Delta Soils Research Articles

Birdwatching preferences reveal synergies and tradeoffs among recreation, carbon, and fisheries ecosystem services in Pacific Northwest estuaries, USA

Coastal ecosystems provide multiple ecosystem services that are valued in diverse ways. The Nisqually River Delta (the Delta), an estuary in Puget Sound, Washington, U.S.A., is co-managed by the Nisqually Indian Tribe and the Billy Frank Jr. Nisqually National Wildlife Refuge. In an ecosystem services assessment, we used different service-appropriate methods including citizen science, statistical and geospatial models, and scenario analysis to evaluate three ecosystem services – recreational birdwatching, soil carbon accumulation and fishery production – indicated as priorities for the Refuge, Nisqually Indian Tribe, and surrounding communities. We developed a generalized additive mixed model set based on eBird mobile application birdwatching observations to understand the biological and landscape features that influence birdwatching and to project birdwatching visitation based on scenarios of Delta habitat change. We evaluated ecosystem service synergies and tradeoffs associated with habitat change for three coastal habitat types using scenario outputs from the birdwatching model and published results on Delta soil carbon accumulation and fishery production. The highest-ranked birdwatching models explained 88 % of the deviance and showed that visitation was greatest in winter months when distance to major cities was approximately 20 km. Recreational birdwatching increased with increasing area of forested wetland, emergent wetland, aquatic vegetation bed, open access, and total estuary. With increasing forested and emergent wetland area, recreational birdwatching, out-migrating juvenile Chinook salmon weight and soil carbon accumulation all increased. With increasing aquatic vegetation bed (resulting from sea level rise), recreational birdwatching increased, but salmon weight and soil carbon accumulation decreased. We identified practical ways in which ecosystem services may be incorporated into adaptive management frameworks that support climate adaptation decision making. This study illustrated how use of ecosystem services can help managers make decisions that have greater benefit for wildlife and people, communicate the societal value of decisions and increase local support and participation.

Spatial variability of CH4 uptake in aerated soils of Yellow River Delta

The widespread occurrence of aerated plain soils underscores their significant role in the global soil methane (CH4) sink budget. However, plain soils are poorly characterized in terms of spatial variability of CH4 uptake and the relevant control. We investigated the intra- and inter-site spatial variability of CH4 uptake through flux measurements in intact soil cores from five non-wetland sites within the Yellow River Delta, each representing a distinct land use/cover type. Methane uptake rates were highest in undisturbed forest cores. The rates were very low, often falling below the detection limit, in cores from the other four sites. The significant correlation between CH4 uptake and bulk density across sites suggests the integrative role of bulk density for the effects of different disturbances (including salt stress and succession) on CH4 uptake. Methane uptake was heterogeneous at the within-site scale as indicated by large coefficients of variations (CVs). Soil texture variation manipulated the within-site pattern of CH4 uptake in the low-salinity sites. Salt affected the spatial variation of CH4 uptake only at high level of salinity. Neither Potter's nor Ridgwell's models effectively captured the within-site variation of CH4 uptake due to a texture-associated bias in the models. Establishing a quantitative relationship between CH4 uptake and clay content at the field scale in alluvial plain soils will facilitate the refinement of model parameters linked to texture and rectify biases in CH4 estimation. These results provide an insight for the biogeochemical control of CH4 uptake in alluvial plain soils and have important application for improving CH4 models.

Residual distribution and risk assessment of neonicotinoids in urban green space soils of the pearl river delta, South China: A socioeconomic analysis

Urban green spaces are the soil component in cities that interacts most closely with humans. This study investigated the residues of seven neonicotinoids (NEOs) in soils from urban green spaces within the Pearl River Delta (PRD) region and analyzed the correlation between the residue characteristics and the region's economic development. Notably, we introduced the Nemerow Index method, a comprehensive approach, to quantify the overall pollution level of NEOs in the soil of urban park green spaces and utilized this to assess the cumulative exposure probability risks for different populations in this scenario. We found that: (1) The soil of urban park green spaces exhibited varying degrees of NEOs contamination (Σ7NEOs: N.D.–137.31; 6.25 μg/kg), with imidacloprid and clothianidin constituting the highest proportions (89.46 % and 83.60 %); (2) The residual levels of NEOs in Children's Park were significantly higher than those in community parks within Guangzhou, with an average value of 13.30 μg/kg compared to 3.30 μg/kg; (3) The residual characteristics of NEOs exhibited a positive correlation with regional economic development; specifically, the per capita GDP well correlated with IMIRPF, a summation of seven NEOs in imidacloprid equivalents via relative potency factors (R2 =0.86). Regions with higher economic development typically exhibited elevated IMIRPF levels; (4) The fitted cumulative probability distributions for average daily exposure doses revealed that children's exposure was an order of magnitude higher than adults'. Despite this, the exposure risks for both groups remained within acceptable limits.

A highly stable membrane-free potentiometric pH sensor with nickel cobalt sulfide as the solid contact layer and ion recognition

In this work, a new NiCo2S4 based H+ ion-selective electrode (ISE) without a polymer membrane was proposed and used to rapidly monitor the pH values of wetland soils in the Yellow River Delta in China. This NiCo2S4-based potentiometric pH sensor without an ion-selective membrane (ISM) exhibited a near-Nernstian response slope (50.9 ± 0.4 mV/dec) and good sensitivity. Furthermore, the developed pH sensors using NiCo2S4 as a solid contact (SC) layer present good reproducibility and the standard deviation of Eo is only 0.75 mV (n = 6). The water layer at the SC/ISM interface of the NiCo2S4-based membrane-free potentiometric pH sensor vanished, thus yielding excellent long-term potential stability (8.6 ± 0.4 μV/h over 264 h). This pH sensor offers a new design strategy for the construction of miniaturized highly stable ISEs without ISM.

Soil Salinity Inversion in Yellow River Delta by Regularized Extreme Learning Machine Based on ICOA

Soil salinization has seriously affected agricultural production and ecological balance in the Yellow River Delta region. Rapid and accurate monitoring of soil salinity has become an urgent need. Traditional machine learning models tend to fall into local optimal values during the learning process, which reduces their accuracy. This paper introduces Circle map to enhance the crayfish optimization algorithm (COA), which is then integrated with the regularized extreme learning machine (RELM) model, aiming to improve the accuracy of soil salinity content (SSC) inversion in the Yellow River Delta region. We employed Landsat5 TM remote sensing images and measured salinity data to develop spectral indices, such as the band index, salinity index, vegetation index, and comprehensive index, selecting the optimal modeling variable group through Pearson correlation analysis and variable projection importance analysis. The back propagation neural network (BPNN), RELM, and improved crayfish optimization algorithm–regularized extreme learning machine (ICOA-RELM) models were constructed using measured data and selected variable groups for SSC inversion. The results indicate that the ICOA-RELM model enhances the R2 value by an average of about 0.1 compared to other models, particularly those using groups of variables filtered by variable projection importance analysis as input variables, which showed the best inversion effect (test set R2 value of 0.75, MAE of 0.198, RMSE of 0.249). The SSC inversion results indicate a higher salinization degree in the coastal regions of the Yellow River Delta and a lower degree in the inland areas, with moderate saline soil and severe saline soil comprising 48.69% of the total area. These results are consistent with the actual sampling results, which verify the practicability of the model. This paper’s methods and findings introduce an innovative and practical tool for monitoring and managing salinized soils in the Yellow River Delta, offering significant theoretical and practical benefits.

Spatial distribution, enrichment and potential sources of seldom monitored trace elements in soils of Yellow River Delta, China

Spatial distribution, enrichment and potential sources of seldom monitored trace elements in soils of Yellow River Delta, China

Assessing the impacts of oil contamination on microbial communities in a Niger Delta soil

Oil spills are a global challenge, contaminating the environment with organics and metals known to elicit toxic effects. Ecosystems within Nigeria's Niger Delta have suffered from prolonged severe spills for many decades but the level of impact on the soil microbial community structure and the potential for contaminant bioremediation remains unclear. Here, we assessed the extent/impact of an oil spill in this area 6 months after the accident on both the soil microbial community/diversity and the distribution of polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenase (PAH-RHDGNα) genes, responsible for encoding enzymes involved in the degradation of PAHs, across the impacted area. Analyses confirmed the presence of oil contamination, including metals such as Cr and Ni, across the whole impacted area and at depth. The contamination impacted on the microbial community composition, resulting in a lower diversity in all contaminated soils. Gamma-, Delta-, Alpha- proteobacteria and Acidobacteriia dominated 16S rRNA gene sequences across the contaminated area, while Ktedonobacteria dominated the non-contaminated soils. The PAH-RHDαGN genes were only detected in the contaminated area, highlighting a clear relationship with the oil contamination/hydrocarbon metabolism. Correlation analysis indicated significant positive relationships between the oil contaminants (organics, Cr and Ni), PAH-RHDαGN gene, and the presence of bacteria/archaea such as Anaerolinea, Spirochaetia Bacteroidia Thermoplasmata, Methanomicrobia, and Methanobacteria indicating that the oil contamination not only impacted the microbial community/diversity present, but that the microbes across the impacted area and at depth were potentially playing an important role in degrading the oil contamination present. These findings provide new insights on the level of oil contamination remaining 6 months after an oil spill, its impacts on indigenous soil microbial communities and their potential for in situ bioremediation within a Niger Delta's ecosystem. It highlights the strength of using a cross-disciplinary approach to assess the extent of oil pollution in a single study.

25-years of stewardship programs enhance regenerative outcomes in river delta soils of southwestern British Columbia, Canada

Agricultural stewardship programs that incentivize practices such as winter cover cropping (WCC), grassland set-asides (GLSA), and hedgerows (HR) for intensive annual agricultural production are often implemented to improve both soil conditions and provision of wildlife habitat in coastal agricultural systems of the Fraser River Delta, British Columbia (BC). Although these programs have been shown to support numerous ecosystem services, it is unclear how they contribute to regenerative agricultural outcomes. Regenerative agricultural practices aim to increase soil carbon inputs and reduce carbon dioxide losses which in turn improves soil structure, optimizes soil water regulation, and provides climate mitigation and resiliency of agricultural systems. The objectives of this study were to quantify the effects of agricultural stewardship programs for regenerative outcomes through indicators of climate mitigation and adaptation. Twenty-six fields in the southwestern, BC were grouped by those that participated in stewardship programs between 1992 and 2016 and those that did not. In the spring of 2018, soil samples were collected; soil organic carbon (SOC) concentrations were measured, and stocks were calculated; pedo-transfer functions were used to estimate soil water regulation indicators; and differences among stewardship program and non-program fields were statistically analyzed using a linear mixed effects model. The SOC (mg kg−1) from 0 to 15 cm was greater with implementation of stewardship programs. Topsoil equivalent soil mass SOC stocks (t/ha) were 71 % and 63 % greater in HR and WCC + GLSA program fields, respectively, compared to non-program fields. Soil workability threshold was 25 % and 14 % greater in HR and WCC + GLSA program fields, respectively, compared to non-program. Our results indicate that stewardship programs that include hedgerows and grassland set-asides promote accrual of soil carbon and improved soil water regulation and show that these programs can effectively enhance regenerative outcomes and improve agroecosystem resilience in this important agricultural region.

Integrated Management of Slow- release Nitrogen Fertilizer Types and Rates for Wheat Production under Middle Nile Delta Soil Conditions

Integrated Management of Slow- release Nitrogen Fertilizer Types and Rates for Wheat Production under Middle Nile Delta Soil Conditions

Spatial distribution and source identification of potentially toxic elements in Yellow River Delta soils, China: An interpretable machine-learning approach

Identifying the driving factors and quantifying the sources of potentially toxic elements (PTEs) are essential for protecting the ecological environment of the Yellow River Delta. In this study, data from 201 surface soil samples and 16 environmental variables were collected, and the random forest (RF) and Shapley additive explanations (SHAP) methods were then combined to explore the key factors affecting soil PTEs. An innovative t-distributed random neighbor embedding-RF-SHAP model was then constructed, based on the absolute principal component score and multivariate linear regression model, to quantitatively determine PTE sources. Although average PTE concentrations did not exceed the risk control values, PTE distributions exhibited significant differences. It was found that sodium, soil organic matter, and phosphorus contents were the three most important factors affecting PTEs, and human activities and natural environmental factors both influence PTE contents by altering the soil properties. The proposed model successfully determined PTE sources in the soil, outperforming the original linear regression model with a significantly lower RMSE. Source analysis revealed that the parent material was the main contributor to soil PTEs, accounting for more than half of the total PTE content. Industrial and agricultural activities also contributed to an increase in soil PTEs, with average contributions of 19.91 % and 17.44 %, respectively. Unknown sources accounted for 10.83 % of the total PTE content. Thus, the proposed model provides innovative perspectives on source parsing. These findings provide valuable scientific insights for policymakers seeking to develop effective environmental protection measures and improve the quality of saline-alkali land in the Yellow River Delta.

Long Term Effect of Organic and Inorganic Manures on Rice Productivity and Major Nutrient Dynamics in 33 Years Old Rice-Rice Cropping System of Godavari Delta

Aim: To study the “Long Term Effect of Organic and Inorganic Manures on Rice Productivity and Major nutrient dynamics in 33 years old Rice- Rice Cropping System of Godavari Delta”.
 Place and Duration of Study: A field experiment was carried out during kharif 2022 at Regional Agricultural Research Station, Maruteru, West Godavari district in the ongoing All India Coordinated Rice Improvement Project (AICRIP) on Long term soil fertility management in low land rice soils of Godavari delta under rice-rice cropping system.
 Study Design and Methodology: Treatments imposed in this study were T1: Control, T2: 50 % NPK, T3: 50% NPK + 50 % N-FYM, T4: 50 % NPK + 50% N-Green Manure, T5: 50 % NPK + 50 % N-Azospirillum, T6: FYM @ 10t/ha, T7: 100 % NPK+Zn+S, T8: 100 % NPK +Zn+S+FYM @ 5 t ha-1. All together 8 treatments laid out in RBD with three Replications. The application of fertiliser was carried out in accordance with the treatments. The prescribed fertiliser dose (90:60:60) was administered in the following forms: urea (46% N), single superphosphate (16% P2O5), muriate of potash (60% K2O), and zinc sulphate (ZnSO4.7H2O) @ 50 kg ha-1. The total dosage of phosphorus, potassium, and zinc were applied as basal. Three equally divided applications of nitrogen were made: one at the basal, one at the tillering stage, and one at the panicle initiation stage. Well decomposed farmyard manure (FYM) manure and Pheltophorum (green leaf manure) were applied one week before transplanting. Popular cultivar of Kharif rice MTU 1064 (Amara) was used for the study.
 Results: Long-term application of organic and inorganic fertilizers and their combination didn’t show any marked difference on physico-chemical properties of soil (pH and EC). Bulk density was recorded lowest in FYM @ 10 t ha-1 and it was on par with (T8, T3, T4, T5). Organic carbon was observed highest in FYM @ 10 t ha-1 and it was on par with (T8 and T3). There was a significant impact of long-term application of organic and inorganic fertilizers and their combination on soil chemical properties, highest available N, P, K, S and Zn was observed highest in conjunctive treatment (T8) 100 % NPK + Zn + S + FYM @ 5 t ha-1 whereas, lowest was recorded in control. There was a significant impact on grain and straw yields. Highest grain and straw yields were recorded in (T8) 100 % NPK + Zn + S +FYM @ 5 t ha-1 and it was on par with (T7) 100 % NPK + Zn + S.
 Conclusions: After the investigation, present study concludes that conjunctive and combined application of organics with inorganics improve soil physical, physico-chemical and chemical properties of the soil.

Study on ecological stoichiometry homeostasis characteristics of different halophytes in the Yellow River Delta

AbstractEcological stoichiometric homeostasis represents the physiological and biochemical adaptations of organisms to variations in environmental conditions and plays a pivotal role in maintaining ecosystem stability. However, existing literature predominantly concentrates on the changes in plant homeostasis under different external environments. There is a paucity of comparative analyses focusing on the stoichiometric homeostasis attributes among different types of halophytes, particularly using these halophytes as a primary investigative lens. In this study, by analyzing the differences in organ and soil ecological stoichiometry as well as salt accumulation characteristics of three halophytes (Phragmites communis, Suaeda salsa, and Tamarix chinensis) in the Yellow River Delta, we revealed the salt ion enrichment capacity and stoichiometric homeostasis characteristics of the three halophytes and clarified the adaptive capacity of the three halophytes in saline soil environments. Our results indicated that S. salsa accumulated more Na+ and Mg2+, while P. communis maintained a low salt content in its surrounding soil. The soil C:N ratios of P. communis and S. salsa negatively correlated with most ions, while T. chinensis displayed a positive correlation with ions. S. salsa demonstrated the highest ion enrichment but the least homeostasis, whereas T. chinensis showed superior homeostasis. We hypothesize that T. chinensis might have experienced a faster growth rate during the study period, and P. communis' topsoil appears to be more conducive for plant growth. The different salt tolerance strategies of these plants influenced homeostasis, with S. salsa demonstrating greater adaptability to soil modifications and higher potential in saline land management. These insights enhance our understanding of the physiological and ecological adaptations of halophytes and their contribution to improving the quality of saline soils in the Yellow River Delta.

Increase the Efficient Use of Phosphorus Fertilizer for Maize in the Calcareous Soils

ABSTRACT Phosphorus (P) is one of the 17 essential plant nutrients, and it is critical for plant metabolism, photosynthesis, and growth. P fertilizers are also critical for crop production and global food security. Type and application method of P fertilizer may lead to increased P accumulation and crop production in the Ganges delta soils. The aim of the present study is to increase the P use efficiency (PUE) by two different P application methods for maize cultivation. The experiment comprised a factorial combination of two methods (broadcasting and furrow placement) and three rates of P fertilizer (36, 48, and 60 kg P/ha). Considering P application methods, furrow placement gave 8.66–27.92% yield benefit over broadcasting method. Maize yield, PUE by crop plant, partial factor productivity, economic efficiency, and P concentration in leaf were remarkably higher in furrow placement than conventional broadcasting method of P application. The furrow placement exhibited higher yield at lower rate of P application (36 and 48 kg P/ha), while no significant changes were observed for grain yield between two methods for high P rate (60 kg/ha). Thus, it is concluded that furrow placement of P application at 36 and 48 kg/ha would give the best grain yield of maize in the Ganges delta floodplain soils.

Soil Quality Improvement with Increasing Reclamation Years in the Yellow River Delta

The saline soils in the Yellow River Delta are primarily affected by seawater intrusion resulting from the intersection of land and sea, which exhibit variations in salinity. The quality of these soils is also influenced by anthropogenic reclamation, including fertilization and irrigation. This study quantitatively evaluated the distinct soil properties and soil quality characteristics of the Yellow River Delta during different reclamation years (i.e., 0a, 1a, 5a, 10a, and 20a) using principal component analysis (PCA) and the Soil Quality Index (SQI). The findings indicated that the soil salt content (SSC) significantly decreased (p < 0.05) from 6.60 g/kg in the initial reclamation year (0a) to 1.63 g/kg in the 10th year (10a) and then slightly increased to 2.85 g/kg in the 20th year (20a). Consequently, the soil salinity level shifted from saline soil to slight salinity and then increased to medium salinity. Ammonium nitrogen (NH4+-N) notably increased by 8.31 mg/kg during the first five years of reclamation (0a to 5a) and gradually decreased by 2.56 mg/kg in the 20th year (20a). On the other hand, nitrate nitrogen (NO3−-N) experienced a significant decrease of 2–5 times after reclamation but continued to increase by 8.96 mg/kg with subsequent reclamation years. The available nitrogen (AN), available phosphorus (AP), and soil organic carbon (SOC) exhibited a significant increase of 24.87 mg/kg, 10.11 mg/kg, and 6.76 g/kg, respectively, with increasing reclamation years. However, available potassium (AK) gradually decreased after reclamation and then increased in the 20th year (20a). The values of SQI for different reclamation years were 0.307 for 0a, 0.339 for 1a, 0.320 for 5a, 0.318 for 10a, and 0.327 for 20a, indicating an increasing trend with increasing reclamation years. It was discovered that long-term reclamation significantly reduced soil salinity and improved soil quality, leading to the sustainable development of reclaimed saline soils in the Yellow River Delta.

Green remediation and enhanced metal accumulation using moringa oleifera leaf extracts and hydrocarbon-degrading microorganisms in crude oil-impacted soils of the niger delta, nigeria

This emerging technology called “Phytoremediation” which uses plants to remove pollutants from the environment is preferred over traditional methods, because it offers site restoration, partial decontamination, and maintenance of biological activity and physical structure whilst being potentially cheap, visually unobtrusive and with a possibility of bio-recovery of metals. Because of these advantages, phytoremediation is considered as a 'green', sustainable pollution removal process. The present study was designed to evaluate Phytoremediation potential of Moringa oleifera leaf extract on soil contaminated with Spent Engine Oil. Top soil (0-15cm depth) was randomly collected and 5kg each of the composite samples were transferred into fifty (50) plastic buckets with drainage holes at the base, plugged with cotton wool to retain the soil. The Plastic buckets were arranged into five treatment groups with Ten (10) replicates each. The polythene bags were arranged in a completely randomized block design. Spent Engine oil obtained from mechanic shops in Bedwell Calabar, Cross River State, was applied as the pollutant. The Spent engine oil was introduced at different concentration levels (0.3, 0.5, 0.7, and 1.0 l/5kg) into the treatment groups apart from the control (0.0 l/5kg).The results across the various treatment levels where subjected to statistical analysis, using Analysis of variance (ANOVA) and the results showed that physicochemical parameters (soil pH and organic carbon), Heavy Metals present, Total Petroleum Hydrocarbon and Microbial Counts were significantly higher (P<0.05) in treatment groups than the control. The result also showed a significant reduction (P<0.05) of the Total petroleum hydrocarbon after treatment.

Microbial communities associated with landfarming amendments during bioremediation of crude oil in Niger Delta soils

Landfarming is a widely utilized process that involves using bacterial biodegradation to remediate contaminated soil resulting from oil spillages. Its effectiveness can be improved using amendments that include fertilizers, biosurfactants, enzymes, and natural sorbents. The effects of these amendments on biodegradation efficiency and the microbial community composition were investigated using 16S rRNA gene amplicon sequencing analyses performed on soil samples collected from a large-scale mesocosm experiment. The results showed that the use of amendments had a profound influence on the microbial community, which decreased with time following application of the amendment. Interestingly, the relationship between observed microbial diversity and biodegradation efficiency changed over time. During the initial phase, a higher biodegradation rate correlated with lower biodiversity indices, while during the later phase this relation reversed, and a higher biodegradation rate correlated with higher biodiversity indices. Two mesocosms types, one with biochar plus rhamnolipids and the other with agricultural lime, both in combination with fertilizer, degraded the oil significantly better than the ‘oil-only control’ with biodegradation improvements of 32.5 % and 25.8 %, respectively. Both combinations of amendments also promoted different adaptive responses of the microbial community with higher abundances of members of the genus Sphingomonas in both cases.

Methane Anaerobic Oxidation Potential and Microbial Community Response to Sulfate Input in Coastal Wetlands of the Yellow River Delta

In the context of global warming and carbon neutrality, reducing greenhouse gas emissions is fundamental to achieving sustainable development. As an important greenhouse gas, methane has a much stronger warming effect than CO2, and studies have demonstrated that anaerobic oxidation of methane (AOM) is important for global methane emissions. This paper systematically investigated the AOM potential and microbial community response to the input of SO42− in the three typical salt marsh soils of the Yellow River Delta: Reed, Suaeda salsa, and Tamarisk, using SO42− as the electron acceptor and a combination of indoor anaerobic culture and high-throughput sequencing. The results showed that after adding an appropriate concentration of SO42−, the AOM potential was significantly promoted in Tamarix soil (p < 0.05) and significantly inhibited in Reed and Suaeda salsa soil (p < 0.05); soil AOM potential and SO42− input concentration and background values were correlated. At the microbial level, SO42− input affected the abundance of some microorganisms. At the phylum level, the relative abundance of Proteobacteria was increased in Suaeda salsa soil, decreased in Tamarisk soil, and did not change significantly in Reed soil; that of Crenarchaeota and Desulfobacterota was significantly increased in Tamarisk soil. At the genus level, Methylophaga, Methylotenera, and Methylomonaceae became the dominant populations, and it can be inferred that these bacteria are involved in the anaerobic oxidation of methane after the input of SO42−. This study will be of great significance to the mechanistic study of AOM and the conservation of microbial diversity in the Yellow River Delta Coastal Wetland, as well as provide a scientific basis for CH4 reduction in coastal wetlands.

Formation regime of some soils of Western Delta, Egypt.

Formation regime of some soils of Western Delta, Egypt.

Leaching and migration characteristics of nitrogen during coastal saline soil remediation by combining humic acid with gypsum and bentonite

Coastal saline soil is an important resource that is widely-distributed and available for mitigation, development and utilization. Adding exogenous materials to improve saline soil has been shown to be an effective measure to increase its agricultural productivity. However, there is limited information about the risk of nitrogen (N) leaching during coastal saline soil improvement process. Therefore, the leaching and migration characteristics of N in saline soils of the Yellow River Delta (Shandong Province, China) with the addition of weathered coal humic acid (HA), gypsum and bentonite, were examined using soil columns and 15N isotope tracers. The results showed that co-application of HA and gypsum could significantly increase the soil penetration rate (SPR) and reduce the pH of saline soil but did not increase N leaching, specifically an application ratio of 1:3 (HA: gypsum) based on weight. The co-application of HA and bentonite could not increase the SPR and reduce the pH, but could inhibit nitrification and better conserve 15N of saline soil. Therefore, we believe that bentonite cannot replace gypsum but could be used as an auxiliary agent to achieve better N retention. The mixed addition of HA and gypsum can achieve the dual effect of improving saline soil and maintaining N, which is beneficial to environmental protection and high-quality development of agricultural production in the Yellow River Delta.

Chemical processes and sustainability of rice-shrimp farming on saline acid sulfate soils in mekong delta

In the history of rice-shrimp farming (RSF) in the Mekong Delta, in saline acid sulfate soils (ASS), RSF has proved its sustainability as there is no long-term accumulation of acidity and salinity that adversely affect RSF production. However, the soil processes involved in this phenomenon are not well understood. This study aimed to determine the significant changes in soil and water chemical indicators associated with soil processes during different stages of RSF. Sampling was conducted in six stages to determine the pH and electrical conductivity (EC) of canal and field water, and the pHe, ECe, and sodium-soluble saturated extract (Na-sol) of surface soil (surS) and subsurface soil (subS) in the low-salinity area (LSA) and high salinity area (HSA) of Bac Lieu province. Putative exchange (exch.) Na+ hydrolysis occurs at the beginning of the rainy season when excess salts are leached. This drastically increases the pH of the field water by 0.6 pH units, from 8.2 to 8.8 in stages 1 to 2, respectively. Putative sulfurization has been shown to occur in subS in both LSAs and HSAs, with a significant decrease of 0.5 pH units from stages 4 to 5, leading to a decrease in the Na-sol of subS through exch. Na+ transformation. Simultaneously, with active soil preparation and liming for RSF, chemical processes such as exch. Na+ hydrolysis, sulfurization, and Na+ transformation are the main factors promoting exch. Na+ desorption, which help to reduce the long-term build-up of salinity and acidity that adversely affect RSF production. Although gypsum is considered an effective material in improving saline soils, in Vietnam, gypsum is the liming material of CaSO4; however, it is not commonly used in agriculture because of its high cost. By using CaCO3 or dolomite as a liming material in saline ASS, the dissolution of lime by sulfuric acid can provide a good opportunity for soil improvement and rice growth in RSF.