Soil pH Research Articles

Strategic management of nano-fertilizers for sustainable rice yield, grain quality, and soil health

Conventional fertilizers, although widely available, are relatively low in nutrient use efficiency and cause serious environmental concerns like eutrophication, greenhouse gas (GHG) emissions, nitrate poisoning, and soil pollution. With this in mind, a randomized block design (RBD) experiment was conducted in an experimental field taking 10 treatments and 3 replications to investigate the effects of integrated approaches of nano-formulated DAP fertilizer applications on rice growth, yield, and nutrient use efficiency over conventional approaches. The result revealed that plant height, panicle length, number of tillers hill−1, total number of grain panicle−1, and root length were maximum in T10 treatment (50% of the soil test recommended doses (STD) for N and P + seedling root dipping (SRD) with nano DAP at 5 mL L−1 + twice foliar sprays (FS) with nano DAP at 4 mL L−1 at 25 and 45 DAT (date after transplanting). The highest mean grain yields (4.12 and 4.05 Mg ha−1) and nutrient uptake were recorded in the T2 treatment (100% STD), but this was at par with T10 treatment. The highest benefit–cost ratio (2.26) was recorded in T10, which was 3.5% higher than T2. N and P agronomic use efficiency (AUE) ranged from 7.5% to 31.5% and 15% to 63%, and recovery efficiency (RE) ranged from 30% to 94.2% and 11.2% to 90.4%. The highest nutrient use efficiency was recorded with T10, followed by T9, and lowest in T4. Post-harvest soil pH and available N and P were significantly highest in T10. Soil MBC, MBN, MBP, urease, and phosphatase activity were found significantly higher in T2, followed by T10. The integrated application of 50% STD for N and P + SRD with nano DAP at 5 mL L-1 + twice FS with nano DAP at 4 mL L−1 at 25 and 45 DAT application can be a suitable substitute for conventional DAP and urea for rice in climate-smart agriculture as it possibly reduces environmental pollution while undisturbing crop yield over the 100% STD.

Application of composite persulfate oxidation to remediate weathered lubricating oil-contaminated soils: Batch and pilot-scale studies

In this study, two novel composite persulfate (PS) oxidants [base pulverized NaOH composite persulfate (BPS) and metal (iron and manganese) composite persulfate (MPS)] were developed. The feasibility, mechanisms, and optimal conditions for remediating weathered lubricating oil (WLO)-contaminated soils using composite PS oxidants were evaluated. BPS was prepared by blending PS and NaOH powders (molar ratio = 1:0.3), while MPS was prepared by mixing PS, FeCl2, and KMnO4 at a molar ratio of 1:0.3:0.05 for PS:Fe:Mn. The oxidation of rhodamine B (RhB) dye using BPS and MPS followed second-order kinetics. MPS process was more effective in organic oxidation, likely due to its electron transfer mechanism. The generation of •SO4- in the BPS process required activation by •OH, potentially leading to more efficient and stable •SO4- generation and subsequent organic chemical oxidation. Radical analyses revealed that •SO4- was present in the pH range of 3–12, with the strongest •OH signal at pH 7–9. Employing hybrid BPS and MPS for WLO-contaminated soil remediation could achieve optimal TPH removal efficiency due to the combined generation of •OH (high reactivity) and •SO4- (stable characteristics). The addition of BPS helped neutralize acidified soils and maintained a higher soil pH (around 6.1). The multi-stage oxidation using the hybrid composite PS oxidants (MPS + BPS) at a 1:1 ratio (w/w) achieved 84 % TPH removal (initial TPH = 7721 mg/kg) after three oxidation stages (5 % w/w oxidant dosage). The composite oxidation process offers a more reactive oxidation potential with an extended oxidant life without causing a substantial pH drop.

Investigating drivers of N2 loss and N2O reducers in paddy soils across China

Denitrification plays a pivotal role in nitrogen (N) cycling in rice paddies, significantly impacting N loss and greenhouse gas emissions. Accurate quantification of net N2 emissions from paddy fields is therefore essential for improving fertilizer N use efficiency. However, challenges in directly measuring gaseous N2 hinder our understanding of microbially-mediated N loss in paddy soils at large scales. In this study, we investigated net N2 loss and its influencing factors in 45 paddy soils across China using membrane inlet mass spectrometry and N2/Ar technique, complemented by microbial community analysis via metagenomics. Potential N2 loss rates varied from 0.41 to 3.58 nmol N g−1 h−1, with no significant regional differences. However, soils from rice-upland rotation (1.72 ± 0.64 nmol N g−1 h−1) and mono-rice cropping systems (1.41 ± 0.53 nmol N g−1 h−1) exhibited higher N2 loss rates compared to double-rice cropping soils (1.13 ± 0.62 nmol N g−1 h−1). Our results revealed a unimodal relationship between soil N2 loss rates and soil pH, with N2O reducers and soil properties primarily regulating regional variations in N2 loss. Significant ecological differentiation was observed within both nosZ Clade I and Clade II, with soil pH emerging as the key factor shaping their community composition. Specifically, in rice-upland rotations, soil moisture and pH significantly influenced nosZ Clade I, while in double-rice cropping systems, soil texture and pH were the main factors affecting nosZ Clade II, thereby driving N2 loss. These findings enhance our understanding of N2 loss dynamics in paddy soil ecosystems, underscoring the critical role of N2O reducers on microbial-derived N2 loss and highlighting the importance of developing strategies to mitigate N2O emissions by balancing N2 loss through the manipulation of N2O-reducing and N2O-producing microbes.

Dry season irrigation promotes nutrient cycling by reorganizing Eucalyptus rhizosphere microbiome

In southern China, seasonal droughts and low soil phosphorus content constrain the productivity of Eucalyptus trees. To understand the rhizosphere microbiome response to the dry season, metagenomic sequencing analysis was used to investigate the 6-year-old Eucalyptus rhizosphere microbiome under four different irrigation and fertilization treatments. The results showed that irrigation and fertilization during the dry season significantly altered the composition of microbiome in the rhizosphere soil of Eucalyptus plantations. The soil physicochemical properties and enzyme activity explained 30.73 % and 29.75 % of the changes in bacterial and fungal community structure in Eucalyptus rhizosphere soil, respectively. Irrigation and fertilization during the dry season significantly altered the physicochemical properties of rhizosphere soil. Compared with the seasonal drought without fertilizer treatment (CK), the dry season irrigation with fertilizer treatment (WF) significantly increased the content of total nitrogen (46.34 %), available nitrogen (37.72 %), available phosphorus (440.9 %), and organic matter (35.34 %). Soil organic matter (OM), pH, and available phosphorus (AP) were key environmental factors influencing the microbial community composition. Moreover, irrigation and fertilization promoted carbon fixation and nitrogen and phosphorus mineralization, increasing soil OM content and the availability of inorganic nitrogen and phosphorus. Meanwhile, compared to the CK, the increase of acid phosphatase (16.81 %), invertase (146.89 %)and urease (59.45 %) in rhizosphere soil under irrigation (W) treatment further proves that dry season irrigation promote the soil carbon, nitrogen and phosphorus cycles. Irrigation and fertilization treatment alleviated the constraints of low phosphorus in southern China's soil, which promoted Eucalyptus productivity. In conclusion, we suggest implementing reasonable irrigation and fertilization strategies in the production practice of Eucalyptus and utilizing microbial resources to improve soil fertility and Eucalyptus productivity.

Thermal desorption technique to speciate mercury in carbonate, silicate, and organic-rich soils

Thermal desorption is a well-assessed technique to speciate mercury (Hg) in soils and sediments. However, the effects related to the different matrices are still not properly assessed. In this study, thermal desorption was applied to Hg-free calcite mixed with Hg standard and soils rich in carbonate and silicate minerals, as well as organic matter. Hg0, HgCl2, HgO, α-HgS, β-HgS and organo-mercuric compounds were recognized, pointing out that the soil matrix operates notable differences in terms of breakdown temperatures of the Hg-compounds and suggesting that the mineralogical composition of soil has to be investigated before applying the thermal desorption technique. Furthermore, the presence of Hg0 was carefully evaluated since, as already observed, it forms Hg2+, which increases mercury mobility in the pedological cover with important consequences for those soils contaminated and located close to decommissioned or active mining areas and/or industrial sites (e.g. chloro-alkali industries). Experimental runs were thus carried out by using carbonate-, silicate- and organic-rich soils doped with liquid Hg. It was observed that Hg0 tends to be oxidized to form Hg+ and then Hg2+ as a function of soil matrix and reaction time. Surprisingly, the oxidation rate is rather fast, since after 42 days the initial content of Hg0 is halved, thus following an exponential decay. This implies that in Hg0-polluted areas, the fate of the resulting Hg2+ can be that to: i) be adsorbed by organic matter and/or Fe–Mn–Al oxides and/or ii) feed shallow aquifers. This study is a further step ahead to understand the behavior of Hg in contaminated soils from industrial and mining areas where liquid Hg is occurring in different soil matrices and may provide useful indications for remediation operations.

Let the dust settle: Impact of enhanced rock weathering on soil biological, physical, and geochemical fertility

Terrestrial enhanced rock weathering (ERW) is a promising carbon dioxide removal technology that consists in applying ground silicate rock such as basalt on agricultural soils. On top of carbon sequestration, ERW has the potential to raise the soil pH and release nutrients, thereby improving soil fertility. Despite these possible co-benefits, concerns such as heavy metal pollution or soil structure damage have also been raised. To our knowledge, these contrasted potential effects of ERW on soil fertility have not yet been simultaneously investigated. This field trial aimed at assessing the impact of ERW on biological, physical, and chemical soil properties in a temperate agricultural context. To do so, three vineyard fields in Switzerland were selected for their distinct geochemical properties and were amended with basaltic rock powder at a dose of 20 tons per hectare (2 kg.m−2). On each field, basaltic rock powder was either applied one year before the sampling campaign, one month before the sampling campaign, or not applied (control) for a total of 27 plots with 9 repetitions of each level. Overall, basaltic rock powder addition had a predominantly positive to neutral effect on soil fertility. Most soil properties showed no significant change either 1 month or 1 year post application. Nevertheless, our study highlighted a significant increase in earthworm abundance (+71 % on average), soil respiration (+50 %) and extractable sodium concentration (+23 %) as early as 1 month post application. The higher soil respiration raises the question of CO2 losses from organic matter mineralization that could limit ERW's efficiency. The increase in sodium raises concerns about a sodification risk potentially damaging soil fertility. These elements now require further investigation before enhanced rock weathering can be considered a viable and secure carbon dioxide removal technology.

Perspective of soil carbon sequestration in Chilean volcanic soils

We analysed a large dataset consisting of 457 soil profiles of Andisols and Ultisols of volcanic origin compared to 60 non-volcanic soils. We hypothesised that soil pH has a greater impact on the development of Al-organomineral complexes in volcanic soils compared to non-volcanic soils, in the latter, the silt and clay fractions play a crucial role. Soil pH >4.5 strongly influenced the formation of Al-organomineral complexes in volcanic soils, while an increase in allophane content led to a decrease in SOC. Ultisols with more crystalline clays, such as halloysite and disordered kaolinite, the pH had a weaker impact and there was no effect on non-volcanic soils. Instead, a positive correlation (R2 = 0.63, p < 0.01) was found between silt and clay and SOC in non-volcanic soils, supporting our second hypothesis. Soil pH played a significant role in the interplay between Al-organomineral complexes and allophane formation, while crystalline mineralogy has a direct effect on SOC levels in non-volcanic soils.

Rare bacterial and fungal taxa respond strongly to combined inorganic and organic fertilization under short-term conditions

Soil microbial communities play a crucial role in driving multiple ecosystem functions. Although numerous studies have investigated the effects of fertilization on the entire soil microbial community, the responses of abundant (relative abundance ≥ 1 % in all samples, or ≥ 1 % in some samples but never < 0.01 % in any samples) and rare (relative abundance < 0.01% in all samples, or < 0.01% in some samples but never≥ 1% in any samples) microbial taxa, as along with their relative contributions to ecosystem functions in agricultural soils under combined organic and inorganic fertilization, have been less explored. Here, a field experiment revealed that rare bacterial and fungal taxa were more sensitive to short-term fertilization than abundant taxa. The combined application of inorganic and organic fertilizers maintained the alpha-diversity of rare bacterial taxa and enhanced the alpha-diversity of rare fungal taxa. The significant impact of fertilization on the bacterial community was primarily induced by alterations in soil pH (decreased from 6.01 to 5.46), total phosphorus (0.32 – 0.37 g/kg), available phosphorus (1.24 – 4.76 mg/kg), and available potassium (41.11 – 58.78 mg/kg), whereas the fungal community was less influenced by fertilization. The dissimilarity of both abundant (Mantel r = 0.38, P = 0.001) and rare (Mantel r = 0.26, P = 0.014) bacterial taxa exhibited positive relationships with ecosystem multifunctionality. Additionally, ecosystem multifunctionality was positively associated with the relative abundance of specific genera and keystone species, particularly rare bacterial taxa (e.g., Melioribacter, Aquisphaera, Sunxiuqinia, Methylobacterium, and Thermosporothrix), the abundant fungal genus Achroiostachys, and rare fungal taxa (e.g., Paraphelidium, Pseudallescheria, Scutellinia, Niesslia, Tilletia, Coprinopsis, Poaceascoma, Entrophospora sp., Acremonium persicinum, Hydropisphaera erubescens, and Rozellomycota sp.) (ρ = 0.52–0.75, P < 0.05). A partial least-squares path model indicated that soil nutrients (path coefficient = 0.83, p = 0.001) and microbial beta-diversity (path coefficient = 0.18, p = 0.049) exerted primary direct and positive effects on ecosystem multifunctionality, with soil nutrients also indirectly influencing ecosystem multifunctionality through microbial beta-diversity. Collectively, these findings underscore the significant response of rare, rather than abundant, microbial taxa and their contributions to ecosystem multifunctionality. This highlights the potential of appropriately combined inorganic and organic fertilizers, which promote rare microbial taxa, to enhance the multifunctionality of agricultural ecosystems.

Modified biochar affects CO2 and N2O emissions from coastal saline soil by altering soil pH and elemental stoichiometry

The application of biochar in degraded farmland improves soil productivity while achieving the recycling of agricultural waste. The collapse of the physical structure of coastal saline soils will greatly reduce the carbon sequestration potential of biochar. Phosphorus- and magnesium-modified biochar greatly improve the stability of biochar, which endows them with the potential to greatly improve the organic carbon pool of coastal saline soil. However, changes in the properties of modified biochar increase the uncertainty of microbial driven CO2 and N2O release by affecting soil chemistry properties. In this study, through laboratory soil microcosmic experiment, we investigated the effects of magnesium-modified biochar (BCMg) and phosphorus-modified biochar (BCP) on CO2 and N2O releases from coastal saline soils, and further uncovered their potential mechanisms. Compared with unapplied biochar (CK) and unmodified biochar (BC) treatment, BCMg reduced both the releases of CO2 and N2O, and BCP decreased N2O release but enhanced CO2 release. pH is the medium through which BCMg affects the release of CO2 and N2O. Specifically, BCMg increased soil pH above 8.5, which reduced the metabolic activity of the microbial community, and the abundance of bacteria directly or indirectly involved in N2O production, thereby decreasing the releases of CO2 and N2O. The amendment of BCP changed soil elemental stoichiometry causing microbial N-limitation. Increasing CO2 release and decreasing N2O release were strategies for microorganisms to cope with N-limitation. These findings suggested that BCMg is superior to BCP in mitigating greenhouse gas emissions, providing a basis for the application of modified biochar to improve the carbon pool and reduce greenhouse gas emissions of coastal saline soil.

Correlation analysis between Radix Pseudostelariae quality and rhizosphere soil factors of Pseudostellaria heterophylla in a cultivation region, China.

Pseudostellaria heterophylla, known for its significant bioactive ingredients, offers potential health benefits. Amounts of bioactive compounds of the tuberous root of cultivated Pseudostellaria heterophylla are sensitive to environmental conditions. We selected 22 sampling sites in Guizhou Province, China, a primary Pseudostellaria heterophylla planting area. We analyzed polysaccharides, water-soluble extractives, total ash and inorganic elements (Fe, Mn, Zn, Mg and Ca) in Radix Pseudostellariae, and pH, organic carbon (OC), available nitrogen (AN), available phosphorus (AP), available potassium (AK) and inorganic elements in the soil. Our study revealed a substantial presence of polysaccharides (85.00-181.00 mg g-1), water-soluble extractives (47.52-57.63%) and total ash (1.87-3.39%) in Radix Pseudostellariae. Polysaccharides and total ash showed no sensitivity to soil pH. Radix Pseudostellariae collected from soil with pH > 7 exhibited slightly higher levels of water-soluble extractives, Mg and Ca than that from soil with pH < 5. Conversely, soil with a pH less than 5 had higher OC, AN, AP and AK contents. Water-soluble extractives in Radix Pseudostellariae were negatively correlated with soil pH but positively correlated with OC and AN. The results imply that the sequestration of soil nutrients over long-term Pseudostellaria heterophylla cultivation could negatively impact the accumulation of some bioactive ingredients in Radix Pseudostellariae. This study has a profound implication for enhancing the quality of Radix Pseudostellariae of artificially cultivated Pseudostellaria heterophylla. © 2024 Society of Chemical Industry.

451 Establishing producer research sites for the development of beef and bison climate-smart agriculture

Abstract Greenhouse gas (GHG) emissions and livestock production are topics that are increasingly intertwined. While livestock production is frequently presented as harmful to the environment, this perception fails to consider the carbon sequestration that takes place in livestock grazing systems and the role that grazing ruminants have in maintaining healthy grassland ecosystems. Grazing lands, which are often unsuited to row crop agriculture, are estimated to account for 25% of the global soil sequestration potential for soil carbon storage. Grazing livestock producers are often overlooked in the GHG reduction conversation, despite over 70% of beef GHG emissions being attributed to the cow-calf sector, which is primarily grazing. Furthermore, there is a relative lack of data surrounding the implementation of climate-smart agriculture practices on grazing operations and a lack of cost-effective methods to measure carbon/GHG sinks and sources on these landscapes. The potential climate benefits are considerable, with nearly 940 million acres of rangelands in the U.S. supporting forage-based livestock production. South Dakota State University recently received funding to support a large-scale climate-smart project focused on grazing beef and bison. For this project, we are utilizing the Cottonwood Field Station that has over 80 yr of historical grazing data, along with six grazing beef and bison ranching operations in the Northern Great Plains. The work on these ranches will focus on measuring and monitoring the impacts of climate-smart NRCS land practices, including cover crops, improved pasture and range seedings, prescribed grazing, and prescribed burning. A significant focus will be extensive, annual soil sampling across these operations to continuously monitor changes in soil organic carbon, bulk density, texture, pH, and soil microbiome community profiles. Each operation will have GreenFeed methane pasture units deployed for 5 yr to monitor changes in beef cattle and bison methane emissions in response to climate-smart practice adoption. We are also assessing biodiversity pre and post climate-smart practice adoption, as biodiversity improvements may be one of the most overlooked and yet most important responses to climate-smart land practice implementation. Over the duration of this project, a large-scale, comprehensive data collection will be achieved and used to refine GHG and carbon sequestration estimates associated with range livestock systems. Data resulting from this project will be used to inform research protocols and prediction models, fill knowledge gaps, and shape science-based discussions and marketing strategies for climate-smart agricultural commodities.

Invasive Amaranthus spp. for heavy metal phytoremediation: Investigations of cadmium and lead accumulation and soil microbial community in three zinc mining areas

Amaranthus spp. are a group of strongly invasive and vigorous plants, and heavy metal phytoremediation using alien invasive Amaranthus spp. has been a popular research topic. In this study, the bioconcentration factor (BCF) and translocation factor (TF) of Amaranthus spp. were evaluated, focusing on the accumulation potential of cadmium (Cd) and lead (Pb) by plants from three different zinc mining areas, namely Huayuan (HYX), Yueyang (LYX), and Liuyang (LYX). The HYX area has the most severe Cd contamination, while the LYX area has the most apparent Pb contamination. The results showed that Amaranthus spp. had a strong Cd and Pb enrichment capacity in low-polluted areas. To elucidate the underlying mechanisms, we used high-throughput sequencing of 16S rRNA and internal transcribed spacer (ITS) regions to analyze rhizosphere bacterial and fungal communities in three areas. The results showed significant differences in the structure, function, and composition of microbial communities and complex interactions between plants and their microbes. The correlation analysis revealed that some key microorganisms (e.g., Amycolatopsis, Bryobacterium, Sphingomonas, Flavobacterium, Agaricus, Nigrospora, Humicola) could regulate several soil factors such as soil pH, organic matter (OM), available nitrogen (AN), and available phosphorus (AP) to affect the heavy metal enrichment capacity of plants. Notably, some enzymes (e.g., P-type ATPases, Cysteine synthase, Catalase, Acid phosphatase) and genes (e.g., ZIP gene family, and ArsR, MerR, Fur, NikR transcription regulators) have been found to be involved in promoting Cd and Pb accumulation in Amaranthus spp. This study can provide new ideas for managing heavy metal-contaminated soils and new ways for the ecological resource utilization of invasive plants in phytoremediation.

Effect of Ni and Fe Co-Application on the Soybean Crop Grown in Nickel and Iron Deficient Soils of Mirzapur District

ABSTRACT Considering the importance of nickel and iron nutrition for the soybean crop, their deficiency inhibits the yield drastically specially in the area where soybean crop is dominant. To encounter this problem, a pot experiment was conducted in glass house on low nickel and iron soil in Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, during 2019–20 and 2021–22. The study was carried out to investigate the effect of Ni (nickel) and Fe (iron) on the post-harvest soil parameters, growth, yield, nutrient uptake and nutrient content of soybean crop. There were 10 treatments with two levels of Ni (5 and 10 mg kg −1) and Fe (10 and 20 mg kg−1) with recommended dosage of fertilizers nitrogen, phosphorus, potassium (8.93, 35.71, and 17.86 mg kg−1) applied to all treatments except control. The result of the experiment revealed that the co-application of nickel and iron@10 mg kg−1 and 20 mg kg−1 (RDF + Ni10Fe20), resulted in the increase in plant height, greeness index, no of seed per pod, no of pod per plant, seed yield, and stover yield. Similar, findings for the post- harvest soil parameter indicated that there was increase in pH, electrical conductivity, and organic carbon content of soil. DTPA (Diethylenetriaminepentaacetic acid) extractable Ni, Fe, Zn, and Cu, also found highest in treatment where nickel and iron@10 mg kg−1 and 20 mg kg−1 (RDF + Ni10Fe20) were applied in soil, but in case of DTPA extractable Mn, the highest amount was found in treatment where nickel and iron@10 mg kg−1 and 10 mg kg−1 (RDF + Ni10Fe10) was applied in soil. The soil microbial biomass carbon and urease activity was also found highest in the treatment where nickel and iron@10 and 20 mg kg−1 was applied in soil. The minimum plant height, greeness index, no of seed per pod, no of pod per plant, seed, and stover yield was recorded in treatment where only RDF(T1) was applied. Similar, result recorded for the post-harvest soil parameters. So, overall findings of the pot experiment revealed that the conjoint application of nickel and iron has resulted in better yield of soybean crop.

Effects of long-term continuous cultivation on the structure and function of soil bacterial and fungal communities of Fritillaria Cirrhosa on the Qinghai-Tibetan Plateau.

Fritillaria cirrhosa, an endangered medicinal plant in the Qinghai-Tibet Plateau, is facing resource scarcity. Artificial cultivation has been employed to address this issue, but problems related to continuous cultivation hinder successful transplantation. Imbalanced microbial communities are considered a potential cause, yet the overall changes in the microbial community under continuous cropping systems remain poorly understood. Here, we investigated the effects of varying durations of continuous cropping on the bacterial and fungal communities, as well as enzymatic activities, in the rhizospheric soil of F. cirrhosa. Our findings revealed that continuous cropping of F. cirrhosa resulted in soil acidification, nutrient imbalances, and increased enzyme activity. Specifically, after 10 years of continuous cropping, there was a notable shift in the abundance and diversity (e.g., Chao1 index) of soil bacteria and fungi. Moreover, microbial composition analyses revealed a significant accumulation of harmful microorganisms associated with soil-borne diseases (e.g., Luteimonas, Parastagonospora, Pseudogymnoascus) in successively cropped soils, in contrast to the significant reduction of beneficial microorganisms (e.g., Sphingomonas, Lysobacter, Cladosporium) that promote plant growth and development and protect against diseases such as Fusarium sp.These changes led to decreased connectivity and stability within the soil microbial community. Structural equation modeling and redundancy analysis revealed that alkaline hydrolytic nitrogen and available phosphorus directly influenced soil pH, which was identified as the primary driver of soil microbial community changes and subsequently contributed to soil health deterioration. Overall, our results highlight that soil acidification and imbalanced rhizosphere microbial communities are the primary challenges associated with continuous cropping of F. cirrhosa. These findings establish a theoretical foundation for standardized cultivation practices of F. cirrhosa and the bioremediation of continuously cultivated soils.

Agronomic potential of maize stover biochar under cowpea–maize sequential cropping in Northern Uganda

Biochar is a nature-based solution for sustainable agriculture but its potential adoption in some parts of sub-Saharan Africa is still minimal. In this study, we evaluated the agronomic potential of maize stover biochar in cowpea-maize sequential cropping in Uganda under field conditions. The treatments included; the common farmer practice of no inorganic fertilizer and no biochar (CTR), inorganic fertilizer (F), 10 t ha−1 biochar (B10), 40 t ha−1 biochar (B40), 10 t ha−1 biochar + inorganic Fertilizer (FB10), and 40 t ha−1 biochar + inorganic Fertilizer (FB40), arranged in a randomized complete block design (RCBD) with three replications. The results showed that cowpea seed yield was not significantly affected by biochar and fertilizer application but the haulm yield was significantly improved only in FB40 treatment. Maize grain and stover yield was significantly improved only in the FB40 treatment but biochar showed a high potential to also improve yield even without inorganic fertilizer. The potential for biochar to improve maize yield either in the presence or absence of fertilizers could be attributed to the residual soil fertility from cowpeas. In both seasons, biochar significantly improved soil pH, EC, SOC, total N, available P, exchangeable K and Ca, irrespective of fertilizer application. However, exchangeable Mg did not significantly vary among the treatments. This study further revealed that in cowpea-maize rotation, optimum yield could also be possible with sole biochar application. Therefore, instead of burning the maize stovers after harvest, farmers should convert the residues into biochar and return it to the soil so as to achieve sustainable food systems.Graphical

Adsorption-desorption mechanisms and migration behavior of fluchlordiniliprole in four different soils under varied conditions

Utilizing infrared spectroscopy coupled with batch equilibrium methods, the adsorption and desorption characteristics of the novel Insecticide fluchlordiniliprole were assessed in four different soil types. It was found that fluchlordiniliprole’s adsorption and desorption in these soils were consistent with the Freundlich isotherm, exhibiting adsorption capacities (KF-ads) ranging from 8.436 to 36.269. Temperature fluctuations, encompassing both high and low extremes, impaired the ability of soil to adsorb fluchlordiniliprole. In addition, adsorption dynamics were modulated by several other factors, including soil pH, ionic strength, amendments (e.g., biochar and humic substances), and the presence of various surfactants and microplastics. Although capable of leaching, fluchlordiniliprole exhibited weak mobility in most soils. Therefore, it appears that fluchlordiniliprole seems to pose a threat to surface soil and aquatic biota, but a minimal threat to groundwater. Synopsis StatementThis research examines the dynamics of fluchlordiniliprole in soil, an will aid in maintaining ecological safety and managing agricultural pesticides. The study's comprehensive analysis of adsorption, desorption, and soil migration patterns significantly contributes to our understanding of pesticide interactions with diverse soil types. The results of this study will enable the development of environmentally responsible agricultural practices.

PH Nonlinearly Dominates Soil Bacterial Community Assembly along an Altitudinal Gradient in Oak-Dominant Forests.

Soil bacteria, the predominant microbiota in soil, are subject to the law of minimum and the law of tolerance, but the assembly patterns of soil bacteria in response to environmental factors remain far from clear. Here, we took advantage of an altitudinal gradient (1020-1770 asl) in oak-dominant forests and assessed whether soil bacteria linearly or nonlinearly respond to environmental properties through the changes in the community diversity and composition. We found that soil bacteria decreased with increasing altitude in terms of the species richness and phylogenetic structure, while they were unchanged with increasing altitude in terms of community composition. The species richness was nonlinearly affected by the soil pH (19.9%), C:N ratio (14.3%), SOC (11.4%), and silt + clay content (9.9%). Specifically, the species richness peaked at a pH of 5.5-6.5, and an SOC of 25-50 g kg-1, and it showed abrupt decreases and increases at a C:N ratio of 14.5 and a silt + clay content of 70%. The community composition was significantly affected by the soil pH (28.2%), then by the SOC (3.6%), available phosphorus (1.0%), and silt + clay content (0.5%), and it showed less turnovers at a pH of 6.0, SOC of 50 g kg-1, and available phosphorus > 3.0 g kg-1. These findings imply that environmental filtering processes nonlinearly shape bacterial communities.

Effects of mixed biocrusts on soil nutrients and bacterial community structure: a case study from Hilly Loess Plateau, China

The ecological function of biological crusts in arid and semi-arid areas is of great importance. Bacteria, as a crucial microbial group in biological crusts, play a key role in the formation, nutrient cycling, and regulation of these crusts. However, the succession of biological crusts and the diversity of bacterial communities, along with key environmental factors in the Loess Plateau’s hilly and gully areas, remain unclear. This study investigated soil bacterial abundance and diversity in bare soil (BS), alga-lichen mixed crust (MC), and alga-lichen mixed crust subsoil (MCS) using high-throughput sequencing methods. It explored the relationship between the bacterial community in biological crusts and key environmental factors. The results indicated that the Chao1, Shannon index, and phylogenetic diversity of bacteria significantly increased with the succession of biological crusts. There were notable differences in the community composition and structure of bacteria at different stages of crust development, with Rubrobacteria and Cyanobacteriia dominating in MCS. Effective phosphorus, available potassium, nitrogen, pH, and total organic carbon were identified as key environmental factors affecting soil bacterial communities. In summary, the succession of biological crusts alters soil physicochemical characteristics and creates different ecological niches for bacterial communities. Soil nutrients and pH play a crucial role in the selection of bacterial species and the shaping of bacterial communities in the Loess Plateau’s hilly and gully areas.

Effect of fortified pine needle biochar on green fodder yield, nutrient uptake of oat and soil properties

In the Himalayan region, the low green fodder supply to livestock necessitates agronomic interventions, including the use of fortified pine needle biochar, a viable option for slow-release nutrients, to enhance fodder oat production, improve soil health, and safely manage the abundant pine needles that pose a fire risk. In a greenhouse study, the effect of different levels of pine needle biochar (0, 0.02, 0.04, 0.11 and 0.22 % of soil weight) fortified with 0, 75 and 100 % of the recommended dose of fertiliser (RDF, 80 kg N: 60 kg P2O5: 40 kg K2O ha−1) was examined on the green fodder yield, nutrient concentration and uptake of oat, and general soil properties and extractable nutrients. Application of 0.02 % biochar fortified with 75 % RDF gave a fodder yield (56.9 g pot−1) which was 46.6 percent higher than the control (38.8 g pot−1) but statistically similar to the yield with 100 % RDF alone (54.9 g pot−1). The highest fodder yield (72.0 g pot−1) was recorded with 0.22 % biochar fortified with 100 % RDF. Higher doses of biochar without fortification decreased the N concentration but increased the K concentration and brought no significant change in P concentration in the fodder oat. Biochar fortified with 75 and 100 % RDF enhanced the uptake of N, P, and K by fodder oat. The moderate levels of biochar (0.02 and 0.04 %) fortified with 75 % RDF and all levels of biochar fortified with 100 % RDF decreased soil pH while higher levels of biochar fortified with 100 % RDF increased soil EC and organic C. The treatments receiving the highest level of biochar addition (0.22 %) with 0 % RDF, 0.11 and 0.22 % biochar fortified with 75 % RDF and all levels of biochar fortified with 100 % RDF significantly increased soil extractable N, P and K after crop harvest except for K under 0.22 % biochar fortified with 100 % RDF. Pine needle biochar fortified with RDF helped to achieve higher oat fodder production and maintain soil fertility than solo application of biochar or chemical fertilisers.

Impact of Dolomite Liming on Ammonia-Oxidizing Microbial Populations and Soil Biochemistry in Acidic Rice Paddy Soils

Background and Aims: Over the last few decades, rampant nitrogen fertilization has exacerbated soil acidification in agricultural ecosystems. To counteract this, liming has become an essential technique for rehabilitating fertility in acid-degraded agricultural soils. Our research aimed to shed light on the response of ammonia oxidizers to liming in acidic soils within a controlled rice paddy experiment. We conducted a pot experiment with rice, featuring three different treatments: a control with only soil, a low dolomite dose (LD), and a high dolomite dose (HD). Various soil properties were investigated throughout the study. Under flooding, soil pH values rose across the treatments, from 5.4 in the control to 6.8 in HD. Ammonium and nitrate levels peaked in the HD treatment, reaching 30 and 22 mg kg−1, respectively. Similarly, dissolved organic carbon and microbial biomass carbon surged at mid-season aeration, hitting highs of 101 and 30 mg kg−1, respectively, in the HD treatment. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) were responsive to dolomite-lime application, with distinct reactions; AOB abundance and potential nitrification rates were positively affected by higher lime doses, whereas AOA numbers decreased over time and with dolomite application. Additionally, soil enzymes such as urease, catalase, invertase, phenol oxidase, and phosphatase also increased progressively, mirroring the rise in soil pH. This study identified increased soil pH as the critical factor influencing various soil parameters, especially the balance between AOA and AOB populations. Both AOB and AOA were sensitive to liming; AOA decreased while liming stimulated AOB abundance.