Soil Plant Nutrient Research Articles

Microbial Inoculants Drive Changes in Soil and Plant Microbiomes and Improve Plant Functions in Abandoned Mine Restoration.

The application of microbial inoculants holds promise for the sustainable restoration of abandoned mine sites by affecting soil nutrients and microbial communities. However, the responses of plant microbial communities to microbial inoculants in mine restoration remain largely unknown. To bridge this knowledge gap, we conducted a 4-year field experiment at an abandoned carbonate mine site to assess the impacts of microbial inoculants on the soil-plant microbiome. Our findings revealed that microbial inoculants significantly changed roots, fine root bacterial and fungal communities. Further, no significant correlations were observed between the soil-plant nutrient content (Z-score) and microbial alpha diversity. However, a significantly positive correlation was found between the relative abundance of the keystone ecological cluster (Module #1) and soil-plant nutrient content. The application of microbial inoculants also increased complexity, albeit decreased stability of plant microbiome networks, alongside a reduction in stochastic assembly. Conversely, they decreased the complexity but increased the stability of soil microbiome networks, accompanied by an increase in stochastic assembly. Notably, the number of specifically enriched microbiome functional traits of roots and root nodules under the microbial inoculant treatments surpassed that of the control. In summary, our findings underscored the potential of microbial inoculants to enhance soil-plant functionality at abandoned mine restoration sites.

Mangrove afforestation as an ecological control of invasive Spartina alterniflora affects rhizosphere soil physicochemical properties and bacterial community in a subtropical tidal estuarine wetland

Background The planting of mangroves is extensively used to control the invasive plant Spartina alterniflora in coastal wetlands. Different plant species release diverse sets of small organic compounds that affect rhizosphere conditions and support high levels of microbial activity. The root-associated microbial community is crucial for plant health and soil nutrient cycling, and for maintaining the stability of the wetland ecosystem. Methods High-throughput sequencing was used to assess the structure and function of the soil bacterial communities in mudflat soil and in the rhizosphere soils of S. alterniflora, mangroves, and native plants in the Oujiang estuarine wetland, China. A distance-based redundancy analysis (based on Bray–Curtis metrics) was used to identify key soil factors driving bacterial community structure. Results S. alterniflora invasion and subsequent mangrove afforestation led to the formation of distinct bacterial communities. The main soil factors driving the structure of bacterial communities were electrical conductivity (EC), available potassium (AK), available phosphorus (AP), and organic matter (OM). S. alterniflora obviously increased EC, OM, available nitrogen (AN), and NO3−-N contents, and consequently attracted copiotrophic Bacteroidates to conduct invasion in the coastal areas. Mangroves, especially Kandelia obovata, were suitable pioneer species for restoration and recruited beneficial Desulfobacterota and Bacilli to the rhizosphere. These conditions ultimately increased the contents of AP, available sulfur (AS), and AN in soil. The native plant species Carex scabrifolia and Suaeda glauca affected coastal saline soil primarily by decreasing the EC, rather than by increasing nutrient contents. The predicted functions of bacterial communities in rhizosphere soils were related to active catabolism, whereas those of the bacterial community in mudflat soil were related to synthesis and resistance to environmental factors. Conclusions Ecological restoration using K. obovata has effectively improved a degraded coastal wetland mainly through increasing phosphorus availability and promoting the succession of the microbial community.

Optimizing nitrogen fertilization in maize: the impact of nitrification inhibitors, phosphorus application, and microbial interactions on enhancing nutrient efficiency and crop performance.

Despite the essential role of nitrogen fertilizers in achieving high crop yields, current application practices often exhibit low efficiency. Optimizing nitrogen (N) fertilization in agriculture is, therefore, critical for enhancing crop productivity while ensuring sustainable food production. This study investigates the effects of nitrification inhibitors (Nis) such as Dimethyl Pyrazole Phosphate (DMPP) and Dimethyl Pyrazole Fulvic Acid (DMPFA), plant growth-promoting bacteria inoculation, and phosphorus (P) application on the soil-plant-microbe system in maize. DMPFA is an organic nitrification inhibitor that combines DMP and fulvic acid for the benefits of both compounds as a chelator. A comprehensive rhizobox experiment was conducted, employing varying levels of P, inoculant types, and Nis, to analyze the influence of these factors on various soil properties, maize fitness, and phenotypic traits, including root architecture and exudate profile. Additionally, the experiment examined the effects of treatments on the bacterial and fungal communities within the rhizosphere and maize roots. Our results showed that the use of Nis improved plant nutrition and biomass. For example, the use of DMPFA as a nitrification inhibitor significantly improved phosphorus use efficiency by up to 29%, increased P content to 37%, and raised P concentration in the shoot by 26%, compared to traditional ammonium treatments. The microbial communities inhabiting maize rhizosphere and roots were also highly influenced by the different treatments. Among them, the N treatment was the major driver in shaping bacterial and fungal communities in both plant compartments. Notably, Nis reduced significantly the abundance of bacterial groups involved in the nitrification process. Moreover, we observed that each experimental treatment employed in this investigation could select, promote, or reduce specific groups of beneficial or detrimental soil microorganisms. Overall, our results highlight the intricate interplay between soil amendments, microbial communities, and plant nutrient dynamics, suggesting that Nis, particularly DMPFA, could be pivotal in bolstering agricultural sustainability by optimizing nutrient utilization.

Leaching and vertical distribution of Fe and Zn citrate nanoparticles in Indian red soil

This research aims to address common constraints in the effective utilization of plant nutrients in soil, such as fixation, mobility, leaching, and reactions with soil colloids. To mitigate these issues, Fe and Zn citrate nanoparticles were synthesized and applied as nanochelators in a reconstructed soil profile column. We evaluated the mobility, release, and leaching behaviors of these nanoparticles. Results revealed that, no leaching of Fe and Zn citrate nanoparticles occurred even after a 90-day incubation. The release profiles exhibited a peak at 60 and 90 days for Fe and Zn respectively. In the mobility studies, Fe and Zn availability was highest in the 0–15 cm soil depth. Fe citrate and Zn citrate nanoparticles demonstrated the highest availability at 264.7 mg/kg and 86.26 mg/kg of soil, respectively as compared with commercial samples. The superior performance of Fe and Zn citrate nanoparticles was observed in terms of reduced leaching and improved accessibility, indicating their potential as efficient and environmentally-friendly plant nutrient sources. The study concludes that Fe and Zn citrate nanoparticles are stable nutrient sources that can enhance plant use efficiency with minimal environmental impact.

Evaluating the effect of organic NPK granules on yield, nutrient uptake, post-harvest soil fertility and soil microbial population in rice (Oryza sativa L.)

Rice is the most important and staple food crop for more than two third of population of India. India is the second largest rice producing country in the world after China. Although, rice planted area in India is 40 per cent higher than in China, Indian rice production is 30 percent below Chinese production because of lower yields. Among several constraints of production, nutrient management plays a key role in realizing sustainable yield from any given cultivation practices. Integrated nutrient management system plays a vital role in balancing the soil fertility and plant nutrient supply to an optimum level through the judicious and efficient use of chemical fertilizers, green manure, FYM and biofertilizers leading to an eco-friendly approach and economically viable solution for this problem. Continuous integrated use of organic manures with chemical fertilizers would be quite promising in assessing the sustainability of a cropping system vis-à-vis monitoring the soil properties. To investigate further, a field experiment was conducted at the Experimental Farm, Department of Agronomy, Annamalai University, Annamalai Nagar, Cuddalore district of Tamil Nadu from June to September 2023 with a key objective of evaluating the effect of combined application of graded levels of conventional fertilizers along with organic NPK granules in lowland rice. The experiment was laid out in randomized block design with seven treatments comprised of different levels of conventional fertilizers along with organic NPK granules. Among the nutrient management evaluated, all the yield attributes of lowland rice viz., grain yield, straw yield, uptake of nutrients and post-harvest soil available nutrients were significantly influenced by the application of 70% NPK through synthetic fertilizers and 30% NPK through organic granules. Combining conventional fertilizers along with organic NPK granules improved nitrogen use efficiency via metabolite production, enzyme activity stimulation, and microbial rhizosphere interactions significantly enhancing the yield attributes and yield.

Fertile island variation depends on species differences in the deserts of Northwest China

Desert ecosystems are extremely arid and nutrient poor. “Fertile islands” formed by mobile sand dunes and perennial desert plants are crucial for maintaining the structure and function of these ecosystems. However, the impacts of fertile islands created by different plant species at various spatial locations on soil physicochemical properties such as soil nutrients remain unclear. This study focused on the legumes (Astragalus flexus Fisch.), and non-legume (Eremurus inderiensis (M. Bieb.) Regel) plants widely distributed in the Gurbantunggut Desert in northwestern China. We analyzed the soil physicochemical properties of fertile islands formed by these two desert plants at different horizontal distances (0–140 cm) and vertical depths (0–15 cm). In addition, we investigated the relationship between plant functional shape and soil physicochemical properties. This study yielded the following results. (1) The fertile island was observed within the 0–140 cm soil layer of Astragalus flexus and Eremurus inderiensis and gradually weakened with increasing horizontal distance and soil depth. (2) The two plants had different nutrient enrichment rates. Eremurus inderiensis had higher TP and AK enrichment rates than Astragalus flexus. In contrast, Astragalus flexus demonstrated significantly higher enrichment rates for TN, NH4+-N, and NO3−-N, especially NH4+-N, highlighting the ability of legumes to fix and uptake N. (3) The correlation between plant height, crown width, and soil nutrient enrichment rate was more significant for Eremurus inderiensis than for Astragalus flexus. In general, both plants formed the fertile islands that gradually decreased with the increasing distance (both horizontal and vertical). Different plants exhibited varying abilities to enrich soil nutrients and form fertile islands, which presented a clear species effect. Therefore, protecting the diversity of desert plants to form stable fertile islands could be crucial for maintaining the soil fertility in desert ecosystems.

Composting of Cow-Dung-Amended Soil by the Dung Beetle Catharsius molossus L. Improves Bacterial Ecological Functions Related to Nitrogen Mineralization and Human and Plant Pathogenesis

The Asian dung beetle (Catharsius molossus L.; Coleoptera: Scarabeidae) has been shown to positively affect soil bacterial diversity and the agronomic features of crop plants. In this study, we used bioinformatic tools to investigate the differences in bacterial functional phenotypes and ecological functions between control soil, cow dung-amended soil (CD), and cow dung-amended soil composted by dung beetles (DB). The soil bacterial metagenomes were sequenced and analyzed with the bioinformatic packages BugBase, PICRUSt2, Tax4Fun, and FAPROTAX to evaluate the effects of dung beetle-mediated composting on bacterial functions such as human and plant pathogenicity, trophic strategies, and soil nutrient transformation. BugBase proved useful for the determination of differences in major functional phenotypes, whereas FAPROTAX was effective at identifying differences in bacterial ecological functions between the treatments. Both tools suggested a relative decrease in human pathogens in the DB soil. This was corroborated by the pairwise comparison of abundances in bacterial species, which showed a significant reduction in the abundance of the broad-host-range pathogen Pseudomonas aeruginosa in the DB soil. In addition, FAPROTAX suggested a decrease in plant pathogens and an increase in chitinolytic bacteria, meaning that the DB treatment might be beneficial to the plant-growth-promoting bacteria involved in biological control. Finally, FAPROTAX revealed an array of ecological functions related to trophic strategies and macro- and micronutrient metabolism. According to these results, the activity of C. molossus beetles enhanced methanotrophy, ammonification, nitrification, sulfate reduction, and manganese oxidation, whereas iron respiration was decreased in the DB-treated soil. Our results represent a collection of general insights into the effects of C. molossus beetles on soil bacterial functions, which also reflect on the nutrient composition of dung beetle-composted soil.

Effect of Nano-Zinc Oxide, Rice Straw Compost, and Gypsum on Wheat (Triticum aestivum L.) Yield and Soil Quality in Saline-Sodic Soil.

The salinity and alkalinity of soils are two fundamental factors that limit plant growth and productivity. For that reason, a field study conducted at Sakha Agric. Res. Station in Egypt during the 2022-2023 winter season aimed to assess the impact of gypsum (G), compost (C), and zinc foliar application in two images, traditional (Z1 as ZnSO4) and nanoform (Z2 as N-ZnO), on alleviating the saline-sodic conditions of the soil and its impact on wheat productivity. The results showed that the combination of gypsum, compost, and N-ZnO foliar spray (G + C + Z2) decreased the soil electrical conductivity (EC), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) by 14.81%, 40.60%, and 35.10%, respectively. Additionally, compared to the control, the G + C + Z2 treatment showed improved nutrient content and uptake as well as superior wheat biomass parameters, such as the highest grain yield (7.07 Mg ha-1), plant height (98.0 cm), 1000-grain weight (57.03 g), and straw yield (9.93 Mg ha-1). Interestingly, foliar application of N-ZnO was more effective than ZnSO4 in promoting wheat productivity. Principal component analysis highlighted a negative correlation between increased grain yield and the soil EC and SAR, whereas the soil organic matter (OM), infiltration rate (IR), and plant nutrient content were found to be positively correlated. Furthermore, employing the k-nearest neighbors technique, it was predicted that the wheat grain yield would rise to 7.25 t ha-1 under certain soil parameters, such as EC (5.54 dS m-1), ESP (10.02%), OM (1.41%), bulk density (1.30 g cm-3), infiltration rate (1.15 cm h-1), and SAR (7.80%). These results demonstrate how adding compost and gypsum to foliar N-ZnO can improve the soil quality, increase the wheat yield, and improve the nutrient uptake, all of which can support sustainable agriculture.

Plant growth and physiological responses of the invasive plant Acmella radicans to contrasting light and soil water conditions

Acmella radicans (Jacquin) R.K. Jansen is a new invasive species record for Yunnan Province, China, as of 2017 and little is known about its invasion mechanisms. To better understand its invasive strategies, we investigated the growth, physiological and soil nutrient use parameters of the invader under combined conditions of light (25%, 50%, 75%, and 100% of light availability) and soil water content (full, high, medium, and low soil water content) in the glasshouse. The results showed that light level, soil water content and their interaction had a significant effect on all plant morphological, physiological and soil nutrient parameters for A. radicans (P < 0.05). For the most part, plant height, total branch length, leafstalk length, leaf area, inflorescence number, seed number, leaf biomass, stem biomass, aboveground biomass, and total biomass of A. radicans were significantly increased with increased shading rate and soil water content and were generally greater at intermediate light levels and intermediate to high soil water levels. Under high-irradiance conditions, the chlorophyll content was greatly reduced compared to other treatments. We also observed that leafstalk length, leaf area, Pn, chlorophyll a, and chlorophyll b of A. radicans were markedly increased with increased shading rate and soil water content, and were generally highest under intermediate irradiance and soil water conditions, but many plant physiological parameters also exhibited relatively high values under waterlogging conditions. The concentrations of organic matter, available N and available K of A. radicans soils at high-irradiance and full-high soil water content treatments and medium-irradiance and high-medium soil water content treatments were often less than those of other treatments indicated that hypothetically soil absorption was increased by moderate shading and high soil water. This was the first study demonstrating that A. radicans thrives best under moderate light conditions in combination with high soil water. Furthermore, we surmised that its higher phenotypic and physiological plasticity contributes to its invasion success.

Dairy manure influences soil properties, plant nutrient uptake, and tuber quality in potatoes

AbstractDairy manure applications are a common practice in Idaho potato (Solanum tuberosum L.) production, however the impacts on tuber yield and quality are not well understood. Our objectives were to determine (1) how repeated dairy manure applications impact soil properties and plant nutrient uptake, and (2) how these changes influence plant nutrient interactions, tuber yield, and quality. Stockpiled dairy manure was fall‐applied over a 6‐year period to two adjacent potato production fields in Kimberly, ID. Eight treatments included application frequency (annual and biennial), manure application rate (18, 36, and 52 Mg ha−1 application−1 [dry weight basis]), fertilizer‐only, and a non‐amended control. Manure treatments were supplemented with fertilizer to prevent nutrient‐limiting conditions. Compared to fertilizer treatments, mean soil organic matter, total N, and K were greater for annual manure by 53%, 47%, and 426%, and biennial manure by 24%, 23%, and 199%, respectively. For annual applications only, mean soil nitrate, P, and electrical conductivity were greater than fertilizer treatments by 247%, 431%, and 222%, respectively. Manure promoted P and K luxury consumption with increasing application rate and frequency. Foliage Ca, Mg, Zn, Mn, and Cu correlated negatively against foliage K, potentially due to cation competition and translocation disruption. Annual applications decreased mean tuber specific gravity from 1.078 to 1.073, which may be attributed to saline‐sodic conditions and delayed maturity from late‐season N mineralization. Our findings suggest that biennial manure applications may prevent specific gravity issues. Agronomic parameters related to N, K, and soluble salts should be closely monitored in these systems.

Effect of biochar amendment on bacterial community and their role in nutrient acquisition in spinach (Spinacia oleracea L.) grown under elevated CO2

Global climate change is anticipated to shift the soil bacterial community structure and plant nutrient utilization. The use of biochar amendment can positively influence soil bacterial community structure, soil properties, and nutrient use efficiency of crops. However, little is known about the underlying mechanism and response of bacterial community structure to biochar amendment, and its role in nutrient enhancement in soil and plants under elevated CO2. Herein, the effect of biochar amendment (0, 0.5, 1.5%) on soil bacterial community structure, spinach growth, physiology, and soil and plant nutrient status were investigated under two CO2 concentrations (400 and 600 μmol mol−1). Findings showed that biochar application 1.5% (B.2.E) significantly increased the abundance of the bacterial community responsible for growth and nutrient uptake i.e. Firmicutes (42.25%) Bacteroidetes (10.46%), and Gemmatimonadetes (125.75%) as compared to respective control (CK.E) but interestingly abundance of proteobacteria decreased (9.18%) under elevated CO2. Furthermore, the soil available N, P, and K showed a significant increase in higher biochar-amended treatments under elevated CO2. Spinach plants exhibited a notable enhancement in growth and photosynthetic pigments when exposed to elevated CO2 levels and biochar, as compared to ambient CO2 conditions. However, there was variability observed in the leaf gas exchange attributes. Elevated CO2 reduced spinach roots and leaves nutrient concentration. In contrast, the biochar amendment (B2.E) enhanced root and shoot Zinc (494.99%–155.33%), magnesium (261.15%–183.37%), manganese (80.04%–152.86%), potassium (576.24%–355.17%), calcium (261.88%–165.65%), copper (325.42%–282.53%) and iron (717.63%–177.90%) concentration by influencing plant physiology and bacterial community. These findings provide insights into the interaction between plant and bacterial community under future agroecosystems in response to the addition of biochar contributing to a deeper understanding of ecological dynamics.

Effect of AMF Inoculation on Reducing Excessive Fertilizer Use.

Excessive use of chemical fertilizer is a global concern. Arbuscular mycorrhizal fungi (AMF) are considered a potential solution due to their symbiotic association with crops. This study assessed AMF's effects on maize yield, fertilizer efficiency, plant traits, and soil nutrients under different reduced-fertilizer regimes in medium-low fertility fields. We found that phosphorus supplementation after a 30% fertilizer reduction enhanced AMF's positive impact on grain yield, increasing it by 3.47% with pure chemical fertilizers and 6.65% with mixed fertilizers. The AMF inoculation did not significantly affect the nitrogen and phosphorus fertilizer use efficiency, but significantly increased root colonization and soil mycelium density. Mixed fertilizer treatments with phosphorus supplementation after fertilizer reduction showed greater mycorrhizal effects on plant traits and soil nutrient contents compared to chemical fertilizer treatments. This study highlights that AMF inoculation, closely linked to fertilization regimes, can effectively reduce fertilizer use while sustaining or enhancing maize yields.

Multiple cropping effectively increases soil bacterial diversity, community abundance and soil fertility of paddy fields

BackgroundCrop diversification is considered as an imperative approach for synchronizing the plant nutrient demands and soil nutrient availability. Taking two or more crops from the same field in one year is considered as multiple cropping. It improves the diversity and abundance of soil microbes, thereby improving the growth and yield of crops. Therefore, the present study was conducted to explore the effects of different multiple winter cropping on soil microbial communities in paddy fields. In this study, eight rice cropping patterns from two multiple cropping systems with three different winter crops, including Chinese milk vetch (CMV), rape, and wheat were selected. The effects of different multiple winter cropping on soil microbial abundance, community structure, and diversity in paddy fields were studied by 16 S rRNA high-throughput sequencing and real-time fluorescence quantitative polymerase chain reaction (PCR).ResultsThe results showed that different multiple winter cropping increased the operational taxonomic units (OTUs), species richness, and community richness index of the bacterial community in 0 ~ 20 cm soil layer. Moreover, soil physical and chemical properties of different multiple cropping patterns also affected the diversity and abundance of microbial bacterial communities. The multiple cropping increased soil potassium and nitrogen content, which significantly affected the diversity and abundance of bacterial communities, and it also increased the overall paddy yield. Moreover, different winter cropping changed the population distribution of microorganisms, and Proteobacteria, Acidobacteria, Nitrospira, and Chloroflexi were identified as the most dominant groups. Multiple winter cropping, especially rape-early rice-late rice (TR) andChinese milk vetch- early rice-late rice (TC) enhanced the abundance of Proteobacteria, Acidobacteria, and Actinobacteria and decreased the relative abundance of Verrucomicrobia and Euryarchaeota.ConclusionIn conclusion, winter cropping of Chinese milk vetch and rape were beneficial to improve the soil fertility, bacteria diversity, abundance and rice yield.

Riparian plant-soil-microbial C:N:P stoichiometry: are they conserved at plant functional group level?

As a consequence of the tight linkages between plants, soil, and microorganisms, we hypothesized the variations in plant species would change soil and microbial stoichiometry. Here, we examined the plant leaf carbon (C):nitrogen (N):phosphorus (P) ratios of nine species coming from three plant functional groups (PFGs) in the riparian zones of Hulunbuir steppe during near-peak biomass. The soil C:N:P, microbial biomass carbon (MBC):microbial biomass nitrogen (MBN), and extracellular enzyme's C:N:P were also assessed using the soils from each species. We found that plant tissue, soil nutrient, microbial, and enzyme activity stoichiometry significantly differed among different PFGs. Plant leaf and soil nutrient ratios tended to be similar (p > 0.05) between different species within the same PFGs. The variations in leaf C:N:P significantly correlated with the changes in soil C:N:P and MBC:MBN ratios. The homeostatic coefficients (H) < 1 suggested the relationships between plants and their resources C:N:P ratios might be non-homeostatic in the examined riparian zone. By assessing plant tissue and its soil nutrient stoichiometry, this study provided a perspective to understand the linkages of plant community, soil nutrient, and microbial characteristics.

Overview of the Impact of Compost on Bulk Density, Aggregate Consistency and Cation Exchange Capacity of Soils and its Consequential Effect on Crop Productivity

Organic fertilizers offer several advantages over chemical fertilizers and are an environmentally friendly alternative that could help sustainably farmed land. Reviewing indigenous knowledge of the agronomic applications of organic manure and its possible contribution to agricultural growth was the goal of this article. It is evident that organic manures from various plant and animal sources can be used to satisfy certain field needs. However, the use of organic manures is still primarily conventional since they have not been well received by agricultural strategies. When bulky organic manures are directly applied to soil, they accelerate mineralization and reduce the rate at which nutrients, especially nitrogen, are released. Compared to raw resources, which have limited value and certain disadvantages, composting these wastes appears to offer significant potential. The majority of researchers verified that adding compost might enhance the soil's organic matter content, nutrient status, and physical, chemical, and biological properties. Soil organic matter concentrations rise in every long-term compost treatment study. But since they contain more stable carbon than fresh or immature composts, mature composts raise Soil organic matter considerably more effectively. Furthermore, because compost has so many beneficial effects on the physical, chemical, and biological aspects of soil, it helps to stabilize and improve crop quality and yield. As a result, the majority of studies have demonstrated that compost has an equalizing influence on seasonal and annual variations in soil temperature, air, water, and plant nutrient availability, as well as crop yields. mostly due to the nutrients' gradual release and availability in compost-combined fertilization techniques, which frequently yield positive outcomes. Therefore, composting can be a useful choice for building effective plant-nutrient management methods in many settings for sustainable agricultural systems within small-scale farming in impoverished nations.

English

The district Toba Tek Singh is located in the center of Punjab province. It occupies 2nd important position in national citrus production after Sargodha, with citrus orchard area of 11412 hectares and annual production of 160758 tons. Citrus productivity in Pakistan, in general, and Toba Tek Singh, in particular, is far below its its potential which could be attributed to several factors but poor soil health and inadequate soil fertility may be considered an important reason. A comprehensive nutrient indexing survey of thirty citrus orchards grown in different parts of district Toba Tek Singh was conducted to evaluate the soil characteristics and plant nutrient status. GPS coordinates of selected sites were recorded prior to sampling. Soil samples were collected at 0-20 cm, 21-40 cm and 41-60 cm depth using standard procedure. Five soil samples were collected from each site to get a composite sample for each depth. The leaf samples were collected from the 7-month-old non-fruiting branches of plants around the tree canopy during the month of September, 2022. Five healthy and uniform citrus trees were sampled from each site to get a composite leaf sample. The soil samples were analyzed for pH, electrical conductivity (EC), soil organic matter (SOM) and calcium carbonate (CaCO3). The soil and leaf samples were analyzed for macro and micronutrients. It was found that most of orchard soils of district Toba Tek Singh were moderately alkaline (pH 7.52-8.90), slight to strong calcareous (2-15% CaCO3), non-saline (0.77-3.0 dS m-1 EC) and low in SOM (0.23-1.49%) with low to medium nitrogen (0.01-0.06%) and phosphorus (0.58-10.52 mg kg-1) while medium to high potassium (56.47-315.34 mg kg-1). The sampled soils were low to marginal in boron (0.09-0.72 mg kg-1), copper (0.05-0.59 mg kg-1), iron (0.23-10.75 mg kg-1) and zinc (0.03-1.83 mg kg-1) while adequate in manganese (1.35-26.20 mg kg-1). Leaf analysis revealed that almost 50% orchards were deficient in phosphorus (0.05-0.23%) and potassium (0.40-1.76%), while having low to marginal values of copper (1.96-20.99 mg kg-1), zinc (4.13-31.96 mg kg-1), boron (3.12-95.40 mg kg-1), manganese (42.62-96.46 mg kg-1) but adequate iron (171-552 mg kg-1). The surveyed orchard soils were mostly alkaline calcareous, deficient in organic matter and having low to moderate macro and micronutrients.

Microarthropods improve oat nutritional quality and mediate fertilizer effects on soil biological activity

AbstractSoil biological processes are important drivers of crop productivity in agroecosystems. Soil microarthropods play key roles in nutrient cycling and plant nutrient acquisition, though little is known about how these effects manifest in crop production under different organic fertilizer amendments. We explored the interactive effects of microarthropods and fertilizers on crop productivity in two greenhouse experiments: experiment one involved a single Collembola species, and experiment two involved diverse microarthropod communities. Oats were grown as a model crop in both experiments under one of three initial fauna abundance levels (none, low, and high). In both experiments, four organic fertilization treatments were compared: alfalfa green manure, Kreher's Poultry Litter Compost, Chilean nitrate, and a nonamended control. Oat growth and development were evaluated weekly. During each experiment, 48 pots were selected randomly for destructive harvest at two separate times to mimic forage and grain harvest stages. At each harvest, multiple soil metrics (microarthropods, microbial biomass, microbial enzymes, and soil carbon and nitrogen) and plant metrics (biomass, reproduction, and tissue carbon and nitrogen content) were evaluated. Our findings indicated that microarthropods, both single species and diverse communities, stimulated nitrogen cycling and enhanced crop nutrient status. As microarthropod abundance and diversity increased, microarthropods exerted more effects on soil microbial activity. The effects of the microarthropods enhance the breakdown of fertilizers, ultimately making fertilizer choice less important for soil processes and plant nutrient availability. Our findings suggest that microarthropods drove oat production yields primarily through their effects on soil biological processes.

Short-term effects of understory removal on understory diversity and biomass of temperate forests in northeast China

IntroductionUnderstory removal is a traditional practice in forest management to reduce fire risk and promote seedling regeneration. However, its effect on understory diversity, biomass and soil nutrients in temperate forest ecosystems is less known, which limits our assessment of the effectiveness of understory vegetation management.MethodsWe quantified the composition of the understory species, their diversity, and the biomass of the understory and factors driving changes in these parameters in primary mixed broad-leaved Pinus koraiensis forest (BKF), secondary Betula platyphylla forest (BF), and Larix gmelinii plantation (LF) in northeast China after a 5-year understory removal.ResultsAfter understory removal, the number of shrub and herb species in BKF and LF decreased, while the number of shrub species in BF increased significantly and that of herb species decreased; the species with strong light preference, Equisetum hyemale, Impatiens noli-tangere, and Filipendula Palmata, were dominant in the herb layer of the three forest types; Shannon–Wiener diversity, Pielou evenness, and Simpson diversity of the herb layer in LF increased significantly (P &amp;lt; 0.05), while those of the shrub and herb layers in BF and LF showed no significant changes (P &amp;gt; 0.05). The total understory biomass of understory of BKF and LF decreased by 0.94 t·hm−2 and 1.32 t·hm−2, respectively, while that of BF increased by 1.31 t·hm−2; soil NH4+-N and total phosphorus (TP) were the key factors regulating understory vegetation diversity and biomass, respectively.ConclusionThese results suggest that understory removal is a beneficial management strategy for increasing shrub biomass and diversity in secondary forests, while it should be avoided in primary forests and plantations to prevent the reduction of understory plant diversity and soil nutrient loss.

Root exudate-mediated plant–microbiome interactions determine plant health during disease infection

Understanding the interactions between plants and microbes during pathogen infection is crucial for plant health improvement. However, the integrated role of soil nutrients, root exudates, and plant microbiomes in plant health during disease outbreaks remains unclear. In this study, we hypothesized that root exudate-mediated healthy microbiomes (HealthyBiome) would facilitate the escape of soil-borne pathogen infection, whereas a root exudate-mediated disease-conductive microbiome (PathoBiome) would induce disease occurrence. Using watermelon wilt disease caused by Fusarium oxysporum as a model, we investigated these interactions and their implications in plant disease. We examined the pathogen load across plant compartments during the pathogen accumulation (AH) and disease outbreak periods. We analyzed the plant microbiomes and root exudates during the outbreak, which was associated with the emergence in both healthy (BH) and diseased (BD) plants. Compared with AH and BD plants, BH plants had the lowest F. oxysporum density in the root–soil system (0.74–0.84 times that of AH and BD plants). BD plants showed an elevated amino acid metabolism (2.84–3.38 times that of healthy plants), whereas BH plants showed a higher metabolism of phenolic compounds (1.73 times that of diseased plants). BH plants secreted more palmitic acid (1.53 times that of diseased plants) and recruited more nitrogen (N)-fixing bacteria (e.g., Paenarthrobacter, Sphingomonas), which potentially alleviated N scarcity in the soil, promoted plant growth, and improved the plant defense. Structural equation modeling highlighted the interactions among soil nutrients, root metabolites, and plant nutrients in recruiting pro-growth bacteria to the rhizosphere and roots for healthy plant growth. Our findings provide novel evidence of how root exudates influence plant–microbiome interactions during pathogen infections, highlighting the importance of a balanced root exudate profile and its associated “HealthyBiome” in promoting plant health and growth.

Competition mode and soil nutrient status shape the role of soil microbes in the diversity-invasibility relationship.

Understanding the relationship between plant diversity and invasibility is essential in invasion ecology. Species-rich communities are hypothesized to be more resistant to invasions than species-poor communities. However, while soil microorganisms play a crucial role in regulating this diversity-invasibility relationship, the effects of plant competition mode and soil nutrient status on their role remain unclear. To address this, we conducted a two-stage greenhouse experiment. Soils were first conditioned by growing nine native species separately in them for 1 year, then mixed in various configurations with soils conditioned using one, three, or six species, respectively. Next, we inoculated the mixed soil into sterilized substrate soil and planted the alien species Rhus typhina and native species Ailanthus altissima as test plants. We set up two competition modes (intraspecific and interspecific) and two nutrient levels (fertilization using slow-release fertilizer and nonfertilization). Under intraspecific competition, regardless of fertilization, the biomass of the alien species was higher in soil conditioned by six native species. By contrast, under interspecific competition, the biomass increased without fertilization but remained stable with fertilization in soil conditioned by six native species. Analysis of soil microbes suggests that pathogens and symbiotic fungi in diverse plant communities influenced R. typhina growth, which varied with competition mode and nutrient status. Our findings suggest that the soil microbiome is pivotal in mediating the diversity-invasibility relationship, and this influence varies according to competition mode and nutrient status.