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【Objective】The Hetao Irrigation District, the largest irrigation district in Inner Mongolia, relies primarily on water diverted from the Yellow River. However, long-term irrigation has led to increasing soil salinization. This study aims to analyze the spatiotemporal variations in drainage volume and mineralization within the district to inform sustainable drainage water reuse strategies.【Method】The analysis was based on drainage water and its mineralization measure from 2006 to 2020 in the irrigation district. The Mann-Kendall trend test was applied to assess the spatiotemporal variations in both drainage volume and mineralization across three irrigation areas: Jiefangzha, Yongji, and Yichang. Additionally, the Spearman correlation coefficient was used to evaluate the relationship between annual drainage volume and mineralization in each area.【Result】From 2006 to 2020, all three irrigation areas exhibited a significant increasing trend in drainage volume. Mineralization levels remained stable in the Jiefangzha area, while both Yongji and Yichang area experienced a significant decrease in mineralization. The Spearman correlation coefficients between annual drainage volume and mineralization were -0.02 for Jiefangzha and -0.81 for both Yongji and Yichang, indicating a strong negative correlation of drainage volume and mineralization in the latter two areas. Monthly data further revealed significant variations in drainage volume and mineralization, generally displaying a negative correlation. Spatially, the highest average annual drainage volume was recorded in Yichang (2.492 hundred million m3), followed by Jiefangzha (1.897 hundred million m3) and Yongji (1.305 hundred million m3). Notably, before 2014, mineralization levels in Yongji and Yichang were higher than those in Jiefangzha; however, this trend reversed after 2014.【Conclusion】Effective reuse of drainage water in the Hetao Irrigation District requires a comprehensive evaluation of both drainage volume and mineralization. Region-specific strategies that consider crop salt tolerance and local soil properties are essential for optimizing the sustainable utilization of drainage resources.

【目的】从非常规水资源化利用角度出发，探究盐渍化灌区农田排水变化规律，为灌区排水资源化利用提供基础支撑。【方法】基于河套灌区2006—2020年排水量和排水矿化度，应用Mann-Kendall趋势检验法分析了研究区解放闸、永济及义长灌域排水量和排水矿化度时空分布特征和变化趋势，采用Spearman相关分析研究了3个灌域年排水量和排水矿化度关系。【结果】时间分布上，研究区3个灌域2006—2020年排水量均呈上升趋势；解放闸灌域排水矿化度呈平稳态势，永济和义长灌域排水矿化度呈下降趋势；3个灌域的年排水量和排水矿化度的相关系数ρ分别为-0.02、-0.81、-0.81，解放闸灌域的月排水量和排水矿化度弱负相关，永济和义长灌域的月排水量和排水矿化度高度负相关；各灌域月排水量和排水矿化度变化显著。空间分布上，义长灌域年排水量大，解放闸灌域次之，永济灌域相对较小，其值分别为2.492亿、1.897亿、1.305亿m3；永济和义长灌域年排水矿化度在2014年之前高于解放闸灌域，之后均低于解放闸灌域。【结论】盐渍化灌区排水资源化利用应在综合考虑排水量与排水矿化度基础上，结合不同地区种植作物耐盐性、土壤特性等采取适宜的分级利用方式，以便达到排水资源的最优利用。

Salinization in arid or semiarid regions with water logging limits cropland yield, threatening food security. The highest level of farmland salinization, that is, abandoned salinized farmland, is a tradeoff between inadequate drainage facilities and sustainable farming. The evolution of abandoned salinized farmlands is closely related to the development of cropping systems. However, detecting abandoned salinized farmland using time-series remote sensing data has not been investigated well by previous studies. In this study, a novel approach was proposed to detect the dynamics of abandoned salinized farmland using time-series multispectral and thermal imagery. Thirty-two years of temporal Landsat imagery (from 1988 to 2019) was used to assess the evolution of salinization in Hetao, a two-thousand-year-old irrigation district in northern China. As intermediate variables of the proposed method, the crop-specific planting area was retrieved via its unique temporal vegetation index (VI) pattern, in which the shape-model-fitting technology and the K-means cluster algorithm were used. The desert area was stripped from the clustered non-vegetative area using its distinct features in the thermal band. Subsequently, the abandoned salinized farmland was distinguished from the urban area by the threshold-based saline index (SI). In addition, a regression model between electrical conductance (EC) and SI was established, and the spatial saline degree was evaluated by the SI map in uncropped and unfrozen seasons. The results show that the cropland has constantly been expanding in recent decades (from 4.7 × 105 ha to 7.1 × 105 ha), while the planting area of maize and sunflower has grown and the area of wheat has decreased. Significant desalinization progress was observed in Hetao, where both the area of salt-affected land (salt-free area increased approximately 4 × 105 ha) and the abandoned salinized farmland decreased (reduced from 0.45 × 105 ha to 0.19 × 105 ha). This could be mainly attributed to three reasons: the popularization of water-saving irrigation technology, the construction of artificial drainage facilities, and a shift in cropping patterns. The decrease in irrigation and the increase in drainage have deepened the groundwater table in Hetao, which weakens the salt collection capacity of the abandoned salinized farmland. The results demonstrate the promising possibility of reutilizing abandoned salinized farmland via a leaching campaign where the groundwater table is sufficiently deep to stop salinization.

China is one of the countries most seriously affected by soil salinization, while the impact of salt-controlled irrigation on the relationship between soil dissolved organic matter (DOM) and microbial in farmland affected by salinization remains largely unexplored. We conducted a comprehensive survey of soil DOM and a microbial survey of Ordos’s salinized farmland in China before and after salt-controlled irrigation. Our findings reveal a reduction of 18.4 mg/L in surface soil (0–10 cm) DOC following irrigation, whereas the subsurface soil (20–40 cm) DOC increased by 20.7 mg/L. Moreover, irrigation led to an increase in the aromaticity and humification of the soil, with the salt content of the subsurface soil rising from 2.7 to 3.7 mg/g. Additionally, the total dissolved solids (TDS) in the drained water were 2463 mg/L higher than in the irrigation water (1416.3 mg/L). This suggests that the DOM and salts from the surface soil either leached into deeper layers or were lost via runoff. Furthermore, SEM analysis and a Mantel test revealed that microbial composition significantly influenced soil DOM contents, especially increased levels of Marmoricola and MND1, which are associated with decomposing organic matter and may contribute to the leaching of soil DOM in deep layers following irrigation.

This experiment was conducted in a greenhouse at Janat Al-Nakheel company located in khazmiah/Baghdad from 1/9/2020 to 1/6/2021 and aimed to study the effect of inoculation with fungal and bacterial biofertilizers on the growth and flowering of Lilium spp. under the influence of alternating irrigation with salt water. The experiment was implemented as a factorial experiment using the RCBD randomized complete block design with two factors, the first factor included inoculation with biofertilizers, while the second factor included alternating irrigation with saline water and the interaction between them. The results showed that the interaction between biofertilizers and tap water gave the highest recordings of vegetative and flowering growth in terms of plant height (48.63) cm, stem diameter (9.9) mm, leaf area (878.0) mm, concentration of proline in leaves (2.06) and peroxidase enzyme activity (6.95) The content of MDA leaves (0.531), flowering period (31.17) days, flower diameter (16.75) cm, number of flower buds (9.5) flower bud, carotene pigment concentration in flowers (3.027) and flowering age (22.00) days, as well as root length (22.03) cm and the percentage of dry matter in the roots (12.45)%.

On the basis of monthly rainfall data over 50 years, we analyzed temporal properties of annual and seasonal rainfall variability by using and comparing two kinds of continuous wavelet transforms. Furthermore, we deduced its impacts on soil salinization in the area of Huang-Huai-Hai Plain, China. Results showed that the annual rainfall collected by the studied area showed a decreasing trend during period 1960–2009 at a climatic tendency rate of 14.43 mm/10 years. The Morlet wavelet is better at capturing local feature of rainfall oscillatory behaviors at fine time scales, and the Mexican Hat wavelet is better at revealing global feature of rainfall period. Combining Wavelet transform with wavelet power spectrum and its confidence test, we found the 8-year dominant period of annual rainfall and the 5-, 6-, 10- and 12-year dominant periods of seasonal rainfall, respectively. The annual and seasonal rainfall trends in the near future and their impacts on soil salinization are deduced based on the rainfall dominant periods and the prominent correlation between rainfall and soil salinity changes. The annual rainfall will still be in a relatively low period in the subsequent year after 2009 and then revert to a relatively high period during 2011–2014. The subsequent summer variability of rainfall may be helpful for reducing the soil salinization, while the opposite trends of spring and autumn rainfall variability may aggravate the soil salinization. This suggests sustainable irrigation and drainage measures to prevent soil salinization in this area.