Soil pH Research Articles

Assessment of Soil Fertility Status in Vegetable Growing Area of Daman-Palung, Nepal

Soil fertility assessment is essential for sustainable planning for a particular area. Considering this, a study was conducted in November 2018, to determine the soil fertility status of the vegetable growing area of Makwanpur district, Nepal. In total, 50 soil samples were collected randomly from a depth of 0-20 cm using a soil sampling auger. A standard analytical method was used to analyze the texture, soil pH, (Organic matter (OM), Nitrogen (N), Phosphorus (P2O5), and Potassium (K2O) status of samples at the National Soil Science Research Centre, Khumaltar. The sand, silt and clay content were 45.67±2.08, 35.6±51.37 and 18.49±0.93 respectively and were indicated as loam and sandy loam in texture. The soil was moderately acidic (pH 5.11±0.5) in nature. Soil organic matter ranged from low to medium but the medium (3.37±1.72 %) was prevalent. Total nitrogen content (0.22±0.01 %) and available phosphorus (230.58 ±85.61 ppm), were found to be high. Furthermore, available potassium (97.4±70.04 ppm) content was medium in the soil. The purpose of this soil fertility assessment is to help researchers and farmers in Daman, Palung know the soil fertility status of their area and to guide sustainable soil fertility practices. This soil fertility assessment aims to help researchers and farmers in Daman, Palung understand soil fertility status and determine the best soil fertility practices for their area.

Enhancing the Growth of Chili Plants and Soil Health: Synergistic Effects of Coconut Shell Biochar and Bacillus Sp. Strain Ya-1 on Rhizosphere Microecology and Plant Metabolism

To mitigate soil degradation and decrease dependency on chemical inputs in agriculture, this study examined the joint effects of coconut shell biochar and Bacillus strain Ya-1 on soil fertility, rhizosphere bacterial communities, and the growth of chili (Capsicum annuum L.). A controlled pot experiment with four treatments was conducted: control (CK), biochar only (C), Bacillus strain Ya-1 only (B), and a combination of both (BC). The BC treatment significantly enhanced the soil carbon and available phosphorus contents by approximately 20% and the soil nitrogen content and pH by 18% and 0.3 units, respectively, compared to the control. It also increased microbial biomass carbon and nitrogen by 25% and 30%, respectively, indicating improved soil microbial diversity as shown by the highest Pielou evenness index and Shannon index values. The combined application of biochar and the Ya-1 strain resulted in a 15% increase in chili plant height and a 40% improvement in root dehydrogenase activity, suggesting enhanced nutrient uptake and metabolism. Metabolic profiling showed shifts in stress response and nutrient assimilation under different treatments. Collectively, these results indicate the potential of biochar and microbial inoculants to significantly promote soil and plant health, providing a sustainable strategy to improve agricultural productivity and reduce reliance on chemical inputs.

The impact of combined application of biochar and fertilizer on the biochemical properties of soil in soybean fields.

Heilongjiang Province is a major soybean production area in China. To improve soil structure and increase soybean yield, this study examined the effects of combined biochar and chemical fertilizer application on the biochemical properties of soil in a maize-soybean rotation system. The research were conducted from 2021 to 2022 at Heshan Farm Science Park in Heilongjiang Province, this field plot experiment utilized two soybean varieties, Heihe 43 (a high-protein variety) and Keshan 1 (a high-oil variety). In 2021, two plots with similar fertility levels were selected for planting soybeans and maize. In 2022, a maize-soybean rotation was implemented with five treatments: conventional fertilization (CK), increased biochar+reduced fertilizer 1 (F1+B), reduced fertilizer 1 (F1), increased biochar+reduced fertilizer 2 (F2+B), and reduced fertilizer 2 (F2). The study systematically analyzed the effects of combined biochar and chemical fertilizer application on soil chemical properties and microbial characteristics. Over 2 years, results showed that combined application effectively improved soil chemical traits. Compared to conventional fertilization (CK) and reduced fertilization (F1, F2), t he combined application of biochar and chemical fertilizer (F1+B, F2+B) increased soil pH, EC and the absolute value of zeta potential of soil surface, the CEC of soil significantly increased by 15.6-44.3%, the soil surface charge density and the soil surface charge quantity significantly increased by 16.4-73.5%. The combined application of biochar and chemical fertilizer also effectively enhanced the abundance and diversity of soil microbes. Dominant bacterial groups in soybean field soils under different treatments included Actinobacteria, Acidobacteria, Chloroflexi, and Proteobacteria; while dominant fungal groups were Ascomycota, Basidiomycota, and Mortierellomycota. Alpha and Beta diversity analyses revealed that the F1+B treatment significantly enhanced the species richness and diversity of bacteria and fungi in the soil, increasing the proportion and evenness of dominant and beneficial genera.

Enrichment of Phytopathogen Dominated by Volutella in the Rhizosphere May Be an Important Cause of Continuous Cropping Obstacles in Sweet Potatoes

ABSTRACTObstacles related to the continuous cropping of sweet potatoes (Ipomoea batatas (L.) Lam.) restrict its intensive production. However, the effects of continuous cropping on soil properties and/or the rhizosphere microbial community are largely unclear. In this study, we analyzed changes in rhizosphere soil chemical properties and microbial communities of sweet potatoes across different cultivation years. We observed that the microbial diversity and complexity of the fungal ecological network in rhizosphere soils of sweet potatoes were decreased after 5 years of continuous cropping, with significant enrichment in Sphingobium, Gemmatimonas, Volutella, and Neoidriella. Tuber yield, soil pH, and available potassium (AK) content were significantly reduced after continuous cropping, with the soil microbial community having the highest correlation with pH, AK, and ammonium nitrogen (NH4+‐N). Specifically, soil pH and AK were positively correlated with Bacillus and Gaiella, and negatively correlated with some plant‐pathogenic fungi (Volutella and Neoidriella), while NH4+‐N showed the opposite trend. In addition, soil pH, AK, and the relative abundance of Bacillus were positively correlated with tuber yield, while Volutella showed the opposite trend. In summary, the continuous cropping of sweet potatoes negatively affects rhizosphere soil health, resulting in imbalanced soil fertility and an increased abundance of pathogens. These results improve our understanding of factors driving obstacles faced with the continuous cropping of sweet potatoes, enabling future studies and the development of technologies to overcome these obstacles.

Soil metabolic disturbance drives replant disease (intraspecific negative plant–soil feedback): Insights from an experiment examining soil impacts up to 20 years after a ginseng crop

Replant diseases (RDs), intraspecificnegativeplant–soilfeedback, often stem from nutrient deficiency, allelopathy, or pathogen accumulation. However, the RDs of certain crops are long-lasting and their causes remain unknown. We examined Panax quinquefolius RD in a space-for-time soil sequence representing crop rotation restoration over 1, 10, and 20 years using multiomics and bioassays. Compared with the soils with no ginseng cultivation history, we found 110 significant potential factors related to RD, surprisingly, 53 of which remained unrestored after 20 years. Soil pH and the levels of organic nutrients (amino acids, carbohydrates, and alditols), allelopathic-promoting metabolites (phenolic acids, amines, pyridines, etc.), and beneficial bacteria (Sphingomonas, Burkholderia-Caballeronia-Paraburkholderia, and Terrabacter) and fungi (Acremonium, Penicillium, and Naganishia) decreased, while the levels of allelochemicals (pyruvic and fatty acids) increased. The expression of all metabolic pathways was significantly down-regulated, with the exception of the up-regulated fatty acid-related metabolic pathways. We confirmed that decreased organic nutrient levels and increased levels of allelochemicals impaired P. quinquefolius growth. Soil metabolic factors rather than microbial factors were dominant by network analysis. In conclusion, we found that the overall changes in nutrient levels and metabolic and microbial factors contributed to short-term RD (1–10 year) persistence, whereas long-term RD (after 20 years) primarily resulted from disordered soil metabolite levels and pathways. This research will help deepen our understanding of the relationship between RD and potential changes in the factors influencing RD that are caused by soil legacy effects of valuable plants and provide theoretical guidance for effective soil quality improvement.

Effect of tobacco–radish rotation for different years on bacterial wilt and rhizosphere microbial communities

Tobacco bacterial wilt is a major limiting factor for tobacco production and development, and it is more likely to occur under perennial single cropping of tobacco. In recent years, the rotation of tobacco-radish has gradually become popular. Therefore, we studied the effects of years of tobacco–radish rotation on tobacco bacterial wilt occurrence and rhizosphere microorganisms. The results indicated that both SY and TY could significantly reduce the risk of tobacco bacterial wilt occurrence, and SY had the lowest disease index. The rotation of radish plants significantly increased the soil pH but decreased the contents of alkali-hydrolysed nitrogen and organic matter in the soil. Alkali-hydrolysed nitrogen and pH are the key factors affecting the composition of the bacterial community. Furthermore, radish rotation changed the composition of the soil microbial community, increased the diversity of the bacterial community, and significantly altered the bacterial community structure. At the genus level, the abundance of Sphingomonas species negatively correlated with Ralstonia increased significantly, while the relative abundance of Rhodanobacter species positively correlated with Ralstonia decreased significantly. Disease index, pH and available phosphorus were the main factors affecting the variation in different bacterial genera. The network analysis results showed that Ralstonia was less connected in the network than in the CK group, and the SY treatment group had a more complex bacterial network structure. Overall, 2 years of tobacco and radish rotation improved the bacterial community structure of the rhizosphere soil and alleviated the harm caused by tobacco bacterial wilt, which is highly important for the stability and health of the rhizosphere soil ecosystem.

The long-term effect of biochar application to Vitis vinifera L. reduces fibrous and pioneer root production and increases their turnover rate in the upper soil layers

Fibrous and pioneer roots are essential in the uptake and transport of water and nutrients from the soil. Their dynamic may be influenced by the changing of soil physicochemical properties due to the addition of biochar, which, in turn, has been shown to improve plant growth and productivity in the short term. However, the long-term effects of biochar application on root dynamics are still widely unknown. In this study, we aimed to investigate the long-term effects of biochar application on grapevine fibrous and pioneer root dynamics and morphological traits in relation to soil characteristics. To this aim, grapevine plants amended in 2009 and 2010 respectively with one and two doses of biochar, were analyzed in their fibrous and pioneer root production and turnover rate, standing biomass, length, and specific root length, over two growing seasons. Our findings demonstrate that in the long term, biochar application significantly increased soil pH, nutrient availability, and water-holding capacity causing a decrease in the production of fibrous and pioneer roots which is reflected in a reduction of the root web characterized though by a higher turnover rate. Furthermore, we observed that these root morpho-dynamical changes were of higher magnitude in the upper soil layers (0-20 cm) and, at least in the long term, with no significant difference between the two doses. These results suggest that in the long term, biochar can be a powerful tool for improving soil quality, which in turn lowers carbon-cost investment toward the root production and maintenance of a reduced root web that might be directed into grapevine growth and productivity. Such effects shed some light on the root plastic and functional adaptation to modified soil conditions facilitated by the long-term application of biochar, which can be used for implementing adaptive agricultural practices to face the current climate change in a frame of sustainable agricultural policies.

Bulk Density and pH Relationships on Sandy Soils in Three Florida Fields

Bulk density is an important physical property of soils as it impacts the airflow, water retention, and structure of a soil. pH is a chemical property that affects the availability of nutrients in the soil. Both properties directly affect crop health and production and are often measured as indicators of soil health and crop suitability. Previous studies on this relationship between bulk density and pH focus on silty soils, and there is limited information on relationships between pH and physical soil properties on the sandier type of soils that are prevalent in Florida. This study aimed to investigate potential relationships between bulk density and pH in sandy soils by sampling the soils of three different crop production systems in north-central Florida: a silage corn field in Citra, peanut field in Chiefland, and turfgrass plot in Gainesville. Each of the sites were treated with pH-altering treatments, including ammonium nitrate, gypsum, and lime. While the soils in the turfgrass plot showed no observable relationship between bulk density and pH, the soils in the silage corn and peanut fields did show a slight relationship. In the peanut and silage corn fields, each plot was sampled both within the crop rows and between crop rows. In these fields, samples taken in the root area showed significant differences in pH (p < 0.001) and bulk density (p < 0.01) from the area between rows. Understanding relationships in the soil environment is important to maximize crop health and production, therefore further research is needed in this area.

Remediation of Cd-As-Ni co-contaminated soil by extracellular polymeric substances from Bacillus subtilis: Dynamic improvements of soil properties and ecotoxicity

As the primary reservoir of heavy metals in nature, soil is highly susceptible to significant co-contamination with Cd-As-Ni. In current study, extracellular polymeric substances (EPS) from Bacillus subtilis were utilized as a novel improver to simultaneously enhance soil property and restrain ecotoxicity in Cd-As-Ni co-contaminated soil. Our findings revealed that EPS effectively bound and immobilized free Cd, As, and Ni in soil and decreased the 49.73 % of soil available Cd, 79.16 % of As and 77.87 % of Ni contents by increasing soil pH, soil organic matter and cation exchange capacity. The EPS was also found to inhibit the Cd-As-Ni induced ecotoxicity in Caenorhabditis elegans by increasing the activities of antioxidant enzymes including superoxide dismutase, glutathione, and catalase. The remediation of EPS showed progressive improvement over time, and maintained a lasting effect after achieving peak efficiency. Our results might provide a new perspective on the potential of EPS in remediation of soil heavy metal pollution and the development and utilization of microbial biomass resources in a wider range.

Rhizophagus intraradices symbiosis with Amaranthus hypochondriacus improves rhizosphere soil pH and nutrient status in sodic soil

As a forage crop belonging to the Amaranthaceae family (often considered as non-mycorrhizal plants), Amaranthus hypochondriacus can grow in sodic soil. It is worth exploring whether arbuscular mycorrhizal fungi (AMF) can successfully form a symbiotic relationship with A. hypochondriacus to alleviate the environmental stress it experiences and improve rhizosphere soil quality. This study aims to evaluate the potential for AMF to form a symbiotic relationship with salt-tolerant Amaranthaceae plants. By measuring the colonization rate, biomass, and rhizosphere soil chemical properties of the plants, we assessed the response of A. hypochondriacus to AMF under different concentrations of saline-alkali stress. The results showed that Rhizophagus intraradices could form a good symbiotic relationship with A. hypochondriacus and reduce the rhizosphere soil pH and increase the effective nutrient content.

Complex interactions of deer herbivory, soil chemistry, and competing vegetation explain oak–hickory forest tree regeneration in central Pennsylvania, USA

The root causes of forest tree regeneration failure are difficult to resolve, although numerous studies show ungulate herbivory, soil conditions, and competition from undesirable vegetation as likely contributors. To better understand the relative importance of each issue, we conducted a 7-year manipulative experiment to assess the interactive effects of white-tailed deer ( Odocoileus virginianus) herbivory, soil acidity, and competing vegetation on tree regeneration in oak–hickory forests of central Pennsylvania, USA. Outcomes depended on initial tree seedling abundance, and all three factors had significant interactions. At low initial seedling abundance, fencing resulted in the greatest increase, but all treatments had a positive effect on seedling growth and abundance. At higher initial seedling abundance, abundance failed to recover 7 years after herbicide treatment and soil pH was an important predictor. When soil pH was >4.6 from lime application, seedling growth and abundance in unfenced controls with high initial abundance was comparable to the fenced-only treatment. Competing vegetation, assumed to be a symptom of excessive, long-term deer herbivory, does not seem to be the primary factor limiting tree regeneration in our study area. Ameliorating acid deposition warrants greater consideration as a management action because it could provide long-lasting benefits compared to short-term fence installations.

Effects of Intercropping of Sisal and Three Different Leguminous Plants on Soil Bacterial Diversity

Intercropping is widely utilised in agricultural production to enhance land use efficiency because of its benefits, such as heightened crop productivity and optimised resource utilisation. We investigated the effects of Pinto peanut/sisal (HST), Stylo/sisal (strT) and Grona styracifolia/sisal (JqT) intercropping systems on soil bacterial communities compared with sisal continuous cropping (CK) by using Illumina MiSeq high-throughput sequencing technology. The intercropping system significantly increased the total nitrogen (TN), soil pH and soil moisture levels and decreased the levels of available phosphorus (AP) and available potassium (AK). Minimal variations were observed in Shannon’s and Simpson’s diversity indices between the monoculture and intercropping systems as well as among different intercropping systems. The most abundant phyla observed within the four groups were Proteobacteria, Acidobacteria, Cyanobacteria and Bacteroidetes. At the phylum level, the relative abundances of Proteobacteria, Acidobacteria, Cyanobacteria and Bacteroidetes were 37.37–54.35%, 10.54–21.21%, 3.46–20.43% and 2.15–5.67%, respectively. Compared with ZCK, StrT, JqT and HST treatments led to higher abundance of Cyanobacteria (from 3.46% to 20.43%, 11.37% and 16.58%, respectively) and Bacteroidetes (from 2.15% to 5.67%, 5.21% and 5.10%, respectively). The results of the linear discriminant analysis of effect sizes demonstrated notable variations in the relative abundance of bacterial taxa among various intercropping systems. The dominant categories of the genus in strT and JqT groups were Blastocatellia and Blastocatellaceae-Subgroup4, while Firmicutes was the dominant category of the genus in the HST group. The structure of bacterial communities did not vary between intercropping and monoculture systems. The findings indicated that the impact of the intercropping system on the bacterial community structure was not contingent on the specific intercropping patterns employed.

Nitrification inhibitor effect on manganese and phosphorus shoot concentrations in maize under different textured soils from northern Germany

High soil pH can result in Mn2+ and P deficiency, leading to crop yield losses. Therefore, supplying soil with NH4+-N fertilizer in stabilized or unstabilized form can increase soil Mn2+ availability and shoot concentration. Nitrification inhibitors (NIs) have been proposed to lower rhizosphere soil pH, thus improving plant P uptake and preventing P deficiency in soils with high pH. Thus, this study investigated whether NI-stabilized or unstabilized NH4+-N could increase Mn2+ availability in three differently-textured soils (sand, loamy sand, and silt loam) and promote Mn2+ and P shoot concentration in maize. Two greenhouse experiments were conducted to investigate the effects of applying NH4+-N fertilizer with or without the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) combined with different nitrogen (N) sources (calcium nitrate (CN), ammonium nitrate (AN), and ammonium sulphate (AS)). The measured variables were bulk and rhizosphere soil pH and Mn2+ availability, maize biomass, as well as Mn2+ and P shoot concentrations. The results indicated that DMPP-stabilized AS significantly decreased rhizosphere pH by 7.2 % in loamy sand soil texture compared with unstabilized AS. Similarly, only in the loamy sand texture, DMPP-stabilized AS increased Mn2+ availability and shoot concentration by 86 % and 47 %, respectively, relative to unstabilized AS. Furthermore, DMPP-treated AS and AN promoted P shoot concentration by 30 % and 21 % in the loamy sand and silt loam soil textures, respectively, relative to the corresponding N sources without DMPP. Conversely, DMPP did not impact the investigated variables in the sand texture for all N sources. Moreover, AN and AS increased biomass yield, Mn2+ availability, and shoot concentration by 72 %, 30 %, and 46 %, respectively, in relation to the CN fertilizer in the sand soil texture. In conclusion, this study confirmed the effectiveness of DMPP-induced rhizosphere acidification in enhancing Mn2+ and P shoot concentration in loamy sand soil textures, as well as P shoot concentration in fine-textured soil.

Enriched Linz-Donawitz (LD) slag application for improving grain yield and quality of wheat grown under nutritionally poor degraded soil

Aim: To evaluate the impact of enriched steel slag on the physico-chemical characteristics of soil and yield attributes of wheat under poor quality degraded soil. Methodology: Steel slag was biologically and organically amended with natural sources of phosphorus (P), sulfur (S), potassium (K) and nitrogen (N) and characterized for its nutrient content along with biological activity. The impact of resultant products was assessed on soil quality and yield component traits of wheat for two consecutive years (2021-2022 and 2022-23). Results: Application of slag based products significantly (p<0.05) improved the plant height, biological yield, grain yield and ear bearing tillers (EBT) of wheat even with 80% of recommended fertilizer dose (NPK). Further, in comparison to control, a moderation of soil pH (8.6 to 8.8), EC (0.18 to 0.20 dS m-1), OC (0.22 to 0.24 %) and essential mineral macronutrients viz., N (126 to 130 kg N ha-1), P (8.0 to 13.0 kg ha-1), K (100 to 125 kg ha-1) were observed with the application of amended steel slag products. No significant change with respect to existing heavy metal concentration viz., Co, Ni, Cd and Pb in soil was observed when supplemented with amended slag products. Interpretation: Steel slag can be transformed favorably for on-farm application to improve wheat yield besides serving as an environmentally sustainable alternate of soil conditioner for the management of degraded soil. Key words: Degraded soil, Heavy metals, Steel slag, Waste management, Wheat

Enhancing tomato growth and soil fertility under salinity stress using halotolerant plant growth-promoting rhizobacteria

Soil salinization is a critical issue that not only hampers the efficiency and sustainability of global agricultural production but also poses significant challenges to the achievement of sustainable development goals across environmental, economic, and social dimensions. Halotolerant plant growth-promoting rhizobacteria (HPGPR) have the potential to mitigate abiotic stress, foster plant growth, and bolster the stress resistance capabilities of crops. This study conducted the isolation, identification, and characterization of HPGPR originating from a saline-alkali orchard area in northwest China. The efficacy of the isolated bacterial strains was evaluated through potted plant experiments, assessing the growth of tomato plants under in vitro conditions and under varying salinity stress. Ultimately, the study investigated the influence of these HPGPR on soil physicochemical properties, enzymatic activities, and the structure and composition of the microbial community. Upon isolating 12 bacterial strains, we conducted an in vitro assessment of their salt tolerance, ultimately singling out three robust isolates, which exhibited exceptional salt tolerance. Detailed 16S rRNA gene sequencing and meticulous taxonomic evaluation systematically assigned these isolates to Priestia endophyticus GSCK1 (accession number: OR569048), Bacillus atrophaeus GSCK2 (accession number: OR569061), and Serratia fonticola GSCK6 (accession number: OR569062), respectively. These strains exhibited notable biochemical and plant growth-promoting traits, including enzymatic activities and the production of indole-3-acetic acid. They significantly enhanced plant growth metrics and soil fertilities, particularly strain GSCK6, which also reshaped the soil microbial community, augmenting beneficial microbe abundance. The HPGPR treatment notably improved soil pH, nutrient availability, enzymatic activities, and reduced soil electrical conductivity, underscoring their potential in agricultural resilience against salinity. The eco-friendly salt stress mitigation strategy of HPGPR not only enhances soil quality and promotes plant growth by regulating the composition and function of microbial communities, but also provides a novel solution for global agricultural production. This approach is conducive to increasing crop yield and quality, reducing the limitations of saline-alkali land on agricultural production, and promoting food security and sustainable agricultural development.

Terra Preta production from Ghanaian and Zambian soils using domestic wastes

Quests for productive soils to close yield gaps call for innovative strategies. This study tested an off-site formation of the Amazonian Terra Preta (TP) in a potential modern analogon under coastal savannah climatic conditions of Ghana. Four Ghanaian and two Zambian soils; two types of biochar (i.e., rice husk biochar and charcoal residues); domestic wastes (i.e., kitchen leftovers, animal manures, human urine, and kitchen ash) were mixed with the soils wetted to 100% water holding capacity, and incubated under aerobic conditions for nine months. Indicators of the TP include total carbon (C), pH, base saturation, basic cations, and plant-available P, which were measured using standard methods of soil analysis. The TP formation enhanced soil pH by 0.02 to 2.9, ranging from pH 7.2 to 8.2, with charcoal residues having the highest effect on pH. The modern TP was characterized by relatively high total C, pH, K, Ca, Mg, Na, base saturation, and plant-available P. These properties reflect unique interactions between the chars, wastes, and soils, suggesting the potential for on-site TP formation. It calls for further studies, commitment, and perseverance in their formation in the future.

Remediation of PBDE-contaminated soil using biochar-based bacterial consortium QY2Y

Biochar-immobilized microbial technologies hold substantial promise for the remediation of environmental contaminants. However, the understanding of remediation efficiency and the operation of microbial consortia in complex soil environments using biochar as a carrier remains limited. In this study, we explored the impacts of biochar combined with bacterial consortium QY2Y (consisting of Chitinophaga sp. MH-1, Achromobacter sp. YH-1, Methylobacterium sp. ZY-1, and Sphingomonas sp. GY-1) on BDE-47 dissipation in contaminated soil, as well as its effects on soil-plant systems. The findings indicated that the immobilization of biochar and QY2Y not only stimulated the biodegradation of BDE-47 (61.50%) but also decreased the bioavailability of BDE-47, subsequently reducing the concentration of BDE-47 in the edible portion of rapeseed (Brassica napus L.) by 82.00%. In addition, the combined treatment notably increased soil pH, enhanced the physicochemical properties and nutrient conditions of the soil, and amplified soil dehydrogenase, catalase, urease, and acid phosphatase activities by 58.72%, 69.25%, 54.24%, and 74.74%, respectively. The application of biochar-based QY2Y improved the soil microbial community structure, bolstered the interspecific symbiotic and cooperative relationships, and restructured the keystone taxa. The key species microbes had direct and significant positive effects on BDE-47 degradation, soil nutrients, and soil enzyme activity. This study deepens our understanding of the potential applications of immobilized microbial consortia in treating PBDE-contaminated soils and offers guidance for the management and remediation of contaminated soils.

Effect of Humic Acid Application Methods on Nutrients Availability and Growth and Yield of Okra(ABELMOSCHUS ESCULLANTUS L.)

A field experiment was conducted at the Agricultural Research Station, College of Agriculture, University of Basrah during the growing season of 2021- 2022 to study the effect of adding humic acids either to soil or spraying on plant along with recommended chemical fertilizers(NPK) on availability of N, P, and K and EC and pH of soil as well as growth and yield of okra. The results showed an increase in the availability of N,P and K by adding humic acid to the soil while spraying of humic acid had no clear differences with chemical fertilizers treatments. Addition of humic acid to soil decreased EC while addition as foliar application increase EC of soil. Addition of humic acid along with chemical fertilizers to soil or spraying on plant led to an increase in concentrations of N, P, and K in the leaves and their uptake with superiority of spraying treatment over soil application treatments. Increasing humic acid level spraying on plant from 0.5 to 1.0gL-1 significantly decreased N,P and K concentrations and uptakes. Similar findings were obtained for dry matter and fruits yield. The lower the level of humic acid ,The higher the dry matter and yield. The highest value of okra fruit yield 2791.06 kgha-1 was obtained with treatment involved spraying of 0.5gL-1 humic acid plus full recommended chemical fertilizers.

Effect of Caragana microphylla Lam. on Desertified Grassland Restoration

Background: The restoration of the degraded sandy grasslands in Hulun Buir is crucial for maintaining the local ecological balance and sustainable development. Caragana microphylla Lam., a shrub species widely employed in the restoration of sandy vegetation. It is essential to understand its impact on the understory vegetation and soil properties during this process. Methods: This study employed ANOVA, Pearson correlation, and redundancy analysis to systematically analyze the impact of C. microphylla on the three critical stages of desertified grassland vegetation recovery: semi-fixed dunes, fixed dunes, and sandy grasslands. It provided strategies for the restoration of desertified grassland vegetation and offered additional theoretical evidence for the role of vegetation in promoting the recovery of sandy lands. Results: (1) As the degree of vegetation recovery in desertified grasslands increases, the species richness of understory vegetation, Shannon–Wiener index, community height, and biomass also increase. Both the community height and biomass within shrublands are higher than outside, with species richness within the shrublands being higher than outside during the semi-fixed and fixed-sand land stages. (2) In both the 0~10 cm and 10~20 cm soil layers, soil water content showed an increasing trend, peaking in the sandy grassland stage (1.2%), and was higher within the shrublands than outside. The soil water content at 10~20 cm was higher than in the 0~10 cm layer. In both layers, clay and silt content gradually increased with the degree of vegetation recovery in the sandy land, and higher within the shrublands than outside, while the opposite was true for sand content. (3) In both soil layers, soil organic carbon gradually increased with the degree of vegetation recovery, peaking in the sandy grassland stage (4.12 g·kg−1), and was higher within the shrublands than outside. Total nitrogen increased from the semi-fixed-sand land stage to the fixed-sand land stage, with higher levels within the shrublands than outside at all stages. Soil pH within the shrublands decreased as the degree of vegetation recovery increased. There was no significant change in the total phosphorus content. (4) In both soil layers, soil physicochemical characteristics accounted for 59.6% and 46.9% of the vegetation changes within and outside the shrublands, respectively, with the main influencing factors being the soil particle size, total nitrogen, soil water content, and soil organic carbon. Conclusions: In the process of sandy grassland restoration, C. microphylla facilitates the growth and development of vegetation by enhancing the underlying soil physicochemical properties, specifically regarding the soil particle size distribution, soil water content, soil organic carbon, and total nitrogen.

The Effects of Acid-Modified Biochar and Biomass Power Plant Ash on the Physiochemical Properties and Bacterial Community Structure of Sandy Alkaline Soils in the Ancient Region of the Yellow River

The application of biochar can effectively enhance soil organic matter (SOM) and improve soil structure. Biomass power plant ash (BPPA) is also rich in essential nutrients for plants, with similar carbon content. Considering production cost and agricultural waste recycling, it is beneficial to apply BPPA to improve soil fertility and quality. However, it remains unclear whether its ameliorative effects surpass those of biochar in alkaline soils. In the study, we set up seven pot experiments of faba beans in sandy alkaline soils from the ancient region of the Yellow River, including the controls (CK), different amounts of acid-modified BPPA (A1, A2, A3), and the same amounts of acid-modified biochar (B1, B2, B3), to compare their effects on soil physiochemical properties and bacterial community structure. The results indicate that the application of both biochar and BPPA can improve soil physiochemical properties. At the same dosage, the biochar application outperformed BPPA treatment in terms of soil physical properties such as bulk density (BD), maximum water-holding capacity (FC), and soil capillary porosity (SP2). Conversely, BPPA treatment displayed advantages in chemical properties such as readily oxidizable organic carbon (ROOC), total nitrogen (TN), alkaline nitrogen (AN), available phosphorus (AP), available potassium (AK), and electrical conductivity (EC). All the treatments enhanced the richness and diversity of bacterial communities, increasing the relative abundance of eutrophic groups such as Bacteroidota and Firmicutes while decreasing that of oligotrophic groups like Actinobacteriota. BPPA also increased the relative abundance of Proteobacteria, while the opposite was observed for biochar. Correlation analysis showed that the environmental factors such as soil pH, EC, TN, AK, SOM, and SP2 emerged as primary factors influencing the bacterial community structure of alkaline soils, significantly affecting their diversity and abundance. Among them, SP2 and SOM were the dominant physical and chemical factors, respectively. Overall, the application of both acid-modified BPPA and biochar can enhance the physiochemical properties of sandy alkaline soils, while the application of BPPA is superior for improving soil nutrient content and enhancing bacterial community structure. The study explores the potential mechanisms through which the application of acid-modified BPPA affects soil characteristics and microbial features, providing new insight into developing optimizing fertilization strategies for enhancing soil quality in the ancient region of the Yellow River.