Low Soil pH Research Articles

Influence of Vegetation Dynamics on Soil Organic Carbon and Its Fractions in a Coastal Wetland

Coastal wetland ecosystems are highly efficient in sequestering carbon (C) to mitigate climate change. However, it is still unclear how vegetation dynamics affect soil organic carbon (SOC) and its fractions (labile and recalcitrant C (LC and RC)) in coastal wetlands. Here, we quantified the effects of saltmarsh vegetation dynamics on the SOC and its fractions using the invasiveSpartina alternifloraand co-occurring nativePhragmites australiscommunities as a model. SOC contents in these 2 communities showed similar spatial patterns with an inverted U-shaped curve from tidal mudflats to vegetated marshes. Our results suggested that plant ecophysiological traits play a primary role in regulating the spatial distribution of SOC. In addition, the lower ratio of leaf to shoot inP. australiscommunity facilitates the accumulation of RC, while the lower soil pH inS. alternifloramay accelerate the decomposition of RC. The findings indicated thatS. alternifloracould accumulate more C in the soil owing to its greater plant biomass and photosynthesis rate. However, the reduced soil pH byS. alterniflorainvasion might restrain SOC accumulation. Our findings shed light on the impacts of long-term species invasion on SOC and its fractions in coastal wetlands under global changes.

Mycorrhizal fungi and soil factors influence toxic element uptake in urban grown produce

AbstractDespite the need for more urban‐grown produce, toxic elements contaminated soils continue to be a major barrier to food production and food sovereignty in urban areas and a continued health and environmental justice issue. Although the US EPA provides recommendations regarding levels of soil lead that are safe for gardening, soil abiotic and biotic factors as well as plant identity play a major role in determining the actual crop uptake of toxic elements. This study evaluated the role of crop identity, harvested tissue, and soil factors, including arbuscular mycorrhizal (AM) fungi on crop uptake of lead (Pb) and arsenic (As) in an urban community farm. Crop species varied in their Pb and As accumulations, both by crop identity and also by plant tissue. Crop uptake of lead increased with lower soil pH (range 5.3–6.9) and lower soil P (range 365–1771 mg kg−1 total P). For mycorrhizal crops, greater intensity of AM fungal colonization and the prevalence of arbuscules were associated with greater lead uptake, but the presence of more storage vesicles was related to less As uptake into leaves. These findings can help inform crop selection and soil management to improve soil stabilization of toxic elements in moderately contaminated soils while serving as a platform for community conversations about the importance of soil management in healthy urban food production.

Presence of rhizobia nodulating common birdsfoot trefoil (Lotus corniculatus L.) in soils of Serbia

Common birdsfoot trefoil (Lotus corniculatus L.) is a perennial forage legume tolerant to adverse environmental conditions such as low soil pH, poor drainage, various insects and plant diseases. Owing to its ability to establish a symbiosis with nitrogen-fixing bacteria, rhizobia, thrives on soils of low fertility and is used in grass mixtures to enrich the soil with nitrogen. The aim of the work was to investigate the presence of rhizobia that nodulate birdsfoot trefoil in the soils of Serbia and to perform the isolation and evaluation of their nitrogen fixation potential. The presence and abundance of birdsfoot trefoil rhizobia in 28 soil samples from different localities and types of soil in Serbia, as well as different ways of use, was tested. From positive samples the rhizobial strains were isolated and their efficiency of nitrogen fixation was tested under controlled conditions. The presence of rhizobia that nodulate birdsfoot trefoil was recorded in 23 samples, while all 5 samples where the presence of rhizobia was not recorded are characterized by the absence of the host plant. The number of rhizobia in samples where there was no host plant was significantly less than in its presence. A total of 49 rhizobial strains were isolated, and in some samples of low abundance it was not possible to isolate strains. In controlled conditions during reinoculation, 80% of the strains were active, achieving 2.5 times greater dry above-ground mass than non-inoculated plants. The percentage of nitrogen in plants ranged from 1.6% in the case of inactive strains to 4.6% in the case of highly active strains. The results of the study indicate the necessity of inoculation, that is, the application of rhizobia on the lands where the common birdsfoot trefoil is sown for the first time due to their reduced number and activity.

Growth and yield of soybeans at different dosages of NPK and dolomite fertilizer in ultisols of Bengkulu

Soybean cultivation in Ultisols is constrained by low soil pH and soil fertility levels. Dolomite and NPK fertilization are used to improve soil quality. The goal of this study was to find the best amounts of Dolomite and NPK fertilizer for black soybean growth and yield on Ultisols and how Dolomite and NPK fertilizers affect each other on Ultisols. This study used a completely random design (CRD) 2 factors and 3 replicates. The first factor was Dolomite with four levels: A1 = 0 ton/ha (control), A1 = 0.5 x Al-dd, A2 = 1 x Al-dd, and A3 = 1.5 x Al-dd. The second factor was NPK fertilizer with four levels: N0 = 0 kg/ha (Control), N1 = Urea 25 kg/ha, TSP 100 kg/ha, KCL 80 kg/ha, N2 = Urea 50 kg/ha, TSP 125 kg/ha, KCL 100 kg/ha, and N3 = Urea 75 kg/ha, TSP 150 kg/ha, KCL 120 kg/ha. The collected data were statistically analyzed using Analysis of Variance (ANOVA) at the 5% F level test. Research results show: 1) There is no interaction of single dose of dolomite and NPK on growth and yield of soybean Detam 4 2) Dolomite dose 1.5 times Al-dd gave the best effect on plant height and number of leaves 7 WAT and weight of 100 seeds, 3) There was no significant effect of giving NPK on soybean growth and yield except for the number of leaves 2 WAP.

Soil Acidity and its Distribution in Laterite Soils of Northern Kerala: A Descriptive Analysis

Soil acidity is one of the major constraints of crop production in tropical soils. A study was conducted to examine different forms of soil acidity, contribution of each fraction to total acidity and distribution of exchangeable Al+3, exchangeable H+ detrital laterite rice wetlands of Kerala. Among the series, the Kalikkadavu series reported the highest exchangeable acidity with a mean of 1.66 ± 0.23 meq/100g at a depth of 0-15 cm. Soils from Angadipuram series showed high values for exchangeable hydrogen with a mean of 0.71 ± 0.87 meq/100g and a range of 0.2- 3 meq/100g. Kalikkadavu series reported a high value for exchangeable hydrogen with a mean value of 1.29 ± 0.23 meq/100 g. Regarding potential acidity, Nanminda series reported the highest with a mean value of 40.2 meq/100g. Descriptive statistics of pH dependent acidity data revealed highest acidity for Nanminda series in surface layer with a mean value of 39.27 ± 1.77 meq/100g while in subsurface soils, Arathil series has reported the highest with a mean value of 32.21 ± 3.28 meq/100g. From the paired t-test analysis, significant variations of potential acidity and pH-dependent acidity were observed across surface and subsurface while exchangeable acidity, exchangeable Al+3, exchangeable H+ have shown non-significant variation.Hence, we recommend a proper soil management system that lowers the surface and subsoil acidity in low-pH soil. Again, for best effects in terms of biomass production and economic crop yields, amelioration of soil acidity should be followed by optimum plant nutrient inputs.

Edaphic controls on genome size and GC content of bacteria in soil microbial communities

Nutrient limitation has been shown to reduce bacterial genome size and influence nucleotide composition; however, much of this work has been conducted in marine systems and the factors which shape soil bacterial genomic traits remain largely unknown. Here we determined average genome size, GC content, codon usage, and amino acid content from 398 soil metagenomes across a broad geographic range and used machine-learning to determine the environmental parameters that most strongly explain the distribution of these traits. We found that genomic trait averages were most related to pH, which we suggest is primarily due to the correlation of pH with several environmental parameters, particularly soil carbon content. Low pH soils had higher carbon to nitrogen ratios (C:N) and tended to have communities with lower GC content and larger genomes, potentially a response to increased physiological stress and a requirement for metabolic diversity. Conversely, communities in high pH and low soil C:N had smaller genomes and higher GC content—indicating potential resource driven selection against AT base pairs, which have a higher C:N than GC base pairs. Similarly, we found that nutrient conservation also applied to amino acid stoichiometry, where bacteria in soils with low C:N ratios tended to code for amino acids with lower C:N. Together, these relationships point towards fundamental mechanisms that underpin genome size, and nucleotide and amino acid selection in soil bacteria.

Angiosperms distribution under the influence of microclimatic factors across a polluted ecosystem

Plant species represent the hierarchical expression of vegetation as it is affected by different ecological, environmental factors and pollution variables. This study assesses the impact of a different hidden treasure or factors on angiosperm plants in the marble waste polluted environment. Quadrat quantitative ecological techniques were adapted for sampling of vegetation. Size of the quadrats was kept 1 × 1m, 5 × 5m and 10 × 10m for herbs, shrubs and tree species, respectively. Soil physicochemical properties were carried out using standard protocols. All the collected data were put in MS Excel for analysis in PCORD, CANOCO, STATA and SPSS software's. The degrees of relationship among variables and with abundant plants were measured using Pearson correlation and regression analysis. The structural relationship between environmental variables and abundant angiosperms was determined through Structural Equation Modeling to examine the admired dignity of diverse environmental factors. A total of one hundred two plant species belong to ninety-five genera and forty-eight families were reported from a marble waste polluted environment. Cluster Analysis via Jaccard distance measurement and ward linkage methods gave rise to three plant communities i.e. (i) Populus alba-Arundo donax-Erigeron canadensis plants community, (ii) Morus alba- Rosa webbiana- Centaurium tenuiflorum plants community and (iii) Dalbergia sissoo- Dodonaea viscosa- Panicum antidotale plants community. Among all the measured environmental variables, the dominant plants of the first plant community comprehend positive and significant relationships with soil pH, potassium and negative plus significant relationship with electrical conductivity and organic matter. The abundant plants of 2nd plant community were under the influence of higher potassium concentration and lower soil pH as compared to other communities. Third community exhibits a negative and significant relationship with soil pH in conjunction with higher electrical conductivity in the region. The aforementioned techniques could be used to find out the relationship between plant species distribution and microclimatic variables.

Soil Acidification in Nutrient-Enriched Soils Reduces the Growth, Nutrient Concentrations, and Nitrogen-Use Efficiencies of Vachellia sieberiana (DC.) Kyal. & Boatwr Saplings.

Nitrogen (N) and phosphorus (P) nutrient enrichment is important for grasslands. This study aimed to determine how soils enriched with N and P influenced soil concentration correlations and affected the growth kinetics, mineral nutrition, and nitrogen-use efficiencies of Vachellia sieberiana grown in a greenhouse experiment. The soils used as the growth substrate were analysed and showed extreme acidity (low soil pH, 3.9). Nitrogen-enriched soils were more acidic than P-enriched soils. Exchangeable acidity was strongly negatively correlated with an increase in soil pH, with soil pH between 3.9 and 4.1 units showing the strongest decline. Plant saplings showed increased root biomass, shoot biomass, total biomass, and plant N and P concentrations when grown in soils with high soil P concentrations. Extreme soil acidification in N-enriched soil was one of the main factors causing P unavailability, decreasing sapling growth. Extreme soil acidification increased concentrations of toxic heavy metals, such as Al which may be alleviated by adding lime to the extremely acidic soils. Research implications suggest that soil pH is an important chemical property of the soil and plays a significant role in legume plant growth. Legume species that are unable to tolerate acidic soils may acquire different strategies for growth and functioning.

Problems, Management, and Prospects of Acid Sulphate Soils in the Ganges Delta

Soil is a finite natural resource and is indispensable for human civilization because it is the medium for food production for the biosphere. Continued soil degradation is a forerunner of catastrophe for the living world. The protection of healthy soils and the restoration of problem soils are strongly needed in the current agricultural scenario as competition for urbanization and other human needs for land resources limits the scope for the further availability of land for agriculture. Naturally occurring degraded soils, such as acid sulphate soils, can be restored with scientific interventions and advanced management strategies. The Ganges Delta is a densely populated region, where the inhabitants’ major livelihood is agriculture. Soil acidity and salinity restrict crop performance in this coastal region, particularly the acid sulphate soils (ASSs) posing a risk to agriculture. ASSs are developed from land-use changes from mangrove forest to agricultural land in this region. There is no systematic study on these soil types covering Bangladesh and India. This paper unfolds several aspects related to the characteristics, problems, and detailed management strategies of ASSs relevant to the Gangetic Delta region where these soils continue to be used for intensive agriculture to meet the livelihood needs. Crop yields are very poor in the unmanaged ASSs due to a very low soil pH (<3.5), hampering the growth and development of crops due to nutrient deficiencies and/or toxicities, coupled with soil salinity. There is toxicity of water-soluble Fe, Al, and Mn. The phosphorus nutrition of crops in these soils is affected owing to a high soil P fixation capacity. A deficiency of micronutrients, such as Zn and Cu, was also observed; however, K availability is variable in the soil. The soil acidity is a general problem throughout the soil profile; however, extreme acidity (pH < 3.5) in particular soil horizons is a typical soil characteristic, which creates problems for its efficient management. Specific operations, such as the selective use of soil layers with good properties for crop root growth, major and minor nutrient applications, and soil amendments, including green manuring, application of biofertilizers, and soil microbes, are gradually improving the properties of these soils and bringing back the potential for good crop production. Scientific water/drainage management is needed to gain an agronomic advantage. Evidence of increased crop yields in these soils observed from green manuring, lime, basic slag, and rock phosphate application are presented.

Testing the concept of edaphism for the quartz island flora of the Knersvlakte, South Africa

• Plant-functional traits are useful to study floras on unusual soils. • Quartz island flora, traits and environment differ from the surrounding. • Taxonomic, functional and edaphic diversity are high on quartz islands. • The flora of unusual edaphic habitats is worthy of particular protection. Edaphically unusual sites harbor a flora that is often unique in its taxonomic as well as functional composition and contain many endemic species. While this edaphic endemism, edaphism, has been discussed previously on various special soils, in this study we relate it for the first time to the floristic characteristics of so called “quartz islands”, edaphically driven special habitats in South Africa, and their surroundings (matrix habitat). We sampled the vegetation and soil for 245 vegetation plots in the Knersvlakte Nature Reserve and examined 336 plant species with respect to their evolutionary (plant family, habitat specificity), biogeographical (distributional range) as well as functional traits (life form, leaf succulence, flowering onset, dispersal mode). Based on the floristic uniqueness of the quartz islands, we expect them to host a highly specialized and locally endemic flora with smaller life forms, pronounced leaf succulence (both indicative of resource-conservative economics) and distinct reproductive traits than their surroundings. We find that, compared to the matrix habitat, quartz islands have significantly higher salinity and lower soil pH, and show higher proportion of leaf-succulent species of smaller life forms – some of which are restricted to quartz islands and have different timing of flowering onset, while dispersal via zoochory is less important. Like other special soils, quartz islands harbor unique plant species, which are distinguished by distinct trait patterns. We conclude that the concept of edaphism can be applied to quartz islands.

Magnetic Susceptibility Profile, Fe Content and pH Analysis of Apple Orchard Soil and the Relation to Fruit Diameter

The measurement of magnetic susceptibility, pH, element concentration of Fe and apples diameter has been conducted in orchard soil of Malang, East Java Indonesia. The measurement was performed in two orchards, namely Pujon and Poncokusumo with two different kind of apples in each orchard. This research aimed at exploring in detail linked between magnetic properties, the existence of magnetic mineral as magnetic property carrier in the soil, soil pH, as well as the size of apple diameter to evaluate the quality of apple production in the both areas. The results shows that the soil with lower susceptibility, it was expected that the magnetic mineral of magnetic property carrier to be smaller, low soil pH, meaning that the soil was more acidic which implied on a larger size of apple diameter for Rumbeauty type of apple. Meanwhile, when the soil had a higher susceptibility, and it is expected that the magnetic mineral is also high as well as having high pH, this growing media is appropriate to develop Manalagi type of apple. Based on the observed soil magnetic properties and pH from both observed orchards, it can be suggested that Manalagi apple is appropriate to be planted in Poncokusumo area, while Rumbeauty is appropriate to grow in Pujon area.

Phosphorus Sorption following the Application of Charcoal and Sago (Metroxylon sagu) Bark Ash to Acid Soils

Acidic cations such as Al, Fe, and Mn tend to fix P in soils, and this reaction make P unavailable for plant uptake. Several conventional strategies for farmers had been proposed to ameliorate Al toxicity either via liming or continuous P fertilization. However, these approaches are not only expensive but are also environmental unfriendly. Thus, a sorption study was carried out using charcoal and sago bark ash as soil amendments to determine their effects on P sorption characteristics of low pH soils. Phosphorus sorption determination was based on standard procedures and the P adsorption data for the samples tested in this study were fitted to the Langmuir equation. The results suggest that the combined use of charcoal and sago bark ash decreased P adsorption and increased P desorption relative to the untreated soils. Organic matter in the charcoal reduced P sorption by providing more negatively charged surfaces, thus increasing anion repulsion. Apart from increasing the amount of P adsorbed in the soil, the use of the sago bark ash increased the amount of P desorbed because the primary reaction between the sago bark ash and soils is an acid neutralization reaction. These improvements do not only reduce P fixation in acid soils but they also promote the effective utilization of nutrients via the timely release of nutrients for maximum crop production. In conclusion, the incorporation of charcoal and sago bark ash to the soil had a positive effect on replenishing the soil solution’s P. The organic matter of the charcoal reduces P sorption capacity by blocking P binding sites, increasing the negative electric potential in the plane of adsorption, causing steric hindrance on the mineral surfaces and decreasing goethite and hematite-specific surface areas. However, there is a need for the inclusion of more soil chemical, physical, and mineralogical properties in predicting soil P sorption to enhance the reliability of the findings.

Interactive climate-soil forces shape the spatial distribution of foliar N:P stoichiometry in Vaccinium uliginosum planted in agroforests of Northeast China

In regions with a ban on forest logging, fruit-bearing shrubs are favored as an alternative source of ecological products over the harvesting of timber. The introduction of cultured shrubs from their habitat to newly developed lands has to be decided according to nutrient availability. Foliar nitrogen (N) and phosphorus (P) stoichiometry is an easily measured and reliable parameter to quickly indicate possible limits in imbalanced N-P availability. When attempting to create a spatial distribution map of the foliar N:P ratio in an objective shrub species, it is helpful to first explore its potential acclimation to the N:P imbalance caused by the joint forces of soil property and regional climate. This study evaluated the cultivated populations of Vaccinium uliginosum in northeastern China's agroforests, using Vaccinium uliginosum as a model shrub species. A total of 51 populations were selected from 51 managed stands, of which 34 were in forests and 17 on farmlands. Foliar N and P concentrations, soil physical and chemical properties, and topography were investigated in 2018, and regional climatic factors were assessed by averaging previous 5-year records (2013–2018). V. uliginosum was determined to have a foliar N:P ratio lower than 4.4, which can be characterized as a limit of N relative to that of P. On forested lands, soil pH negatively impacted regressed foliar N:P, which was also part of the contributions of soil total P content and average temperature to foliar N concentration. On farmlands, low soil pH also resulted in a reduced foliar N:P ratio with joint contributions of ammonium N, nitrate N, and available P contents in soils and air humidity. Spatial interpolation indicated that western forests could benefit from introduced V. uliginosum with a higher foliar N concentration, while the introduction to eastern farmlands can lead to a higher foliar N:P ratio up to 14.6. Our study demonstrates recommended locations with expected soil and meteorological conditions by mapping spatial distributions, which can be referred to by other species and regions.

Changes in soil microbial communities in response to repeated application of nitrification inhibitors

In order to assess the changes in soil physio-chemistry, the abundances and community structures of the N-cycling microorganisms, as well as total bacteria, after repeated application of dicyandiamide (DCD) and 3,4-dimethylpyrazolphosphate (DMPP), samples of soil were obtained from a field experiment where DCD and DMPP had been applied along with fertilizer annually for over 13 years. A randomized complete block design was used that included four treatments: no fertilization (CK), fertilizer application (NPK), NPK + DCD, and NPK + DMPP; each treatment with three replicates. Results showed that repeated chemical fertilizer application led to lower soil pH, significantly higher potential nitrification rates (PNRs) and increased population sizes of ammonia oxidizers compared with the control. However, soil pH was unaffected by the application DMPP or DCD over 13 years. Application of DMPP decreased the PNR and the abundance of ammonia-oxidizing bacteria (AOB) and nirK genes, compared to NPK, but DCD addition exhibited inhibitory effects only on PNR. There were no inhibitor- or fertilizer-induced changes in the abundances of nirS, nosZ and 16S rRNA genes. In addition, the results demonstrated that the community compositions of total bacteria and ammonia oxidizers were not altered by N addition and use of inhibitors at the phylum level. The DCD and DMPP inhibitors, therefore, appear to be effective mitigation technologies targeting specific microorganisms with no long-term adverse impact on the soil ecosystem.

Alteration in Forest Soil Biogeochemistry through Coarse Wood Debris in Northeast China

Coarse woody debris (CWD) has a strong influence on nutrient dynamics and hinders its availability through fixation. The CWD decaying logs, with two states (three and four) impacting on carbon (C) capture, nutrient dynamics and enzymatic properties, were investigated under and away (50 cm) from the logs in three forest types, i.e., the Picea koraiensis-Abies nephrolepis-Pinus koraiensis forest (PAPF), Betula costata-Pinus koraiensis forest (BPF) and Tilia amurensis-Pinus koraiensis forest (TPF). The results showed that soil organic carbon (OC), nitrogen (N), soil pH, other soil nutrients and enzymatic activity were significantly affected by the forest types, decay class and distance from decaying logs in three forests. The CWD, with decay class IV under CWD, resulted in the optimum OC 64.7 mg g−1, N 6.9 mg g−1 and enzymatic activity in the PAPF forest, and the distance effect was negligible for all the forests. A lower soil pH value of 3.8 was observed at decay class IV in the soil collected from the immediate vicinity of the deadwood. CWD play a key role in decaying logs in forest ecosystems to enhance C and the nutrient budget with the improved enzymatic activity of the soil. It was concluded from this research that CWD is a critical factor in the nutrient cycling process of forest ecosystems that contributes functionally to the forest floor by inducing the spatial heterogeneity of enzymatic activity, C and nutrient turnover.

Tree species traits and mycorrhizal association shape soil microbial communities via litter quality and species mediated soil properties

Soils harbor a vast diversity of soil microbiota, which play a crucial role in key ecosystem processes such as litter transformation and mineralization, but how complex plant-soil interactions shape the diversity and composition of soil microbiota remains elusive. We performed amplicon sequencing of DNA isolated from mineral topsoil of six common European trees planted in multi-site common garden monoculture stands of broadleaved maple and ash associated with arbuscular mycorrhiza (AM), broadleaved beech, lime and oak associated with ectomycorrhizal fungi (ECM) and coniferous spruce associated with ECM. The main aim of this study was to evaluate the effects of tree species identity, traits and mycorrhizal associations on diversity, community structure, cohesion, and shift in the relative abundance of taxonomic and functional groups of soil bacteria, fungi and nematodes. Our results revealed that soils beneath broadleaved trees hosted higher OTU richness of bacteria, fungi, and nematodes than under Norway spruce. Broadleaved tree species associated with AM fungi showed higher cohesion of bacterial and fungal communities than broadleaved trees associated with ECM fungi, but the cohesion of nematode communities was higher under trees associated with ECM fungi than under trees associated with AM fungi. Copiotrophic bacteria, fungal saprotrophs and bacterivorous nematodes were associated with ash, maple and lime having high soil pH, and high litter decomposition indices, while oligotrophic bacteria, ectomycorrhizal fungi and fungivorous nematodes were associated with beech, oak and Norway spruce that had low soil pH and low litter decomposition indices. Tree species associated with AM fungi had a high proportion of copiotrophic bacteria and saprotrophic fungi while trees associated with ECM fungi showed a high relative abundance of oligotrophic bacteria, ECM fungi and fungivorous nematodes. The different abundances of these functional groups support the more inorganic nutrient economy of AM tree species vs the more organic dominated nutrient economy of ECM tree species. The bacterial community was indirectly affected by litter quality via soil properties, while the fungal community was directly affected by litter quality and tree species. The functional groups of nematodes mirrored the communities of bacteria and fungi, thereby indicating the main and active groups of the tree species-specific microbial communities. Our study suggested that tree species identity, traits, and mycorrhizal association substantially shape microbial communities via a direct effect of litter chemistry as well as via litter-mediated soil properties.

Rhizospheric microbial consortium of Lilium lancifolium Thunb. causes lily root rot under continuous cropping system.

Tiger lily (Lilium lancifolium Thunb.) is a cash crop with a long history of cultivation in China. Its roots have long been used as a valuable component of Chinese medicine. Continuous cropping, the conventional planting approach for tiger lily, often leads to severe root rot disease, but it is not yet clear how this planting method leads to root rot. In this study, we analyzed the rhizosphere microbiome and predicted microbial protein function in tiger lily planted with the continuous cropping method in three different geological types of soil. In order to explore the specific rhizosphere microbiota triggering root rot disease, tiger lily was compared to maize grown in a similar system, which showed no disease development. An analysis of the chemical elements in the soil revealed that the Pseudomonas and Streptomyces genera, with pathogenic functions, were dominant in the tiger lily rhizosphere. The lower soil pH of tiger lily compared to maize supports the accumulation of pathogenic bacteria in the tiger lily rhizosphere. Meanwhile, we discovered that bacteria of the Flavobacterium genus, with their predicted phosphate transport function, specifically accumulated in the maize rhizosphere. Our findings suggest that Pseudomonas and Streptomyces bacteria may result in continuous cropping-induced root rot disease in tiger lily and that Flavobacterium could serve to protect maize from pathogenic bacteria.

Silicon actively mitigates the negative impacts of soil cadmium contamination on garlic growth, yield, quality and edible safety

Potential health risks of cadmium (Cd) in agroecosystems migrating to the human body along the food chain have become a worldwide hotspot issue, but information on phytotoxicity mitigation and product quality and safety assessment of Cd-stressed garlic is still lacking. Thus, based on the response performance of garlic yield and quality to soil pH and Cd level, this study systematically revealed the effects of silicon (Si) on the growth, yield, quality, photosynthesis, fluorescence, antioxidant system, tissue Cd residues and edible safety of Cd-stressed garlic. The results showed that garlic yield and quality decreased with increasing soil Cd levels, while the lower soil pH exacerbated Cd contamination. When exposed to 1.2 mg kg−1 Cd, the bulb yield at pH 5.50 was 5.51% lower than that at pH 6.89, while the Cd residues in the bulb were 8.77% higher. Notably, 0.67∼2.0 g kg−1 Si application enhanced bulb yield (by 12.09%∼39.32%) and quality (e.g., allicin, by 6.67%∼40.00%) and simultaneously reduced Cd absorption, translocation and accumulation (e.g., bioconcentration coefficient, by 13.01%∼86.17%). Si mitigated Cd-induced phytotoxicity mainly by improving root activity, antioxidant enzyme activity, photosynthesis and fluorescence. Si increased the soil pH, which contributed to Cd fixation. These results provide significant theoretical guidance for garlic safety production and heavy metal risk prevention in agroecosystems.

Profiles of citrus orchard nutrition and fruit quality in Hunan Province, China

ABSTRACT Understanding of orchard nutrition status can facilitate the proper management of orchards for higher fruit yield and quality. From 2011 to 2019, the nutrition status of orchards in Hunan Province, a major citrus-producing area in china, were assessed. A total of 361 soil samples, 378 leaf samples and 285 fruit samples of sweet oranges including navel orange (citrus sinensis l. Osbeck ‘newhall’) and common sweet orange (citrus sinensis l. Osbeck ‘bingtangcheng’), and mandarins including satsuma mandarin (citrus unshiu marc. ‘miyagawa’) and ponkan (citrus reticulata blanco ‘xinnu’) were collected. These samples were from112 sweet orange orchards and 140 mandarin orchards. Parameters of soil, leaf and fruit nutrition and fruit quality were analyzed based on these samples. The results revealed that soil acidification occurred in 79.0% of sweet orange orchards (ph 3.56 to 8.12) and 74.7% of mandarin orchards (ph 2.75 to 8.15). Soil organic matter (om) was abundant in both sweet orange orchards (21.3 g/kg on average) and mandarin orchards (19.77 g/kg on average). Nutrient analysis demonstrated deficiencies of nitrogen (n), potassium (k) and boron (b) in soils and leaves of sweet orange and mandarin orchards. Zinc (zn) was abundant in soils but deficient in leaves, suggesting a low zn utilization efficiency in these orchards. Besides, excessive iron (fe), magnesium (mn) and copper (cu) were found in sweet orange and mandarin leaves, which may be associated with low soil ph and fungicides application in this area. The average contents of n, phosphorus (p) and k in the fruit were about 0.80%, 0.11% and 0.51%, respectively, with a ratio close to 1:0.14:0.6. Multiple linear regression (mlr) analysis revealed that leaf npk and molybdenum (mo) significantly affect fruit fresh fruit weight (ffw) and total soluble solids (tss), and leaf p is closely correlated with fruit titratable acid (ta).

The Composition of the Organic Matter Fractions of Loamy Sand after Long-Term FYM Application without Liming

The key to soil organic matter management is understanding the transformation processes of fresh organic matter to permanent humus that control soil organic carbon dynamics. This paper presents the results of the effect of long-term soil fertilization with increasing doses of (manure) FYM and ammonium nitrate on the composition of humus compounds not limed of loamy sand. The study showed that both crop rotation and manure fertilization significantly affected organic matter fractions and humus humification index. The soil in crop rotation B (with enriching effect) accumulated significantly larger amounts of soil organic carbon in 0–30 cm layer despite a lower soil pH, but had lower soil organic quality compared to the soil in crop rotation A (with depleting effect). In both rotations, FYM was applied once per 4-year rotation at a dose of 40 t·ha−1 which improved the soil organic carbon content. Depleting crop rotation (A) showed no increase in soil accumulation of humins fractions (H), while the “enriching” crop rotation (B) had such a tendency. Mineral nitrogen fertilization significantly affected the composition of the humic acids fraction. The soil in crop rotation B was characterized by a significantly higher content of fulvic acid (FA) and lower of humins (H) carbon fraction. The large input of organic matter into the soil under lower content pH conditions may hinder its transformation into permanent humus. Changes in the humification index were the consequence of changes in the carbon content of humic and fulvic acids, under the influence of plant selection in crop rotation and manure fertilization. According to the criterion of this parameter, soil in crop rotation A and soil fertilized with manure had lower loss of the more labile FA fraction (lower value of humification index—1.48).