The negative impact of climate change is potentially damaging agroecosystem services that have constrained agricultural production and caused water scarcity in Central Asian countries, particularly in Uzbekistan. This study evaluates the efficiency of full (FDI) and deficit (DDI) drip irrigation regimes for amaranth (Amaranthus spp.) cultivation in the Tashkent region of Uzbekistan using the HYDRUS-1D simulation model. Field experiments were conducted over two growing seasons, accompanied by soil moisture monitoring, root zone analysis, and crop performance measurements while the accuracy of the obtained results was assessed against ground measured data. The results showed that compared to the FDI regime, amaranth under the DDI improved water productivity by 56.5% while exhibiting tolerance to water scarcity. The Pearson correlation analysis revealed a strong relationship between the simulated and observed SWC data for both irrigation regimes (R2 = 0.862 for FDI and R2 = 0.936 for DDI), indicating the model's predictive reliability. Although FDI produced higher yield (2004 kg/ha) over the two-year period, which was 25% (2 t ha-1) higher than the DDI regime (1,604 kg/ha). However, DDI demonstrated significantly greater water productivity (56.5% higher), attributed to reduced unproductive evaporation and the C4 nature of amaranth. Root system analysis revealed deeper penetration under DDI, suggesting adaptive responses to water stress. The findings of this study suggest that implementing precise irrigation technology in amaranth cultivation combined with the use of the HYDRUS-1D model in the context of inevitable climate change, can ensure the long-term sustainable management of water and land resources in arid regions.

Soil salinization is a severe environmental issue limiting the growth and yield of crops worldwide. Subsurface drip irrigation with micro-nano bubble hydrogen water (SDH) is an innovative way to realize the role of hydrogen gas (H2) in improving plant resistance to salt stress in practical agricultural productions. Nonetheless, limited information is available on how SDH affects the plant salt tolerance performance. Especially, the underlying physiological respond, hormone-regulated and soil microbial-mediated mechanisms have not been reported so far. In this study, the effects of SDH on lettuce (Lactuca sativa L.) growth, photosynthesis, root development, antioxidant system, phytohormone, and soil microbial community were investigated under normal and salt stress conditions. The results showed that, with salt stress, SDH significantly enhanced the lettuce fresh weight, photosynthesis activity, and root growth. The leaf antioxidant enzyme activities increased and reactive oxygen species (ROS) content decreased to reduce the oxidative damage. The decreased malondialdehyde (MDA) content indicated a low membrane lipid peroxidation responsible for cellular damage. SDH also helped to maintain osmotic homeostasis, which was reflected by the increased soluble protein (SP) content. Reduced Na+/ K+ ratio and ROS did not trigger excessive production of stress response hormones abscisic acid (ABA) and jasmonic acid (JA), which alleviated the mediated growth inhibition effects. SDH enriched the abundance of the plant growth-promoting rhizobacteria (PGPR) in the soil, such as Arthrobacter and Pseudomonas. That might be the reason for explaining the increase in hormone indoleacetic acid (IAA) in lettuce and 1-aminocyclopropane-1carboxylate (ACC) deaminase activity in the soil, which was beneficial for inhibiting ethylene production and promoting plant growth. Under the normal condition, variations of physiological and growth indicators as affected by SDH were similar to those under the salt stress condition, except for root development. High concentration of dissolved hydrogen gas in water might expel the oxygen. The induced soil anoxic environment limited oxygen diffusion, in turn inhibited root respiration and growth. The effect of hydrogen concentration on the plant tolerance against salt stress under different salt content could be further studied.

A vertical tube surface drip irrigation system was designed to address the damage caused by soil drought and high surface temperature to sand-fixing seedlings in a plant sand-fixation area. Numerical simulation and experimental verification were used to study soil water movement with vertical tube infiltration and surface drip irrigation for four aeolian sandy soils with different hydraulic conductivity (Ks), drip discharge (Q), vertical tube diameter (D), and vertical tube buried depth (B). The results show that a power function relationship exists between the soil-stable infiltration rate (if) and Ks, D, and B given the condition of vertical tube water accumulated infiltration, and its coefficient is 0.17. The power function indices of Ks, D, and B are 0.87, 1.89, and -0.37, respectively. The if can be used to determine the maximum drip discharge (Qmax) of the dripper in the vertical tube to ensure that the sand-fixing plants are not submerged during drip irrigation through the vertical tube (Qmax=if). The wetting front transport distance in the three directions increased with increasing Ks and Q but decreased with increasing D and B. After determining the time required for water to reach the bottom of the vertical tube, an estimation model of soil wetting body transport for vertical tube surface drip irrigation, including Ks, Q, D, and B, was constructed. Compared with the experimental data, the root mean square error (RMSE) is between 0.17 and 0.42 cm, and the Nash-Sutcliffe efficiency (NSE) is at least 0.88. Therefore, the model is appropriate and can provide valuable practical tools for the design of vertical tube surface drip irrigation in different plant sand fixation areas. A surface drip irrigation system and pipe protection technology were combined to form a vertical tube surface drip irrigation system to address the damage caused by soil drought and high surface temperature to sand-fixing seedlings. However, this irrigation technology has the problem that it is difficult to quantify the matching of drip discharge and pipe parameters (vertical tube diameter and burial depth), wetted soil volume, and plant roots due to the single soil sample used in the laboratory experiments. This paper considers the influence of soil differences in diverse plant sand-fixing areas and establishes a stable infiltration rate model to determine the maximum drip discharge. Additionally, a soil wetted volume prediction model was developed by combining HYDRUS-2D simulations and experimental verification. The model is simple and has high prediction accuracy, which is convenient for designers to determine the appropriate vertical tube parameters for different plant sand-fixation areas.

This study, focusing on porous sheet mulching cultivation for high -quality and annual steady production of Satsuma mandarin, investigated trees photosynthetic oxidation stress according to the soil moisture in the porous mulching cultivation. Leaf, vesicle tissue water status, chlorophyll fluorescence, plant hormone abscisic acid (ABA) and jasmonic acid (JA) activity were measured using a phychrometer sample chamber, potable fluorescene meter and UHPLC and MS/MS were measured. Leaf water potential fluctuated according to the change in soil moisture content between the non -sheet mulching (control) and restoring the porous sheet (mulching) groups throughout this experiment period, and about 2 weeks intervals drip irrigation after the mulching (Mul. + Drip). In September, the leaf water potential of the control (-0.9 similar to -1.3 MPa) was higher than that of the mulching (-2.5 similar to -2.7 MPa), and Mul. + Drip (-2.2 similar to -2.3 MPa) groups. In October, due to continuous dry weather, the results of control and mulching were -3.0 MPa and -4.0 MPa or below respectively, which were lower than Mul. + Drip (-2.64 MPa). The water potential of vesicle tissue also fluctuated similarly to that of the leaf water potential. The osmotic potential was tendentially higher in the control than that in mulching and Mul. + Drip group. The turgor pressure remained constant at 0.5 MPa in October and November except for the time in September. The soluble solids content (SSC) of fruit at harvest was higher at 14.55 degrees Brix in the mulching and 13.96 degrees Brix in the Mul. + Drip, which were both higher than 11.05 degrees Brix in the control, showing a significant difference and confirming a rise in the SCC caused by osmotic control. The degree of oxidative damage according to water stress level caused by drought stress was investigated by the comparison of the maximum quantum efficiency value of (Fv/Fm), the initial fluorescence value (Fo) value, and the change in photosynthetic rate. The concentration of ABA in the leaf, fruit peel, and flesh was relevant to the leaf moisture stress and fruit sugar content. The concentration of JA varied as the concentration of ABA changed. In conclusion, Fv/Fm and Fo of chlorophyll PSII and ABA regarding photosynthetic oxidative damage were found to be indicators of the degree of damage according to tree water stress levels.