Increased Soil Microbial Diversity Research Articles

Effects of AMF on Maize Yield and Soil Microbial Community in Sandy and Saline Soils.

This study aimed to investigate the effects of applying arbuscular mycorrhizal fungi (AMF) on maize root growth and yield formation under different soil conditions. This study was conducted under sandy soil (S) and saline-alkali soil (Y), with treatments of AMF application (AM) and no AMF application (CK). The root characteristics, yield, and quality of maize were measured. High-throughput sequencing technology was employed to assess the impact of AMF on the soil microbial community structure, and the correlation between soil microbes and soil physicochemical properties was elucidated. The results show that under both sandy and saline-alkali soil conditions, AMF application significantly enhanced maize root growth, yield, grain quality, and soil available nitrogen (AN), available phosphorus (AP), and available potassium (AK) contents compared to the CK treatment. Soil microbial Alpha diversity analysis indicated that AMF application effectively increased soil microbial diversity and richness. Principal coordinate analysis (PCoA) and microbial community structure analysis revealed significant differences in bacterial communities between AM treatment in sandy soil (SAM) and CK in sandy soil (SCK), and significant differences in both bacterial and fungal communities between AM treatment in saline-alkali soil (YAM) and CK in saline-alkali soil (YCK). Furthermore, significant correlations between microbial communities and soil physicochemical properties were found, such as AN, AP, AK, soil salinity (SS), and organic matter (OM) content. AMF application had a greater impact on bacterial communities than on fungal communities. This study demonstrated that the use of AMF as a bio-fungal fertilizer was effective in improving spring maize yields, especially in terms of yield increase and quality stability in sandy and saline soils, thereby contributing to safe and sustainable cropping practices.

Long-term cover crop monocultures and mixtures improve soil multifunctionality and shift microbial communities and functions

Long-term cover crops are an emerging approach for achieving sustainable agriculture by reducing fertilizer use and enhancing soil quality. However, soil microbial communities, multifunctionality (i.e., the ability of soil ecosystems to simultaneously provide and maintain multiple ecological functions), and their relationships in cover crops remain poorly understood, especially in cover crop mixtures. To address these issues, here, we conducted a 15-year field experiment under different cover crop deployments (one legume and one brassica grown in monoculture or in mixture) in Carya cathayensis plantations. We found that cover crops significantly increased soil microbial diversity and multifunctionality, especially in mixtures. The bacterial and fungal compositions was significantly affected by cover crops. Interestingly, some taxa may serve as potential indicator species for nutrient status (i.e., bacterial Subgroup_2, Subgroup_6 and Subgroup_17). Cover crops significantly increased beneficial microbial functions (e.g., nitrogen fixation) but decreased pathogen-related functions (e.g., pathotroph). Bacterial and fungal community assemblages under cover crops were dominated by stochastic processes. Cover crops, especially mixtures, had a higher habitat niche breadth (Bcom). In addition, cover crops have more complex and stable bacterial and fungal networks. Partial least squares path modeling further confirmed that the variations in soil multifunctionality were largely related to nutrient resources. Importantly, the relative abundance of rare microbial taxa was also highly correlated with soil multifunctionality. Overall, our study illustrates that the use of cover crops in the long term can foster soil microbial specific taxa and contribute to improved soil multifunctionality. Our study provides support for the benefits of a legume-brassica mixture over monocultures of either and a theoretical basis for exploring cover crops as an ecological management model.

Polyaspartic Acid Urea Increased Maize Yield by Enhancing Leaf N Turnover Efficiency and Soil Microbial Diversity

The release rates of different nitrogen (N) fertilizers and their matching with plant demand determine crop yields. A field experiment was conducted to investigate the effect of using no fertilizer (N0), regular urea applied at rates of 180 kg ha−1 (N180) and 240 kg ha−1 (N240), controlled-release urea applied at a rate of 180 kg ha−1 (H180), and polyaspartic acid urea (PASP) on maize seed yield, soil microbial community diversity, and leaf N-converting enzymes. XianYu 688 was selected as the test maize variety. All cobs in the sample plots were collected per unit area to estimate maize yield. The enzyme-linked immunosorbent assay (ELISA) was used to determine leaf N-converting enzyme activities. Soil DNA was extracted using the Power Max Soil DNA Isolation Kit and subsequently sequenced using the Illumina HiSeq platform (PE 2500) to determine the microbial diversity and communities. The results showed that the highest seed yields were obtained under N240 and PASP180 treatments. The N-partial factor productivity of the PASP180 fertilizer was significantly higher than that of the other treatments. PASP treatment significantly increased maize seed yield due to the potential of storing more N in the ear leaves. Additionally, partial N productivity showed a significant positive correlation with the soil microbial Shannon, Chao1, and ACE indices, indicating that increased soil microbial diversity promoted N efficiency in maize. Further analysis revealed that PASP treatment increased seed yield by promoting leaf N-converting enzyme activity and soil microbial diversity. The results revealed that nitrate reductase (NR), glutamate synthase (GOGAT), and glutaminase (GLNS) enzyme activities in maize leaves were higher under the PASP treatment than under other fertilizer treatments. The PASP treatment significantly enhanced soil microbial diversity at different maize stages. Our study revealed the effects of using different N fertilizers on seed yield by examining their impact on soil microbial diversity and leaf N-converting enzyme activity. This study provides essential insights into maize production and soil fertility maintenance in the North China Plain.

Fertilization enhances rice productivity by promoting phosphorus uptake and altering soil microbiota

Fertilization can enhance crop yield and improve soil health. However, its effects on nutrient uptake, soil microbiota, and rice yield remain unclear. Herein, we designed a double-cropping system with different fertilization treatments to determine their contributions to paddy soil agroecosystem and rice yield. Soil samples were collected before planting the early rice, after harvesting early rice, and after harvesting the late rice. Soil physicochemical properties, and rice yield, and rice nutrient (total nitrogen, phosphorus, and potassium contents) were determined. Variation of soil microbiota were also determined by high-throughput sequencing. We found that soil potassium content significantly improved during the planting process (P < 0.05), while rice phosphorus displayed significant variation under fertilization (P < 0.05). Notably, late rice yield was significantly higher than early rice yield (P < 0.001) after fertilization treatment. Furthermore, rice yield was positively correlated with available soil phosphorus (P < 0.05), indicating that fertilization promoted phosphorus uptake. Organic fertilizer altered the soil microbiota and increased Chloroflexi phyla abundance, while organic fertilizer combined with a compound microbial agent increased the diversity of soil microbial communities. A partial least squares path model revealed that fertilizer treatment directly positively affected rice yield by influencing phosphorus uptake and Shannon index (P < 0.01). Collectively, this study demonstrates that organic fertilization with compound microbial agents can stabilize soil nutrients, increase soil microbial diversity, and improve rice yield, thereby offering a guide for enhancing fertilizer utilization and improving agroecosystems.

Effect of different fertilization strategies on the yield, quality of Euryales Semen and soil microbial community

IntroductionEuryales Semen, a medicinal herb widely utilized in Asia, faces a critical constraint in its production, primarily attributed to fertilizer utilization. Understanding the impact of different fertilization schemes on Euryales Semen (ES) planting and exploring the supporting mechanism are crucial for achieving high yield and sustainable development of the ES planting industry.MethodsIn this study, a field plot experiment was conducted to evaluate the effects of four different fertilization treatments on the yield and quality of ES using morphological characteristics and metabolomic changes. These treatments included a control group and three groups with different organic fertilizer to chemical fertilizer ratios (3:7, 5:5, and 7:3). The results of this study revealed the mechanisms underlying the effect of the different treatments on the yield and quality of Euryales Semen. These insights were achieved through analyses of soil physicochemical properties, soil enzyme activity, and soil microbial structure.ResultsWe found that the quality and yield of ES were the best at a ratio of organic fertilizer to chemical fertilizer of 7:3. The optimality of this treatment was reflected in the yield, soil available nitrogen, soil available phosphorus, and soil enzyme activity of ES. This ratio also increased soil microbial diversity, resulting in an increase and decrease in Proteobacteria and Firmicutes abundances, respectively. In addition, linear discriminant analysis showed that Chloroflexi, Gammaproteobacteria, and Hypocreales-incertae-sedis were significantly enriched in the ratio of organic fertilizer to chemical fertilizer of 7:3. Variance partitioning analysis showed that the soil properties, enzyme activities, and their interactions cumulatively can explain 90.80% of the differences in Euryales Semen yield and metabolome. In general, blending organic and chemical fertilizers at a 7:3 ratio can enhance soil fertility, boost Euryales Semen yield and quality, and bring forth conditions that are agriculturally beneficial to microbial (bacteria and fungi) dynamics.DiscussionThis study initially revealed the scientific connotation of the effects of different fertilization patterns on the planting of Euryales Semen and laid a theoretical foundation for the study of green planting patterns of Euryales Semen with high quality and yield.

Biochar alleviates apple replant disease by reducing the growth of Fusarium oxysporum and regulating microbial communities

Apple replant disease (ARD) negatively affects plant growth and reduces yields in replanted orchards. In this study, biochar was applied to apple replant soil with Fusarium oxysporum. Our aim was to investigate whether biochar could promote plant growth and alleviate apple replant disease by reducing the growth of harmful soil microorganisms, changing soil microbial community structure and improving the soil environment. This experiment included five treatments: apple replant soil (CK), methyl bromide fumigation apple replant soil (FM), replant soil with biochar addition (2%), replant soil with F. oxysporum spore solution (8 × 107 spores · mL−1), and replant soil with biochar and F. oxysporum spore solution addition. Seedling biomass, the activity of antioxidant enzymes in the leaves and roots, and soil environmental variables were measured. Microbial community composition and community structure were analyzed using 16S rDNA and ITS2 gene sequencing. Biochar significantly reduced the abundance of F. oxysporum and increased soil microbial diversity and richness. Biochar also increased the soil enzyme activities (urease, invertase, neutral phosphatase, and catalase), the biomass (plant height, fresh weight, dry weight) and the activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase). The root indexes of apple seedlings was also increased in replant soil by biochar. In sum, biochar promoted the growth of plants, improved the replant soil environment, and alleviated apple replant disease.

Inconsistent responses of soil bacterial and fungal community's diversity and network to magnesium fertilization in tea (Camellia sinensis) plantation soils

Soil microbes are important drivers of nutrient cycling that regulate plant growth and productivity. Yet, a holistic understanding of the effect of magnesium (Mg) fertilizer on the soil microbial community is still poorly understood. Here, a four-year field experiment was conducted to investigate the impact of different rates of Mg application, including 0, 17.5, 35, 52.5, and 70 kg of MgO ha−1, on soil bacterial and fungal communities (Illumina 16S and ITS amplicon sequencing) associated with tea plantations. Results showed that Mg application significantly increased the soil pH and improved the soil acidity, carbon, and available nitrogen, calcium, and Mg contents. Hence, Mg application also significantly increased soil bacterial diversity but did not affectfungal diversity. Moreover, Mg fertilization increased the relative abundance of beneficial bacterial genera belonging to nitrogen fixation and phosphorus mineralizing groups, such as Gemmatimonas, Rhizomicrobium and Sphingomonas. In addition, the Mg fertilization decreased the relative abundance of some pathogen fungi, such as Pestalotiopsis, Chaetomium, and Coniosporium. Network analysis indicated that the Mg application increased the complexity of the bacterial network by enhancing node numbers and connectivity links, while for fungal networks, the low rate of Mg fertilizer increased total nodes and edges. However, the higher amount of Mg fertilizer decreased the complexity of the fungal network. Correlation analysis between soil properties and microbial communities showed that pH, total carbon and nitrogen, available carbon, and exchangeable Mg were the key soil factors that significantly influenced the microbial community structure. These findings suggest that Mg fertilization could increase soil microbial diversity, alter the microbial structure and improve the microbial network structure of the tea plantation soils. These findings could help to improve soil health, sustainability, and crop productivity. Therefore, Mg fertilization can be considered a viable strategy for improving the health and productivity of tea plantation soils.

Optimally combined application of organic and chemical fertilizers increases grain yield and improves rhizosphere microecological properties in rice ratooning

AbstractField tests were conducted at experimental station of Chongluo, Nanping city, Fujian province, China in 2018–2019 to explore the action and physiological mechanism of organic nitrogen in rice ratooning under the configurations with different proportions of organic and inorganic nitrogen. The results showed that sole chemical fertilizer (CF) led to a significant decrease in soil nutrient availability, especially at late growth stage, and reduced grain yield of the main and ratooning crops compared with the optimal fertilizer configuration (GM2) in 30% organic nitrogen with 70% chemical nitrogen fertilizer in the premise of total application rate at 225 kg N/ha. Further studies have revealed that GM2 relative to CF treatment promoted to produce more productive panicles of the main crop and had carryover effect on the regeneration rate of ratooning rice due to national C13‐assimilates partitioning in rice–rhizosphere systems, which resulted in increased soil microbial diversity and soil fertility, thereby enhanced yields of the main and ratooning rice crops. These findings help to better understand the action and mechanism of the proper combined application of organic and inorganic nitrogen fertilizer via improving remobilization of 13C assimilates in rice–rhizosphere system, and ultimately increasing grain yield in rice ratooning.

Understory ferns promote the restoration of soil microbial diversity and function in previously degraded lands

Microorganisms facilitate the recovery of previously degraded soils, such as degraded lands experiencing vegetation restoration and understory expansion, through vital soil functions like nutrient cycling and decomposing organic matter. Despite the role of microorganisms in recovery, little is known about the effects of the process on microbial diversity and function. Here, we performed an understory fern, Dicranopteris dichotoma (Thunb.) Berhn removal treatments nested within three Masson pine (Pinus massoniana L.) plantations with different restoration years in subtropical China. Three ferns treatments including no ferns cover, with ferns cover, and the ferns removal treatments were established to assess the impact of the ferns on soil microbial diversity and function during revegetation and drivers of observed changes. We combined high-throughput sequencing, network structure modeling, and function prediction of soil bacterial and fungal communities to determine microbial diversity and functions. Our results showed that soil bacterial and fungal diversity increased with restoration time. Understory ferns significantly increased soil microbial diversity in the un-restored land but the effect became smaller in two restored sites. Understory ferns significantly increased the relative abundance of bacterial phyla Proteobacteria and Acidobacteria, but decreased that of Chloroflexi and Firmicutes. Furthermore, the presence of ferns increased the abundance of Basidiomycota, but increased the abundance of Ascomycota. Co-occurrence network analysis revealed that the presence of ferns leads to more complex of bacterial networks with more connections, nodes, average degrees, betweenness, and degrees. The functional predictions indicate that aerobic chemoheterotrophy, chemoheterotrophy, and nitrogen fixation functional groups play key roles in the nutrient cycling of soils with ferns cover. The bacterial and fungal community compositions were strongly affected by revegetation and understory ferns as litter biomass and soil nitrogen were identified as the key environmental factors. Our study highlights the role of understory in facilitating microbial diversity and function recovery during degraded lands restoration.

The Effect of Rotational Cropping of Industrial Hemp (Cannabis sativa L.) on Rhizosphere Soil Microbial Communities

Crop rotation affects soil properties and soil microbial diversity and structure. Currently, it is not well understood how soil microbial diversity changes following different crop rotation systems of industrial hemp, an ancient and economically important crop. Therefore, these changes were analyzed in this study. Our results showed that different rotation systems significantly affected the wilt disease incidence, plant height, yield, soil physicochemical properties and soil microbial communities in the greenhouse. The rotation systems used in this study significantly reduced the plant mortality and increased the yield compared with a monoculture system. The levels of alkaline hydrolysis and available phosphorus in the soil decreased significantly compared with a monoculture cropping system. Using MiSeq high-throughput sequencing, we showed that the soil diversity and number of bacteria and fungi were significantly higher for rotation systems and controls compared to the monoculture system. The relative abundance of pathogens increased with a monoculture system. Redundancy analysis suggests that soil properties may also affect the soil microbial composition. Taken together, different rotation systems used in this study significantly decreased the disease incidence, increased plant yields and increased soil microbial diversity compared with monoculture for industrial hemp. We believe that applying these rotation systems is an efficient and eco-friendly approach to control soil borne pathogenic diseases and increase floral yields.

Network Analysis Reveals the Combination of Controlled-Release and Regular Urea Enhances Microbial Interactions and Improves Maize Yields.

Increased complexity of microbial networks can contribute to increased biodiversity and multifunctionality and thus crop productivity. However, it is not clear which combination ratio of regular and controlled-release urea will increase the soil microbial community complexity and improve maize yield in the North China Plain. To address this knowledge gap, a 2-year field experiment was conducted to explore the effects of the combination of regular (U) and controlled release (S) urea ratios [no fertilizer control (CT), regular urea alone (U), controlled-release urea alone (S), controlled-release urea mixed with regular urea 3:7 (SU3), controlled-release urea mixed with regular urea 5:5 (SU5), and controlled-release urea mixed with regular urea 7:3 (SU7)] on XianYu 688 yield and its rhizosphere and bulk soil microbial community composition and network complexity at different fertility stages. The combination of controlled-release and regular urea increased the N agronomic efficiency, N partial factors productivity, maize yield, and grain number per spike, with the maximum maize yield (9,186 kg ha–1) being achieved when the ratio of controlled-release urea to regular urea was 3:7 (SU3, p < 0.05). Maize yield increased by 13% in the SU3 treatment compared to the CT treatment. Rhizosphere soil microbial diversity remained stable at the silking stage of maize while increased at the physiological maturity stage of maize, with the increasing controlled-release to regular N fertilizer ratios (from 3:7 to 7:3, p < 0.05). This result suggests that a combination of regular and controlled-release N fertilizer can still substantially increase soil microbial diversity in the later stages of maize growth. The combination of controlled-release and regular urea is more effective in improving microbial network total links and average degree, and N agronomic efficiency (R2 = 0.79, p < 0.01), N partial factor productivity (R2 = 0.79, p < 0.01), spikes per unit area (R2 = 0.54, p < 0.05), and maize yield (R2 = 0.42, p < 0.05) increased with the microbial network complexity. This result indicates that the higher microbial network complexity is strongly associated with the higher N agronomic efficiency and N partial factors productivity and maize yield. In conclusion, the ratio of controlled-release to regular urea at SU3 not only increases the yield of maize and N agronomic efficiency but also enhances microbial diversity and network complexity in the North China Plain.

Reclamation of abandoned saline-alkali soil increased soil microbial diversity and degradation potential

Reclamation of abandoned saline-alkali soil increased soil microbial diversity and degradation potential

The Phlorizin-Degrading Bacillus licheniformis XNRB-3 Mediates Soil Microorganisms to Alleviate Apple Replant Disease.

In this study, an endophytic phlorizin-degrading Bacillus licheniformis XNRB-3 was isolated from the root tissue of healthy apple trees, and its control effect on apple replant disease (ARD) and how it alleviates the pathogen pressure via changes in soil microbiomes were studied. The addition of strain XNRB-3 in Fusarium infested soils significantly reduced the number of pathogens in the soil, thus resulting in a lower disease incidence, and the relative control effect on Fusarium oxysporum reached the highest of 66.11%. The fermentation broth can also protect the roots of the plants from Fusarium oxysporum, Fusarium moniliforme, Fusarium proliferatum, and Fusarium solani infection. These antagonistic effects were further validated using an in vitro assay in which the pathogen control was related to growth and spore germination inhibition via directly secreted antimicrobial substances and indirectly affecting the growth of pathogens. The secreted antimicrobial substances were identified using gas chromatography-mass spectrometry (GC-MS) technology. Among them, alpha-bisabolol and 2,4-di-tert-butylphenol had significant inhibitory effects on many planted pathogenic fungi. Butanedioic acid, monomethyl ester, and dibutyl phthalate promoted root development of Arabidopsis plants. Strain XNRB-3 has multifarious plant growth promoting traits and antagonistic potential. In pot and field experiments, the addition of strain XNRB-3 significantly promoted the growth of plants, and the activity of enzymes related to disease resistance [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] was also significantly enhanced. It also reduced the abundance of four species of Fusarium and the content of phenolic acids in the rhizosphere soil, improved soil microbial community structure and nutritional conditions, and increased soil microbial diversity and activity, as well as the soil enzyme activity. The above results indicated that B. licheniformis XNRB-3 could be developed into a promising biocontrol and plant-growth-promoting agent.

The planting of licorice increased soil microbial diversity and affected the growth and development of apple trees

ABSTRACT Grass cultivation is an important soil management practice for improving orchard soil quality. A suitable grass variety can enhance the soil microenvironment and increase fruit yield and quality. In the arid regions of northwestern China, licorice is often planted between apple trees. To clarify the effects of licorice on the soil microenvironment and apple tree growth and development,apple trees and licorice were grown in a root limiter under the following three treatment conditions: apple alone (A), intercropping of apple and licorice (AL), and licorice alone (L). Several soil properties (e.g., salt, soil organic matter, nitrogen, phosphorus, and potassium contents) were analyzed. Additionally, soil microbial communities were characterized via the high-throughput sequencing of bacterial and fungal rRNA gene markers. Apple tree growth and development indices were also determined.The soil organic matter, total and available nitrogen, and the available phosphorus contents were significantly higher in the L treatment soil than in the original soil or the A and AL treatment soils. The compositions of the dominant bacteria and fungi were similar among treatments. Soil bacterial and fungal richness and diversity were greater for the L and AL treatments than for the A treatment. At the phylum level, the characteristic bacteria for the A and L treatments were Gemmatimonadetes and Chloroflexi species, respectively. Some soil properties, including soil organic matter, available N, available P, and available K contents, were significantly correlated with bacterial and fungal taxa. Furthermore, the apple tree growth and development indices trunk diameter, crown size, 1-year-old branch length, and the proportion of short shoots were respectively 25.66%, 21.70%, 28.23%, and 20.78% lower for the AL treatment than for the A treatment.Cultivating licorice alone or intercropping with apple trees can increase or maintain the soil organic matter, total and available nitrogen, and available phosphorus contents as well as the microbial composition and abundance. However, intercropping with licorice will restrict fruit tree growth and development (e.g., proportion of short shoots and the trunk diameter).

Effects of Corn Intercropping with Soybean/Peanut/Millet on the Biomass and Yield of Corn under Fertilizer Reduction

Corn (Zea mays L.) is one of the key grain crops in China. In fields, the two crops of soybean (Glycine max L.) and peanut (Arachis hypogaea L.), which have nitrogen-fixing capacity (NFC), are generally used to intercrop with corn to improve plant physiology and production ability of corn even under fertilizer reduction. To explore a more scientific and reasonable way to plant corn, and simultaneously reduce the use of chemical fertilizers and pesticides, the impacts of corn intercropping with two NFC crops (including soybean and peanut) and the a non-NFC crop (i.e., millet (Setaria italica)) through five planting patterns, including three intercropping patterns (2 corn rows to 2, 3, and 4 NFC-crop rows or 2, 4, and 6 millet rows) and two sole crop patterns of corn and soybean, peanut, or millet under normal (600 kg/ha) and reduced (375 kg/ha) levels of NPK (N:P2O5:K2O = 15:15:15) fertilization levels on the activity of N-metabolism-related enzymes in corn rhizosphere soil and corn leaves, and plant biomass and yield of corn were researched in this study. The results showed that fertilizer reduction significantly decreased the plant biomass and grain yield of the sole crop corn. The intercropping type and planting pattern both had significant effects on the activities of N-metabolism-related enzyme of soil alkaline protease (S-ALPT), and glutamine oxoglutarate aminotransferase (GOGAT), glutamate synthetase (GS), and nitrate reductase (NR) in the leaves of corn plants. The intercropping type of corn with soybean through the planting pattern of 2 corn rows to 4 soybean rows significantly improved the activities of N-metabolism-related enzymes in soil and corn leaves even under the fertilizer reduction. The intercropping pattern of corn-soybean was the most beneficial to increase the total nitrogen content in soil and corn leaves. In addition, the intercropping significantly increased the soil microbial diversity under normal fertilizer. Furthermore, fertilizer reduction significantly increased soil microbial diversity of the corn sole crop. Therefore, it is concluded that for corn in intercropping systems, the best and the worst companion crop were, respectively, soybean and millet.

The Planting of Licorice Increased Soil Microbial Diversity and Affected the Growth and Development of Apple Trees

The Planting of Licorice Increased Soil Microbial Diversity and Affected the Growth and Development of Apple Trees

Effects of exogenous microorganisms on seedling growth and soil microbial community of Casuarina equisetifolia

With a pot experiment, the Biolog microplate and phospholipid fatty acid (PLFA) technology were used to explore whether the application of bacteria, Bacillus amyloliquefaciens (YB706) and Burkholderia (BK8), could improve the soil nutrient, microbial community and growth of Casuarina equisetifolia. The results showed that the concentrations of soil alkali-hydrolyzed nitrogen and available phosphorus of C. equisetifolia treated with YB706 and BK8 increased significantly compared with the control (CK), but the concentrations of total nitrogen, total phosphorus, total potassium and available potassium changed little, plant height increased by 59.1% and 63.9%, respectively, and the chlorophyll content of plant treated with BK8 increased by 81.9%. The average well color development values showed a pattern of YB706>CK>BK8. The utilization rate of different carbon sources showed the same trend except the amino acids. Both YB706 and BK8 treatments significantly increased the richness and quantity of soil microorganisms. The PLFA of all kinds of microorganisms was BK8>YB706>CK except actinomycetes. The ratio of soil fungi to bacteria was increased compared with CK. The Simpson, Shannon, Brillouin and McIntosh indices of rhizosphere soil microbial community in YB706 and BK8 treatments were significantly increased. Our results suggested that application of YB706 and BK8 could improve the growth rate of C. equisetifolia seedlings, effectively increase the contents of soil available nutrients, increase soil microbial diversity, and improve soil microbial environment.

Effects of long-term fertilizer management on soil labile organic carbon fractions and hydrolytic enzyme activity under a double-cropping rice system of southern China.

Fertilization is an effective way to improve soil quality, increase soil fertility and soil microbial diversity in paddy soil. To explore the changes of soil labile organic carbon (C) fractions and hydrolytic enzyme activity after 34 years fertilization treatments in a field experiment in double-cropping rice system of southern China. There were four treatments, including chemical fertilizer alone (MF), rice residue and chemical fertilizer (RF), 30% organic matter and 70% chemical fertilizer (OM), and the control without fertilizer input (CK). We measured soil organic carbon (SOC) content, soil labile organic C fractions, SOC related hydrolytic enzyme activity, correlation coefficients of soil enzyme activity with SOC content and its labile organic C fractions. The results showed that MF, RF and OM increased SOC content by 4.5%, 22.4% and 53.5%, respectively. Compared with MF and CK, RF and OM increased soil labile organic C fractions [cumulative C mineralization (Cmin), permanganate oxidizable C (KMnO4-C), particulate organic C (POC), dissolved organic C (DOC), light fraction organic C (LFOC), microbial biomass C (MBC)] and the proportion of each labile organic C fractions to total organic C. The contents of Cmin, KMnO4-C, POC, DOC, LFOC and MBC under OM treatment were 3.5, 3.1, 3.7, 1.9, 1.2 and 1.9 times higher than CK treatment, respectively. The proportion of labile organic C fractions to total organic C of RF and OM treatments was significantly higher than that in CK. The order of soil hydrolytic enzyme activity [α-glucosidase (αG), β-glucosidase (βG), β-xylosidase (βX), cellobiohydrolase (GBH), and N-acetyl-β-glucosaminidase (NAG)] was OM&gt;RF&gt;MF&gt;CK. The soil hydrolytic enzyme activity under OM treatment increased by 111.8%, 14.1%, 127.3%, 285.6% and 91.4% compared with CK, respectively. Furthermore, RF and OM treatments were beneficial to soil peroxidase (POD) activity. MF treatment was beneficial to soil polyphenol oxidase (PPO) activity. There was a significant positive correlation between soil hydrolytic enzyme activity and SOC content and its labile organic C fractions. In conclusion, the combined application of organic manure, rice straw returning and chemical fertilizer is an effective method to improve soil labile organic C fractions and hydrolytic enzyme activity in a double-cropping rice paddy field of southern China.

Plant-Dependent Soil Bacterial Responses Following Amendment With a Multispecies Microbial Biostimulant Compared to Rock Mineral and Chemical Fertilizers.

Biostimulants are gaining momentum as potential soil amendments to increase plant health and productivity. Plant growth responses to some biostimulants and poorly soluble fertilizers could increase soil microbial diversity and provide greater plant access to less soluble nutrients. We assessed an agricultural soil amended with a multispecies microbial biostimulant in comparison with two fertilizers that differed in elemental solubilities to identify effects on soil bacterial communities associated with two annual pasture species (subterranean clover and Wimmera ryegrass). The treatments applied were: a multispecies microbial biostimulant, a poorly soluble rock mineral fertilizer at a rate of 5.6 kg P ha–1, a chemical fertilizer at a rate of 5.6 kg P ha–1, and a negative control with no fertilizer or microbial biostimulant. The two annual pasture species were grown separately for 10 weeks in a glasshouse with soil maintained at 70% of field capacity. Soil bacteria were studied using 16S rRNA with 27F and 519R bacterial primers on the Mi-seq platform. The microbial biostimulant had no effect on growth of either of the pasture species. However, it did influence soil biodiversity in a way that was dependent on the plant species. While application of the fertilizers increased plant growth, they were both associated with the lowest diversity of the soil bacterial community based on Fisher and Inverse Simpson indices. Additionally, these responses were plant-dependent; soil bacterial richness was highly correlated with soil pH for subterranean clover but not for Wimmera ryegrass. Soil bacterial richness was lowest following application of each fertilizer when subterranean clover was grown. In contrast, for Wimmera ryegrass, soil bacterial richness was lowest for the control and rock mineral fertilizer. Beta diversity at the bacterial OTU level of resolution by permanova demonstrated a significant impact of soil amendments, plant species and an interaction between plant type and soil amendments. This experiment highlights the complexity of how soil amendments, including microbial biostimulants, may influence soil bacterial communities associated with different plant species, and shows that caution is required when linking soil biodiversity to plant growth. In this case, the microbial biostimulant influenced soil biodiversity without influencing plant growth.

Beneficial Effects of Mixing Kentucky Bluegrass With Red Fescue via Plant-Soil Interactions in Black Soil of Northeast China.

Continuous monoculture of cool-season turfgrass causes soil degradation, and visual turf quality decline is a major concern in black soil regions of Northeast China. Turf mixtures can enhance turfgrass resistance to biotic and abiotic stresses and increase soil microbial diversity. Understanding mechanism by plant-soil interactions and changes of black soil microbial communities in turf mixture is beneficial to restoring the degradation of urbanized black soils and maintaining sustainable development of urban landscape ecology. In this study, based on the previous research of different sowing models, two schemes of turf monoculture and mixture were conducted in field plots during 2016–2018 in a black soil of Heilongjiang province of Northeast China. The mixture turf was established by mixing 50% Kentucky bluegrass “Midnight” (Poa pratensis L.) with 50% Red fescue “Frigg” (Festuca rubra L.); and the monoculture turf was established by sowing with pure Kentucky bluegrass. Turf performance, soil physiochemical properties, and microbial composition from rhizosphere were investigated. Soil microbial communities and abundance were analyzed by Illumina MiSeq sequencing and quantitative PCR methods. Results showed that turfgrass quality, turfgrass biomass, soil organic matter (SOM), urease, alkaline phosphatase, invertase, and catalase activities increased in PF mixture, but disease percentage and soil pH decreased. The microbial diversity was also significantly enhanced under turf mixture model. The microbial community compositions were significantly different between the two schemes. Turf mixtures obviously increased the abundances of Beauveria, Lysobacter, Chryseolinea, and Gemmatimonas spp., while remarkably reduced the abundances of Myrothecium and Epicoccum spp. Redundancy analysis showed that the compositions of bacteria and fungi were related to edaphic parameters, such as SOM, pH, and enzyme activities. Since the increasing of turf quality, biomass, and disease resistance were highly correlated with the changes of soil physiochemical parameters and microbial communities in turf mixture, which suggested that turf mixture with two species (i.e., Kentucky blue grass and Red fescue) changed soil microbial communities and enhanced visual turfgrass qualities through positive plant-soil interactions by soil biota.