios, respectively. The optimized crop parameters can effectively improve the yield simulation accuracy of the WOFOST model and reduce RMSE. Yinchuan and Huinong are projected to experience an increase of 19.8 % and 15.8 % in their average yield under the ssp585 scenario in the short-term future, compared to the average yield during the baseline period. Qingtongxia is expected to reach a 20.2 % increase under the ssp126 model, while Zhongning will undergo an increase of 12.3 % under the ssp585 model, and Litong will observe an 11.2 % increase under the ssp245 model. Qingtongxia showed the highest long-term production growth, with increases of 18.0 % and 15.3 %, respectively, under the ssp126 and ssp245 scenarios. Higher temperatures, radiation levels, and PR are typical features of the future climate in the study area. The CMIP6 data simulations and the optimized WOFOST model predict that spring wheat yield will increase soon but will not increase as much in the long run.

[Objectives]With the adjustment of agricultural cultivation structure in Ningxia Yellow River Irrigation Region,the area of greenhouse increased greatly.The objectives of this study were to investigate the nitrate nitrogen（N） pollution in shallow groundwater and to analyze its relationship with soil nitrate N in intensive greenhouse planting areas,and then to provide theoretical basis for effective control of groundwater nitrate N pollution in Ningxia and other similar areas of China.[Methods]A total of 214 groundwater samples and 102 soil samples were obtained from seven typical greenhouse intensive planting areas in different periods,and the contents of nitrate N and salts of groundwater and soil were analyzed.[Results]Results showed that the contents of nitrate N in groundwater samples exceeded the grade Ⅲ standard of groundwater by 53.3%and there were great differences in the pollution degree of groundwater nitrate N among the 7 intensive planting areas.The contents of groundwater nitrate N increased from summer and autumn fallow period to winter planting period.There was a significant positive correlation between groundwater salinity and groundwater nitrate N concentration in intensive greenhouse planting area,especially when the groundwater nitrate N content was greater than 40 mg L -1 ,and the groundwater salinity increased dramatically From the aspect of soil salinity,nearly 80%of the samples showed different degrees of salinization,in which moderate salinization accounted for 57.12%.There was an extremely significant linear relationship between soil salinity and nitrate N content in 0–20 cm soil,with a determination coefficient of 0.376.Meanwhile,there was a very significan exponential function relationship between soil nitrate N content and groundwater nitrate N content and an extremely significant linear function relationship between soil salinity and groundwater salinity.[Conclusion]The groundwater nitrate N pollution in typical greenhouse intensive planting areas in Ningxia is considerably serious.The accumulation of nitrate N in soil and soil salinization are partly caused by nitrate N content and salinity of groundwater,and the large accumulation of soil nitrate N might be the main source of groundwater nitrate N.

Drip technologies have been suggested as practical for irrigation under conditions of high salinity and for reclamation of saline soils. Drip irrigation triggered by soil water potential thresholds was applied to both reclaim a severely saline calcareous gypsiferous soil and irrigate a waxy corn crop (Zea mays L. sinesis Kulesh). However, there is a lack of knowledge on the sustainability of reclamation of saline soils with drip irrigation and the changes in soil salinity and salt ion composition during the amelioration process. Therefore, effects on soil salinity, its ionic composition, and on crop growth and yields were evaluated in an experiment conducted in the Yinchuan Plain, northwest China. Treatments included fields in their first to fourth years of the drip irrigation reclamation-cropping scheme and adjacent native, non-cropped or irrigated saline-sodic land as control. Yield of waxy corn increased and days of growth to maturity decreased as a function of time and reclamation management. The improvement in crop performance could be largely credited to the reduction of soil salinity and changes in salt composition under the drip-irrigated reclamation protocols. The drip irrigation regime created a region of low salinity proximal to the emitters conducive to germination and plant growth. Deleterious ions for crop growth such as Na+ and Cl- were reduced while Ca2+ and Mg2+ concentration increased, especially in the upper 40 cm of soil. After only a single season of drip-irrigated waxy corn production, both Cl-/ ratios and sodium adsorption ratio (SAR) decreased dramatically. The SO2- 4 results suggested that drip irrigation is an effective technology for reclamation of severely saline-affected soils, such as those widely distributed over the Ningxia Plain in China and that this or similar reclamation strategy could be appropriate for reclamation of other hard to manage calcareous and gypsiferous soils.

为探明在引黄灌区春小麦生产中减施化肥对土壤供氮与春小麦吸氮的影响,通过田间小区试验,分析不同氮、磷、钾用量对耕层土壤矿质态氮累积与春小麦氮素吸收利用的影响.结果表明:(1)施氮量120～180 kg·hm-2时,土壤矿质态氮累积量和植株氮素累积量最高为102.58 kg·hm-2和294.92 kg· hm-2,与常规施氮量(240 kg·hm-2)相比,氮素利用率、氮肥贡献率及氮肥农学效率均显著提高,增幅分别为138.97％、29.23％、136.35％,氮肥偏生产力和依存率降低至41.2 kg·kg-1和68.35％;籽粒产量增加3.54％～15.66％.可见,适量减氮有利于耕层土壤氮素矿化,促进氮向籽粒转移,提高氮肥利用率和籽粒产量.(2)从常规施磷量(120 kg·hm-2)减施至48～96 kg·hm-2时,土壤矿质态氮累积量和植株氮累积量均升高,最高为98.61 kg·hm-2和242.79 kg·hm-2,比常规施磷平均高26.69％和9.91％;施磷量为48 kg· hm-2时,氮肥利用率和贡献率较不施磷提高295.24％和29.91％,氮依存率降低至68.56％,而与常规施磷相比籽粒产量并未降低,说明适当施磷可提高耕层土壤矿质态氮和小麦植株氮累积量,从而提高氮肥利用效率和籽粒含量.(3)施钾量30～60 kg·hm-2时,较不施钾的土壤矿质态氮累积量提高8.48％和12.87％,拔节期提高显著,对氮肥利用效率和籽粒产量无显著影响,说明适量钾肥促进土壤氮素矿化和拔节期植株氮素累积.宁夏引黄灌区,施氮、磷和钾量对土壤矿质态氮和春小麦植株氮积累量有显著影响,施氮120～180 kg· hm-2、施磷48～96 kg·hm-2、施钾30～60 kg·hm-2利于耕层土壤矿质态氮和春小麦植株氮积累,从而提高氮肥利用率.

Chloride stress is one of the main factors limiting the yield and quality of watermelon in Ningxia due to long-term irrigation with underground chlorinated brackish water. Nitrogen could alleviate the chlorine toxicity of crops. Therefore, it is crucial to explore the regulatory mechanism of nitrogen on the chloride stress by applying nitrogen fertilizer rationally and controlling chlorosis of watermelon under chloride stress. In this study, a soil culture experiment was conducted to determine the effects of different nitrogen application rates [0, 0.10, 0.15, 0.20, 0.25 g∙kg−1 (oven-dry soil)] on anion-cation balance, organic osmotic regulators, antioxidant enzyme activity, oxidative damage, and nitrogen uptake and utilization in watermelon seedlings under chloride stress of 160 mg(Cl−1)∙kg−1 (oven-dry soil). The test crop was the ‘Jincheng No. 5’ variety of watermelon. The results showed that nitrogen application considerably reduced Cl− and Na+ contents in the roots, stems, and leaves of watermelon while significantly increased NO3− and K+ contents at P<0.05; thus the ratios of Cl−/NO3− and Na+/K+ of the whole plant decreased by 46.0%−69.5% and 31.0%−54.3% compared with that of 0 g∙kg−1 nitrogen rate, respectively. Moreover, the contents of soluble sugar and proline, the activities of superoxide dismutase (SOD) and catalase (CAT) in leaves all reached the maximum levels at 0.15 g∙kg−1 N, which statistically increased by 75.6%, 70.1%, 55.8%, and 54.8% at P<0.05 compared with those at 0 g∙kg−1 N, respectively; while the content of malondialdehyde (MDA) significantly decreased by 59.3%. Moreover, when nitrogen was applied at 0.15 g∙kg−1, the nitrogen accumulation of watermelon increased by 157.7%, activity of nitrate reductase (NR) increased by 62.4%, and nitrogen uptake efficiency and nitrogen use efficiency were 26.25% and 97.10%, respectively. Thus, the fresh and dry weights of the plant increased by 96.9% and 29.0% at P<0.05, respectively. Cluster and correlation analyses of nitrogen application rate and physiological growth indexes of watermelon showed that the mitigation effect of nitrogen application on watermelon chloride stress was 0.15 g∙kg−1 > 0.20 g∙kg−1 > 0.10 g∙kg−1 > 0.25 g∙kg−1. There was significant positive correlation between biomass and dry matter accumulation with nitrogen uptake, utilization efficiency, and nitrogen accumulation; while there were also significant positive correlations between nitrogen accumulation and antioxidant enzyme activity and osmo-modulator content, and negative correlations with Na+/K+ ratio, Cl−/NO3− ratio, and MDA content. Based on the curve fitting results of each index, the nitrogen application rate of 0.14−0.18 g∙kg−1 was available for the growth and physiological activity of watermelon when the chloride concentration was 160 mg(Cl−1)∙kg−1(oven-dry soil). This indicates that appropriate nitrogen application under chloride salt stress can maintain ion homeostasis in plants by adjusting the Na+/K+ and Cl−/NO3− ratios, as well as improve the content of osmoregulatory substances and antioxidant enzyme activities, thereby reducing cell membrane oxidative damage, enhancing the physiological resistance of watermelon plants, and achieving a regulatory effect on chloride stress.

【Objective】Brackish water has been used as a supplementary irrigation resource in some arid and semi-arid regions in northwestern China， but the impact of its long-term application on soil environment and crop growth and quality is not well understood. The objective of this paper is to fill this knowledge gap using watermelon as an example.【Method】The experiment was conducted in fields with sand mulch， where brackish water has been used as a supplementary irrigation resource for varying periods ranging from 2 to 14 years. During the experiment， we measured the distribution of soil water and salt in the 0～60 cm soil layer， soil bulk density， as well as the yield and quality of watermelon. An uncultivated piece of land nearby was used as the control.【Result】Soil salt content increased with the increase in duration of brackish water irrigation in both tendril elongation and harvest stage. The highest soil salt content was in the 20-40 cm soil layer for the control， and in the 40～60 cm soil layer for the sand-mulched field. The supplementary brackish water irrigation increased the soil moisture content in flowering and fruit-setting stages， but the increase varied in that with the increase in the duration of the brackish water irrigation， the soil water content increased first and then declined. The highest soil moisture content in the sand-mulched field was in the surface layer （0～10 cm）， while for the control it was in the 10～20 cm soil layer. Sand mulch increased soil bulk density in the 0～40 cm soil layer and soil compaction in the 0～8 cm soil layer. It was also found that with the increase in length of brackish water irrigation， the yield and soluble solids content in the watermelon decreased， while the fruit quality improved first followed by a decline.【Conclusion】Long-term use of brackish water for supplementary irrigation in the sand-mulched fields increased soil bulk density and compaction in the upper soil layers， as well as soil moisture and salt content. As the years of brackish water irrigation increased， the yield of watermelon decreased while the quality of its fruits showed an initial improvement before deteriorating.

Sensitivity analysis, calibration, and verification of crop model parameters improve crop model efficiency and accuracy, facilitating its application. This study selected five sites within the Ningxia Yellow River Irrigation Area. Using meteorological data, soil data, and field management information, the EFAST (Extended Fourier Amplitude Sensitivity Test) method was used to conduct first-order and global sensitivity analyses of spring wheat parameters in the WOFOST (World Food Studies Simulation) Model. A Structural Equation Model (SEM) analyzed the contribution of crop parameters to different simulation indices, with parameter sensitivity rankings being discussed under varying water supply and climate conditions. Finally, the adapted WOFOST model was employed to assess its applicability in the Ningxia Yellow River Irrigation Area. TMNFTB3.0 (correction factor of total assimilation rate at 3 °C), SPAN (life span of leaves growing at 35 °C), SLATB0 (specific leaf area in the initial period), and CFET (correction factor transpiration rate) showed higher sensitivity index for most simulation indices. Under the same meteorological conditions, different water supply conditions have a limited impact on crop parameter sensitivity, mainly affecting leaf senescence, leaf area, and assimilate conversion to storage organs. The corrected crop parameters significantly enhanced the wheat yield simulation accuracy by the WOFOST model (ME = 0.9964; RMSE = 0.2516; MBE = 0.1392; R2 = 0.0331). The localized WOFOST model can predict regional crop yield, with this study providing a theoretical foundation for its regional application, adjustment, and optimization.

【Objective】Gravel mulching combined with drip irrigation is an improved agronomic technique for crop production in northwestern China. The purpose of this study is to investigate the impact of dripping rate of the emitters on soil water and salt redistribution, as well as the growth and yield of watermelon.【Method】The field experiment had three treatments with the dripping rate controlled at 2 L/h（Q1）, 3 L/h（Q2）, or 4 L/h（Q3）,respectively. In each treatment, we measured the spatiotemporal variation in soil water and salt, water use efficiency,as well as growth, yield and fruit quality of the watermelon.【Result】Horizontal advancement of the wetting front in the soil increased with dripping rate. After harvest, soil salt content in the 0～100 cm soil layer decreased, with the decreasing rate increasing as the dripping rate increased. Also, with the increase in dripping rate, the soluble sugar content in the fruits increased first followed by a decline. Of the three dripping rates we compared, Q2 increased the soluble sugar content in the fruit the most, up by 54.3% and 22.3%, respectively, compared to Q1 and Q3. With the increase in dripping rate, the vitamin C content in the fruits decreased first and then ramped up. Q3 gave the highest vitamin C content, increasing by 53.7% compared to Q2. Increasing dripping rate boosted both fruit yield and water use efficiency. Compared to Q1 and Q2, Q3 increased fruit yield by 6.20% and 3.56%, and water use efficiency by 6.49% and 3.72%, respectively.【Conclusion】Taking soil water and salt redistribution, as well as watermelon yield and quality into account, the optimal dripping rate for watermelon growth in the gravel-mulched soil was 4 L/h when using the local saline water for irrigation.

In order to solve the problems of high nutrient loss and poor maturity in sludge composting in arid area of northwest China, a large-scale sludge composting experiment was carried out to study the effects of auxiliary material parameters and turning-over technology on the dynamic changes of C and N nutrients of compost during the composting period, and then Topsis analysis was used to screen the optimal treatment.Results showed that when the ratio of corn straw was 15%, the total nitrogen loss was the smallest, which was3.67%. The nitrate nitrogen content of compost increased continuously during the composting period, while the ammonium nitrogen content increased first and then decreased. At the end of composting, the content of nitrate nitrogen and ammonium nitrogen decreased with the increase of straw ratio, which were 0.99 g.kg -1 and 0.78g.kg -1 , respectively. The organic matter content of compost increased with the increase of straw ratio, and the organic matter content of 15% straw increased by 10.08% and 6.61% compared with that of 10% and 5% straw respectively. The C/N ratio of compost showed a W-shaped change trend during the composting process and it decreased with the increase of straw ratio at the end. The seed germination index（GI） increased with the increase of straw ratio. When the ratio of corn straw was 15%, the seed germination index exceeded 100%.Topsis analysis showed that the optimum compost treatment was T7（15% straw ratio+5 cm straw particle size+conventional turning over）, which might be a suitable strip-stack composting method for arid areas in northwest China. The results of this study can provide theoretical basis and technical support for sludge window composting in this area.

To explore the toxic mechanism of chlorine on watermelon,and to provide theoretical basis for the safe utilization of chlorine-containing fertilizer and chlorine-containing brackish water,the effects of different chloride varieties and concentration on root biomass,malondialdehyde content,root activity,Clcontent and NO 3 - content of watermelon Jincheng No.5 were studied through hydroponic experiment.The results showed that the growth of watermelon root system was affected by both different chlorine varieties and concentrations.Compared with the control without chlorination,the NO 3 - content in roots treated with NaCl,NH 4 Cl,CaCl 2 and KCl decreased by 44.16%—47.95%and 35.96%—49.62%,respectively,a medium and high concentrations（80 mmol/L and 160 mmol/L）.The content of Cl - increased by 0.71—1.34 times and 1.24—1.86 times,respectively,and the aboveground and underground fresh weight decreased by 41.39%—57.78%,31.31%—44.73%and 57.28%—72.13%,49.35%—67.38%.NaC treatment did not significantly affect the content of MDA.Other chlorides significantly reduced MDA content by 31.87%—45.05%and 25.27%—28.57%.For different chlorides,NaCl treatment aggravated oxidation loss compared with other chlorides,and NH 4 Cl treatment promoted Cl - absorption to a certain extent.Watermelon root activity significantly increased by 41.18%—104.17%under medium-concentration CaCl 2 treatment compared with other chlorides.The underground dry weight increased by 36.00%—112.50%compared with other chlorides.Correlation analysis showed that fresh weight and dry weight were significantly correlated with Cl - and NO 3 - content.We can conclude that exogenous chlorine can reduce NO 3 - content by increasing Cl - content in roots,thus reducing root vitality and inhibiting root growth.With different ions,the inhibition degree and mechanism of chlorine on watermelon are different.The toxic effect of CaCl 2 and KCl on watermelon root growth was less than that of NaCl and NH 4 Cl.

通过分析宁夏回族自治区 12 个气象站 1980-2019 年气象数据,对干热风进行评判,探讨了宁夏春小麦种植区干热风的时空变化规律及气象因子对干热风的影响规律.结果表明,通过M-K检验法发现宁夏地区近40 年间干热风天数总体呈显著上升态势,但地区之间存在差异:中宁、中卫、银川、同心、惠农地区干热风天数总体呈上升的趋势,而吴忠、陶乐、盐池地区干热风天数近些年有逐步减少的趋势.从干热风发生的空间分布来看,干热风影响范围逐渐扩大,重心有南移的趋势,同时海拔对干热风的发生有显著影响;通过Pearson's相关分析看出,高温低湿型干热风受日最高气温影响最大,其次是相对湿度,风速影响相对较小;而雨后青枯型干热风受温度变化影响最大,其次是降水量.构建了基于气象因子的全区和各个农业生态区干热风天数回归方程,其预测结果可信度较高.

基于1985-2018年宁夏主要粮食作物播种面积、产量、单位面积收入等数据,利用数理统计和灰色关联度分析法,研究宁夏主要粮食作物种植结构的变化过程及其驱动因素.结果表明:1985-2018年宁夏小麦的种植面积及其占比呈现急剧下降趋势,种植面积由1985年的28.24 万hm2下降到2018年的12.83 万hm2,下降了54.56%,种植面积占比从34.10%下降到11.02%;玉米的种植面积及其占比呈现快速增加趋势,种植面积增长了7.78倍,其占比由4.28%增长到26.69%;水稻的种植面积及其占比变化较小,种植面积稳定在5万～8 万hm2,占比维持在6.5%左右.这三大粮食作物种植结构与粮食作物单产、单位面积收入、肉蛋奶产量关联度较强,引起种植结构变化的主要驱动因子是社会需求和经济利益.由此可知,1985-2018年,宁夏主要粮食作物中,小麦种植面积呈断崖式减少,而玉米种植面积大幅度增加,这一变化与经济社会发展带来的城乡居民生活水平的提高和种植经济效益的变化密切相关.

The effects of successive oilseed rape cropping on the absorption and utilization of residual nitrogen and water, and nitrogen use efficiency in spring wheat stubble was studied to provide a theoretical basis for the effective utilization of residual nitrogen in post-spring wheat soil and for the prevention and control of agricultural non-point source pollution. A field trial was conducted to investigate the effects of nitrogen application (conventional application, 270 kg∙hm−2; reduced application, 202.5 kg∙hm−2; and no application, 0 kg∙hm−2) and irrigation quota (conventional irrigation, 400 mm; 20% water-saving irrigation, 320 mm; and 40% water-saving irrigation, 240 mm) on the yield and nitrogen uptake of succession oilseed rape crops, as well as the dynamic changes involving soil moisture and mineral nitrogen in the 0–100 cm layer. Nitrogen balance analysis was also conducted for both seasons. The results revealed that residual nitrogen in spring wheat stubble had a notable effect on the yield and nitrogen uptake of successive oilseed rape, and the residual effect of nitrogen fertilizer was positively correlated with the nitrogen applied to spring wheat stubble. When the nitrogen fertilizer application rate in spring wheat stubble was 270 kg·hm−2, the yield and nitrogen uptake of succession oilseed rape were the highest, reaching 6640 kg·hm−2 and 25.7 kg·hm−2, respectively, which were 11.8%–43.5% and 14.8%–58.8% higher than those under reduced or no nitrogen application. Irrigation quota had no substantial effect on oilseed rape yield but had a significant effect on nitrogen uptake. Nitrogen uptake of oilseed rape under conventional nitrogen application was increased by 9.6%−10.2% compared with the water-saving treatments. Compared with before planting, mineral nitrogen levels in the 0–100 cm soil layer under nitrogen application treatment after oilseed rape harvesting decreased by 18.8–96.1 kg·hm−2, indicating that succession oilseed rape cropping has an absorption capacity for residual nitrogen. The mineral nitrogen content of soil decreased by 96.1 kg·hm−2 under conventional nitrogen application and conventional irrigation treatment compared with no or reduced nitrogen application. After the succession oilseed rape was crushed and turned over and returned to the field after winter freezing and thawing, the mineral nitrogen in the 0−100 cm soil layer increased by 86.1 to 171.8 kg·hm−2. This increase was positively correlated with the nitrogen application rate in the spring wheat season. Conventional nitrogen application combined with conventional irrigation had a small effect on soil water storage, and the residual effect of nitrogen fertilizer significantly improved irrigation water use efficiency, water use efficiency, and precipitation productivity of oilseed rape. Conventional nitrogen application combined with a 20% water-saving treatment had the highest irrigation water use efficiency and precipitation productivity, whereas conventional nitrogen application combined with a 40% water-saving treatment had the highest oilseed rape water use efficiency. Under these experimental conditions, the cumulative utilization rate of nitrogen fertilizer was the highest at 89.8% with reduced nitrogen combined with a 20% water-saving treatment. Nitrogen application rates of 270 kg·hm−2 and an irrigation quota of 320−400 mm considerably improved the yield, nitrogen uptake, water use efficiency, irrigation water use efficiency, and precipitation productivity of succession oilseed rape crops and reduced soil mineral nitrogen content under nitrogen application treatment. Turning over and returning the succession of oilseed rape to the field significantly increased soil mineral nitrogen content after winter freezing and thawing.

掌握不同灌溉方式下压砂地土壤水盐及pH的空间分布规律可以有效提高微咸水的利用效率.利用田间取样、经典统计学、地统计学以及克里格插值法对比分析了滴灌和微喷灌0～40 cm土层土壤含水率、电导率和pH值的空间变异特征.结果表明:微喷灌的土壤含水率略低于滴灌,0～40 cm土层土壤含水率属于中等变异性,且具有中等强度的空间相关性.微喷灌0～20 cm土层土壤平均电导率和离散化程度小于滴灌,同时,2种灌溉方式下0～20 cm和20～40 cm土层电导率的空间分布均表现出中等变异且具有较强的空间相关性;20～40 cm土层的平均电导率小于0～20 cm土层.无论微喷灌还是滴灌,调查地块的土壤电导率表现为中间位置低而地边较高,土壤含水率则在中间位置高而地边低.灌溉方式对土壤pH值的影响不显著,其空间变异性属于弱变异,但微喷灌条件下pH值具有较强的空间相关性.微咸水灌溉条件下压砂地抑制了表层土壤盐分累积,并存在向未覆砂的地块边缘聚积的现象.不同灌水方式下压砂地土壤水分和盐分均存在中等的空间变异性和空间自相关性,而pH值空间变异性较弱.研究结果可以为压砂地的微咸水合理利用提供理论依据.

为揭示氯盐胁迫下氮素对西瓜根系的调节机制和提供西瓜氯毒害调控理论依据,以西瓜为供试作物,采用土培试验,研究不同施氮量(0,0.1,0.15,0.2,0.25 g/kg)对氯盐胁迫下西瓜根系的影响,并应用主成分分析法对各施氮量下根系生长情况进行综合评价.结果表明,(1)与不施氮相比,施氮0.15 g/kg处理可使西瓜根系生物量、干物质累积量、脯氨酸含量、可溶性糖含量、根系活力分别显著提高58.83％、20.83％、98.33％、70.37％和29.44％,丙二醛含量显著降低40.30％,同时使总根长、总根表面积、根尖数、分枝数分别显著增加103.42％、46.41％、64.44％、87.80％,总根体积和总根系直径分别减少23.05％和40.15％.(2)在本试验氯盐胁迫条件下,施氮0.14～0.17 g/kg时西瓜具有较理想的根系构型和较高的根系活力.(3)根系分枝数、根系活力、总根体积、根尖数可作为氯盐胁迫下氮素对西瓜根系生长影响的综合评价指标,各施氮水平对氯盐胁迫的缓解效果表现为0.15 g/kg＞0.20 g/kg＞0.10 g/kg＞0.25 g/kg.可见,在氯盐胁迫下,适量施氮有助于西瓜建立良好的根系构型,提高根系渗透物质含量,降低细胞渗透势,减少根系丙二醛含量,维持较强的根系活力,增加根系生物量和干物质,缓解高浓度氯盐对西瓜生长的抑制作用.