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In order to explore the effect of fishponds on soil water, salt transport and salinization in cropland wasteland, a study on soil water balance and salt distribution pattern in a cropland–wasteland–fishpond system was carried out in 2022–2023 in a typical study area selected from the Yichang Irrigation Area of the Hetao Irrigation District. A water balance model was established for the cropland–wasteland–fishpond system to analyze the effects of irrigation on soil salinity at the boundaries of the cropland, wasteland, and fishpond. The results showed that the lateral recharge from the cropland to the wasteland during spring irrigation in 2022 was 24 mm, the lateral recharge generated by fishponds to wasteland was 18 mm, and the lateral recharge from fishponds to fishpond boundaries was 34 mm. In the fertility period of 2023, the lateral recharge from cropland to wasteland was 15 mm, the lateral recharge from fishponds to wasteland was 9 mm, and the lateral recharge from fishponds to fishpond boundaries was 21 mm. Due to the low salinity content of fishpond water, it diluted the groundwater of the wasteland, and the soil salinity at the boundary between the wasteland and the fishpond was monitored. The data show that the soil salinity at the boundary of the fishpond was smaller than that of the wasteland, which indicates that the migration of fishpond water to the wasteland will not lead to an increase in the soil salinity of the wasteland, but rather to a decrease in the soil salinity of the wasteland. Fishpond regulation has a significant impact on soil and groundwater, and when the topographic conditions of the Hetao irrigation area allow, the model of cropland–wasteland–fishpond can be appropriately adopted to solve land degradation and increase the economic income of farmers; the results of the study provide a contribution for the improvement of the management of land use and soil salinization in the Hetao irrigation area.

In order to investigate the influence of freshwater fish ponds on water and salt transport in cultivated wasteland in salinized areas, a typical study area was selected in the middle and lower reaches of the Hetao Irrigation District in China in the Yichang Irrigation Domain, and the temporal and spatial changes in the salinity of soil and salinity of groundwater and fish pond water in the cultivated–wasteland–fish pond system were characterized through the monitoring of the environmental information of soil and groundwater at the boundaries of the cultivated land, wasteland, and fish ponds. Salinity changes and groundwater migration in different periods were determined, and the response of soil salinity to the depth of groundwater burial was analyzed, as well as the effect of fish ponds on soil salinization. The results showed that the amount of groundwater migrating from cropland to wasteland during the simulation period in 2022 was 2700 m3, the amount of groundwater migrating from wasteland to fish ponds was 630 m3, and the amount of groundwater migrating from fish ponds to wasteland during the fall watering period was 440 m3. From an overall perspective, the average soil salinity of wasteland was 1.56 times higher than that of the boundary of fish ponds. Not only do fish ponds play a positive role in the ecosystem, but they also have a desalinization effect that reduces soil salinity significantly. Groundwater depth and soil salinity have an exponential relationship; when the depth of groundwater is greater than 1.75 m, the soil salinity varies little with the depth of groundwater and the soil salinity is less than 0.66 ds/m, which can be determined as the critical depth, and the average depth of groundwater in cultivated land in the study area is 1.5 m. Therefore, it is necessary to reasonably control the water level of fish ponds, so as to make the groundwater depth of cultivated land control between 1.75 m and 2.0 m, and to prevent soil salinization.

The Hetao Irrigation District is a typical salinized irrigation district in China, and soil salinization restricts agricultural development. To explore the spatial and temporal variability of soil water and salt and the coupling relationship in the Hetao Irrigation District, a field experiment was carried out at the scale of the Yichang Irrigation District branch canal in the downstream of the Hetao Irrigation District. Fifty-three soil sampling points were established to analyze the spatial and temporal variability of soil water content and total salt content and the coupling relationship using geostatistics and the coupling degree model. The results showed that soil water content in the study area belonged to medium variability and weak variability, and soil total salt content belonged to strong variability and medium variability. The theoretical models of soil water content and total salt content semi-variance function in the study area following the Gaussian model, with the block-base ratio less than 25%, with strong spatial autocorrelation, and the spatial correlation gradually increased with the increase of soil depth. The total salt content of the soil in the study area was interpolated with higher accuracy using radial basis functions as compared to ordinary kriging interpolation. In terms of temporal changes in salinity, the average salt accumulation rate of the 0–100 cm soil layer in the study area was 20.17% when salinity increased from May to June; the average desalination rate was 16.37% when salinity decreased from June to August. The main factors affecting soil salinity in cultivated land during the growing period were irrigation, precipitation, and planting crops, and the main factors affecting soil salinity in wasteland were precipitation and topography. The average coupling degree of soil water and salt in wasteland in the study area was lower than that of cultivated land, ranging from 65.15% to 86.59% of that of cultivated land. The level of coordination is marginal coordination for cultivated land and marginal disorder for wasteland. The study provides a theoretical basis for the prevention and control of soil salinization in arid areas.