The development of water-saving management relies on understanding the physiological response of crops to soil drought. The coordinated regulation of hydraulics and stomatal conductance in plant water relations has steadily received attention. However, research focusing on grain crops, such as winter wheat, remains limited. In this study, three soil water supply treatments, including high (H), moderate (M), and low (L) soil water contents, were conducted with potted winter wheat. Leaf water potential (Ψ_leaf), leaf hydraulic conductance (K_leaf), and stomatal conductance (g_s), as well as leaf biochemical parameters and stomatal traits were measured. Results showed that, compared to H, predawn leaf water potential (Ψ_PD) significantly reduced by 48.10% and 47.91%, midday leaf water potential (Ψ_MD) reduced by 40.71% and 43.20%, K_leaf reduced by 64.80% and 65.61%, and g_s reduced by 21.20% and 43.41%, respectively, under M and L conditions. Although g_s showed a significant difference between M and L, Ψ_leaf and K_leaf did not show significant differences between these treatments. The maximum carboxylation rate (V_cmax) and maximum electron transfer rate (J_max) under L significantly decreased by 23.11% and 28.10%, stomatal density (SD) and stomatal pore area index (SPI) under L on the abaxial side increased by 59.80% and 52.30%, respectively, compared to H. The leaf water potential at 50% hydraulic conduction loss (P₅₀) under L was not significantly reduced. The g_s was positively correlated with Ψ_MD and K_leaf, but it was negatively correlated with abscisic acid (ABA) and SD. A threshold relationship between g_s and K_leaf was observed, with rapid and linear reduction in g_s occurring only when K_leaf fell below 8.70 mmol m⁻² s⁻¹ MPa⁻¹. Our findings demonstrate that wheat leaves adapt stomatal regulation strategies from anisohydric to isohydric in response to reduced soil water content. These results enrich the theory of trade-offs between the carbon assimilation and hydraulic safety in crops and also provide a theoretical basis for water management practices based on stomatal regulation strategies under varying soil water conditions.

Subsurface pipe drainage (SPD) is an important technique for the improvement of saline–alkali lands in China. Winter irrigation after crop harvest is a key measure used in the Yellow River irrigation area in northwest China to reduce soil salinity in the root zone of crops. To optimize winter irrigation under SPD, the calibrated HYDRUS-2D model was utilized in this study to investigate the effects of soil texture (clay loam, silt loam, loam, and sandy loam), initial soil salinity (1, 3, 5 g/kg), and the winter irrigation quotas (80, 100, 120, 150, 180 mm) on the rate of soil desalination. In this study, soil salinity levels during the stable production of common crops such as sunflower and corn in the Yinbei Irrigation District in Ningxia, China, were taken as the thresholds, efficient utilization of irrigation water was considered, and suitable crops and appropriate winter irrigation quotas for different soil textures and levels of soil salinity were proposed. Soil with a salt content of 1~3 g/kg is suitable for the planting of corn with 80 mm of irrigation water. Sandy loam soil with a salt content of 3~5 g/kg is suitable for sunflower–corn intercropping with 120 mm of irrigation water. Sandy loam soil with a salt content exceeding 5 g/kg is suitable for the planting of sunflower with 80 mm of irrigation water. Other types of soils need to be improved by reducing the spacing between subsurface pipes, using desulfurized gypsum, biochar, and other additives. People engaged in agriculture can utilize this research to determine the appropriate volumes of irrigation water, crop types, planting systems, and subsurface pipe parameters based on local conditions.

Drought stress severely limits agricultural productivity, with atmospheric and soil water deficits often occurring simultaneously in field conditions. While plant responses to individual drought factors are well-documented, recovery mechanisms following combined atmospheric–soil drought remain poorly understood, hindering drought resistance strategies and irrigation optimization. We set up two VPD treatments (low and high vapor pressure deficit) and two soil moisture treatments (CK: control soil moisture with sufficient irrigation, 85–95% field capacity; drought: soil moisture with deficit irrigation, 50–60% field capacity) in the pot experiment. We investigated wheat’s hydraulic transport (leaf hydraulic conductance, K_leaf) and gas exchange (stomatal conductance, g_s; photosynthetic rate, A_n) responses to combined drought stress from atmospheric and soil conditions at the heading stage, as well as rewatering 55 days after treatment initiation. The results revealed that: (1) high VPD and soil drought significantly reduced leaf hydraulic conductance (K_leaf), with a high VPD decreasing K_leaf by 31.6% and soil drought reducing K_leaf by 33.2%; The high VPD decreased stomatal conductance (g_s) by 43.6% but the photosynthetic rate (A_n) by only 12.3%; (2) After rewatering, g_s and A_n of atmospheric and soil drought recovered relatively rapidly, while K_leaf did not; (3) Atmospheric and soil drought stress led to adaptive changes in wheat’s stomatal regulation strategies, with an increasing severity of drought stress characterized by a shift from non-conservative to conservative water regulation behavior. These findings elucidate wheat’s hydraulic–stomatal coordination mechanisms under drought stress and their differential recovery patterns, providing theoretical foundation for improved irrigation management practices.

This work involves the development of a hydrodynamic fertilizer injector (HFI), which uses an integrated axial-flow turbine (AFT) and a diaphragm pump to absorb liquid fertilizer. Three structural parameters—the number of impellers (M₁), average number of blades per impeller (M₂), and arrangement pattern (M₃)—are considered, and 12 AFT designs are developed. Using a combination of CFD numerical simulations and hydraulic performance testing, the response of the AFT output power (P), blade negative pressure (NP), and fertilizer injection flow rate (Q_inj) to structural parameters and inlet pressure (H) is investigated. The results show that the normalized root mean square error between the simulated outlet flow rate (Q_s) and the measured flow rate (Q_m) is 5.1%, indicating high accuracy in the grid motion simulation method. P increases first and then decreases with the increase in impeller speed (n). The maximum P (P_max) ranges from 150.1 to 201.4 W. P_max increases with H, decreases with increasing M₁ and M₂, and shows little change with M₃. At H = 0.14 MPa, M₁ and M₂ have a significant influence, and at H ≥ 0.14 MPa, M₁ becomes the most significant factor (p < 0.05). Low-speed flow and negative pressure cavitation zones at the leading edge of the blade suction surface cause flow blockage and affect the lifespan of the AFT. These regions decrease in size as H increases but increase with M₁. The negative pressure (NP) decreases as M₂ increases. When M₁, M₂, and M₃ are 2, 3, and identical (D33), the P_max of the AFT is maximized, increasing by 6.7% to 33.5% compared with those of the other combinations. The Q_inj of D33, D34, D43, and D44 at H = 0.12~0.18 MPa range from 288.6 to 847.3 L/h, which is 38.7% to 461.0% higher than that of domestic and international venturi injectors. When considering cavitation issues and the manufacturing cost of the AFT mold, D44 may be chosen. Although its Q_inj is 7.0% lower than that of D33, NP is reduced by 37.9%. These findings provide a basis for the development of the HFI with AFT as the driving unit.

Automatic flushing valve (AFV) can improve the anti-clogging ability of the drip fertigation system. The minimum inlet pressure (H_amin) required for automatic closing and the maximum flushing duration (FD_max) are two important performance indexes of AFV. The existing AFV products have the problem of larger H_amin and smaller FD_max, which result higher investment and operating cost, and poor flushing efficiency. Based on the mechanical analysis of the AFV elastic diaphragm and the derivation of the FD, elastic diaphragm hardness (E), ascending channel offset distance (D), and drain hole width (W) were selected as the experimental factors, and nine AFVs were designed by L₉(3³) orthogonal test method to investigate the influence of elastic diaphragm hardness and structural parameters on the hydraulic performance of AFVs. The hydraulic performance test results showed that the H_amin of the nine AFVs ranged from 0.026 to 0.082 MPa and FD_max ranged from 36.3 to 95.7 s. H_amin was positively correlated with E and D and negatively correlated with W. FD_max was negatively correlated with E and W and tended to increase and then decrease with D. All elastic diaphragm hardness and structural parameters had a significant effect on H_amin, and E and W had a significant effect on FD_max. Based on the range analysis, two new combinations of AFV elastic diaphragm hardness and structural parameters with minimum H_amin (E = 40 HA, D = 0 mm, W = 2 mm) and maximum FD_max (E = 40 HA, D = 2 mm, W = 1.68 mm) were determined, and the corresponding H_amin was 0.022 MPa, 63.3% lower than that of the existing product, and FD_max was 116.4 s, 71.2% higher than that of the existing product. In this study, two ternary nonlinear mathematical regression models of H_amin and FD_max with elastic diaphragm hardness and structural parameters was constructed. The simulation accuracy of the models is good and can be used to quickly predict the optimal combination of AFV parameters to satisfy the actual engineering-required H_amin and FD_max.