The North China Plain serves as a crucial grain production base in our country. Accurately predicting the spatial distribution changes of soil organic carbon density (SOCD) in the North China Plain is of great significance for maintaining regional food security and promoting sustainable development. Digital Soil Mapping (DSM), is a powerful method for accurately simulating the spatial distribution of soil organic carbon density (SOCD) by selecting appropriate covariates. In this study, we selected the North China Plain as the research area and employed Support Vector Machine (SVM), XGBoost, and Random Forest (RF) models respectively for modeling, using multi-source environmental variables as input factors to investigate the spatial distribution characteristics of SOCD. Additionally, phenological variables were introduced to compensate for missing climate information and climate features, exploring the impact degree of these phenological variables on the spatial distribution prediction of SOCD. Results indicated that surface temperature-related variables were key factors influencing the spatial distribution of SOCD in this region. After introducing phenological variables, the prediction accuracy of the SVM, XGBoost, and RF models all showed an upward trend, with the precision of the RF model increasing by approximately 12%, XGBoost by about 16.4%, and SVM by approximately 12.2%. The improved RF model, after incorporating phenological variables, achieved the highest prediction accuracy, with an R2 value of 0.475. From the perspective of SOCD spatial distribution characteristics, there was a trend of higher values in the southern and northern parts and lower values in the central and eastern parts, with the highest SOCD content found in the south. This study emphasizes the significant role of phenological variables in improving SOCD spatial prediction accuracy, providing valuable guidance for regional soil management and sustainable agricultural practices.

To explore the impact of C. sinensis cultivation on soil aggregate stability and organic carbon characteristics in the hilly areas of southern Jiangxi, this study selected navel orange plantations with 1 year (1 a), 4 years (4 a), and 15 years (15 a) of cultivation as research subjects, using local mixed coniferous and broad-leaved forest as the control (CK). The results showed that the mean weight diameter (MWD), geometric mean diameter (GMD) and＞0.25 mm water-stable aggregate content(WR _0.25) of 1a C. sinensis increased by 42.79%~58.98%, 46.88~62.88, 34.59%~28.82%, respectively, compared with CK. These parameters showed an overall increasing trend with planting age, while the percentage of aggregates destroyed (PAD _0.25) and soil erodibility factor (K) exhibited a decreasing trend. The organic carbon content in soil aggregates across different particle sizes was lower in C. sinensis forests than in the CK, following the order: CK>15 a>1 a>4 a. The organic carbon content in soil aggregates was highly positively correlated with MWD and GMD (P<0.01) and positively correlated with WR _0.25 (P<0.05). In conclusion, during the early stages of converting coniferous and broad-leaved mixed forests to C. sinensis forests, both soil aggregate stability and organic carbon content significantly decreased. And as the planting duration increased, soil aggregate stability showed a gradual recovery. Increasing organic carbon content could contribute to enhancing soil aggregate stability.

Plant morphological and physiological indicators can effectively reflect crop responses to water stress. In order to investigate the changes of plant morphology, leaf temperature and spatial distribution of crops subjected to water deficit, this paper utilizes infrared thermography coupled with laser three-dimensional phenotyping to carry out research on the morphology of cabbage, leaf air temperature difference and vertical temperature deviation index under water deficit conditions. Results indicated that plant average height and leaf-air temperature difference initially decreased rapidly and then slowed down under water deficit conditions. Based on an integrated dataset combining infrared thermal imagery and three-dimensional point cloud data, a vertical temperature deviation index was proposed. This index initially increased slowly and then rose sharply under increasing water deficit, closely corresponding with changes in plant water content. When the index exceeded 1.5, cabbage mustard plants suffered irreversible physiological damage. Thus, this index provides a rapid approach for assessing and providing early warning signals of water deficit stress in crops.

In order to further explore the freezing damage mechanism and process of the trapezoidal channel with arc-shaped slope toe under the effect of high groundwater level and winter irrigation, a hydro-thermal-mechanical coupled model was established based on COMSOL software based on the Qinqu Canal in Ningxia Yellow River Diversion irrigation District, and a comparative analysis was carried out with the measured data. The results show that: The distribution law of temperature field, moisture content distribution and displacement field is consistent with that of a two-year prototype monitoring program, and the rationality of the numerical coupling model is verified. Under the condition of high groundwater level buried depth of 1.0m, the frozen depth expression, water migration and frost heave deformation distribution of the laid benzene plate are improved to some extent compared with the non-benzene plate during the freezing period, so as to improve the stress distribution of the lower section. Compared with the non-benzene board, the 6-cm-thick benzene board can only effectively improve the water and heat distribution of the subsoil by 20 cm. It is still necessary to increase the thickness reasonably, and further deepen the design of non-equal thickness differential anti-frost heave structure at the bottom of the canal and on the side of the negative slope within the range of freezing depth, as well as the study on the numerical coupling model considering the leakage and recharge of winter irrigation.

In order to study the influence of canal lining on water utilization coefficient of canal system, this paper deduces an improved formula of canal water utilization coefficient considering the influence of lining on the basis of Kostiakov infiltration equation. Taking Yingke Irrigation District in Gansu Province as an example, 6 different lining scenarios were set up according to the measured data, and the water utilization coefficients of typical channels and canal systems were simulated by using improved formula. The improved formula shows that there is a power exponential relationship between channel water utilization coefficient and channel lining ratio. Compared with the downstream section, the upstream section of the lining has lower water loss and higher water utilization coefficient. The calculation results show that the water utilization coefficient of canal network system is larger for concrete lining with smaller reduction coefficient. With the increase of canal lining rate, the average growth rate of water utilization coefficient of canal system is 23%. When all the three channels are lined, the water utilization coefficient of the canal system reaches 0.917. If there is only a single-stage channel lining, the canal system water utilization coefficient is the largest. Although the channel water utilization coefficient increases the most when the trunk channel is lined, the trunk channel has the longest channel length and the amount of lining capital is also large, so the canal is preferred for lining.

To explore the influence of the filtration stage of desilting basin on the sediment sedimentation of the Yellow River, clarify the sedimentation principle of multi-stage sedimentation tank, and determine the suitable operating conditions and arrangement series of the multi-stage sedimentation tank. For the removal of high concentration of fine granular sediment in the multi-stage sediment sedimentation pool, an eight-stage desilting basin filtration system was designed to conduct the full-scale sedimentation experiment under three kinds of operating flow rates (20, 40 and 60 m³/h) to analyze the sedimentation effect of the sediment of fine particles of the Yellow River with high concentration. Under 3 operating flow rates, the sediment content at the outlet of the 8th level sedimentation tank was 0.80~1.36 kg/m³, and the sediment removal rate was 84.13%~90.73%. The outlet sediment particle sizes D ₉₀、D ₅₀ and D ₁₀ were 39.87~45.36, 19.92~24.50 and 2.86~3.97 μm, respectively; About 76.84% to 84.78% of the sediment in the first to fourth level sedimentation tanks settles, playing the main sedimentation role. Only 5.95% to 7.29% of the sediment in the fifth to eighth level sedimentation tanks settles, playing a secondary sedimentation role. This is because after the sediment settles in the previous level sedimentation tank, the difficulty of settling the sediment in the next level sedimentation tank increases; Furthermore, stages 4~5 are connected through overflow weirs, and the inlet water flow of the fifth stage sedimentation tank is the surface water flow at the end of stage 4, further increasing the difficulty of settling sediment in stages 4~5 sedimentation tanks. This study found that for sediment with a particle size range of 0~350 μm and a concentration of about 8.5 kg/m³, the optimal number of stages for the sedimentation tank model at flow rates of 20, 40 and 60 m³/h are 4、5 and 6, respectively, and the suitable operating flow rate is 20 m³/h.

In practice, the water distribution conditions in irrigation districts often vary. Variations in water supply flow rates and the duration of water flow significantly impact the formulation of water distribution plans and the precision of channel distribution. Therefore, it is necessary to establish a corresponding model for optimizing canal water distribution. In this paper, considering the influence of the real-time change of water supply flow and the hydraulic response time of water flow on the water distribution scheme, a real-time optimal water distribution model based on hydraulic response time is established. When the water supply flow rate increases or decreases, the model provides two distribution methods: Method 1 prioritizes adjusting the flow rate before adjusting the number of distribution channels, while Method 2 involves increasing or decreasing the number of lower-level distribution channels. The model employed the water distribution flow, start water distribution time and end water distribution time of each water distribution branch as decision variables, and the shortest water distribution duration and the minimum water transmission loss of the channel as the objective function. It was solved by the elite strategy Non-dominated Sorting Genetic Algorithm II (NSGA-II). The results indicate that the water distribution flow rates for both methods were within the upper and lower limits, satisfying the distribution requirements. The calculation of response time provided a more precise distribution schedule. Method 1 ensured uninterrupted water distribution in all channels, though some channels experienced lower distribution flow rates, with a total distribution duration of 128.66 hours. In Method 2, all channels received high flow rate distributions, with stable flow rates, and a total distribution duration of 122.13 hours. However, some channels experienced interruptions in water distribution. The real-time canal system optimization water distribution model of irrigation area with hydraulic response time can provide water distribution scheme when the water supply flow changes. Compared with mode 2, mode 1 has larger water distribution flow fluctuation, larger channel water transmission loss, and longer water distribution time by 6.54 hours. Both methods considered the effect of hydraulic response time on the water distribution scheme, improving scheduling precision. This model serves as a valuable guide for the water distribution activities in irrigation districts, enhancing the efficiency and accuracy of the distribution process.

To explore the optimal aeration drip irrigation system for greenhouse strawberries, an experimental study was conducted from October 2022 to March 2023 in a strawberry greenhouse in Jurong City, Jiangsu Province. Two irrigation methods were set up: conventional subsurface drip irrigation (CK) and aerated subsurface drip irrigation (A). Eight treatments combining aerated drip irrigation at different growth stages (budding, flowering, and fruit expansion stages) were set up to study their effects on strawberry growth, yield, and fruit quality. The Analytic Hierarchy Process (AHP) and entropy weight method were introduced to assign weights to the combination of strawberry fruit yield and quality indicators, and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was used to construct a comprehensive evaluation system for strawberry yield and quality. The results showed that aerated drip irrigation significantly affected the yield and quality of greenhouse strawberries (P<0.05), with the highest yield in treatment A3 (aeration during the fruit expansion stage) at 26.75 t/hm², an increase of 123.85% compared to CK. Treatment A4 (aeration during both budding and flowering stages) resulted in the highest vitamin C, soluble sugar, total soluble solids, sugar-acid ratio, and the lowest total organic acid content. According to the TOPSIS comprehensive evaluation, treatment A4 scored 0.64 points, ranking first. Therefore, simultaneous aeration during the budding and flowering stages is the optimal aeration drip irrigation scheme that balances strawberry yield and quality.

Integrated water-fertilizer sprinkler irrigation technology in tea gardens utilizes fertilizer droplet collisions with tea foliage to enhance nutrient interception by the canopy, facilitating dual nutrient absorption by tea roots and leaves. This process significantly enhances fertilizer utilization efficiency. However, improper fertilizer concentrations can pose a risk of leaf burning. This review delves into the research progress on the impact mechanism of fertilizer droplets on tea leaves, crop canopy interception dynamics, as well as leaf absorption and burning effects. It is proposed that theoretical analysis, numerical simulation, and experimental validation should be combined to deeply investigate the intricate interaction mechanisms during droplet impact on tea leaves, particularly the complex coupled motion of droplets impacting suspended leaf surfaces anchored at one end. Addressing the impact mechanism, canopy interception, leaf absorption and burning, the prediction model of canopy interception fertilizers and the regulation mechanism of interception fertilizer have also been proposed. These findings lay a theoretical basis for the formulation of an integrated sprinkler irrigation and fertilization system in tea garden, and promote the benign development of sprinkler irrigation and fertilization technology.

Investigating synergistic effects of irrigation, fertilization, canopy management, and fruiting-branch density on photosynthetic performance and yield in jujube (Ziziphus jujuba Mill.) orchards on reclaimed sandy soils, a four-factor, three-level orthogonal experimental design was adopted. This study analyzes the effects of water, fertilizer, fruit-bearing branches, and crown width on the growth, yield, water and fertilizer utilization efficiency, and photosynthesis of jujube trees in sandy land. The results indicate that the order of influence of the four factors on yield is as follows: fruit-bearing branches, irrigation quota, fertilizer amount, and crown width. The order of influence on net photosynthetic rate is irrigation quota, fertilizer amount, crown width, and fruit-bearing branches. The order of influence on water and fertilizer utilization efficiency is irrigation quota, fertilizer amount, fruit-bearing branches, and crown width. The fruit-bearing branches, irrigation quota, fertilizer amount, and crown width have a highly significant effect on the yield of jujube trees, while the irrigation quota, fertilizer amount, and crown width significantly affect the net photosynthetic rate. The irrigation quota, fertilizer amount, and fruit-bearing branches significantly influence the water and fertilizer utilization efficiency of jujube trees. In the arid zone of central Ningxia, the optimal combination of water, fertilizer, crown width, and fruit-bearing branches for jujube trees in sandy land is an irrigation quota of 250 mm, a fertilizer amount of 110 kg/hm², a crown width of 2.0 m, and 60 fruit-bearing branches, which can achieve a yield of 3 485.02 kg/hm², an increase of 67.0% compared to the control group. This research provides data support for the management of jujube orchards in sandy land.

To study the effects of irrigation strategies based on radiation accumulation on tomato yield and quality in vegetable soil cultivation in facilities, we used the tomato variety 'Saint-Sines 313' as the test material for soil cultivation. The experiment employed well-constructed, low-cost professional radiation sensors for facility agriculture, systematically analyzing the irrigation results of different cumulative radiation amounts collected from multiple points in the region. Using the ET ₀ (Reference Crop Evapotranspiration) as a basis, five irrigation treatments were designed (during the flowering and fruit-setting stages and the fruit maturation stage, irrigation amounts equivalent to 70% ET ₀, 85% ET ₀, 100% ET ₀, 115% ET ₀, and 130% ET ₀ were applied at the same irrigation frequency (7-day interval)). The study analyzed tomato growth, photosynthetic parameters, yield components, and water use efficiency, explored the direct relationships between cumulative radiation, crop water demand, and soil water balance, and proposed a precision irrigation decision model for facility-grown vegetables triggered by cumulative radiation. This model aims to achieve precise irrigation and accurate prediction of water use for facility-grown vegetables. The results showed that under the soil cultivation model without mulching, irrigation using a fitted model with 115% ET ₀ and cumulative radiation yielded the best overall performance in terms of photosynthetic indicators, yield, water use efficiency, and yield of the tomatoes. Therefore, the irrigation strategy based on radiation accumulation simplifies the complicated calculation process of tomato water consumption in the past, and the optical radiation sensor is low-cost and easy to deploy, which can be used in the soil cultivation of facilities tomato.

The appropriate water and fertilizer management is an effective approach to achieve stable and high yield of Korla fragrant pear. A field experiment was conducted to evaluate the effects of irrigation amount and nitrogen application rates on soil salinity and nitrogen dynamics, yield, and quality of the labor-saving and close-planting cultivated Korla fragrant pear under subsurface drip irrigation. Three irrigation levels: W1=375 mm, W2=525 mm, W3=675 mm and three nitrogen application levels (100 kg/hm² (N1), 200 kg/hm² (N2), 300 kg/hm² (N3)) were selected. The results showed that irrigation and nitrogen application rates significantly affected soil salt accumulation (p<0.05). Appropriate levels of irrigation and fertilization can effectively reduce soil salinity in the main root zone (20~80 cm). At the end of the growth period, the salt accumulation of the W2 treatment showed 3.3 g/kg and 1.0 g/kg lower salt accumulation than W1 and W3 treatments, respectively. Similarly, the salt accumulation in the N2 and N3 treatments was reduced by 0.6 g/kg and 1.2 g/kg compared to the N1 treatment. respectively. Higher water and fertilizer application can increase single fruit weight, yield, and soluble solids content by 20.0%, 19.6% and 1.6% respectively, while reduce fruit peeling hardness by 3.2%. In summary, considering soil environment, yield and quality, the recommended irrigation and nitrogen application for labor-saving cultivated Korla fragrant pear were 525 mm and 200 kg/hm².

In order to explore the way to purify aquaculture wastewater in coastal saline paddy field, there was a pot experiment. Two factors, irrigation patterns and biochar application, were studied, including three levels of irrigation patterns: shallow water frequent irrigation (I1), shallow flooding irrigation (I2), and deep flooding irrigation (I3), and two levels of biochar application: with biochar (B1) and without biochar (B0), resulting in a total of six treatments. The concentrations of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) of surface water in paddy field were measured for three consecutive days after each irrigation, and rice yield was also recorded after rice matures. The results showed: ① the removal rate of TN, TP and COD were 65.84%~71.10%, 65.06%~70.66% and 41.00~95.27% after 3 days of retention in paddy fields. ② The application of biochar improved the effect of purifying aquaculture wastewater in paddy fields. With biochar, the 3-d removal rate of TN, TP and COD increased by 11.45%~31.06%, 10.35%~39.52% and 27.29%~41.63%, respectively. And the removal efficiency increased by 17.4%~22.9%, 14.8%~19.8% and 10.9%~16.9%, respectively. ③ With the irrigation water with the depth of 100~150 mm, The removal efficiency of TN, TP and COD increased by 90%~190%, 90%~170% and 80%~170%. And the treatment capacity per unit area increased by 100% and 200%. ④ After the regreening stage, the irrigation depth of 100~150 mm maintaining of three days would not reduce the yield of rice. The research found that the paddy field with coastal saline soil could reduce the concentration of pollutants in wastewater of aquaculture, and the application of biochar and the increase of irrigation water depth could improve the purification efficiency, which did not reduce the yield. This study provided an optimization mode for the purification of aquaculture wastewater in paddy field with coastal saline soil, which was biochar application with the irrigation depth of 100~150 mm.

This study aimed to analyze the effects of ciprofloxacin, an antibiotic, on the growth and antioxidant activity of lettuce under reclaimed water irrigation. A pot experiment with lettuce was conducted, involving four ciprofloxacin (CIP) spiking levels: 5 (T1), 50 (T2), 100 (T3), and 200 (T4) mg CIP /kg soil as the treatment groups, and reclaimed water (T0) and groundwater irrigation (CK) without ciprofloxacin as the control groups. Parameters including lettuce fresh weight, leaf chlorophyll content (SPAD), total nitrogen content, and the antioxidant enzyme activities (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) in both the aboveground and underground parts of the lettuce were monitored. The results indicated that reclaimed water irrigation significantly increased the fresh weight of lettuce and significantly increased leaf SPAD values and total nitrogen content. Reclaimed water irrigation also promoted SOD, POD, and CAT activities in both the aboveground and underground parts of the lettuce. Increasing ciprofloxacin concentrations significantly inhibited fresh weight, with SPAD values and total nitrogen content first increasing and then decreasing with higher ciprofloxacin levels. For antioxidant enzyme activity, there was no significant difference between T1 and T0 for SOD, POD, and CAT activities in both the aboveground and underground parts. At 18 days after transplanting, SOD and POD activities increased with higher ciprofloxacin levels, while CAT activity remained unchanged aboveground but increased underground. By day 48, SOD activity decreased as ciprofloxacin concentration increased, while the differences in CAT and SOD activities among treatments became more significant. In conclusion, reclaimed water irrigation enhanced lettuce growth and antioxidant activity, and moderate antibiotic accumulation promoted growth, but excessive ciprofloxacin levels disrupted cellular signaling due to excessive oxidase activity, negatively affecting plant growth. This study provides theoretical support for the rational use of reclaimed water for irrigation and offers important guidance for maintaining the health of soil-crop systems.

Rainfall is a crucial source of irrigation water for paddy fields, and its efficient utilization is vital for alleviating water resource pressure and improving water use efficiency. However, the impact of rainfall during the rice growing season on irrigation water demand and rainfall utilization in southern China remains unclear. Based on daily meteorological data from six representative stations (Lushan, Wuning, Jingdezhen, Nanchang, Zhangshu, and Guixi) in the Jiangxi Poyang Lake Plain from 1957 to 2020, this study constructs a water balance model to analyze the water balance components for 18 rice varieties, quantitatively assessing rainfall utilization and contribution rates. Rainfall distribution characteristics were analyzed using precipitation concentration degree, concentration period, Gini coefficient, and Lorenz asymmetry index. Mann-Kendall tests were used for trend analysis, and Pearson correlation coefficients were calculated to evaluate relationships among indicators. The results show that early rice receives abundant rainfall (681.0 mm), which largely meets irrigation demand, with a high rainfall contribution rate (73%). However, due to the mismatch between the rainfall concentration period and the peak water demand period, rainfall utilization is relatively low (48%). In contrast, mid- and late-season rice received less rainfall (472.2 mm and 310.8 mm, respectively), but have higher rainfall utilization rates (61% and 69%) and show an increasing trend in rainfall contribution. However, with the rising frequency of heavy rainfall events during the rice growing season, mid- and late-season rice may face a risk of further declining rainfall utilization rates. Future studies should develop intelligent irrigation strategies based on rainfall distribution patterns to enhance the overall efficiency of rainfall utilization.

In order to analyze the spatial and temporal characteristics of meteorological drought in Dongting Lake area, the daily precipitation data of 18 meteorological stations from 1961 to 2022 were used to calculate the standardized precipitation index (SPI) based on different time scales, and compared with the historical drought events, and then the SPI of the most suitable scale was obtained to analyze the characteristics of regional meteorological drought. The results showed that the coincidence rate of three-month SPI in identifying historical drought events reached 91.67%, which was better than other time scales and was suitable for regional meteorological drought monitoring. Monthly scale analysis showed that the short-term drought in 1~3 months was the main drought, and the average drought frequency in July was the highest (8.94%). Drought occurred frequently in the central and southern parts, and the drought duration and intensity in the northwest and central parts were large. In the seasonal scale, the trend of drought in spring (0.084/10 a) was dry, the trend of drought in summer (-0.125/10 a) and winter (-0.133/10 a) was reduced, and the trend of drought in autumn (-0.004/10 a) was not significant. The characteristics of spring drought in the central and northern parts are obvious, the influence range of summer drought is wide, the autumn drought in the central and eastern parts is frequent, and the winter drought is mainly distributed in the northwest. The trend of drought is weakened on the annual scale; in the 1960s, the drought center shifted to the northeast, and the high value area shifted to the central and western regions in the 1970s. The drought gradually eased from the 1980s to the 1990s, but the drought characteristics in the northwest were still obvious. At the beginning of the 21st century, the center of drought severity shifted toward the southeast, and the drought duration and intensity in the south-central region increased in the 2010s. These results provide valuable information for regional disaster prevention, water resources management, and agricultural planning, and offer critical guidance for selecting appropriate drought monitoring time scales.