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Purpose: to state hydraulic characteristics and determine priority directions for improving the irrigation module design for combined drip and micro-sprinkler irrigation. Materials and methods. The study is based on the joint use of theoretical methods – a well-known mathematical model for calculating the hydraulic characteristics of the irrigation module and experiment, which allows assessing the problem state and scale solutions in any necessary proportions. Results. According to calculations, the uniformity of watering is maintained at an acceptable level at a lower head level in the range of 1.56–1.68 atm when installing six microsprinklers on a drip line. When installing eight sprinklers, the water head along the length of the drip pipeline decreased to an unacceptable 1.39–1.40 atm. Experimental studies have shown that there is only an option with two sprinklers installed on the pipeline above the level of 1.5 atm. Already with the installation of four sprinklers, the water head along the length of the pipeline decreased to 1.45–1.47 atm. At the same time, the variation in the actual microsprinkler performance reached 16 % or more. The discrepancy between experimental and model data is explained by the fact that the calculation model does not fully take into account local resistances that arise when connecting sprinklers. Conclusions. Two main reasons of the increased uneven distribution of irrigation water over the irrigated area have been identified. The first reason is a significant increase in water flow in the irrigation pipeline when emitters and sprinklers work together. The solution to this problem is to develop structures that make it possible to separate the water flow through emitters and through sprinklers in time. The second reason is an increase in local resistance in the water diversion units to the sprinklers. The solution to this problem is to develop special water diversion structures that would be characterized by minimal local resistance.

To address the issues of both water resources allocation and sustainable management in agriculture areas with rising food demand, a simulation-optimization framework based on Flopy and Pymoo was proposed and developed for canal-well combined irrigation districts. The proposed framework first solved the many-objective water resources allocation problem which integrates groundwater simulation, crop production, and farmer income modules to quantitatively reveal the various trade-offs and synergies by using NSGA-III algorithm. The Entropy-TOPSIS method was then applied to recommend proper water allocation schemes. The proposed framework was further tested in Baojixia irrigation district considering various water supply and crop demand scenarios based on Copula-based uncertainty analysis. The Key findings are as follows: (1) the proposed framework could effectively optimize conjunctive water resources allocation problems of both surface water and groundwater; (2) low supply combined with high demand (p=0.17) is more likely to occur than high supply with high demand (p=0.02); (3) increased crop demand and restricted surface water negatively impact both water productivity and groundwater sustainability; and (4) the cumulative groundwater drawdown of recommend schemes is 36.9 % and 6.5 % higher under low to medium supply scenarios, while water productivity of recommend schemes decreases 28.2 % and 9.7 % with high and medium demand. This framework could provide useful insights for sustainable agricultural water management in canal-well combined irrigation district with various uncertainties in supply and demand scenarios.

There are no doubts about the advantages of using drip irrigation, however, it does not solve the problem of regulating plant phytoclimate in open ground during periods of high temperatures in the Lower Volga region when the biological development of vegetable crops is inhibited, which leads to a decrease in yield. The use of combined irrigation in the combination of drip and fine solves the problem of reducing thermal stress and increases moisture on the soil surface. Based on the research and publications of Russian scientists, the main requirements for the functioning of combined irrigation systems have been identified. These include the provision of drip and fine (aerosol) irrigation, the system should work both jointly and separately, the regulation of plant phytoclimate, the possibility of using foliar feeding and chemical protection, etc. To solve this problem, a number of technical solutions have been considered, which will allow to partially or fully satisfy all the requirements for the stability of the technological process of growing crops under combined irrigation and eliminate the above-mentioned negative environmental conditions of the Lower Volga region. The FGBNU VNII “Raduga” developed the KAU-1M aerosol humidification kit, and the scientists of the Volgograd State Agrarian University developed technical solutions Spray Nozzle of the Combined Irrigation System for Cultivation of Vegetable Crops). The proposed technical solutions for the combined irrigation system will improve operational reliability, provide the plants with soil moisture, control the temperature, nutritional regime of the plants, which will make it possible to obtain stable yields of agricultural crops and environmental safety of the environment.

Purpose: development of a computer algorithm for a quantitative assessment of the hydraulic parameters of an irrigation and drainage system with the possibility of integrating different irrigation methods. Materials and methods. The design of structures for combined irrigation is based on hydraulic calculation. A feature of such systems is the ability to change irrigation methods, which is associated with a significant change in hydraulic parameters and the complication of hydraulic design of structures. Automation of hydraulic calculations based on a universal computer algorithm is the most acceptable way to solve the problem and the basis for designing combined irrigation systems. Results. A feature of the proposed algorithm for determining the quantitative parameters of the combined irrigation system is the use of a step-by-step approach followed by the formation of a generalized hydraulic screenshot of the entire structure. A screenshot of hydraulic parameters here means a quantitative assessment of hydraulic indicators for all nodal points of a structure, implemented by a calculation method for given, stationary modes of system operation. A set of this kind of static screenshots allows you to evaluate the process in dynamics, as well as to carry out comparative assessments of hydraulic parameters under different operating modes of the combined irrigation system. The algorithm offers an original way to identify objects based on the use of a linear coordinate system. The method makes it possible to organize an enumeration of the structural elements of the system and a step-by-step calculation of hydraulic parameters from the inlet section of the design segment to any given nodal point. Conclusions. The calculation results according to the proposed algorithm make it possible to form a specially organized data array, which is a set of symbolic-numeric values that determine the pressure level and water flow rate and identify them with the nodal point of the system.

Modern irrigation areas often use a combination of channels and pipes for irrigation. Due to changes in terrain, inflow, and pipe diameter, pipelines are often prone to experiencing a state of no pressure. This lack of pressure affects not only the velocity distribution and water surface profile of the main channel but also the velocity distribution and flow distribution of the pipeline. Therefore, in this study, we employed a combination of physical model experiments and theoretical analysis to study the influence of non-pressure pipelines on the hydraulic characteristics of channel–pipe combined irrigation systems filled to different degrees. Through this, the variation laws of the flow velocity distribution, turbulence intensity, water surface, diversion width, and diversion ratio under different filling degrees were obtained. The non-pressure pipeline flow velocity expression was obtained through dimensional analysis, and the calculation formula for the non-pressure pipeline flow velocity coefficient was fitted using linear regression analysis. The relative error between the calculated value and the measured value did not exceed 8.81%. The research results presented in this article can provide technical support for the design and maintenance of channel–pipe combined irrigation systems. [ABSTRACT FROM AUTHOR]

Brackish water has to be used to irrigate crops for harvest due to the scarcity of freshwater resources. However, brackish water irrigation may cause secondary soil salinization. Whether the combined utilization of different non-conventional water resources could relieve the risk of secondary soil salinization has not been reported. In order to explore the safe and rational utilization of brackish water in areas where freshwater resources are scarce, a pot experiment was conducted to study the risk of secondary soil mixed irrigation and rotational irrigation using brackish water and reclaimed water or freshwater. The results indicated that: (1) Short-term irrigation using reclaimed water did not cause secondary soil salinization, although increasing soil pH value, ESP, and SAR. The indices did not exceed the threshold of soil salinization. (2) Compared with mixed irrigation using brackish–freshwater, the contents of soil exchangeable Ca2+, K+, and Mg2+ increased, and the content of soil exchangeable Na+ decreased under rotational irrigation using brackish-reclaimed water. In addition, the contents of soil exchangeable Na+ and Mg2+ under mixed irrigation or rotational irrigation were significantly lower, and the exchangeable K+ content of the soil was higher compared with brackish water irrigation. The exchangeable Ca2+ content under rotational irrigation was higher than that of brackish water irrigation, while the reverse was seen under mixed irrigation. (3) For different combined utilization modes of brackish water and reclaimed water, the ESP and SAR were the lowest under rotational irrigation, followed by mixed irrigation and brackish water irrigation. The ESP under brackish water treatment exceeded 15%, indicating a certain risk of salinization, while ESPs under other treatments were below 15%. Under mixed irrigation or rational irrigation using reclaimed-brackish water, the higher the proportion or rotational times of reclaimed water, the lower the risk of secondary soil salinization. Therefore, short-term combined irrigation using brackish water and reclaimed water will not cause the risk of secondary soil salinization, but further experiments need to verify or cooperate with other agronomic measures in long-term utilization.

To address the issues of both water resources allocation and sustainable management in agriculture areas with rising food demand, a simulation-optimization framework based on Flopy and Pymoo was proposed and developed for canal-well combined irrigation districts. The proposed framework first solved the many-objective water resources allocation problem which integrates groundwater simulation, crop production, and farmer income modules to quantitatively reveal the various trade-offs and synergies by using NSGA-III algorithm. The Entropy-TOPSIS method was then applied to recommend proper water allocation schemes. The proposed framework was further tested in Baojixia irrigation district considering various water supply and crop demand scenarios based on Copula-based uncertainty analysis. The Key findings are as follows: (1) the proposed framework could effectively optimize conjunctive water resources allocation problems of both surface water and groundwater; (2) low supply combined with high demand (p=0.17) is more likely to occur than high supply with high demand (p=0.02); (3) increased crop demand and restricted surface water negatively impact both water productivity and groundwater sustainability; and (4) the cumulative groundwater drawdown of recommend schemes is 36.9 % and 6.5 % higher under low to medium supply scenarios, while water productivity of recommend schemes decreases 28.2 % and 9.7 % with high and medium demand. This framework could provide useful insights for sustainable agricultural water management in canal-well combined irrigation district with various uncertainties in supply and demand scenarios. • A framework for food-water-economy-sustainability nexus is proposed. • There is a non-linear trade-off between groundwater sustainability and income. • Imbalance between supply and demand exacerbates trade-offs. • High crop water demand is more likely to face low surface water supply. [ABSTRACT FROM AUTHOR]

Brackish water has to be used to irrigate crops for harvest due to the scarcity of freshwater resources. However, brackish water irrigation may cause secondary soil salinization. Whether the combined utilization of different non-conventional water resources could relieve the risk of secondary soil salinization has not been reported. In order to explore the safe and rational utilization of brackish water in areas where freshwater resources are scarce, a pot experiment was conducted to study the risk of secondary soil mixed irrigation and rotational irrigation using brackish water and reclaimed water or freshwater. The results indicated that: (1) Short-term irrigation using reclaimed water did not cause secondary soil salinization, although increasing soil pH value, ESP, and SAR. The indices did not exceed the threshold of soil salinization. (2) Compared with mixed irrigation using brackish-freshwater, the contents of soil exchangeable Ca 2+ , K + , and Mg 2+ increased, and the content of soil exchangeable Na + decreased under rotational irrigation using brackish-reclaimed water. In addition, the contents of soil exchangeable Na + and Mg 2+ under mixed irrigation or rotational irrigation were significantly lower, and the exchangeable K + content of the soil was higher compared with brackish water irrigation. The exchangeable Ca 2+ content under rotational irrigation was higher than that of brackish water irrigation, while the reverse was seen under mixed irrigation. (3) For different combined utilization modes of brackish water and reclaimed water, the ESP and SAR were the lowest under rotational irrigation, followed by mixed irrigation and brackish water irrigation. The ESP under brackish water treatment exceeded 15%, indicating a certain risk of salinization, while ESPs under other treatments were below 15%. Under mixed irrigation or rational irrigation using reclaimed-brackish water, the higher the proportion or rotational times of reclaimed water, the lower the risk of secondary soil salinization. Therefore, short-term combined irrigation using brackish water and reclaimed water will not cause the risk of secondary soil salinization, but further experiments need to verify or cooperate with other agronomic measures in long-term utilization.

Considering the increasing pressure on freshwater resources due to the constant increase in water consumption and insufficient wastewater control and treatment, recovering wastewater is a path to overcoming water scarcity. The present work describes the potential of reusing treated wastewater (reclaimed water) for irrigation and production of microalgae biomass in an integrated way, through experimental evaluation of plant and microalgae growth, and creation of an application model. First, two parallel experiments were conducted to evaluate the use of reclaimed water produced by a constructed wetland filled with a mix of solid waste: the irrigation of a set of small pots filled with soil and planted with Tagetes patula L., and the cultivation of microalgae Chlorella sp. and a mixed microalgae population with predominant species of the genus Scenedesmus sp. in shaken flasks and tubular bubble column photobioreactors. Results indicated no negative effects of using the reclaimed water on the irrigated plants and in the cultivated microalgae. The growth indicators of plants irrigated with reclaimed water were not significantly different from plants irrigated with fertilized water. The growth indicators of the microalgae cultivated with reclaimed water are within the range of published data. Second, to apply the results to a case study, the seasonal variability of irrigation needs in an academic campus was used to propose a conceptual model for wastewater recovery. The simulation results of the model point to a positive combination of using reclaimed water for the irrigation of green spaces and microalgae production, supported by a water storage strategy. Water abstraction for irrigation purposes can be reduced by 89%, and 2074 kg dry weight microalgae biomass can be produced annually. Besides the need for future work to optimize the model and to add economical evaluation criteria, the model shows the potential to be applied to non-academic communities in the perspective of smarter and greener cities.

In order to save fresh water and reduce soil salt accumulation, reclaimed water-fresh water combined irrigation, i.e, irrigation with reclaimed water for 50 d and then with fresh water till harvest, was used in rice planting. Bacillus subtilis and Saccharomyces cerevisiae were inoculated into the soil at the end of reclaimed water irrigation. The inoculation weight per pot of these microorganisms was as follows: 0 g and 0 g (J0), 5 g and 0 g (J1), 3.75 g and 1.25 g (J2), 2.5 g and 2.5 g (J3), 1.25 g and 3.75 g (J4), and 0 g and 5 g (J5), respectively. Treatment using reclaimed water in the whole stage was used as the control (CK). The plant height, tiller, physical and chemical properties of the soil, and soil bacterial diversity were measured. It was found that the plant height of rice was increased significantly by J1-J5 treatments. The dry weight of rice root, stem, and panicle and the 1000-grain weight increased significantly, while the leaf dry weight decreased. Microorganism inoculation significantly increased the nutrient absorption capacity of the crops. J1, J2, and J4 treatments significantly increased the amount of nitrate-nitrogen, ammonium nitrogen, available phosphorus, and available potassium, while J3, J4, and J5 treatments increased the soil organic matter, and microbial inoculation significantly decreased the EC of soil. J4 treatment induced the largest reduction in EC, and microorganisms treatments increased soil pH. Bacterial function prediction based on the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway indicated that soil metabolic function was not significantly disturbed by the treatments. Organic matter and pH are the two main factors affecting the structure of the bacterial community in soil. 3.75 g of B. subtilis and 1.25 g of S. cerevisiae per pot is the best inoculation ratio. [ABSTRACT FROM AUTHOR]

It is important to clarify the suitable ratio of well–canal combined irrigation and the suitable range for ecological groundwater depth for the ecological stability of the arid zone. The MODFLOW model was used to reconstruct long-term groundwater depth by analyzing the response relationship between vegetation cover and groundwater depth in the Weigan River irrigation district. The suitable range for ecological groundwater depth was obtained, and based on this range, the suitable well–canal combined irrigation ratio in the research area was further simulated. The results show the following: (1) The average annual depth of groundwater in 82.9% of the study area increased from 2012 to 2021, and the average annual depth of groundwater increased by 1.03 m in 2021 compared to 2012. The average depth of the groundwater in the upstream area increased the most, with an increase of 1.96 m. (2) The vegetation cover in the study area from 2012 to 2021 increased in general, with an increase of 0.0461 over the 10-year period, but it fluctuated between years. (3) The depth of the groundwater in the study area suitable for the growth of vegetation in the irrigation area ranged from 3 to 5 m, and the value of NDVI within this range concentrated near 0.564–0.731, which represents a good state of vegetation growth. (4) The ratio of combined well and canal irrigation in the study area from 2012 to 2014 surged from 0.13 in 2012 to 0.48 in 2014, and the irrational harvesting and replenishment relationship led to a rapid increase in the depth of buried groundwater. A suitable well–canal combined irrigation ratio of 0.396 in the study area was obtained. This study is beneficial for maintaining the sustainable development and utilization of water resources and ecological stability in the Weigan River irrigation district. [ABSTRACT FROM AUTHOR]

In areas with shallow saline groundwater, soil salts inevitably accumulate in the root zone during the growth period due to irrigation and upward movement of salts from the groundwater. In Northern China, autumn irrigation (AIR) with large amounts of water is commonly employed post-harvest to mitigate soil salt stress on crop growth in the subsequent year. Optimizing the total irrigation depth during both crop-growth and non-growth periods is challenging because of the movement of soil salts, which is influenced by their two-dimensional distribution around drippers and the impact of the winter freeze-thaw cycles, significantly affecting water flow and solute transport during winter. In this study, the HYDRUS-1D and HYDRUS-2D models were integrated and calibrated using experimental data collected from 2021 to 2023 in China's Ordos south bank irrigation area. This model integration was conducted to assess soil water and salt dynamics during the non-growth and corn-growth periods under different irrigation strategies: a) AIR with high (AH) and low (AL) irrigation depths, and b) drip irrigation (DIR) with high (DH), medium (DM), and low (DL) irrigation depths. The results indicated that HYDRUS effectively modeled the electrical conductivity of the saturation paste extract (ECe) across different irrigation strategies, yielding an average coefficient of determination (R2) and the root mean square errors (RMSE) of 0.87 and 0.53 dS m−1, respectively. Generally, ECe increased during the growth period with DIR and decreased during the non-growth period with AIR. For the 0–40 cm soil layer, ECe decreased by 5.7 % and 12 % for every 100 mm increase in the AIR and DIR depths, respectively. Compared with the AHDM and AHDL treatments, reducing an AIR depth and increasing a DIR depth resulted in lower ECe in the 0–40 cm layer during the growth period and higher crop yield (CY) and irrigation water productivity (WPI). Specifically, the average ECe in the 0–40 cm layer decreased by 4.8 % during the growth period in the ALDH treatment compared to the AHDM treatment, and CY and WPI increased by 7.2 % and 10.3 %, respectively. Additionally, the irrigation strategy was the most effective in reducing ECe when AIR accounted for 35 % of the total irrigation. This study suggested that combining low AIR and high DIR could enhance water and field productivity.

Optimal irrigation-fertilization-aeration subsequently enhance greenhouse tomato yields and fruit quality. In addition, the optimization of these agricultural practices is essential to improve irrigation water productivity (WPI). In this context, the present study aims to assess the effects of combined irrigation, fertilization, and aeration treatments on the greenhouse tomato yield (Y), evapotranspiration (ET), WPI, and fruit quality. To achieve this objective, we applied two cumulative pan evaporation (Epan) -based irrigation (I1: 1.0 Epan; I2: 0.8 Epan), three nitrogen fertilization (F1: 120 kg/ha; F2: 180 kg/ha; F3: 240 kg/ha), and three venturi injector-based aeration rates (A1: single Venturi aeration; A2: double Venturi aeration; CK: unaerated) in triplicates. In total, 15 treatment scenarios were considered in this study, including a control group (CKI1). Each treatment was replicated three times. According to the obtained results, the harvesting time of the cultivated greenhouse tomato was strongly affected by the aeration levels due to the differences in the soil oxygen contents. The A2 treatment demonstrated a stronger promoting effect on early tomato ripening than those under the A1 and CK scenarios. Indeed, the first tomato harvest amount under the A2 treatment was higher than those obtained under the A1 and CK scenarios by 32.24% and 36.45% (P < 0.05), respectively. In addition, there were significant increases in the water productivity (WPC) and WPI values with decreasing irrigation rates. In contrast, the ET and Y substantially decreased. Specifically, the ET and Y values under the I1 treatment scenario were 11.38% and 8.65% higher than those observed under the I2 treatment scenario, respectively. On the other hand, the WPC and WPI values under the I1 treatment were 12.01% and 13.09% lower than those under the I2 treatment, respectively. The results showed also significant irrigation-aeration, irrigation-fertilization, and aeration-fertilization interaction effects on the ET, Y, WPC, and WPI values of the greenhouse tomato (P < 0.01). In addition, the irrigation, fertilization, and aeration treatments considerably influenced the sugar-acid ratio and the organic acid, soluble sugar, and lycopene contents in the tomatoes. In fact, lycopene was an important indicator of tomato quality, showing a significant positive correlation with the comprehensive quality scores. Based on the TOPSIS results, the combined I2-F2-A2 treatment is recommended to enhance the Y, ET, WPC, WPI, and fruit quality of the tomato crop.