To clarify the effects of Bacillus subtilis on the hydraulic properties of aeolian sandy soil, surface soil (0~30 cm) from Lingwu Baijitan National Nature Reserve, Ningxia, was sampled and indoor one-dimensional soil column infiltration tests and soil water retention tests were carried out based on these soil samples. Original soil was used as the control, and five treatments with different mass ratios of Bacillus subtilis (0%, 0.5%, 0.8%, 1.1%, 1.4%) were designed. The results showed that application of the bacterium reduced cumulative infiltration and infiltration rate, and significantly affected the parameters of the Philip model and the algebraic ponded infiltration model. With increasing application, sorptivity and shape coefficient decreased. The bacterium also enhanced soil water retention. At 1.1% application, saturated water content, field capacity, and wilting coefficient reached the highest values, whereas the proportion of available water was relatively low. In conclusion, proper addition of Bacillus subtilis (1.1%) effectively inhibited infiltration and improved water retention of sandy soil under experimental conditions, providing a useful reference for soil improvement in arid areas.

To evaluate the effects of winter irrigation on soil physical properties in arid oasis irrigation districts under residue-retained no-tillage during the fallow period, a two-year field observation was conducted in Minqin (lower Shiyang River Basin) during 2018-2019 and 2019-2020, with separate treatments in wheat and maize fields. Treatments compared no-tillage with and without winter irrigation, and soil bulk density as well as capillary and non-capillary porosity were monitored along the 0~100 cm soil profile. Results showed that soil bulk density generally increased in the 20~60 cm layer for wheat fields and in the 0~60 cm layer for maize fields during the fallow period, while changes in the 60~80 cm layer were not pronounced; winter irrigation did not significantly alter bulk-density dynamics. Capillary porosity generally decreased without winter irrigation; winter irrigation did not change the overall depth-wise direction of variation but reduced the magnitude of capillary-porosity deterioration, suggesting a buffering effect against freeze–thaw-induced pore degradation. Non-capillary porosity increased in shallow layers but decreased in deeper layers, with winter irrigation dampening the overall amplitude of change. These plot-scale findings provide evidence for optimizing the "moisture-freeze-thaw-pore structure" pathway of winter irrigation during fallow management in oasis irrigation areas, and highlight the need for replicated multi-site trials to further quantify the optimal winter irrigation quota and timing.

To address the high soil salinity and large irrigation quota issues in rice cultivation on sandy saline-alkali soils in Xingqing District, Ningxia, "the Longdao 18" variety was selected for pot experiments to explore effective ways for water-saving, salt control, and yield and efficiency improvement. Two irrigation quotas were set: W₁ (13 650 m3/hm2) and W₂ (16 200 m3/hm2), along with two organic amendments: C₁ ("Salt-Reduction" modifier) and C₂ (Multi-micro diatom), with a CK treatment (irrigation quota of 21 300 m3/hm2 without any amendments), making a total of five treatments. The effects of each treatment on rice growth, yield, efficiency, and water-saving and salt-controlling effects were analyzed. Using game theory for a combined weighting of the entropy method and CRITIC method, and applying the TOPSIS model for multi-indicator comprehensive evaluation, the optimal combination of irrigation quota and amendment was determined. The results showed that the optimal combination suitable for local rice was W₂C₁, that is, an irrigation quota of 16 200 m3/hm2 with the application of the Salt Reduction Method amendment. This optimal combination achieved a yield of 9 352.53 kg/hm2, saving 23.94% of water compared to CK, while the desalination rate increased to 59.41% with stable production. Crop water use efficiency, crop water productivity, and irrigation water productivity were improved by 30.41%, 28.61%, and 32.79%, respectively, compared to CK. This study provides a theoretical basis and practical reference for promoting water-saving, salt-controlling, and yield and efficiency-enhancing techniques for rice in Xingqing District.

Coastal saline soils are known for their accumulation of surface salts, poor aeration, and low oxygen content in irrigation water. These conditions cause significant salt stress on crops and reduce soil nutrient-use efficiency, severely constraining agricultural production in coastal areas. This experiment used oxygenated irrigation technology and biochar application, with winter wheat as the test crop, to analyze changes in soil nitrogen content and water-salt transport under different treatments. The aim is to provide a new approach to improving the cultivation environment in saline soil. An outdoor pot experiment was conducted with four treatments: oxygenated irrigation alone (FO, 0 g/kg, 15.5 mg/L), biochar application alone (FC, 10 g/kg, 8.0 mg/L), combined oxygenated irrigation and biochar application (FOC, 10 g/kg, 15.5 mg/L), and a blank control (CK, 0 g/kg, 8.0 mg/L). The study focused on analyzing the differences in soil indicators (nitrogen content, water content, salt content, etc.) throughout the entire growth period of winter wheat. At the jointing stage, in the 0~20 cm soil layer, the FOC treatment significantly increased soil nitrate-nitrogen and total nitrogen content compared with the CK and FO treatments, while the FC treatment significantly increased soil ammonium nitrogen content. At this stage, soil nitrate nitrogen, ammonium nitrogen, and total nitrogen under the FO treatment were relatively low. However, in the 20~40 cm soil layer, soil nitrate nitrogen content under the FO treatment was significantly higher than under the FOC, FC, and CK treatments. The nitrification and mineralization rates under the FO and FOC treatments were significantly higher than those under the FC and CK treatments. This indicates that while oxygenated irrigation alone promotes nitrification by aerobic microorganisms, it may also cause nitrogen leaching, lowering nitrogen content in the plow layer during key growth stages. At the seedling stage, soil desalination rates in the 0~20 cm layer for the FC and FOC treatments were 0.21 and 0.16, respectively, significantly lower than those for the CK and FO treatments (0.29 and 0.25); At the jointing stage, the soil desalination rates for the FC and FOC treatments were 0.24 and 0.26,respectively, representing increases of 28.57% and 45.83% over the CK and FO treatments. This indicates that biochar may initially increase soil salt content after application but ultimately enhances the desalination rate of the topsoil. In contrast, the soil desalination rate under oxygenated irrigation alone was lower than that in the CK treatment (P<0.05). In summary, the synergistic mechanism between oxygenated irrigation and biochar application effectively overcame the aeration issues and structural limitations of saline-alkali soils. Oxygenated irrigation directly activates aerobic nitrification process, which can reduce nitrogen loss. Biochar, on the other hand, consolidates the oxygenation effect by adsorbing and retaining moisture, improving pore structure and promoting salt leaching under dynamic hydrological conditions. The coupling effect of oxygenated irrigation combined with biochar application significantly optimized water-salt transport and nitrogen transformation processes in coastal saline soils, providing a feasible integrated technical solution for the sustainable utilization of coastal saline land.

Applying biochar can significantly increase cotton yield and soil organic carbon contents. However, considerable uncertainties remain regarding the effects of biochar application on yield increase- carbon sequestration-emission reduction. We performed a meta-analysis of 315 observations from 45 field studies to quantify the effects of biochar on cotton yield and soil organic carbon contents, across varying environmental conditions. The magnitude of such effects varied with climatic factors, soil conditions and farmland management measures. Our results show that: ① Biochar addition led to substantial increases in cotton yield (+14.8%) and the soil organic carbon (+25%). ② The comprehensive effects of cotton field yield and soil organic carbon are highest under moderate temperature, precipitation, and sunshine conditions. ③ Grey desert soil areas can increase cotton yield by 18.7% and SOC by 21.3%, and the effect is significantly enhanced when the soil pH is alkaline. ④ An appropriate biochar application rate, along with a small amount of nitrogen fertilizer and an appropriate amount of irrigation, can achieve the synergy of high yield and carbon sequestration.The synergistic effect of high yield and carbon sequestration can be achieved by applying 5~15 t/hm2 biochar and 300~450 mm irrigation combined with a small amount of nitrogen fertilizer. ⑤ The cotton yield and SOC were more sensitive to changes in temperature and the soil pH, respectively. These findings provide insights into the effect of biochar addition on biogeochemical cycles, functions, and services in cotton planting areas across diverse spatial and temporal scales.

To investigate how different preparation parameters affect the water absorption capacity of sludge-based ceramsite, as well as the changes in infiltration properties of typical soils following the application of ceramsite, sludge collected from the reservoir area of a representative reservoir in Shanxi Province was selected as the primary raw material, supplemented with corn straw and clay. Using raw material proportion, calcination temperature, and calcination duration as independent variables, a three-factor, three-level Box-Behnken Design (BBD) experiment was conducted. The 1-hour water absorption rate and saturated water absorption capacity of the ceramsite were then measured to evaluate the impact of each preparation parameter on water absorption performance. Based on these results, ceramsite with a high water absorption capacity was applied to the soil surface for soil column infiltration tests, during which wetting front migration distance, cumulative infiltration volume, and infiltration rate were measured to analyze the resulting changes in soil infiltration characteristics.The results indicate the following: ① The influence of different preparation factors on the water absorption of sludge-based ceramsite decreases in the order of calcination temperature > raw material ratio > calcination time. Additionally, the interaction between calcination temperature and raw material ratio is relatively significant. When the preparation factors are set to a mass ratio of sludge, straw, and clay of 55:35:10, a calcination temperature of 1150°C, and a calcination time of 60 minutes, the sludge-based ceramsite exhibits high water absorption, with measured 1-hour and saturated water absorption values of 70.02% and 72.43%, respectively, and fitted values of 72.65% and 75.21%. ② Applying a sludge-based ceramsite layer slowed the advancement of the wetting front, extending the infiltration time by 30 minutes, increasing cumulative infiltration by 103%, and raising the initial soil infiltration rate by 36.7%. The infiltration model fitting results for the water movement process showed R2 values ranging from 0.958 to 0.998, indicating an accurate simulation of the infiltration process. ③ Applying sludge-based ceramsite increased the average soil moisture content by 9.5% and reduced the variability of soil moisture with depth. Overall, the water absorption capacity of sludge-based ceramsite is significantly influenced by the raw material ratio and firing temperature. Additionally, adding high water-absorption ceramsite can effectively enhance soil infiltration and water-holding capacity. These findings provide valuable technical support for mitigating soil and water loss on the Loess Plateau and for expanding the resource utilization of sludge.

This study investigated the effects of sodium carbonate-modified attapulgite (mass ratio of 40∶1, the N40 group) on the physicochemical and water retention properties of desertified soil in the Kubuqi Desert. Six incorporation rates (0%, 3%, 6%, 9%, 15%, and 20%) were tested. The results showed that the modified attapulgite (Na-AT) exhibited a 23.5% increase in free swelling volume and a 52.1% reduction in fluid loss. The incorporation of Na-AT significantly delayed wetting front migration, reduced soil bulk density, and increased the content of water-stable aggregates (>0.25 mm). Compared to the control group, the cumulative infiltration in treatment D decreased by 39.5%, and the most effective suppression of soil evaporation was achieved at a 9% Na-AT incorporation rate. The Philip and Kostiakov models provided satisfactory fits for the infiltration process (R2>0.88), while the Rose model was more suitable for simulating evaporation (R2>0.94). The sodium-modified attapulgite amendment significantly improved soil water retention and structure, providing theoretical support and a technical framework for desertified soil remediation and the efficient utilization of attapulgite.

This study investigates the spatiotemporal evolution of groundwater depth and its correlations with multiple factors in two typical areas (Wengniute Banner and Songshan District) of Chifeng City within the Upper Xiliao River Basin, providing scientific support for the efficient utilization of water resources and the sustainable socio-economic development in semi-arid regions. Using groundwater depth data from manual monitoring wells from 1990 to 2023, combined with multi-source remote sensing data (NDVI and land use) as well as economic and grain yield data, we employed temporal variation analysis, trend analysis, spatial interpolation statistics, and correlation analysis to systematically explore the spatiotemporal variation of groundwater depth and its correlations with multiple factors. ①From 1990 to 2023, groundwater depth in the study area showed a significant decline; the average groundwater depth in Wengniute Banner and Songshan District dropped from 26.40 and 8.19 m in 1990 to 35.71 and 13.93 m in 2023, with the change rates being 0.384 and 0.282 m/a respectively. ②The study area showed the changing characteristics of "shallow buried areas shrinking and deep buried areas expanding". The area proportion of the 0~7 m buried depth zone decreased from 3.67% to 0.98%, while that of the 28~35 m buried depth zone increased from 6.45% to 50.58%, and this zone is continuously distributed in the central and northern areas. ③Groundwater depth showed a significant positive correlation with NDVI (r=0.734^** in Wengniute Banner, r=0.614^** in Songshan District), strong positive correlations with impervious surfaces and forest coverage, and strong negative correlations with the areas of water bodies, grasslands, and bare land. Additionally, it exhibited significant positive correlations with the regional GDP, the output values of the primary, secondary, and tertiary industries, as well as grain yield. The typical area in the upper reaches of the Xiliao River exhibits a clear overall downward trend in groundwater depth, and this trend has stabilized in recent years. It is driven by regional vegetation changes, agricultural activities, and economic activities. Future efforts should focus on scientifically assessing groundwater availability to achieve the sustainable development of regional water and soil resources.

Agricultural non-point source pollution not only threatens the ecological balance of water bodies but also poses potential risks to human health. For large-scale agricultural regions, especially those experiencing rapid changes in cropping patterns, the mechanisms by which these patterns influence the transport and control of pollution remain difficult to elucidate. This study focuses on the Ningxia Yellow River Irrigation District, employing the LOADEST model to investigate the spatiotemporal characteristics of pollutant loads. By integrating multi-year monitored data on farmland export coefficients and cropping patterns, we assessed the spatiotemporal variability of the impacts of cropping patterns on pollutant loads and economic benefits. The results indicate that pollutant loads in The Fourth Drainage Area (Disipaiyu) of the Ningxia Yellow River Irrigation District demonstrated pronounced spatiotemporal heterogeneity. After optimizing the cropping pattern using an improved simulated annealing algorithm, the economic benefit increased by an average of RMB 855.35 per kg, while the peak total nitrogen load decreased by 73.923 t. Correlation analysis confirmed the potential existence of previously unrecognized implicit relationships between changes in cropping patterns and farmland export coefficients. Furthermore, adjusting the cropping pattern can effectively mitigate agricultural non-point source pollution while concurrently enhancing economic returns.

Hydraulic tomography is a high-resolution method for inverting the spatial distribution of hydrogeological parameters in aquifers through multiple sets of cross-hole pumping tests. However, there is a lack of insightful research on how much additional pumping tests can improve the characterization of aquifer heterogeneity. Based on the iterative ensemble Kalman smoother algorithm, this study validated the role of multiple pumping tests using virtual random field cases and actual site data. In the virtual case, a Gaussian random field was generated as the reference hydraulic conductivity field, and steady-state head drawdowns from 9 pumping tests were simulated as observation data with different levels of added noise. Results showed that as the number of pumping tests increased from 1 to 4, details of the inverted hydraulic conductivity field gradually emerged, with increasingly clear contours of high and low permeability zones. Although noise disturbance reduced resolution, incremental tests still improved estimation accuracy. In the actual case scenario, the first 1 to 4 sets of test data were used to invert the hydraulic conductivity field, and the inversion results were applied to predict heads from the 5th to 9th tests. Prediction accuracy improved with the increase in the number of tests included in the inversion, indicating that additional pumping tests provide non-redundant information and enhance aquifer characterization precision. This study confirms the advantages of hydraulic tomography in the absence of prior knowledge of real parameters and provides a reference for refined management of heterogeneous aquifers.

To investigate the spatiotemporal distribution characteristics of rainfall and its utilization during the rice growing season in Hubei Province, this study analyzed daily meteorological data (2001-2020) from 20 stations. Rainfall distribution patterns were assessed using indices such as precipitation concentration degree (PCD), precipitation concentration period (PCP), Gini coefficient, and Lorenz asymmetry coefficient. A water balance model was established to evaluate water budget components and rainfall utilization efficiency. The results showed significant spatial variations in total rainfall during the rice growing season, with the highest amount in southwestern Hubei and the lowest in the northwest. Continuous heavy rainfall frequently occurred in southeastern Hubei and eastern Hubei, while prolonged dry spells were common in northern Hubei and eastern Hubei, necessitating measures to prevent and mitigate drought risks. Rainfall distribution was more uniform in southwestern and southeastern regions, though without distinct concentration periods. In contrast, northern Hubei and eastern Hubei exhibited higher rainfall concentration, with poor alignment between peak rainfall and water demand in northern Hubei. Most sites relied on irrigation due to insufficient rainfall or uneven spatiotemporal distribution. Rainfall use efficiency was negatively correlated with both total rainfall and its concentration intensity. These findings provide a scientific basis for optimizing regional rice irrigation strategies.

This study addresses the unclear long-term trends and influencing factors of water requirement (evapotranspiration, ET) for single-cropping mid-season rice in the Pi-Shi-Hang Irrigation District. Based on the 35-year (1988-2023) field observation data, we systematically quantified the long-term variation characteristics of ET under the "shallow-wet-intermittent" irrigation mode and clarified the influencing degrees of climatic factors, rice growth indicators, water balance elements and management measures on ET by adopting trend, regression, and correlation analyses. The results indicate that ET during the rice growth period showed a fluctuating but overall upward trend, with a mean value of 357 mm and an increasing rate of 0.427 8 mm/year. Among the climatic factors, daily temperature range (Tar) and cumulative sunshine hours (hsc) were significantly positively correlated with ET and were the main drivers of its increase. In contrast, relative humidity (RH) and wind speed (ws) exhibited declining trends, exerting a certain inhibitory effect on ET. The rice growth duration increased significantly, along with grain number per panicle and yield, while the 1 000-grain weight remained stable. Notably, the increase in yield did not lead to a significant rise in ET. Water balance components (precipitation, irrigation water, and drainage) showed strong interannual variability but had little direct impact on ET. The alternation of rice varieties and optimization of irrigation practices jointly regulated the rice water consumption process. In conclusion, the variation in water requirement for single-cropping mid-season rice in the Pi-Shi-Hang Irrigation District results from the combined effects of climate change, variety renewal, and irrigation system optimization. Under ongoing climate change, continuously optimizing water-saving irrigation systems and variety layouts is an effective strategy to enhance the sustainable utilization of water resources for rice production in the irrigation district.

To clarify the effects of different operating pressures on actual dripper flow rates and soil moisture distribution, this study employed indoor soil trough experiments. Three pressure gradients were set: 0.10 MPa (P1), 0.07 MPa (P2), and 0.04 MPa (P3). Three rated dripper flow rates were tested: 2.7 L/h (W1), 2.2 L/h (W2), and 1.38 L/h (W3). Actual emitter flow rates, wetting front migration, and post-irrigation soil moisture distribution were measured. Results indicate: ①The effect of working pressure changes on the actual flow rate of the drip head is as follows: Compared to P2 and P1, W1 flow decreased by 22.8% and 74.3%, respectively, with irrigation duration extending by 29% and 290.3%. W2 flow decreased by 25.6% and 57.8%, with irrigation duration extending by 34.7% and 138.3%. W3 exhibited the smallest flow reductions of 22.8% and 48.6%, with irrigation durations extending by 30% and 94.3%, respectively, demonstrating greater flow stability at low pressure; ② The effect of work pressure on changes in wetting front parameters is as follows: As operating pressure decreases, the vertical migration distance of the wetting front increases while its horizontal migration distance decreases, resulting in a flatter profile. Furthermore, lower flow rates lead to weaker changes in the wetting front caused by pressure reduction; ③ After irrigation, soil moisture is primarily distributed in the 0~40 cm soil layer. Pressure reduction under W1 and W2 conditions diminishes irrigation uniformity, promoting vertical water movement and increasing deep-layer moisture content. W3 exhibits minimal moisture distribution variation across different pressures. This demonstrates that low-flow emitters maintain more stable flow rates under low pressure, while high-flow emitters exhibit more pronounced fluctuations in soil moisture movement with pressure changes. Therefore, low-flow emitters are recommended for priority use.

To address the challenges of low precision in multi-point water level cooperative control and poor resistance to downstream disturbances in large-scale irrigation open-channel systems under varying operating conditions, this paper proposes an Improved Sliding Mode Predictive Control (ISMPC) method. Firstly, a linear discrete state-space model capturing the coupling of multiple canal pools is established based on the Saint-Venant equations. Secondly, a disturbance observer is introduced to online estimate and compensate for unknown disturbances. Finally, a coordinated control law for the multi-pool system is derived based on a predictive sliding surface, which regulates the upstream and downstream gate openings of different canal pools. Experimental results demonstrate that in a three-pool canal system, the ISMPC method reduces the average water level control error by 28.8% and 41.7% compared to the Linear Quadratic Integral (LQI) and Proportional-Integral-Derivative (PID) control methods, respectively, while the average flow tracking error is reduced by 83.1% and 55.1%. Under step changes in the target flow rate, the average flow control error of ISMPC is reduced by 31.3% and 52.1% compared to LQI and PID, respectively. Furthermore, in an eight-pool canal system, the performance indices of ISMPC also surpass those of the comparative algorithms, validating the effectiveness of the proposed control strategy.

The construction of high standard farmland is an important strategic measure to ensure national food security and promote land security strategy. However, in the process of rapid promotion, it has sparked multidimensional ethical controversies due to unclear legislative ethical thinking, diverse demands from stakeholders, and the special nature of the project itself. This article systematically analyzes the ethical debates and their causes of high standard farmland construction projects from five dimensions: philosophy, society, profession, technology, and environment. The philosophical controversy focuses on the ethical legitimacy of human transformation of the land system; The social dimension involves the issue of fairness in the distribution of benefits and compensation; The professional dimension manifests as the moral deviation between participants' intentions and behaviors; The technological dimension focuses on the ethical goodness of technological applications; The environmental dimension explores the balance between human needs and natural ecological rights. Research has shown that current legislation for high standard farmland construction tends towards resource conservation, neglecting the intrinsic value of nature, and the interest game among multiple stakeholders further exacerbates ethical conflicts. Therefore, it is suggested to reconstruct the ethical concept of land and improve the legislative ethical review mechanism; Establish a collaborative governance platform, optimize benefit distribution and compensation plans; Enhance the ethical awareness and decision-making ability of participants, and promote the development of the project towards a more fair and sustainable direction. By adopting the concept of reflective development and coordinating the relationship between humans, land, and society, ethical support can be provided for the healthy development of high standard farmland construction.

To address the issue of low water and nitrogen use efficiency in spring maize production in the Fenhe Irrigation District of Shanxi Province, this study calibrated and validated the parameters of the SWAP-WOFOST-N model based on field experiments. On this basis, it simulated and analyzed the effects of different water-nitrogen treatments on spring maize yield, water productivity (WP), and partial factor productivity of nitrogen (PFPN), and further proposed relatively optimal water-nitrogen management measures under different hydrological year types. The results showed that the model exhibited high simulation accuracy for soil water content, soil temperature, leaf area index, yield, and nitrogen use efficiency. Specifically, the normalized root mean square error (NRMSE) of soil water content, soil temperature, and leaf area index was below 20% in both the calibration and validation phases, while the relative error (RE) of spring maize yield and nitrogen use efficiency was controlled within 5%. The simulation accuracy for soil salt content and nitrate nitrogen content was slightly lower, but their NRMSE still remained stable within 30%. With the goals of increasing (or stabilizing) yield and improving water and nitrogen use efficiency, the recommended irrigation quota and nitrogen application rate for wet years are 75 mm and 240 kg/hm2, respectively, which can increase the yield, WP, and PFPN by 4.8%, 6.9%, and 8.3% compared with the current status. For normal precipitation years, maintaining the current irrigation quota of 150 mm while reducing the nitrogen application rate to 180 kg/hm2 can significantly increase PFPN by 31.4%. For dry years, the recommended irrigation quota and nitrogen application rate are 225 mm and 180 kg/hm2, respectively, which can increase the yield by 9.4%. Compared with traditional water and fertilizer management, water-nitrogen management strategies based on different hydrological year patterns can reduce irrigation water by 50% in wet years and nitrogen application by 25% in normal and dry years, thereby improving crop yield as well as water and nitrogen use efficiency.