AK Contents Research Articles

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

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

The advantage of afforestation using native tree species to enhance soil quality in degraded forest ecosystems

Different vegetation restoration methods have improved soil quality to varying degrees. This study, focused on the forest–grassland–desert transition zone in the Hebei–Inner Mongolia border region, and employed a systematic grid sampling method to establish fixed monitoring plots in the Saihanba Mechanized Forest Farm and the Ulan Buh Grassland. The differences in soil quality evolution across various vegetation restoration methods under the same climatic and soil historical conditions were analyzed, elucidating the roles of these vegetation restoration methods in degraded forest ecosystems, with the aim of providing a reference for ecological restoration under similar land conditions. This study used a grid method to establish sample points in the forest–grassland–desert transitional zone and assessed five methods of vegetation restoration sites: artificial forest composed of native species of Larix principis-rupprechtii (FL), artificial forest composed of exotic Pinus sylvestris var. mongolica (FP), natural secondary broad-leaved forest (FN), open grassland (GO), and enclosed grassland (GC). The differences in soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkaline hydrolysis nitrogen (AN), rapidly available phosphorus (AP) and rapidly available potassium (AK) among the different vegetation restoration sites were compared via variance analysis, and the soil quality index (SQI) was calculated to assess the soil quality at the sample points. The SOC, TN, and AN contents of forest soil were significantly greater than those of grassland, and the TN, TP, AN, AK, and SOC contents of FL, FN, and GC were significantly greater than those of FP and GO. Among them, the TN, TP, and SOC contents were the highest in the FL, reaching 2.74, 0.39, and 47.27 g kg−1, respectively. In terms of ecological stoichiometric characteristics, the average N:P ratio in the study area was 6.68, indicating a serious lack of N in the study area. Among the different types of restoration sites, the effect was stronger in the FP than in the FL, and the TN and AN contents were only 1.48 g kg−1 and 116.69 mg kg−1, respectively. The SQI in the FL was not significantly different from that in the FN or GC, but it was significantly greater than that in the FP and GO. These findings indicate that native tree species restoration in degraded forest ecosystems significantly improved soil quality, while the introduction of exotic tree species for afforestation had a minimal effect on improving soil quality.

Effects of mulching and flooding on soil nutrients and bacterial community structure under Phyllostachys praecox

Phyllostachys praecox is a shallow-rooted bamboo that often encounters hypoxia conditions which could be induced by long-term organic material mulching or flooding. It is important to uncover the effect of mulching and flooding on soil nutrient, ammonia-oxidizing microbes, and bacterial diversity. We set up field pot experiments with three treatments (control, mulching, and flooding) under P. praecox. Mulching or flooding altered soil conditions significantly, and both increased ammonium-nitrogen (NH4+-N), total phosphorus (TP), available P (AP), and available potassium (AK) concentrations, and decreased oxygen (O2) concentrations over control. Flooding increased pH and decreased nitrate-nitrogen (NO3−-N), while mulching decreased soil pH and NO3−-N. As O2 content decreased, archaeal 16S rRNA, amoA gene copies of ammonia-oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) increased. Mulching and flooding decreased Shannon, ACE and Chao 1 diversity when compared with the control, and as the O2 contents decreased, bacterial diversity decreased. Redundancy Analysis revealed O2, NO3−-N, AK, AP, and pH were the major factors driving bacterial community structure. Correlation Analysis showed AK and O2 contents were highly correlated with bacterial community structure. In addition, structural equation modeling indicated that O2 facilitated efficient soil N use mainly through soil pH, AK content, and bacterial diversity. Mulching or flooding exerted great effects on environment factor and bacterial community structure, which could be exploited to facilitate the regulation of soil O2 conditions for sustainable P. praecox production.

Influences of tobacco straw return with lime on microbial community structure of tobacco-planting soil and tobacco leaf quality.

Soil amendment is an important strategy for improving soil quality and crop yield. From 2014 to 2019, we conducted a study to investigate the effects of tobacco straw return with lime on soil nutrients, soil microbial community structure, tobacco leaf yield, and quality in southern Anhui, China. A field experiment was conducted with four treatments: straw removed (CK), straw return (St), straw return with dolomite (St+D), and straw return with lime (St+L). Results showed that after 5 years of application, the St+L significantly increased the soil pH by 16.9%, and the contents of soil alkaline nitrogen (N) and available potassium (K) by 17.2% and 23.0%, respectively, compared with the CK. Moreover, the St+L significantly increased tobacco leaf yield (24.0%) and the appearance (9.1%) and sensory (5.9%) quality of flue-cured tobacco leaves. The addition of soil conditioners (straw, dolomite, and lime) increased both the total reads and effective sequences of soil microorganisms. Bacterial diversity was more sensitive to changes in the external environment compared to soil fungi. The application of soil amendments (lime and straw) promoted the growth of beneficial microorganisms in the soil. Additionally, bacterial species had greater competition and limited availability of resources for survival compared to fungi. The results showed that soil microorganisms were significantly influenced by the presence of AK, AN, and pH contents. These findings can provide an effective method for improving the quality of flue-cured tobacco leaves and guiding the amelioration of acidic soil in regions where tobacco-rice rotation is practiced.

Changes in the Soil Microbial Community Structure and Driving Factors during Post-Fire Recovery of the Larix gmelinii Rupr. Forest in Northern China

Fire is crucial for shaping northern forest ecosystems and can affect soil microbial community structure. However, there are few studies on the long-term effects of forest fire disturbance on soil microbial community diversity. In this study, we employed high-throughput sequencing of 16S rRNA and ITS1 to assess variations in the abundance of bacterial and fungal communities in dominant populations at 1, 6, and 11 years post-fire. Furthermore, a comprehensive analysis was conducted to examine the relationship between soil microenvironmental changes and soil microbial communities after fire disturbances, considering soil physicochemical properties, including bulk density, moisture content, pH, organic carbon, total nitrogen, ammonium nitrogen, nitrate nitrogen, available potassium, and available phosphorus. We found that fire significantly increased soil pH, NO3−-N, AP, and AK contents, in which the content of NO3−-N basically recovered to the pre-fire level at 11 years after fire. The soil SOC and TN contents decreased significantly 1 year after the fire. However, compared to the unfired site, the SOC content essentially recovered 11 years after the fire, while TN content was still significantly higher 11 years after fire. Furthermore, fire changed the diversity and richness of soil microbial communities to some extent. PCoA and NMDS analyses suggested that the bacterial community structures in soil samples from different burned areas with different recovery periods exhibited similarity. However, notable differences were observed in the fungal community structures between the 1-year and 6-year post-fire study sites when compared to the unburned control site. Bacterial communities predominantly comprised Proteobacteria, Actinobacteria, and Acidobacteria, while fungal communities were mainly dominated by Ascomycota and Basidiomycota. RDA confirmed the significant roles of SOC, TN, and NO3−-N in affecting the diversity of soil microbial communities. Therefore, our study not only enhances our understanding of the long-term effects of forest fire disturbances on soil properties and soil microbial community structure, but also provides insights for further utilizing and controlling carbon and nitrogen content to regulate soil microbial activity and accelerate the recovery process of burned areas.

Influences of season on cattle slurry compositions predicted by micro-NIR spectrometry

In this study, we used a low-cost micro-near-infrared (NIR) spectrometer to analyze the composition of cattle slurries and examined the influence of the season (spring vs. winter) and characteristic wavelength on the performance of the corresponding quantitative models. One hundred and twenty-seven cattle slurry samples collected from five farms in spring and winter (Heilongjiang, China) were characterized in terms of total nitrogen (TN), total phosphorus (TP), total potassium (TK), available phosphorus (AP), available potassium (AK), organic matter (OM), and pH using reference methods. The partial least squares (PLS) method was used to establish seasonal models that involved winter and a mixed model to quantify cattle slurry composition. The characteristic wavelengths were selected using a competitive adaptive reweighted-sampling (CARS) algorithm. The results showed that the winter model successfully predicted the TP content using the full band. The coefficient of determination for prediction (R2p) and ratio of prediction to deviation (RPD) were 0.846 and 3.077, respectively. This model was useful for predicting TK and AK contents and pH (R2p = 0.551–0.773, RPD = 2.251–2.727) and moderately useful for predicting TN and OM contents (R2p = 0.517 and 0.498, respectively; RPD = 1.892 and 2.094, respectively). For all compositions, the prediction performance was better for the winter models than for the mixed models. Although the use of characteristic wavelengths improved the efficiency of model construction, it had no positive effect on the performance of the mixed models. This study enables the setup of a rapid testing method for safely returning slurry to the field.

Combined metagenomics and metabolomic analysis of microbial community structure and metabolic function in continuous soybean cropping soils of Songnen Plain, China

Continuous cropping has a negative effect on soybean yield. In this study, a positioning experiment was conducted starting in 2015, with three treatments: maize–soybean rotation (SMR), 2-year maize, 2-year soybean rotation cropping (SC2), and 8-year soybean continuous cropping (SC8). We determined soybean yields (2015–2022) and analyzed soil microbial communities, functions, and metabolites composition in the 0–20 cm tillage layer using metagenomics technology and GC–MS technology during soybean flowering in 2022. Results indicated that continuous cropping (SC8) significantly reduced soybean yield compared to crop rotation (SMR) during the experimental period, while SC8 showed higher yield than SC2 in 2022. Compared to SMR, SC8 significantly increased soil N content and significantly decreased pH and TP, AP, and AK content. However, the pH and AK contents of SC8 were significantly higher than those of SC2. LeFSe analysis showed that Friedmanniella, Microlunatus, Nitrososphaera, Rubrobacter, Geodermatophilus, Nitriliruptor were enriched in SC8. Gaiella, Sphaerobacter, Methyloceanibacter were enriched in SC2. Sphingomonas, Cryobacterium, Marmoricola, Haliangium, Arthrobacter, Ramlibacter, Rhizobacter, Pseudolabrys, Methylibium, Variovorax were enriched in SMR. And the relative abundance of Cryobacterium, Marmoricola, Haliangium, Arthrobacter, Ramlibacter, Rhizobacter, Methylibium, Variovorax was significantly positively correlated with yield, while the relative abundance of Gaiella and Sphaerobacter was significantly negatively correlated with yield. SC8 significantly increased the abundance of genes in nitrogen metabolism and significantly decreased the abundance of genes related to phosphorus and potassium metabolism compared with SMR. However, the abundance of genes in potassium metabolism was significantly higher in SC8 than in SC2. Metabolomic analysis showed that compared to SMR, SC8 decreased the abundance of carbohydrates, ketones, and lipid. However, the abundance of carbohydrates, ketones, and lipid was significantly higher in SC8 than in SC2. Mantel test showed that soil pH and AK significantly affected soil microbial community, function, and metabolite composition. Correlation analysis showed significant correlation between soil metabolites and microorganisms, metabolic functions.Graphical

County-Scale Spatial Distribution of Soil Nutrients and Driving Factors in Semiarid Loess Plateau Farmland, China

Characterized by a topography of thousands of ravines, the Loess Plateau has highly complex spatial variability in terms of soil nutrients. Therefore, it is of considerable importance to study the soil nutrient spatial distribution, driving factors of precise fertilizer management, and the strategic use of soil nutrient resources. In 2017, 242 soil samples were taken from the semiarid Anding district farming region in northern China. The spatial variability and factors influencing soil nutrients were studied using statistical and geostatistical methods. The results showed that the mean soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), available potassium (AK), and pH values were averaged at 12.64 g·kg−1, 0.84 g·kg−1, 23.20 mg·kg−1, 188.87 mg·kg−1, and 8.60, respectively. The nugget-to-sill ratios for the semi-variograms of SOM, TN, AP, and AK varied from 25.84 to 49.93%, while the coefficients of variation varied from 24.53 to 69.44%, revealing that all four indicators exhibited considerable variability, and that the samples’ geographical variability was produced by a combination of random and structural factors. Overall increasing trends were exhibited from the middle to the northeast and southwest in the distributions of SOM, TN, and AP. The spatial distribution of AK displayed the opposite trend, increasing from the southwest to north and southeast. The texture of the tillage layer was the main factor directly affecting SOM, and explained 8% of its variation. The distribution of TN was mainly influenced by the irrigation method and water source type. AP and AK contents differed significantly between the two parent materials, three textures, and three topography types at the level of p &lt; 0.01. In conclusion, the regional soil fertility was poor, spatial heterogeneity was moderate, and influencing factors were complex, highlighting the need to adopt precise fertilization management and adopting land management measures according to the actual influencing factors of each nutrient, thereby contributing to the enhancement of regional fertility.

Assessment of macronutrients status using digital soil mapping techniques: a case study in Maru'ak area in Lorestan Province, Iran.

The present study was conducted to compare generalized linear model (GLM), random forest (RF), and Cubist to produce available phosphorus (AP) and potassium (AK) maps and to identify the covariates that control mineral distribution in Lorestan Province, Iran. To this end, the locations for collecting 173 soil samples were determined through the conditioned Latin hypercube sampling (cLHS) method, at four different land-uses (orchards, paddy fields, agricultural, and abandoned fields). The performance of the models was assessed by coefficient of determination (R2), root-mean-square error (RMSE), and mean absolute error (MAE) indices. The results showed that the RF model fitted better than GLM and Cubist models and could explain 40 and 57% of AP and AK distribution, respectively. The R2, RMSE, and MAE of the RF model were 0.4, 2.81, and 2.43 for predicting AP and equal to 0.57, 143.77, and 116.61 for predicting AK, respectively. The most important predictors selected by the RF model were valley depth and soil-adjusted vegetation index (SAVI) for AP and AK, respectively. The maps showed higher AP and AK content in apricot orchards compared to other land-uses. No difference was observed between AP and AK content on paddy fields, agricultural, and abandoned areas. The higher AP and AK contents were related to orchard management practices, such as failure to dispose of plant residuals and fertilizer consumption. It can be concluded that the orchards (by increasing soil quality) was the best land-use in line with sustainable management for the study area. However, generalizing the results needs more detailed research.

Improved soil composition promotes nutrient recovery during vegetation restoration in karst peak-cluster depressions

The relationship between the soil structure and nutrient content during vegetation restoration of karst peak-cluster depression remains uncertain. Via field investigations and laboratory experiments, the changes in soil aggregate composition and nutrient distribution characteristics and their relationship during four stages of vegetation restoration (grassland (GL), shrub grass (SG), bush forest (BF) and secondary forest (SF) stages) in a karst peak-cluster depression were evaluated. The results showed that (1) vegetation restoration enhanced the formation of > 0.25 mm aggregates, while the distribution of aggregates in each stage was dominated by > 2 mm aggregates, constituting>72.18 % of the total aggregates, while the content of the other aggregates decreased with decreasing size. (2) Vegetation restoration gradually increased the soil organic matter (SOM), total potassium (TK) and available phosphorus (AP) contents, which peaked at the SF stage; the total nitrogen (TN), total phosphorus (TP), alkali-hydrolyzable nitrogen (AN), rapidly available potassium (AK) and exchangeable calcium (ExCa2+) and magnesium ions (ExMg2+) contents peaked in the BF stage and then slightly decreased, indicating that soil nutrient storage thresholds existed in the karst area. (3) The TN, AP, and ExMg2+ contents increased with decreasing aggregate size, and the AN and AK contents first increased and then decreased with decreasing aggregate size. (4) Among the soil aggregates, the nutrient contribution rate was dominated by > 2 mm aggregates, accounting for 41.42 %∼89.01 % of the total aggregates, with a coefficient of determination ranging from 0.456 to 0.998 according to stepwise regression analysis, suggesting that soil nutrients are highly correlated with the nutrient contents in the > 2 and 2–1 mm aggregates and that the soil aggregate composition determines the aggregate nutrient contribution. Vegetation restoration improves the soil structure and nutrient retention capacity, and the aggregate composition is the decisive factor of the nutrient distribution.

Changes in soil properties in different land use types in a desert-oasis ecotone, Inner Mongolia, China

This study aims to examine the changes in soil chemical properties (soil organic matter, SOM; available nitrogen, AN; available phosphorus, AP; available potassium, AK; total nitrogen, TN; total phosphorus, TP and pH) in three depths (i.e. 0-5, 5–10, 10–20 cm) from different land use types of the Green Beach Desert-oasis Ecotone, Inner Mangolia, China. Using soil chemical properties data, comprehensive soil quality index (SQI) was calculated based on principal component analysis (PCA) of variables across different soil depths for different land use types. Results showed that soil properties differed significantly according to land use type. The eight land use types all showed decreases in TN and TP meaning values for these variables fell below those measured from the control plot (bare ground or ‘CK’). Farmland and protective forest soils showed higher AK, AN, AP and SOM contents with protective forest soil the higher of the two. This contributed to accumulation of soil nutrients. Soil quality index results showed that the soil quality index of abandoned farmland in 5–10 cm and 10–20 cm soil layer is the highest among the eight types of land, therefore, the 5–10 cm and 10–20 cm soil layers of abandoned farmland could help to optimize soil nutrients. The 0–5 cm layer of the protective forest soil also showed obvious nutrient accumulation. These results provide basic reference data and trends for soil quality assessment in arid, ecologically fragile areas.

C, N, P, K stoichiometric characteristics of the “leaf-root-litter-soil” system in dryland plantations

• Tree species and afforestation years affected nutrient cycling of plantations. • The highest C was in fine roots and the highest N, P and K was in green leaves. • Green leaves absorbed more P and maintained P homeostasis to alleviate P limitation. • Caragana korshinskii was more suitable for ecological restoration in drylands. Plantation’s nutrient cycling can regulate and affect the material cycling of ecosystems, which is the key to maintain the sustainable development of the plantation ecosystem. However, the current understanding of the nutrient cycling characteristics of the “leave-root-litter-soil” continuum of dryland plantation ecosystems is limited. Therefore, in the Longzhong Loess Plateau of China, we selected nine typical dryland plantations to carry related research, including two evergreen ( Platycladus orientalis (13-years and 50-years) and Pinus tabuliformis ) and four deciduous ( Caragana korshinskii (13-years, 35-years and 55-years), Armeniaca sibirica , Populus hopeiensis and Tamarix chinensis ) tree species, and measured C, N, P and K contents of green leaves, fine roots, leaf litter and surface soil (0–20 cm). Results showed tree species and afforestation years strongly changed C, N, P and K contents and ratios of green leaves, fine roots, leaf litter and soil components, and also significantly affected leaf N, P and K reabsorption efficiencies. The average N, P and K contents of four components and soil available nitrogen (AN), available phosphorus (AP) and available potassium (AK) contents in deciduous plantations were higher than those in evergreen plantations, resulting in the lower C:N:P:K stoichiometry of deciduous plantations than evergreen plantations. Especially in 55-years C. korshinskii plantation, its soil C, N, AN, AP and AK contents were higher than those in A. sibirica , P. hopeiensis , P. orientalis and P. tabuliformis plantations. Moreover, soil C, N, P, AN, AP and AK contents in C. korshinskii plantations increased significantly with the increase of afforestation years. Thus, C. korshinskii was more suitable for ecological restoration in drylands. Due to the P limitation in plantations, P reabsorption efficiency was higher than N reabsorption efficiency, and significantly negatively correlated with P contents of four components. And green leaves had the homeostasis to soil AP, which may be the nutrient utilization strategies for plantations to alleviate P limitation. Correlation analysis revealed that the C cycling appeared in green leave-fine root and green leave-leaf litter, the N cycling appeared in green leave-leaf litter-soil-fine root, and the P cycling and K cycling appeared in green leave-leaf litter- soil and leaf litter-fine root. These results will provide guidance for ecological restoration and plantation management in drylands.

Effects of disturbances by plateau pikas on soil microbial communities in an alpine ecosystem of the southeast Qinghai-Tibetan plateau, China

Small burrowing herbivores often disturb the grassland soil. Although the plateau pika (Ochotona curzoniae) is widespread in alpine meadows in the Qinghai–Tibet Plateau, their detailed effects on ecosystem properties are not well-established. In this study, we investigated the effects of the densities of plateau pikas on plant characteristics, soil properties, and the composition and diversity of soil microbial communities. Plant coverage, height, aboveground biomass, and belowground biomass decreased with an increase in the densities of active plateau pika burrows. Additionally, pika disturbances led to distinct changes in soil moisture, soil bulk density (SBD), total phosphorus (TP), NH4+-N, available phosphorus (AP), and available potassium (AK) contents. Soil moisture, TP and AK contents were highest under moderate plateau pika disturbance levels, whereas the SBD and AP content were highest under the highest active burrow density. However, soil microbial diversity, as determined by high-throughput sequencing, did not differ significantly among pika disturbance levels. Linear discriminant analysis Effect Size revealed that biomarker bacteria for various levels of disturbances belong to Proteobacteria, Bacteroidetes, and Firmicutes, and most biomarker bacteria were found at moderate disturbance level (D2), while biomarker fungi belong to Ascomycota and Basidiomycota, and most biomarker fungi were found in the highest plateau pika disturbance level (D4). Pika disturbances significantly influenced the microbial community, possibly via alterations in the belowground biomass, SBD, AK and TP contents. Thus, plateau pika disturbances significantly influenced the plant and soil properties and microbial community structure.

Differential response of bacterial diversity and community composition to different tree ages of pomelo under red and paddy soils.

Rhizosphere soil microbial communities substantially impact plant growth by regulating the nutrient cycle. However, dynamic changes in soil microbiota under different tree ages have received little attention. In this study, changes in soil physicochemical properties, as well as bacterial diversity and community structures (by high-throughput Illumina MiSeq sequencing), were explored in pomelo trees of different ages (i.e., 10, 20, and 30 years) under red and paddy soils cultivated by farmers with high fertilizer input. Moreover, soil factors that shape the bacterial community, such as soil pH, AP (available phosphorous), AK (available potassium), and AN (available nitrogen), were also investigated. Results showed that pH significantly decreased, while AP, AK, and AN increased with increasing tree age under red soil. For paddy soil, pH was not changed, while AP was significantly lower under 10-year-old pomelo trees, and AK and AN contents were minimum under 30-year-old pomelo trees. Both soil types were dominated by Proteobacteria, Acidobacteria, and Actinobacteria and showed contrasting patterns of relative abundance under different tree age groups. Bacterial richness and diversity decreased with increasing tree age in both soil types. Overall, bacterial community composition was different under different tree ages. RDA analysis showed that soil pH, AP, and AN in red soil, and pH and AP in paddy soil showed the most significant effects in changing the bacterial community structure. A random forest model showed Sinomonas and Streptacidiphilus in red soil, while Actinoallomurus and Microbacterium in paddy soil were the most important genera explaining the differences among different age groups. The ternary plot further revealed that genera enrichment for Age_30 was higher than that for Age_10 and Age_20 in red soil, whereas specific genera enrichment decreased with increasing tree age under paddy soil. Co-occurrence network revealed that bacterial species formed a complex network structure with increasing tree age, indicating a more stable microbial association under 20 and 30 years than 10-year-old pomelo trees. Hence, contrasting patterns of changes in soil physicochemical properties and soil microbial communities were recorded under different tree ages, and tree ages significantly affected the bacterial community structure and richness. These findings provide valuable information regarding the importance of microbes for the sustainable management of pomelo orchards by optimizing fertilizer input for different ages of trees.

Soil microbiome and metabolome analysis reveals beneficial effects of ginseng–celandine rotation on the rhizosphere soil of ginseng-used fields

Ginseng (Panax ginseng C.A.Meyer) cultivation is hindered by the continuous cropping obstacle, whereby without appropriate rotations yield decline and fields must be abandoned. Organism interactions in the rhizosphere alleviate and improve the obstacles to continuous cropping of ginseng. In this study, high-throughput sequencing and gas chromatography coupled with time-of-flight mass spectrometry (GC–TOF-MS) in combination with analysis of soil chemical properties were used to investigate soil microecological changes after 5 years of celandine (Chelidonium majus L.) cultivation in land previously planted with ginseng for 6 years. Comparison of data for the ginseng–celandine rotation (experimental group) and ginseng–fallow (control group) revealed that the celandine rhizosphere TOC, AN, and AK contents as well as PPO activity and Cat activity were significantly increased. Rotation increased the abundance of some bacteria and fungal in the rhizosphere of celandine rhizosphere soil, such as Arthrobacter, Metarhizium, and Exophiala. The relative abundance of Fusarium in ginseng–celandine rotation soil was lower than that of ginseng–fallow soil, which may effectively reduce the incidence of ginseng root rot. The non-targeted metabolites and microbial community structure of the rhizosphere soil were changed with celandine cultivation. In celandine rhizosphere soil, the abundance of the bacterial and fungal communities was positively or negatively correlated with rhizosphere soil metabolites. Pathway enrichment analysis showed that starch and sucrose metabolism were significantly enriched in the celandine rhizosphere soil, a result consistent with the results shown in bacterial community function prediction and non-targeted metabolomics. The present combined analysis of the soil microbiome and non-targeted metabolome provided insight into the effects and mechanism of ginseng–celandine rotation on the soil micro-ecosystem of ginseng-used fields. Briefly, crop rotation with celandine was beneficial to soil quality, and it is a good option to alleviate Ginseng continuous cropping obstacles.

Land-Use Driven Changes in Soil Microbial Community Composition and Soil Fertility in the Dry-Hot Valley Region of Southwestern China.

The Dry-Hot Valley is a unique geographical region in southwestern China, where steep-slope cultivation and accelerating changes in land-use have resulted in land degradation and have aggravated soil erosion, with profound impacts on soil fertility. Soil microbes play a key role in soil fertility, but the impact of land-use changes on soil microbes in the Dry-Hot Valley is not well known. Here, we compared characteristics and drivers of soil microbial community composition and soil fertility in typical Dry-Hot Valley land uses of sugarcane land (SL), forest land (FL), barren land (BL) converted from former maize land (ML), and ML control. Our results showed that BL and SL had reduced soil organic carbon (SOC), total nitrogen (TN), and total potassium (TK) compared to ML and FL. This indicated that conversion of ML to SL and abandonment of ML had the potential to decrease soil fertility. We also found that fungal phyla Zoopagomycota and Blastocladiomycota were absent in SL and BL, respectively, indicating that land-use change from ML to SL decreased the diversity of the bacterial community. Redundancy analysis indicated that the relative abundance of bacterial phyla was positively correlated with TN, SOC, and available potassium (AK) content, and that fungal phyla were positively correlated with AK. Land-use indirectly affected the relative abundance of bacterial phyla through effects on soil moisture, clay, and AK contents, and that of fungal phyla through effects on clay and AK contents. In addition, land-use effects on bacteria were greater than those on fungi, indicating that bacterial communities were more sensitive to land-use changes. Management regimes that incorporate soil carbon conservation, potassium addition, and judicious irrigation are expected to benefit the stability of the plant–soil system in the Dry-Hot Valley.

The Influence of Soil Erodibility and Saturated Hydraulic Conductivity on Soil Nutrients in the Pingshuo Opencast Coalmine, China.

Soil erodibility (K factor) and saturated hydraulic conductivity (Ks) are essential indicators for the estimation of erosion intensity and can potentially influence soil nutrient losses, making them essential parameters for the evaluation of land reclamation quality. In this study, 132 soil samples from 22 soil profiles were collected to measure soil physicochemical properties (e.g., particle size distribution, bulk density and soil nutrient content) and calculate the K factor and Ks of reclaimed soils across the South Dump of the Pingshuo opencast coalmine in the Loess Plateau, China. Geostatistical analysis and the kriging interpolation were employed to quantify the spatial variations in the K factor and Ks in different layers. The results show that the K factor at 0–10 cm is obviously lower than that of other soil layers due to the external input of organic matter, while the Ks tends to decrease along with soil depth. Horizontally, the K factor at 0–10 cm and 50–60 cm shows a decreasing tendency from west to east, while that of other soil layers seems not to show any spatial distribution pattern along latitude or longitude. Meanwhile, the Ks at 0–10 cm presents a striped distribution pattern, while that of other soil layers shows a patchy pattern. On the other hand, the independent-sample t-test and Spearman’s correlation analysis were carried out to determine the effects of soil erodibility on total nitrogen (TN), soil organic matter (SOM), available phosphorus (AP) and potassium (AK). Overall, the K factor is negatively correlated with TN (r = −0.362, p < 0.01) and SOM contents (r = −0.380, p < 0.01), while AP and AK contents are mainly controlled by Ks. This study provides insight on the optimization of reclamation measures and the conservation of soil nutrients in reclaimed land of similar ecosystems.

The changes in macronutrients and microbial community structure during the co-composting of white wine distillers’ grains and potassium silicate

Composting is a low-cost, efficient, and environmental-friendly treatment method for organic solid wastes. White wine distillers’ grains (WWDG) are the byproducts of alcohol production from grains. How to deal with distillers' grains is becoming an urgent problem for distillers in China. In this article, the composting process of WWDG with an addition of potassium silicate (PS) or not being studied. The results showed that with or without PS, WWGD can be used as the main raw material to produce compost. However, the addition of PS increased the potassium contents in the final compost and contributed to the composting process especially during the early stage of fermentation. The ratio of WWDG: PS = 10:2.5 (weight ratio) was close to optimum for the co-composting process. The addition of PS increased the total potassium (TK) and available potassium (AK) content in the final compost. The TK and AK contents in J1, J2, and J3 treatments were 18.87, 36.76, 42.36 g kg−1, and 6.55, 7.98, 8.46 g kg−1, respectively. Bacillus, Tepdimicrobium, Lactobacillus, and Petrimonas were the key bacterial genera while Monascus, Aspergillus, and Penicillium were the key fungal genera observed during the composting process. The results of the seed germination experiment showed that the final compost was mature and had no phytotoxicity. The results of field trials also showed that the compost produced by WWDG and PS increased the sweet potato yield and improved the soluble sugar contents in sweet potato tubers. This research provided a new direction for the resource utilization of distiller grains composting.

Diversity of microbial communities and soil nutrients in sugarcane rhizosphere soil under water soluble fertilizer.

The dynamics of soil microbial communities are important for plant health and productivity. Soil microbial communities respond differently to fertilization. Organic water soluble fertilizer is an effective soil improver, which can effectively improve soil nutrient status and adjust soil pH value. However, little is known about the effects of water soluble fertilizers on soil microbial community, and the combined effects on soil nutrients and sugarcane productivity. Therefore, this study sought to assess the effects of water soluble fertilizer (1,050 kg/hm2 (WS1), 1,650 kg/hm2 (WS2)) and mineral fertilizer (1,500 kg/hm2 (CK)) on the soil microbial community, soil nutrients and crop yield of sugarcane. The results showed that compared with CK, the application of water soluble fertilizers (WS1 and WS2) alleviated soil acidity, increased the OM, DOC, and AK contents in the soil, and further improved agronomic parameters and sugarcane yield. Both WS1 and WS2 treatments significantly increased the species richness of microorganisms, especially the enrichment of beneficial symbiotic bacteria such as Acidobacteria and Planctomycetes, which are more conducive to the healthy growth of plants. Furthermore, we found that soil nutrient contents were associated with soil microbial enrichment. These results indicate that water soluble fertilizer affects the enrichment of microorganisms by improving the nutrient content of the soil, thereby affecting the growth and yield of sugarcane. These findings therefore suggest that the utilization of water soluble fertilizer is an effective agriculture approach to improve soil fertility.

Increased organic fertilizer application and reduced chemical fertilizer application affect the soil properties and bacterial communities of grape rhizosphere soil

Increasing organic fertilizer application can improve the sustainability of soil productivity, but the effects of increased organic fertilizer application with reduced chemical fertilizer application over different time periods on chemical properties and bacterial community of grape rhizosphere soil in an arid region are not clear. In this study, three years of fixed-point field tests were used to compare the effects of various fertilization treatments on the soil properties and bacterial community in the grape rhizosphere. The results showed that (1) T1 and T2 significantly increased SOM, AN, AP and AK contents in grape rhizosphere soil. TN, TP and TK contents in grape leaves of T2 were the highest of those in five fertilization treatments. (2) The abundances of Proteobacteria and Bacteroidetes phyla and especially of Arthrobacter, Pseudomonas, Nitrosopira and Bacillus genera were higher in T2 than in the other samples. (3) SOM, AP and AN contents in soil were the main factors affecting soil bacterial community and mineral element contents in grape leaves and roots according to an RDA analysis. In summary, the application of organic fertilizer with reduced chemical fertilizer for two years had the greatest impact on the soil properties and bacterial community of the grape rhizosphere soil.