Soil Phosphorus Content Research Articles

Long-Term Effects of Nitrogen Sources on Yields, Nitrogen Use Efficiencies, and Soil of Tilled and Irrigated Corn

Although corn is the most important and nitrogen (N)-fertilized crop, there is a lack of long-term data on the effects of organic and inorganic N fertilizers on the N balance and losses for corn systems under different tillage approaches. From 2012 to 2023, we assessed the effects of the N source on the grain yields from cultivated continuous corn receiving irrigation at a site with minimal erosion in Fort Collins, Colorado, USA, and compared these effects to no-till (NT) and strip till (ST) systems receiving inorganic N. An N balance accounting for N and carbon (C) sequestration found a system nitrogen use efficiency (NUESys) for organic N fertilizer (manure) with a tillage of 86.6%, which was higher than the NUESys of 62.6% with inorganic N fertilizer (enhanced efficiency fertilizer, EEF). Conventional tillage with manure use is a good management practice that contributed to higher grain yields (2 of 11 years), C sequestration (p < 0.05), soil organic N content (p < 0.05), and soil phosphorus (P) content than inorganic N fertilizer with tillage (p < 0.05). The tilled systems, whether receiving organic or inorganic N fertilizer, had higher yields and grain N content than the NT and ST systems receiving inorganic N fertilizer (p < 0.05). The grain production of the cultivated system receiving organic N fertilizer did not decrease with time, while the yields of the cultivated system receiving inorganic N fertilizer decreased with time (p < 0.05), suggesting that cultivated systems receiving organic N fertilizer may be more sustainable and better able to adapt to a changing climate. Additionally, a combination of manure (30% of N input) with EEF (70% of N input) contributed to a synergistic effect that increased the agronomic productivity (harvested grain yields).

Effects of Different Wheat Varieties on Soil Bacterial and Fungal Communities

ABSTRACTThe diversity and stability of soil microbial communities are indispensable components for maintaining the functions and services of agricultural ecosystems and play crucial roles in wheat production. However, the effects of different wheat varieties on soil microbial diversity, network complexity, stability, and assembly mechanisms remain largely unexplored. To bridge this research gap, we conducted field experiments in Chuzhou, China, to study the yield and soil microbial community composition of six different wheat varieties. The soil bacterial and fungal communities were investigated using high‐throughput sequencing of the 16S rRNA and ITS gene regions. Our findings indicated that, compared to common wheat, high‐yielding and disease‐resistant (HD) wheat increased both bacterial and fungal α‐diversity by regulating soil nitrogen and phosphorus concentrations, significantly affecting community structure (Adonis, p < 0.001). HD wheat significantly altered the co‐occurrence network patterns of soil microbial communities. Network analyses revealed that HD wheat increased the complexity of fungal networks while exhibiting the opposite trend for bacterial networks. However, both the bacterial and fungal networks demonstrated increased stability. Furthermore, HD wheat may increase microbial migration rates, influencing assembly processes by promoting stochastic processes in bacterial and fungal communities. Overall, this study provides valuable insights into the ecological functions and driving factors of soil microbes, offering information for the development of ecological management strategies to achieve sustainable wheat cultivation and improve soil quality. Furthermore, HD wheat significantly modified the co‐occurrence network patterns of the soil microbial communities. Network analysis revealed increased fungal network complexity in HD wheat, whereas bacterial networks showed the opposite trend. However, both the bacterial and fungal networks exhibited enhanced stability. Additionally, HD wheat likely increased microbial migration rates, influencing assembly processes by promoting stochastic processes in both bacterial and fungal communities. Overall, this study provides valuable insights into the ecological functions and driving factors of soil microbes, providing information for the development of ecological management strategies to achieve sustainable wheat cultivation and improve soil quality.

Reseeding increased plant biomass production and soil fertility, but not plant species diversity in degraded grasslands in China

Reseeding is a primary measure to restore degraded grasslands. Numerous studies have conducted experiments to investigate how the properties of grassland ecosystems respond to reseeding in China. However, there is a lack of summary of the results of these studies. Here, we conducted a hierarchical random-effects meta-analysis on the effects of reseeding on plant, soil, and microbial properties. We collected 19 variables, including plant biomass, species diversity and richness, soil organic carbon content, soil total and available nutrients, soil water content, soil microbial biomass and diversity, and enzyme activity, from a dataset of 1363 paired observations (degraded vs. reseeded) from 75 publications. The results showed that reseeding increased aboveground and belowground plant biomass by 70.2% and 68.0% on average, respectively. Reseeding increased soil organic carbon, phosphorus, and potassium contents, but did not affect soil nitrogen levels. Reseeding increased soil microbial nitrogen under conditions of tillage and fertilization. Reseeding age was found to have a positive correlation with species richness, while planting type, fertilization, and tillage did not have a significant impact on the species richness and diversity. Under the treatments of fertilization, non-tillage, and mix-planting, the response ratio of aboveground biomass to reseeding was positively correlated with the response ratio of species diversity to reseeding. Our results concluded that current reseeding practices can significantly improve plant biomass production and soil fertility but have minor effects on plant species diversity. These findings indicate that the preservation of biodiversity should receive greater attention from both researchers and practitioners in grassland remediation in China.

Analysis of the composition and function of rhizosphere microbial communities in plants with tobacco bacterial wilt disease and healthy plants

ABSTRACT To explore the factors influencing the occurrence of bacterial wilt, the differences in the physicochemical properties, microbial community composition and function between rhizosphere soil of tobacco plants with bacterial wilt and healthy plants in the tobacco planting area of Fuzhou City, Jiangxi Province were analyzed and compared. The results showed that the rhizosphere soil of diseased tobacco exhibited significantly reduced levels of exchangeable potassium, water-soluble potassium, nitrate nitrogen, total nitrogen and pH, in comparison to the rhizosphere soil of healthy plants. Conversely, the available phosphorus content of the rhizosphere soil of diseased tobacco was significantly increased. The amount of Ralstonia solanacearum in soil was negatively correlated with pH, nitrate nitrogen and total nitrogen, and positively correlated with exchangeable potassium and water-soluble potassium. A total of 43 genera were significantly different between the two groups of rhizosphere soil, of which 24 genera were enriched in the rhizosphere of healthy plants, including Ideonella , Rhizophagus , Rhizobacter , Altererythrobacter and Ignavibacterium associated with plant disease resistance, Thermodesulfovibrio , Syntrophorhabdus , Syntrophus , Chlorobium , Hydrogenophaga and Limnohabitans associated with soil sulfur metabolism, as well as Ignavibacterium , Ideonella , Derxia and Azohydromonas associated with soil nitrogen cycling. Kyoto Encyclopedia of Genes and Genomes functional analysis of the unigenes obtained by metagenomic sequencing also showed that the differential unigenes were significantly enriched in the sulfur metabolism pathway. In addition, the rhizosphere soil of diseased tobacco plants exhibited a higher abundance of antibiotic-producing actinomycetes and an increased load of antibiotic resistance genes compared to that of healthy plants. In general, lower pH value, less content of nitrate nitrogen and total nitrogen, and more content of exchangeable potassium and water-soluble potassium could contribute to onset of bacterial wilt. Twenty-four genera, including Ideonella and Rhizophagus , may construct a healthy microecological network in the rhizosphere of tobacco plants. All these factors may interact with each other to control the development of bacterial wilt. This complicated interaction network needs to be explored further. IMPORTANCE Previous studies have mainly focused on the differences in microbial species composition between healthy and diseased soils, but the differences in microbial community functions between two types of soil have not been well characterized. In this study, soil samples in diseased and healthy plant rhizospheres were collected for physicochemical property testing and metagenomic sequencing. We focused on analyzing the differences in physicochemical properties and microbial community functions between these soils, as well as the correlation between these factors and pathogen content. The results of this study provide a theoretical basis for further understanding the occurrence of tobacco bacterial wilt in the field.

Effects of Microbial Organic Fertilizer, Microbial Inoculant, and Quicklime on Soil Microbial Community Composition in Pepper (Capsicum annuum L.) Continuous Cropping System

The additions of microbial organic fertilizer (MOF), a microbial inoculant (MI), and quicklime (Q) are considered to be sustainable practices to restore land that has been damaged by continuous cropping of pepper (Capsicum annuum L.). However, the combined effects of these three additives on pepper yield, soil chemical properties, and soil microbial communities were unclear. The experimental design consists of 13 treatment groups: the untreated soil (control); soil amended solely with three treatments for each of MOF (1875–5625 kg ha−1), MI (150–450 mL plant−1), and Q (1500–4500 kg ha−1); and soil amended with combinations of MOF, MI, and Q at three comparable concentrations. A significant increase in pepper fruit diameter, length, yield, and soil available nitrogen, phosphorus, and potassium contents occurs upon exclusive and combined applications of MOF, MI, and Q. Pepper yield was greatest (29.89% more than control values) in the combined treatment with concentrations of 1875 kg ha−1 MOF, 150 mL plant−1 MI, and 1500 kg ha−1 Q. The application of Q increased soil pH and reduced soil–fungal richness. The application of MOF, MI, and Q increased the relative abundance of bacterial genera and the complexity of bacterial and fungal co-occurrence networks compared with control levels. The combined application of MOF, MI, and Q resulted in the greatest microbial network complexity. A Mantel test revealed the key role of soil available nitrogen content and bacterial diversity in the regulation of pepper growth and yield. We conclude that the combined application of MOF, MI, and Q improves soil nutrient availability and modifies soil microbial community composition, significantly promoting plant growth and pepper yield during continuous cultivation.

Biofertilizers: A sustainable strategy for enhancing physical, chemical, and biological properties of soil

A biofertilizer is a biologically derived substance that can enhance soil fertility. It is beneficial for enhancing soil fertility by introducing microorganisms that produce organic nutrients and perhaps decreasing plant illnesses. An extensive review was done to examine the efficacy of several biofertilizers in improving soil properties, including their physical, chemical, and biological characteristics. The secondary data and material for the article were gathered from a variety of sources, including government reports, published research papers, reports from various organizations, and pertinent websites that were examined and their conclusions presented. Although biofertilizers have proven to be a very sustainable method for improving soil quality and increasing crop output, there is a lack of extensive research on their effects on soil’s physical, chemical, and biological aspects. This study aims to offer a comprehensive understanding of various biofertilizers and their effects. This investigation indicated that biofertilizers such as Nitrogen-fixing bacteria, phosphate solubilizers, and potassium solubilizers help to increase NPK content in the soil leading to an increase in the productivity of soil. Moreover, biofertilizers help to enhance soil physical properties (soil bulk density, soil moisture, soil temperature, and soil color), chemical properties (soil pH, soil nitrogen content, soil phosphorus content, soil potassium content, and soil organic carbon content), and chemical properties (population of bacteria, fungi, and actinomycetes). Overall, by overcoming the challenges with biofertilizers in agriculture, we can attain agricultural sustainability.

Amending clayey and sandy soils with nano - bio phosphorous for regulating tomato growth, biochemical, and physiological characteristics

Phosphorus is a critical nutrient that significantly enhances tomato production, so maintaining an adequate level of phosphorus plays an essential role in enhancing the growth of tomato by being present in the soil. This study assessed the impact of soil texture and phosphorus content on tomato plant properties using a factorial, complete, randomized design with four replications. Treatments included clayey and sandy soils with varying phosphorus sources: non-phosphorus (P0), calcium phosphate (CaP1 and CaP2), and nano-hydroxyapatite (PN1 and PN2), where 1 indicates a concentration of 0.12 g and 2 indicates a concentration of 0.23 g per 5-kilogram pot of fertilizer. Results indicated that treatments significantly influenced yield parameters such as average fruit weight, juice content, antioxidant activity, and fruit volume. In the clayey soil, CaP2 treatment had a superior effect on yield, average fruit weight, and shoot fresh weight. In comparison with sandy conditions, CaP2 produced a 50% increase in fruit number, 29% increase in average fruit weight, and 91% increase in fruit yield. The treatments then impacted the shoot fresh weight and root length, while the phosphorus concentration appeared to be more dependent on soil type than on phosphorus sources. Similar to the CaP1 and CaP2 treatments, the PN1 treatment in clay soil also resulted in the highest fresh and dry weights of tomato shoots when compared with the control group. Generally, the findings from this study suggest that the use of CaP2 can serve as a reliable method to improve the growth, yield, and fruit quality of tomatoes, especially in clayey soil environments. However, nano-based phosphorous sources need to be tested more to see if they can improve tomato performance in a range of soil conditions. Also, further research should look into the long-term effects of phosphorous interventions on soil health and sustainability.

Maize-Straw Biochar Enhances Soil Properties and Grain Yield of Foxtail Millet in a Newly Reclaimed Land

Large-scale land reclamation has become common in northwestern China; however, low soil fertility and poor soil water-holding capacity limit agricultural production on these reclaimed lands, requiring increased fertilizer and irrigation inputs. Biochar, produced from agricultural waste, has shown potential in improving soil quality and water-holding capacity. In this two-year field study (2021 and 2022), we investigated the effects of biochar produced from maize straw on soil properties and grain yield of foxtail millet grown on newly reclaimed land. Three biochar treatments (3000, 4500, and 6000 kg ha−1) were compared to a control (CK) with no biochar application. Biochar application resulted in increased soil organic matter, total phosphorus, total nitrogen, soil enzyme activity, and soil organic acid content. It also significantly decreased soil pH and bulk density. Compared with the CK, biochar increased available nitrogen from 29.7% to 108% in 2021 and 37.0% to 88.4% in 2022. Similarly, biochar increased available phosphorus from 64.7% to 143% in 2021 and 41.9% to 96.5% in 2022. Grain yields ranged from 3092 to 4753 kg ha−1. Biochar treatments increased grain yield compared to the CK, ranging from 12.2% to 24.6% in 2021 and 27.1% to 53.7% in 2022. Correlation analysis revealed that soil pH was negatively related to soil oxalic acid content, phosphorus content, and sucrase activity. Available nitrogen and phosphorus contents were negatively related to soil bulk density and positively related to catalase activity. Soil water content was negatively correlated with soil bulk density and positively correlated with organic matter. In conclusion, biochar improved the rhizosphere soil pH and the effectiveness of soil fertility in the newly reclaimed soil, resulting in an enhanced grain yield of foxtail millet.

The role of nitrogen and iron biogeochemical cycles in the production and export of dissolved organic matter in agricultural headwater catchments

Abstract. To better understand the seasonal variations in environmental conditions regulating dissolved organic matter (DOM) export in agricultural headwater catchments, we combined the monitoring of nitrate, iron, soluble phosphorus, and DOM concentration (as dissolved organic carbon; DOC) and composition (3D fluorescence) in soil and stream waters at regular intervals during 1 hydrological year. We installed 17 zero-tension lysimeters in organic-rich top soil horizons (15 cm below the surface) in the riparian area of a well-monitored agricultural catchment in French Brittany and collected them at a fortnightly frequency from October 2022 to June 2023. We observed a large increase in DOC concentrations in soil waters during the high-flow period linked to the establishment of Fe-reducing conditions and the subsequent release of DOM. We also noted that the timing and the spatial variability in Fe(II) biodissolution in soils was regulated by nitrate from agricultural origin and the heterogeneity of water flow paths at the hillslope scale. Contrary to our current understanding of DOM export in headwater catchments, these results lead us to consider the winter high-flow period as an active phase of both DOM production and export.

Soil Analysis by Mobile Multinuclear NMR: Quantification of Phosphorus, Aluminum, and Sodium.

Soil analyses are essential to ensure economically and environmentally sustainable crop production while maintaining the soil fertile for future use. Unfortunately, common soil analyses may be highly demanding in terms of time, chemicals, and costs. This applies, in particular, when total quantities of elements are desired. As an easy and fast alternative without consumption of chemicals, we here present mobile 31P, 27Al, 23Na, and 1H NMR for quantification of phosphorus, aluminum, and sodium contents in soil. This enables accurate on-site analysis and is suitable for direct measurement on fresh, undried soil samples since the water content is quantified as well. For demonstration, 40 various Danish agricultural soil samples were analyzed using a mobile NMR sensor, and the results were compared with external laboratory analyses for P, Al, and Na. The laboratory analyses were conducted with ICP-OES after four-acid digestion, which additionally were compared with aqua regia digestion, showing inadequacies in the performance of the latter. Good agreement between NMR and laboratory analyses (correlation coefficients 0.91 for P, 0.98 for Al, and 0.90 for Na, in the concentration ranges 250-1200 ppm P, 1.4-5% Al, and 0.3-1% Na) were obtained with high accuracy using NMR measuring times of 20 min to 1 h for P, 4-12 min for Al, and 6-20 min for Na. Additionally, the NMR measurements provide information on the amount of P associated with paramagnetic centers (e.g., Fe3+). Good correlations were also observed to other parameters such as the clay content, which is predictable from the intensity of the more fast-relaxing of three 27Al NMR components.

Relationship between root system-soil C:N:P and soil microbial diversity at different evolutionary stages of Caragana tibetica scrub in arid desert grassland, Northern China.

Scrub root systems play a crucial role in preventing soil erosion and nutrient loss. However, the effects of the root system configuration on soil nutrient dynamics and microbial changes at various evolutionary stages remain poorly understood. In this study, we investigated the relationship between soil physical and chemical properties and the diversity of bacteria and fungi throughout the evolutionary stages of the scrub root systems. This was achieved through a combination of whole-root excavation and root tracing techniques. The results indicated that root diameter was the main factor contributing to the continuous increase in carbon (C): phosphorus (P) and nitrogen (N): P ratios as the scrub sand pile developed. The soil organic carbon (SOC), total soil nitrogen (TN), and total soil phosphorus (TP) contents in the soil in the four evolutionary stages were the highest during the developmental stage, but the change in TP content was not statistically significant (P > 0.05). Partial least squares path modeling and redundancy analysis (RDA) indicated that root system stoichiometric C and N contents were positively correlated with microbial diversity (R2 = 0.85). There was no correlation between the evolutionary stage and soil nutrient TN, whereas soil nutrient TN was negatively correlated with microbial diversity (R2 = -0.92). These findings elucidate the relationship between the evolutionary stage of root chemical measurement characteristics, soil elements and microorganisms, and their subsequent effects on root elemental composition and microbial diversity. This study enhances the current understanding of plant-soil interactions in desert steppe ecosystems.

Characteristics and Drivers of Soil Carbon, Nitrogen, and Phosphorus Ecological Stoichiometry at the Heavy Degradation Stage of the Alpine Meadow

An in-depth understanding of the soil nutrient status and balance relationship can help the effective recovery and management of alpine degraded meadows. In order to study the balance relationship among soil carbon, nitrogen, and phosphorus nutrients during the heavy degradation stage of meadows, field sampling and investigation, indoor analysis, and mathematical statistics were used to explore the characteristics and driving factors of changes in soil carbon, nitrogen, and phosphorus content, storage, and ecological stoichiometry during the heavy degradation stage of alpine meadows in the Sanjiangyuan region. The results showed that in the heavy degradation stage, miscellaneous grass plants occupied absolute dominance, soil C∶N∶P was approximately 32.83∶3.87∶0.67, and there was certain nitrogen limitation. The coefficients of variation of soil carbon, nitrogen, and phosphorus content were in the following order： organic carbon （1.09） > total nitrogen （0.63） > total phosphorus （0.29）. The organic carbon content and the carbon and nitrogen ratio showed a significant linear decreasing trend with the increase in the grassland degradation index （GDI）, while the total phosphorus content and organic carbon storage showed a significant non-linear change, in which the total phosphorus content showed a significant gentle U-shaped distribution, and the organic carbon storage decreased more gently at the beginning of the heavy degradation stage and then decreased sharply when the GDI was 57.9. The results of Mantel correlation analysis showed that the soil carbon to nitrogen ratio, carbon to phosphorus ratio, and nitrogen to phosphorus ratio showed significant correlation with organic carbon content and storage and total nitrogen storage. The results of structural equation modeling indicated that soil water content had direct effects as well as indirect through vegetation factors, soil carbon, nitrogen, and phosphorus ecological stoichiometry ratios, and soil water content and vegetation factors （height, cover, and biomass） were key environmental factors affecting soil ecological stoichiometry. The research results can provide scientific basis and practical guidance for the restoration of heavily degraded grassland in alpine meadows.

Salinity challenges and adaptive strategies in salinization-affected coastal Bangladesh: Implications for agricultural sustainability and water resource management

Abstract Salinization has become a rising global concern due to its notable effects on agriculture and freshwater resources. Coastal region of Bangladesh has been struggling with elevated levels of soil and water salinity, exacerbated by storm surges and rising sea levels. We assessed nutrient and salinity contents in agricultural and homestead lands, and the level of salinity in pond and canal water in six sub-districts in coastal Bangladesh. Finally, using household (HH) survey, focus group discussion (FGD) and key informant interview (KII), we explored the adaptive practices and challenges of salinity issues in agriculture and drinking water management. Soil nitrogen, phosphorus, and potassium contents exhibited significant variations across the sub-districts, which reflect the diversity of agricultural practices and soil management strategies. However, there was no notable difference in soil salinity across the sub-districts, which underscores the commonality of soil salinity as a pressing concern. Shyamnagar (13.99 dS m−1) recorded the highest level of pond water salinity, followed by Assasuni (13.96 dS m−1), Dacope (13.91 dS m−1), Koyra (13.58 dS m−1), Morrelganj (13.33 dS m−1), and Mongla (13.19 dS m−1) sub-districts, which highlights that water salinity decreased from exposed coast to the landward areas. Respondents in HH surveys, FGDs and KIIs identified salinity as a major challenge in agriculture and drinking water. Furthermore, climate-related stresses were recognized as significant challenges impacting crop productivity. The research highlights the feasibility of rainwater harvesting, with 89%–100% of HHs harvest rainwater in HH tanks, as an effective adaptive practice for managing drinking water. The study emphasizes the positive impact of vermicompost in reducing soil salinity levels, which is demonstrated by the 43%–88% of HHs using this practice, indicating its potential as a nature-based solution to address soil salinization. The findings underscore the need for resilient agricultural systems and sustainable water management approaches to tackle these challenges.

Phosphorus dynamics in volcanic soils of Weizhou Island, China: implications for environmental and agricultural applications

The dynamics of phosphorus are intricately governed by geological and ecological processes. Examining phosphorus dynamics in volcanic islands can enhance our comprehension of its behavior within such unique geological systems. However, research on phosphorus dynamics in volcanic islands remains limited. We investigated the phosphorus content of volcaniclastic rocks and basalt soils from Weizhou Island, China, to understand the influencing factors on phosphorus dynamics. The results indicate that in the volcaniclastic profile, phosphorus concentrates at 20–40 cm (17 mg/kg), decreases at 40–60 cm (11.9 mg/kg), and increases at 80–200 cm up to 46.4 mg/kg proximate to the bedrock, for the basalt profile, phosphorus content increases from the surface (80.2 mg/kg) towards the bedrock (83.9 mg/kg). The differences in phosphorus distribution between volcaniclastic rocks and basalts reflect the influence of parent material, rock weathering degree, carbonate content, topographic elevation, sea level changes, and geological activities. A strong positive correlation (R = 0.96907) between total and available phosphorus has been observed, suggesting that total phosphorus content effectively predicts available phosphorus content. Volcaniclastic rocks in wharves and high-elevation areas show low total phosphorus, while forest land with dense vegetation and neutral to alkaline soil supports higher total phosphorus due to enhanced bioavailability for plant absorption and utilization. Overall, the basalt soil of the volcanic island Weizhou Island demonstrates superior long-term fertility compared to the volcaniclastic soil. Despite its low total phosphorus content, it mainly exists in a highly bioavailable form, facilitating plant absorption, which is crucial for enhancing agricultural yields and ecosystem restoration on volcanic islands.

Effect of potassium fulvate on continuous tobacco cropping soils and crop growth.

Long-term continuous cropping of tobacco causes dysbiosis of soil microbial communities, the imbalance of soil nutrients, and the increase of pathogenic bacteria, which will slow the growth and development of tobacco plants, reduce the production quality, and cause significant losses to tobacco production and tobacco farmers. The application of Potassium fulvic acid can not only provide nutrients, but also inhibit the propagation of pathogens in soil along with raising the amount of organic matter in the soil, which is an effective way to improve soil health. In this experiment, Tobacco variety SNT60 was used as the test material, and 6 treatments were set up by pot test, they were: no fertilisation control group (CK), tobacco special fertiliser (NPK), 3.45 g/kg of potassium fulvic acid fertiliser (T1), 4.65 g/kg of potassium fulvic acid fertiliser (T2), 5.85 g/kg of potassium fulvic acid fertiliser (T3), 7.05 g/kg of potassium fulvic acid fertiliser (T4), Ten replications were set up for each treatment and the soil and fertiliser were mixed and potted before transplanting, 70% as basal fertiliser and 30% as supplementary fertiliser. We also analyzed soil properties, soil microorganisms and agronomic traits of tobacco plants in different treatments to provide reference for mitigating tobacco succession barrier. The test results are as follows: 4.65 g/kg of potassium fulvic acid fertiliser (T2) treatment was the best, soil organic matter, quick nitrogen, phosphorus, potassium, pH, soil catalase, soil sucrase, and soil urease content, compared to CK control, increased by 22.04%, 43.12%, 96.21%, 381.79%, 25.43%, 91.69%, 262.07% and 93.16%. In terms of microbial community, application of potassium fulvic acid fertiliser significantly increased the relative abundance of Ascomycetes, Chlorobacterium, Bacillus, Proteobacteria and Tephritobacterium in the soil. Meanwhile, 4.65 g/kg of potassium fulvic acid fertiliser (T2) promoted the growth of tobacco plants, improved leaf photosynthetic capacity, and enhanced plant disease resistance. This experiment provides practical measures to improve the microbial community of tobacco continuous cropping soils and to reduce the incidence of diseases.

Biochar and wood vinegar altered the composition of inorganic phosphorus bacteria community in saline-alkali soils and promoted the bioavailability of phosphorus

As an important part of the ecosystem, saline-alkali soils are in urgent need of efficient and environmentally friendly soil conditioners. Biochar and wood vinegar are regarded as organic soil improvement and plant growth regulators to improve soil physicochemical properties and promote crop growth. However, the mechanism of how inorganic phosphorus bacteria increase phosphorus when biochar and wood vinegar applied to saline-alkali soils is not clear. Herein, the present study was designed to investigate the effects of biochar and wood vinegar with different rates on physicochemical properties of saline-alkali soils and inorganic phosphorus bacteria diversities and to discuss the mechanism of biochar and wood vinegar on available phosphorus by pot experiments. The application of biochar and wood vinegar exhibited an effect on the decrease in pH and salt contents and the increase in soil porosity, soil nutrients, and hundred-grain weight of rice. The 600 kg ha−1 biochar and 1800 kg ha−1 wood vinegar group showed the most significant increment in available phosphorus, alkaline phosphatase, acid phosphatase, and neutral phosphatase activities, with the increases of 49.24%, 40.35%, 48%, and 149%, respectively. The 600 kg ha−1 biochar and 1200 kg ha−1 wood vinegar group significantly enhanced microbial biomass phosphorus concentrations by 41.29%. Moreover, biochar and wood vinegar shifted inorganic phosphorus bacteria composition structure and promoted its diversities, more so at a higher rate of wood vinegar application. The dominant species of inorganic phosphorus bacteria were Proteobacteria, Gammaproteobacteria, Alphaproteobacteria, Pseudomonas, and Rhizobium in saline-alkali soils. The Alphaproteobacteria and Hydrogenophaga were the key microorganisms reducing pH and salt contents and increasing available phosphorus contents in saline-alkali soils. In conclusion, the application of biochar and wood vinegar was a useful strategy to improve saline-alkali soils.

Responses of diazotrophic network structure and community diversity to alfalfa-maize intercropping are soil property-dependent.

Intercropping and soil properties both affect soil diazotrophic communities. However, the specific effects that alfalfa-maize intercropping has on diazotrophic networks and community diversity under different soil properties remain unclear. In this study, we investigated the soil diazotrophic communities of two crop systems, alfalfa monoculture (AA) and alfalfa-maize intercropping (A/M), in two sites with similar climates but different soil properties (poor vs. average). The diazotrophic network complexity and community diversity were higher at the site with poor soil than at the site with average soil (p < 0.05). Community structure also varied significantly between the sites with poor and average soil (p < 0.05). This divergence was mainly due to the differences in soil nitrogen, phosphorus, and organic carbon contents between the two sites. At the site with poor soil, the A/M system had lower diazotrophic diversity, lower network complexity and greater competition between diazotrophs than the AA system (p < 0.05) because intercropping intensified the soil phosphorus limitation under poor soil conditions. However, in the average soil, it was the A/M system that had an altered diazotrophic structure, with an increased abundance of 11 bacterial genera and a decreased abundance of three bacterial genera (p < 0.05). Our results indicated that the effects of alfalfa-maize intercropping on diazotrophic communities were soil property-dependent.

Drought impairs detritivore feeding activity more strongly in northern than in southern European latitudes

Soil detritivores play key roles in decomposition processes closely related to ecosystem services. Drought and soil organic carbon depletion due to agricultural management are detrimental to soil biodiversity, but their interactive effects on soil biota and associated processes have not been thoroughly investigated. In 2018, we used rain-out shelters to experimentally induce drought in wheat fields of contrasting levels of organic carbon in Sweden, Germany and Spain. That year Europe experienced a climatic dipole, with exceptionally severe droughts in northern latitudes. We assessed the feeding activity of soil detritivores by bait-lamina tests, and measured several abiotic and biotic soil parameters. In the peak of the dipole drought (summer) southern fields had the driest soils. Nonetheless, detritivore feeding activity responded to the experimental drought by shifting to deeper soil layers there. Low soil organic carbon (SOC) levels exacerbated the latter effect. However, in this same period, feeding activity in northern and central Europe was two orders of magnitude lower than in the south, and failed to respond to either the experimental treatment and/or SOC levels. Using mixed-effects longitudinal random forests, we detected various candidate drivers of detritivore feeding activity: soil moisture, phosphorus content, bacteria and nematodes. Different bacterial taxa were associated to detritivory in each country, but their potential influence was pervasive. Thus, our results suggest that drought had adverse effects on detritivore feeding, which were exacerbated northwards due to the climatic dipole. Increased SOC levels mitigated drought effects only in southern soils. Regional adaptation of soil biota to aridity could explain the response of detritivores in southern Europe to drought. Machine learning algorithms arise as useful tools for exploring potential drivers relating biodiversity to soil processes. Overall, future research on the effects of drought on soil biodiversity and processes will be key for tackling climate change impacts in terrestrial ecosystems.

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.

Intercropping in Coconut Plantations Regulate Soil Characteristics by Microbial Communities

Intercropping is a commonly employed agricultural technique that offers numerous advantages, such as increasing land productivity, enhancing soil health, and controlling soil-borne pathogens. In this study, Artemisia argyi, Dioscorea esculenta, and Arachis pintoi were intercropped with coconuts and compared with naturally growing weeds (Bidens pilosa), respectively. The regulatory mechanism of intercropping was examined by analyzing the variability in soil properties and microbial community structure across different intercropping modes and soil depths (0–20 cm, 20–40 cm, and 40–60 cm). The results indicate that intercropping can increase the diversity of soil bacteria and fungi. Moreover, as soil depth increases, the changes in microbial communities weaken. Intercropping reduced soil SOM and increased pH, which is directly related to the changes in the abundance of Acidobacteria in the soil. In various intercropping systems, the disparities resulting from intercropping with A. pintoi are particularly pronounced. Specifically, intercropping with A. pintoi leads to an increase in soil potassium and phosphorus levels, as well as an enhancement in the abundance of Bacillus sp., which plays a crucial role in the suppression of plant pathogenic fungi within the soil ecosystem. The results of the correlation analysis and structural equation modeling (SEM) suggest that the impacts of three intercropping systems on microbial composition and soil indicators exhibit considerable variation. However, a common critical factor influencing these effects is the soil phosphorus content. Furthermore, our findings indicate that intercropping resulted in lower soil nitrogen levels, exacerbating nitrogen deficiency and masking its impact on the microbial community composition.