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Background Soil microbial community and diversity are key in sustaining soil ecosystem health. In recent years, the health of soil ecosystems has been severely threatened by the large input of synthetic fertilizers and the continuous monocropping in greenhouse-based intensive production systems. As a result, the N utilization efficiency has significantly decreased, which has had adverse impacts on soil, water, and the atmosphere. Additionally, soil-borne plant diseases are more frequent in greenhouse-based intensive vegetable systems. Shifts in the microbial community structure and diversity largely account for these continuous cropping problems in vegetable agricultural soils. Scope In this review, soil microbial deterioration, including microbial activities, C source utilization patterns, nitrification, microbial community composition, and arbuscular mycorrhizal fungi are summarized. Soil microbial deterioration is due to the excessive use of fertilizers, which have caused soil secondary salinization and acidification, pollutants brought on by intensive vegetable agriculture, and principally continuous cropping of same or similar vegetable species. Conclusions Therefore, measures must be taken to restore soil microbial communities, including rational fertilization, rotation or intercropping, cultivation of catch or cover crops, and reductive soil disinfestation. Rational fertilization, such as the reduction in chemical N fertilization levels, substitution of chemical fertilizer by organic manure, and the use of bio-fertilizer and bio-organic fertilizer, is of decisive importance. This review provides a better understanding of ecosystem health in vegetable agricultural soils and recommends effective measures to improve the health of these ecosystems.

Nutrient surplus in intense production system such as plastic greenhouse vegetable production (PGVP) may affects soil degradation and further influences sustainable utilization. In this study, we analyzed nutrient balance of nitrogen (N), phosphorous (P) and potassium (K) in PGVP and measured soil fertility properties, pH and electrical conductivity (EC) in the North, the Middle and the South of Shaanxi Province, northwestern China. Considerable nutrient surplus was found in PGVP systems, and the average nutrient balance of N, P and K were 1407.0, 682.9 and 1169.1 kg ha −1  season −1 , respectively. Soil organic matter, total N, total P, total K, available P and available K in PGVP soil were 27%, 49%, 42%, 3%, 200% and 54% greater than those levels in open fields, respectively. Average pH value in greenhouse soil was 0.53 lower than that in open field, and EC value in greenhouse soil (547.11 μS cm −1 ) was more than triple that in open fields (157.14 μS cm −1 ). Soil acidification and secondary salinization has occurred in PGVP. Soil P/K ratio in PGVP systems reflected that nutrient surplus in the South (0.080) and the Middle (0.077) were greater than those in the North (0.061). The differences in nutrient accumulation rate and soil pH changes among different regions were the comprehensive results affecting by both fertilization and soil types. We deduced that fertilization in PGVP in Shaanxi Province was excessive, which may further accelerate soil nutrient accumulation, acidification and secondary salinization.

Significant research has been conducted on the effects of fertilizers or agents on the sustainable development of agriculture in salinization areas. By contrast, limited consideration has been given to the interactive effects of microbial fertilizer (MF) and salinity on hydraulic properties in secondary salinization soil (SS) and coastal saline soil (CS). An incubation experiment was conducted to investigate the effects of saline soil types, salinity levels (non-saline, low-salinity, and high-salinity soils), and MF amounts (32.89 g kg−1 and 0 g kg−1) on soil hydraulic properties. Applied MF improved soil water holding capacity in each saline soil compared with that in CK, and SS was higher than CS. Applied MF increased saturated moisture, field capacity, capillary fracture moisture, the wilting coefficient, and the hygroscopic coefficient by 0.02–18.91% in SS, while it was increased by 11.62–181.88% in CS. It increased soil water supply capacity in SS (except for high-salinity soil) and CS by 0.02–14.53% and 0.04–2.34%, respectively, compared with that in CK. Soil available, readily available, and unavailable water were positively correlated with MF, while soil gravity and readily available and unavailable water were positively correlated with salinity in SS. Therefore, a potential fertilization program with MF should be developed to increase hydraulic properties or mitigate the adverse effects of salinity on plants in similar SS or CS areas.

The scarcity of freshwater resources has increased the use of nonconventional water resources such as brackish water, reclaimed water, etc., especially in water-scarce areas. Whether an irrigation cycle using reclaimed water and brackish water (RBCI) poses a risk of secondary soil salinization to crop yields needs to be studied. Aiming to find an appropriate use for different nonconventional water resources, pot experiments were conducted to study the effects of RBCI on soil microenvironments, growth, physiological characteristics and antioxidation properties of crops. The results showed the following: (1) compared to FBCI, the soil moisture content was slightly higher, without a significant difference, while the soil EC, sodium and chloride ions contents increased significantly under the RBCI treatment. With an increase in the reclaimed water irrigation frequency (Tri), the contents of EC, Na+ and Cl− in the soil decreased gradually, and the difference was significant; the soil moisture content also decreased gradually. (2) There were different effects of the RBCI regime on the soil’s enzyme activities. With an increase in the Tri, the soil urease activity indicated a significant upward trend as a whole. (3) RBCI can alleviate the risk of soil salinization to some extent. The soil pH values were all below 8.5, and were without a risk of secondary soil alkalization. The ESP did not exceed 15 percent, and there was no possible risk of soil alkalization except that the ESP in soil irrigated by brackish water irrigation went beyond the limit of 15 percent. (4) Compared with FBCI, no obvious changes appeared to the aboveground and underground biomasses under the RBCI treatment. The RBCI treatment was conducive to increasing the aboveground biomass compared with pure brackish water irrigation. Therefore, short-term RBCI helps to reduce the risk of soil salinization without significantly affecting crop yield, and the irrigation cycle using reclaimed-reclaimed-brackish water at 3 g·L−1 was recommended, according to the experimental results.

Not only is solving freshwater resource shortages effective but also an important measure for realizing the sustainable development of agriculture through the development and use of unconventional water resources. This pot experiment investigated the role of exogenous silicon in the risk of secondary soil salinization and the growth physiology of Lvxiu pakchoi cabbage under irrigation by using brackish water alone (BW), reclaimed water alone (RW), and compound irrigation with brackish water and reclaimed water at a ratio of 1:1, as well as the distribution of silicon in a soil–crop system. The results showed that with the extension of the spraying period of silicon fertilizer, the electrical conductivity (EC) decreased under 1:1 compound irrigation. The pH values in all treatments ranged from 7.95 to 8.10 without a potential risk of alkalization. Spraying silicon fertilizer had a positive effect on increasing the ratio of exchangeable potassium to sodium in soil. Spraying silicon fertilizer significantly reduced the percentage of exchangeable sodium (ESP) and the sodium adsorption ratio (SAR) in soils irrigated using BW, and increased the soil ESP and SAR under compound irrigation and RW irrigation, but these factors did not exceed the threshold of soil salinization. The proper application of silicon fertilizer had no significant effect on the total silicon content in the soil but increased the total silicon content in the plants to some extent. In addition, the yield was improved through proper silicon fertilizer application. In summary, exogenous silicon has positive effects on soil physical and chemical properties and crop growth, and relieves secondary salinization risk under compound irrigation via brackish water and reclaimed water.

Soil secondary salinization is a major limiting factor of sustainable agricultural production in arid and semi-arid irrigation zones, yet predictive tools for regional water–salt dynamics remain limited. The Yichang Irrigation District, located within the Hetao Irrigation Area, has experienced persistent salinity challenges due to shallow groundwater tables and intensive irrigation. In this study, we aimed to simulate long-term soil water–salt dynamics in the Yichang Irrigation District and evaluate the effectiveness of different engineering and management scenarios using the SaltMod model. Field monitoring of soil salinity and groundwater levels during summer and fall (2022–2024) was used to calibrate and validate SaltMod parameters, ensuring accurate reproduction of seasonal soil salinity fluctuations. Based on the calibrated model, ten-year scenario simulations were conducted to assess the effects of changes in soil texture, irrigation water quantity, water quality, rainfall, and groundwater table depth on root-zone salinity. Our results show that under baseline management, soil salinity is projected to decline by 5% over the next decade. Increasing fall autumn leaching irrigation further reduces salinity by 5–10% while conserving 50–300 m3·ha−1 of water. Sensitivity analysis indicated groundwater depth and irrigation water salinity as key drivers. Among the engineering strategies, drainage system improvement and groundwater regulation achieved the highest salinity reduction (15–20%), while irrigation regime optimization provided moderate benefits (~10%). This study offers a quantitative basis for integrated water–salt management in the Hetao Irrigation District and similar regions.

Groundwater (GW) management is an essential element in irrigated agriculture. This paper analyzes the temporal dynamics of GW table and salinity in Khorezm, a region of Uzbekistan which is situated on the lower Amu Darya River in the Aral Sea Basin and suffering from severe soil salinization. We furthermore identify the critical areas for potential soil salinization by examining GW table and salinity measured during 1990-2000 in 1,972 wells, covering the entire region. Additionally, case studies were performed to assess the contribution of the GW to the soil salinization on a field scale. Over the entire area, GW was only moderately saline averaging 1.75 ± 0.99 g l-¹ However, GW levels were generally very shallow averaging 148 ± 57 cm below the ground surface and thus likely to prompt secondary soil salinization. Three case studies where GW table, soil and GW salinity were closely monitored at the field scale, suggested that the elevated GW levels forced soil salinization by annually adding 3.5-14 t ha-¹ of salts depending on the position and salinity of the GW table. Maps interpolated from the regional dataset revealed that GW was significantly shallower and more saline in the western and southern parts of Khorezm despite the presence of a drainage network which is rather uniformly distributed throughout the region. The results of the current study will assist the development of an improved drainage management in Khorezm.

AbstractThe aim of this work is to evaluate recent changes in soil salinity status at the Generalovskaya irrigation system in the dry-steppe zone of Volgograd oblast of Russia on the second terrace of the Don River near the Tsimlyansk Reservoir. The studied area has not been irrigated since the mid-1990s. We have used materials of terrain soil survey of the area in 1990 and 2020; data on soil water extracts (1 : 5); measurements of the activities of Na+, Ca2+, and Cl– ions with ion-selective electrodes in soil pastes with a moisture content of 40–45%; and aerial photographs (1990) and satellite image (2020). The studied area was subjected to secondary soil salinization in the 1990s due to the groundwater rise above the critical level. In 25 years after the cessation of irrigation, the groundwater table has descended to a depth of more than 5 m, and secondary-saline soils have been subjected to a gradual desalinization with the development of alkalization in the topsoil. The current soil salinity status inherits the pattern that existed 25 years ago, i.e., the spatial distribution of salts in the studied landscape is generally preserved. We have revealed the presence of calcium chlorides in some soils in 2020, which are identified as evidences of secondary salinization developed by the 1990s. It is shown that the catenary method of terrain soil survey may be used in combination with satellite information and digital data processing for mapping the soil cover under post-irrigation conditions. This enables the reflection of the main soil groups, the depth of the upper saline horizon, and the presence or absence of carbonates on the soil surface. Such information is necessary for the development and selection of optimal reclamation measures.

[Objectives] To study the remediation methods of secondary salinization and cadmium pollution in facility soil. [Methods] Two kinds of soil amendments, potassium fulvic acid and limestone powder, were selected to be applied alone or combined together to plant maize to carry out field experiments. Their effects on watermelon yield, watermelon cadmium content, soil available nitrogen, phosphorus, potassium and water-soluble salts were studied. [Results] The application of potassium fulvic acid, limestone powder and their combined application increased the yield and soluble solids of watermelon to different degrees. The contents of seven heavy metals including cadmium, copper, zinc, arsenic, lead, mercury and chromium in the watermelon of all treatments were all lower than the food safety limit stipulated in the national standard. During the harvest period of maize seedlings, all treatments could increase soil pH and decrease soil cadmium availability. In particular, 3 000 kg/ha of limestone powder and 1 500 kg/ha of potassium fulvic acid had the best effect on reducing soil available cadmium content. In reducing soil available cadmium content, there were significant differences between single application of amendment and combined application treatments. In addition, compared with the control CK, all treatments decreased soil available nitrogen, phosphorus, potassium and water-soluble salt content. [Conclusions] Potassium fulvic acid, limestone powder and their combined application can increase the yield of watermelon, and can significantly reduce the available cadmium, nitrogen, phosphorus, potassium and water-soluble salt content in the facility soil of maize cultivation.

By analyzing the process of soil salt accumulation in irrigation area, and discussing the change of irrigation and drainage methods for drought transformed into water, the control scheme of soil secondary salinization in Wujiazi Irrigation Area was analyzed concretely, and the experience was summarized. After in-depth discussion, the importance of irrigation and drainage methods in the prevention and control of soil secondary salinization in irrigation areas was analyzed.