Search Results (18)

Land-use change contributes significantly to climate change mitigation through biophysical changes (albedo, α) and biogeochemical (greenhouse gases, GHG) emissions (here refers to methane, CH₄, and nitrous oxide, N₂O). While the impact of grassland–cropland conversion on global warming potential (GWP) is well-documented globally, research remains scarce in the saline-alkaline agropastoral transition zone (APTZ) of the western Songnen Plain, Northeast China, an ecotone uniquely characterized by soil-crusting and seasonal inundation. We conducted in situ bi-weekly measurements of N₂O and CH₄ fluxes (June–September) to acquire growing season ${\mathrm{GWP}}_{{\mathrm{N}}_2\mathrm{O}}$ and ${\mathrm{GWP}}_{{\mathrm{C}\mathrm{H}}_4}$, alongside α. The study compared an undisturbed fenced meadow (FMD) with three adjacent land-use types, clipped meadow (CMD), saline-alkaline meadow (SAL), and paddy rice field (PDY), converted from FMD from 2018 to 2022. Annual α-induced GWP (GWPΔα) was positive across all converted sites (CMD, SAL, and PDY), indicating a warming effect due to lower α compared to FMD. The PDY exhibited the highest CH₄ emission (5.04 kg CO₂ m⁻² yr⁻¹), exceeding other land uses by three orders of magnitude (p < 0.05). Conversely, N₂O emissions remained consistently minimal and stable across all sites. When integrating the net ecosystem exchange of CO₂ (NEE), the PDY functioned as a net warming source. In contrast, the warming effects of α and non-CO₂ GHGs were effectively offset by the NEE in other land uses. Machine learning identified soil water content (SWC) as the dominant predictor of α across all land uses in growing season. However, a mechanistic divergence was observed, i.e., α in low saline-alkali ecosystems (FMD, CMD and PDY) was shaped by coupled biotic and soil moisture controls, whereas in the degraded SAL ecosystem, α is almost exclusively abiotic-driven. These findings demonstrate that land-use conversion in the Songnen Plain governs complex land-surface feedbacks through distinct pathways. This study provides a quantitative framework for integrating biophysical and biogeochemical impacts to optimize land management for climate resilience in saline-alkaline agropastoral ecotones. Full article

To identify an optimized management strategy for the safe reuse of aquaculture wastewater in saline–alkali paddy fields, a pot experiment was conducted to investigate the interactive effects of irrigation modes (flooded and shallow–wet) and Chlorella application on wastewater purification, nitrogen and phosphorus transport, and rice yield. The results showed that Chlorella effectively improved the removal rates of nitrogen and phosphorus in field surface water, but its efficacy depended on the irrigation mode. The purification efficiency of shallow–wet combined with Chlorella (I_SC_W) was highest, and the removal rate of total phosphorus at the heading stage was 88.67%. The leaching risk of deep nitrate nitrogen (NO₃⁻-N) was the lowest, but the rice yield was significantly reduced. In contrast, flooded irrigation combined with Chlorella (I_FC_W) produced the highest rice yield, whereas its water purification effect was moderate. The entropy-weighted TOPSIS evaluation further indicated a clear trade-off. I_SC_W improved phosphorus removal in surface water, but reduced grain yield by 60.7% compared with I_FC_W. These findings demonstrate that irrigation mode is a key factor in regulating the purification effect of Chlorella and its trade-off with rice yield. These findings provide theoretical support for wastewater resource utilization in saline–alkali regions and contribute to the sustainable development of coastal agriculture. Full article

The combination of controlled-release urea (CRU) and conventional urea (CU) has become an important practical strategy to simultaneously increase rice yield, economic benefits, and nitrogen (N) use efficiency (NUE) with one-time fertilization management. However, the method by which the combination of CRU and CU intervenes with rice yield, economic benefits, and NUE in saline–alkali paddy fields has not yet been established. Accordingly, a two-year field experiment was set up with a total of seven treatments (CK, no N application; CUF, conventional urea split applications; RCUF, CUF treatment with 20% N reduction; CRBF1, 50%CRU + 50%CU one-time base application; CRBF2, 70%CRU + 30%CU one-time base application; RCRBF1, CRBF1 treatment with 20% N reduction; RCRBF2, CRBF2 treatment with 20% N reduction). The results showed that the controlled-release blended fertilizer (CRBF) treatments significantly increased the yield, economic benefits, and NUE over the two years. The CRBF1 and CRBF2 treatments significantly increased the rice yield by 5.10–6.77% and 10.41–11.04%, N recovery efficiency by 13.30–17.40% and 21.69–26.75%, and N agronomic efficiency by 10.40–13.91% and 21.26–22.10% compared to the CUF treatment, respectively. The RCRBF1 and RCRBF2 treatments maintained rice yields and significantly increased NUE compared to the CUF treatment. The analysis of yield components indicated that the greater rice yields of the CRBF were mainly attributed to increased panicle numbers and spikelet numbers per m². Furthermore, the post-anthesis dry matter, N accumulation, flag SPAD values, flag photosynthetic rates, and soil ammonium nitrogen content were higher during the grain-filling stage of the CRBF treatments compared to the CUF treatments. Compared with the CUF treatment, the CRBF1 and CRBF2 treatments increased economic benefits by 8.74–11.16% and 17.14–17.41%. Therefore, the combination of CRU and CU can increase rice yield, economic benefits, and NUE in saline–alkali paddy fields. Moreover, it is recommended to apply CRU and CU at a ratio of 7:3 in a single basal application as a green and efficient alternative N management strategy for saline–alkali paddy fields. The results provide a scientific basis for N management strategies in saline–alkali paddy fields. Full article

The soil carbon pool in saline–alkali land is a research hotspot in the field of agricultural environmental science. However, there are no systematic conclusions regarding the paddy soil carbon pool in the Yellow River Delta in China. Therefore, this study focused on the paddy soil in the Yellow River Delta; using statistical analysis methods and establishing relevant models, we explored the dynamic changes in organic carbon and its active components and their influencing factors in saline paddy fields under two planting patterns. The results showed that there was no significant difference in the dissolved organic carbon (DOC) content between the two planting patterns. However, the rice–wheat rotation pattern was more conducive to the accumulation of microbial biomass carbon (MBC). The soil organic carbon (SOC) and readily oxidizable organic carbon (ROC) contents increased under the two patterns and different salinization treatments. The results of the redundancy analysis and the random forest model indicated that SSA was the key environmental parameter affecting SOC and its active components under the single-season rice pattern. Under the rice–wheat rotation pattern, soil sucrase activity (SSA) was also a key environmental factor for predicting the SOC content, while electrical conductivity (EC) contributed the most to the active components of SOC. The PLS-PM model showed that the soil carbon sequestration capacity could be improved by enhancing soil enzyme activity under the rice–wheat rotation pattern, while the influence of the soil environment on SOC and its active components was not obvious under the single-season rice pattern. In general, the rice–wheat rotation pattern has agricultural advantages in terms of maintaining ecological balance and can be widely promoted in this region. The results of this study have important practical significance for promoting the green and low-carbon development of agriculture in the Yellow River Delta region and also lay a foundation for subsequent long-term positioning observations and studies on multi-factor interactions. Full article

To investigate differences in water and salt transport during irrigation, freezing, and thawing periods in typical saline-affected paddy fields and saline-affected upland fields, field-based automated in situ monitoring was conducted in both types of saline-affected farmland (May 2023 to May 2024). Correlation analysis identified seasonal drivers of water–salt migration, while the HYDRUS-3D model simulated transport and equilibrium processes. The HYDRUS-3D model, equipped with a freeze–thaw module, accurately simulated complex water–salt transport in cold arid regions. Key findings include: (1) During freeze–thaw periods, soil moisture content and electrical conductivity (Ec) increased with the retreating frost front in both upland and paddy soils. During the irrigation period, maximum soil moisture content and Ec values occurred at 80 cm depth in dryland soils and 60 cm depth in paddy soils, primarily influenced by irrigation and capillary rise. (2) Groundwater salt ions significantly affected soil salinization in both farmland types. During the freeze–thaw period, Ec positively correlated with soil temperature. During the irrigation period, Ec positively correlated with evapotranspiration and negatively correlated with precipitation. (3) Salt changes during the irrigation, freezing, and thawing periods were −565.4, 326.85, and 376.55 kg/ha for upland fields, respectively; corresponding changes for paddy fields were −1217.0, 280.07, and 299.35 kg/ha. (4) Both land types exhibited reduced salinity during the irrigation period, with paddy fields showing a reduction 3.36 times greater than dryland fields. During the freezing and thawing periods, both land types experienced salinity accumulation, with dryland fields accumulating higher salinity levels than paddy fields. These results indicate that paddy field irrigation and drainage systems help mitigate salinization, while dryland fields are more prone to springtime salt accumulation. These findings provide a basis for developing targeted management strategies for saline–alkali soils. Full article

The yield and quality of rice are influenced by soil conditions, and the soil issues in saline–alkaline land limit agricultural productivity. The saline–alkaline fields in the northern irrigation area of Yinchuan, Ningxia, China, face challenges such as low rice yield, poor quality, low fertilizer utilization efficiency, and soil salinity and alkalinity obstacles. To improve this situation, this study conducted experiments in 2022–2023 in the saline–alkaline rice–crab integrated fields of Tongbei Village, Tonggui Township, Yinchuan. This study employed a single-factor comparative design, applying 150 mL·hm⁻² of brassinolide (A1), 15 kg·hm⁻² of diatomaceous (A2), 30 kg·hm⁻² of Bacillus subtilis agent (A3), and an untreated control (CK) to analyze the effects of different biological amendments on rice growth, photosynthesis, yield, quality, and microbial communities. The results indicated that, compared with CK, the A3 increased the SPAD value and net photosynthetic rate by 2.26% and 28.59%, respectively. Rice yield increased by 12.34%, water use efficiency (WUE) by 10.67%, and the palatability score by 2.82%, while amylose content decreased by 8.00%. The bacterial OTUs (Operational Taxonomic Units) and fungal OTUs increased by 2.18% and 22.39%, respectively. Under the condition of applying 30 kg·hm⁻² of Bacillus subtilis agent (A3), rice showed superior growth, the highest yield (8804.4 kg·hm⁻²), and the highest microbial OTUs. These findings provide theoretical and technical support for utilizing biological remediation agents to achieve desalinization, yield enhancement, quality improvement, and efficiency in saline–alkali rice–crab co–culture paddies. Full article

The improvement of saline-alkali land plays a key role in ensuring food security and promoting agricultural development. Saline soils modifies the response of the soil microbial community, but research is still limited. The effects of applying phosphogypsum with rice cultivation (PRC) on soil physicochemical properties and bacterial community in soda saline-alkali paddy fields in Songnen Plain, China were studied. The results showed that the PRC significantly improved the physicochemical properties of soil, significantly reduced the salinity, increased the utilization efficiency of carbon, nitrogen, and phosphorus, and significantly increased the activities of urease and phosphatase. The activities of urease and phosphatase were significantly correlated with the contents of total organic carbon and total carbon. A redundancy analysis showed that pH, AP, ESP, HCO₃⁻, and Na⁺ were dominant factors in determining the bacterial community structure. The results showed that PRC could improve soil quality and enhance the ecosystem functionality of soda saline-alkali paddy fields by increasing nutrient content, stimulating soil enzyme activity, and regulating bacterial community improvement. After many years of PRC, the soda-alkali soil paddy field still develops continuously and healthily, which will provide a new idea for sustainable land use management and agricultural development. Full article

Soda saline-alkali significantly hinders rice growth, phosphorus utilization efficiency, and yield formation. The application of biochar can alleviate the adverse effects of saline-alkali stress on crops. However, there is limited research on the interaction between biochar and phosphorus fertilizer concerning ionic accumulation, phosphorus utilization efficiency, and rice yield in soda saline-alkali soils. A two-year field experiment was conducted to study the combined effects of biochar and phosphate fertilizer on ionic accumulation, physiological status, phosphorus utilization efficiency, and rice yield in soda saline-alkali soil. Four treatments were established for the study: NK (225 kg N, 75 kg K ha⁻¹ year⁻¹), NPK (225 kg N, 70 kg P, 75 kg K ha⁻¹ year⁻¹), NK + B [225 kg N, 75 kg K ha⁻¹ year⁻¹, 1.5% biochar (w/w)], and NPK + B [225 kg N, 70 kg P, 75 kg K ha⁻¹ year⁻¹, 1.5% biochar (w/w)]. The findings indicated that the combined application of biochar and phosphorus fertilizer (NPK + B) significantly reduced the Na⁺ concentration, Na⁺/K⁺ ratio, malondialdehyde (MDA), superoxide anion (O₂⁻), and hydrogen peroxide (H₂O₂) levels in rice plants. Furthermore, it resulted in a significant increase in K⁺ concentration and elevated the levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), proline (Pro), soluble protein (SP), soluble sugar (SS), and acid phosphatase (ACP). The NPK + B treatment exhibited a significant difference compared to the other treatments (p < 0.05). Compared with NK, phosphorus accumulation and phosphorus utilization efficiency under NPK + B were significantly increased (p < 0.05). The average of biomass yield, grain yield, and harvest index of NPK + B, NK + B, and NPK significantly surpassed those of NK by 6.28–12.25%, 19.80–42.13%, and 11.59–24.64%, respectively. Moreover, a significant difference was observed between NPK + B and the other treatments (p < 0.05). Principal component analysis of the two-year mean data revealed a strong positive correlation of 89.5% for PC1 and a minor negative correlation of 4.4% for PC2. Our research findings demonstrate that the combination of biochar and phosphorus fertilizer effectively enhances salt and alkali tolerance in rice plants, resulting in increased yield through improved ionic balance and physiological status. Full article

This study examined the agricultural water resource shortage and abundant ditch water resources in the Yinbei region of Ningxia. The effects of ditch water and Yellow River irrigation on the saline–alkali characteristics of soil and paddy were investigated using field monitoring and indoor detection methods in Pingluo County, Ningxia (106°31′ E, 38°51′ N). In addition to monitoring ditch water, four treatment groups were established: direct ditch water irrigation (T1), mixed ditch water and Yellow River water irrigation (T2), alternate ditch water and Yellow River water irrigation (T3), and irrigation solely with Yellow River water (CK). The results show the following: (1) The salinity of ditch water samples collected from the experimental field during the rice growth period was less than 1.60 g/L, and the pH of the samples was lower than 8.62; thus, they were classified as mildly brackish water. The application of ditch water irrigation did not result in soil saline–alkali aggravation and the accumulation of excessive amounts of heavy metals in soils and paddies in Pingluo County, Ningxia. (2) The rice yields for the CK, T1, T2, and T3 treatments were 10,437.5, 8318.4, 9182.1, and 9016.2 kg/hm², respectively. Compared with Yellow River irrigation, the rice yields for the T1, T2, and T3 treatments were 20.3, 12.1, and 13.6% lower than that of CK, respectively, with minimal differences observed among them. Hence, under the condition of a water resource shortage in the Yellow River region, ditch water can be appropriately applied for mixed or alternate irrigation to ensure food security. This research has revealed the influences of ditch water irrigation on the saline–alkali properties of soil and the heavy metal contents of paddies. Full article

Saline–alkali soils seriously restrict the soil functions and the growth and diversity of soil microorganisms. Biochar can alleviate the negative effects of saline–alkali stress. However, it remains unclear how biochar reduces saline–alkali stress by improving soil functions and regulating the abundance and diversity of the soil bacterial community in highly saline–alkali paddy fields. To address this, a paddy field experiment was conducted in a highly saline–alkali paddy field using two nitrogen application levels (0 and 225 kg ha⁻¹) and four biochar application rates (0, 1.5%, 3.0%, and 4.5% biochar, w/w). The results show that, compared with C0, biochar application, especially when combined with N fertilizer, significantly decreased the soil pH, exchangeable sodium percentage (ESP), saturated paste extract (ECe), and sodium adsorption ratio (SAR) while significantly increasing cation exchange capacity (CEC). These indicated that biochar can effectively reduce saline–alkali stress. Biochar application significantly increased soil content of total nitrogen (TN), alkali-hydrolysable N (AN), available P (AP), available K (AK), soil organic matter (SOM), and soil C/N ratio, both with or without N fertilization. Furthermore, biochar application further increased the relative abundance of bacterial communities and modified the bacterial community structure in highly saline–alkali paddy soils. Under C3N2, C2N2, and C1N2, Chao1 increased by 10.90%, 10.42%, and 1.60% compared to C0N2. Proteobacteria, Bacteroidetes, and Chloroflexi were the top three phyla in bacterial abundance. Biochar significantly increased the abundance of Proteobacteria while reducing Bacteroidetes and Chloroflexi, regardless of N fertilization. Correlation analysis results showed that the improvements in soil chemical and saline–alkali properties, as well as nutrient bioavailability after biochar application, had a positive effect on bacterial communities in highly saline–alkali paddy soils. Full article

Modifying saline–alkali soil is crucial for ensuring food security and expanding arable land. Microorganisms play a key role in driving various biochemical processes in agricultural ecosystems. However, limited information exists on the changes in the microbial community and soil structure in soda saline-alkali soil under modified conditions. In this study, we examined the changes in soil physicochemical properties of saline–alkali soil altered by rice planting alone and by combined application of phosphogypsum in the Songnen Plain. The results demonstrated that phosphogypsum significantly improved the soil’s physicochemical properties; it notably reduced salinity and alkalinity while enhancing nutrient structure. Additionally, the utilization efficiency of carbon (C), nitrogen (N), and phosphorus (P) increased. Fungal community diversity also significantly improved, influenced mainly by soil water content (SWC), total organic carbon (TOC), soil organic matter (SOM), total nitrogen (TN) and sodium ion (Na⁺). TOC, SOM, TN, ESP, and Na⁺ served as the primary drivers affecting the fungal community. Our findings indicate that combining rice planting with phosphogypsum application effectively modifies saline–alkali soil, regulates fungal community structure, and enhances long-term soil health. Furthermore, the beneficial effects of phosphogypsum on saline–alkali soil persist for persists for several years, largely owing to its role in promoting microbial community growth. Full article

In recent years, the conversion of saline-alkali land to rice fields has become the most dominant land use change feature in western Jilin, leading to significant surface greening. Saline–alkali land and paddy fields have distinct surface biophysical properties; however, there is a lack of systematic assessment of the moderating effect of planting rice on saline–alkali land on regional climate by changing surface properties. In this paper, multiscale data on the surface temperature of saline–alkali land and paddy fields were obtained using 1 km MODIS product, 30 m Landsat 8 satellite imagery and centimeter-scale UAV imagery in Da’an City, western Jilin as the study area, and the various characteristics of the surface temperature of saline-alkali land and paddy fields in different months of the year and at different times of the day were analyzed. Furthermore, the effect of rice cultivation in saline–alkali land on the local surface temperature was assessed using a space-for-time approach. The results based on satellite observations including both MODIS and Landsat showed that the surface temperature of saline–alkali land was significantly higher than that of paddy fields during the crop growing season, especially in July and August. The high temporal resolution MODIS LST data also indicated the paddy fields cool the daytime surface temperature, while warming the nighttime surface temperature, which was in contrast for saline–alkali land during the growing season. High-resolution UAV observations in July confirmed that the cooling effect of paddy fields was most significant at the middle of day. From the biophysical perspective, the reclamation of saline–alkali land into paddy fields leads to an increase in leaf area index, followed by a significant increase in evapotranspiration. Meanwhile, rice cultivation in saline–alkali land reduces surface albedo and increases surface net radiation. The trade-off relationship between the two determines the seasonal difference in the surface temperature response of saline–alkali land for rice cultivation. At the same time, the daily cycle of crop evapotranspiration and the thermal insulation effect of paddy fields at night are the main reasons for the intraday difference in surface temperature between saline–alkali land and paddy field. Based on the multiscale assessment of the impact of rice cultivation in saline-alkali land on surface temperature, this study provides a scientific basis for predicting future regional climate change and comprehensively understanding the ecological and environmental benefits of saline–alkali land development. Full article

Soil samples from T (0~20 cm) and S (20~40 cm) layers of four saline–alkali rice fields (R5, R15, R20, and R35) with different reclamation years were selected to study the distribution of soil aggregates and the contents of readily oxidizable organic carbon (ROC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), potentially mineralizable carbon (PMC), and soil organic carbon (SOC). The effects of large macroaggregate (>2 mm, LMA), small macroaggregate (0.25 to 2 mm, SMA), and microaggregate (<0.25 mm, MA) particle size, soil layer, and soil physicochemical properties on SOC fractions were also analyzed. The results showed that the LMA size in saline–alkali paddy fields were easily decomposed and was unstable due to the influence of the external environment. With the increase in reclamation years, the proportion of LMA in the S layer decreased gradually. The ROC, DOC, MBC and TOC contents of aggregates in the T and S layers gradually increased with the increase in reclamation years, and SOC fractions contents of aggregates in different grain sizes were SMA > LMA > MA. An effective way to increase carbon sink and improve the ecological environment in western Jilin Province is to change the soil environment by planting rice in saline–alkali land. Full article

Studying land use change and its associated climate effects is important to understand the role of human activities in the regulation of climate systems. By coupling remote sensing measurements with a high-resolution regional climate model, this study evaluated the land surface changes and corresponding climate impact caused by planting rice on saline-alkali land in western Jilin (China). Our results showed that paddy field expansion became the dominant land use change in western Jilin from 2015 to 2019, 25% of which was converted from saline-alkali land; this percentage is expected to increase in the near future. We found that saline-alkali land reclamation to paddy fields significantly increased the leaf area index (LAI), particularly in July and August, whereas it decreased albedo, mainly in May and June. Our simulation results showed that planting rice on saline-alkali land can help decrease the air temperature and increase the relative humidity. The temperature and humidity effects showed different magnitudes during the growing season and were most significant in July and August, followed by September and June. The nonradiative process, rather than the radiative process, played a dominant role in regulating the regional climate in this case, and the biophysical competition between evapotranspiration (ET) and albedo determined the temperature and relative humidity response differences during the growing season. Full article

Western Jilin province has the most serious area of soda salinization in Northeast China, which affects and restricts the sustainable development of agriculture. The effects of physico-chemical properties of rhizosphere and non-rhizosphere soil on soil microbial diversity and enzyme activities (polyphenol oxidase, catalase, invertase, amylase) were evaluated in typical soda saline-alkali paddy field. Community-level physiological profile (CLPP) based on Biolog-ECO plates was used to assess the functional diversity of soil microorganisms. Exchangeable sodium percentage (ESP) and pH were negative correlated with the microbial activity (AWCD), soil enzyme activities (amylase, sucrose, and catalase, except for polyphenol oxidase) in rice rhizosphere and non-rhizosphere soil (P < 0.05). The indexes of microbial diversity in rice rhizosphere soil were significantly higher than that of non-rhizosphere soil. The utilization of amino acids by rice rhizosphere microorganisms was relatively high, while non-rhizosphere soil had relatively high utilization of carboxylic acid, phenolic acid, and amine. Among the selected physico-chemical properties, soil organic carbon (SOC) and soil water content (SWC) had the greatest influence on the variation of microbial diversity indexes and enzyme activities in rhizosphere soil. ESP and pH showed a significant positive correlation with carbon source utilization, especially for amine (AM) and phenolic acid (PA) carbon source utilization (P < 0.05) by means of RDA, and the utilization rate of AM and PA carbon sources by rice rhizosphere and non-root soil microorganisms was P1 < P2 < P3. Full article