Effects of Allelochemicals, Soil Enzyme Activities, and Environmental Factors on Rhizosphere Soil Microbial Community of Stellera chamaejasme L. along a Growth-Coverage Gradient

Allelochemicals released from the root of Stellera chamaejasme L. into rhizosphere soil are an important factor for its invasion of natural grasslands. The aim of this study is to explore the interactions among allelochemicals, soil physicochemical properties, soil enzyme activities, and the rhizosphere soil microbial communities of S. chamaejasme along a growth-coverage gradient. High-throughput sequencing was used to determine the microbial composition of the rhizosphere soil sample, and high-performance liquid chromatography was used to detect allelopathic substances. The main fungal phyla in the rhizosphere soil with a growth coverage of 0% was Basidiomycetes, and the other sample plots were Ascomycetes. Proteobacteria and Acidobacteria were the dominant bacterial phyla in all sites. RDA analysis showed that neochamaejasmin B, chamaechromone, and dihydrodaphnetin B were positively correlated with Ascomycota and Glomeromycota and negatively correlated with Basidiomycota. Neochamaejasmin B and chamaechromone were positively correlated with Proteobacteria and Actinobacteria and negatively correlated with Acidobacteria and Planctomycetes. Allelochemicals, soil physicochemical properties, and enzyme activity affected the composition and diversity of the rhizosphere soil microbial community to some extent. When the growth coverage of S. chamaejasme reached the primary stage, it had the greatest impact on soil physicochemical properties and enzyme activities.

Effects of Salinity on the Biodegradation of Polycyclic Aromatic Hydrocarbons in Oilfield Soils Emphasizing Degradation Genes and Soil Enzymes

The biodegradation of organic pollutants is the main pathway for the natural dissipation and anthropogenic remediation of polycyclic aromatic hydrocarbons (PAHs) in the environment. However, in the saline soils, the PAH biodegradation could be influenced by soil salts through altering the structures of microbial communities and physiological metabolism of degradation bacteria. In the worldwide, soils from oilfields are commonly threated by both soil salinity and PAH contamination, while the influence mechanism of soil salinity on PAH biodegradation were still unclear, especially the shifts of degradation genes and soil enzyme activities. In order to explain the responses of soils and bacterial communities, analysis was conducted including soil properties, structures of bacterial community, PAH degradation genes and soil enzyme activities during a biodegradation process of PAHs in oilfield soils. The results showed that, though low soil salinity (1% NaCl, w/w) could slightly increase PAH degradation rate, the biodegradation in high salt condition (3% NaCl, w/w) were restrained significantly. The higher the soil salinity, the lower the bacterial community diversity, copy number of degradation gene and soil enzyme activity, which could be the reason for reductions of degradation rates in saline soils. Analysis of bacterial community structure showed that, the additions of NaCl increase the abundance of salt-tolerant and halophilic genera, especially in high salt treatments where the halophilic genera dominant, such as Acinetobacter and Halomonas. Picrust2 and redundancy analysis (RDA) both revealed suppression of PAH degradation genes by soil salts, which meant the decrease of degradation microbes and should be the primary cause of reduction of PAH removal. The soil enzyme activities could be indicators for microorganisms when they are facing adverse environmental conditions.

Enhancement of Interplanting of Ficus carica L. with Taxus cuspidata Sieb. et Zucc. on Growth of Two Plants

Medicinal-agroforestry systems are one of the multi-functional medicinal plant production systems, gaining attention as a sustainable alternative to traditional monoculture systems. In this study, three planting patterns were established which included: (1) monoculture F. carica (MF); (2) monoculture T. cuspidata (MT); and (3) interplanting F. carica with T. cuspidata (IFT). The differences of growth biomass, photosynthesis, soil nutrients, soil enzyme activities, soil microorganisms, and main secondary metabolites of F. carica and T. cuspidata under the above three models were investigated. Compared with the MF and MT patterns, IFT pattern for 5 months significantly increased the plant growth biomass, photosynthesis, soil organic carbon, total nitrogen, and secondary metabolites content. The activities of acid phosphatase, sucrase, protease, polyphenol oxidase, urease, dehydrogenase, and catalase in soil of IFT were significantly higher than MF and MT patterns. Results showed that IFT pattern is preferred compared to the MF and MT patterns. Our result will help to provide a feasible theoretical basis for the large-scale establishment of F. carica and T. cuspidata mixed forests and obtain high-quality medicine sources for extracting important active ingredients, psoralen and paclitaxel, which are crucial to the long-term sustainable development and production of medicinal plants.

Rhizospheric Fungal Diversities and Soil Biochemical Factors of Fritillaria taipaiensis over Five Cultivation Years

Fritillaria taipaiensis is a valuable traditional Chinese medicinal plant that has experienced continuous decline over its cropping area. The present study aims to explore the reasons for the quality and growth decline. The fungal diversities and biochemical factors in its rhizospheric soils with cultivation duration from 1 up to 5 years were analyzed and compared. The results showed that rhizospheric fungi of F. taipaiensis belong to six phyla, including Neocallimastigomycota, Glomeromycota, Basidiomycota, Chytridiomycota, Zygomycota and Ascomycota. Thirteen genera (Pseudogymnoascus, Fusarium, Mortierella, Colletotrichum, Laetinaevia, Gibberella, Synchytrium, Lysurus, Trichocladium, Volutella, Monoblepharis, Aquamyces and Trichoderma) constituted the “core community” in the rhizosphere of F. taipaiensis. The dominant fungal genera varied significantly in rhizospheric soils with different cultivation years. The abundance of fungal species in the soil declined with the cultivation year generally. The pH, available P, organic matter and urease activity were the primary factors determining the fungal community composition in the rhizosphere. The content of organic matter, available N, P and K and the activities of urease and alkaline phosphatase decreased with cultivation years. The soil pH increased with cultivation years and was unsuitable for F. taipaiensis growth. These features suggested that long-term single planting altered the fungal community structure, fertility conditions and soil enzyme activities in F. taipaiensis rhizospheric soils, which could be detrimental for plant growth and quality.

Effect of Different Washing Solutions on Soil Enzyme Activity and Microbial Community in Agricultural Soil Severely Contaminated With Cadmium

Soil enzyme activities and microbial communities have a good response to the remediation effect of heavy metal-contaminated soils. To evaluate the effect of three commonly used washing agents, ferric chloride (FC), ethylenediamine-tetra- methylenephosphonic acid (EDTMP) and ethylenediamine tetraacetic acid (EDTA) on soil enzyme activities and microbial community in cadmium (Cd)- contaminated agricultural soil collected around the mining area. The soil enzyme activities, microbial community, chemical forms of Cd and some physicochemical properties of the soil washed with different washing solutions were determined after two months incubation. The results showed that the three washing solutions had moderate removal efficiencies (22.83%-37.56%) for Cd in the tested soil and the breakdown product of EDTMP has a certain stabilizing effect on Cd. The geometric mean and the integrated total enzyme activity index showed that soil washing with FC and EDTA were more beneficial to the restoration of biochemical functions than that with EDTMP. The relative abundance of Gemmatimonadetes in the soil washed with EDTA was significantly higher than that with FC and EDTMP. The relative abundance of Firmicutes in the soil washed with EDTMP was significantly increased, and the relative abundance of Bacteroidetes in the soil washed with FC was significantly decreased. Pearson correlation analysis and redundancy analysis (RDA) indicated that the three washing solutions affected soil enzyme activities and microbial community by altering soil nutrient, total Cd concentration and Cd fractions in soils.

Impact of nanophos in agriculture to improve functional bacterial community and crop productivity

Background Since the World’s population is increasing, it’s critical to boost agricultural productivity to meet the rising demand for food and reduce poverty. Fertilizers are widely used in traditional agricultural methods to improve crop yield, but they have a number of negative environmental consequences such as nutrient losses, decrease fertility and polluted water and air. Researchers have been focusing on alternative crop fertilizers mechanisms to address these issues in recent years and nanobiofertilizers have frequently been suggested. “Nanophos” is a biofertilizer and contains phosphate-solubilising bacteria that solubilises insoluble phosphate and makes it available to the plants for improved growth and productivity as well as maintain soil health. This study evaluated the impact of nanophos on the growth and development of maize plants and its rhizospheric microbial community such as NPK solubilising microbes, soil enzyme activities and soil protein under field condition after 20, 40 and 60 days in randomized block design. Results Maize seeds treated with nanophos showed improvement in germination of seeds, plant height, number of leaves, photosynthetic pigments, total sugar and protein level over control. A higher activity of phenol, flavonoid, antioxidant activities and yield were noticed in nanophos treated plants over control. Positive shift in total bacterial count, nitrogen fixing bacteria, phosphate and potassium solubilizers were observed in the presence of nanophos as compared to control. Soil enzyme activities were significantly (P < 0.05) improved in treated soil and showed moderately correlation between treatments estimated using Spearman rank correlation test. Real time PCR and total soil protein content analysis showed enhanced microbial population in nanophos treated soil. Obtained results showed that nanophos improved the soil microbial population and thus improved the plant growth and productivity. Conclusion The study concluded a stimulating effect of nanophos on Zea mays health and productivity and indicates good response towards total bacterial, NPK solubilising bacteria, soil enzymes, soil protein which equally showed positive response towards soil nutrient status. It can be a potential way to boost soil nutrient use efficiency and can be a better alternative to fertilizers used in the agriculture.

Growth indices, Yield, Nutrient Uptake and Soil Enzyme Activity of wheat as Affected by Residual Effect of Phosphorus and Silicon

Silicon (Si) is known as a beneficial or quasi-essential element particularly for graminaceous crops, as Si increases dry matter accumulation and enhances resistance to lodging and drought. However, the combined application of phosphorus (P) and Si has a tremendous impact on the growth and yield of various crops. While the residual effect of Si and P application on growth, yield and soil biological activity in wheat were not ascertained. Therefore, the present study was conducted to evaluate the residual effect of Si and P on growth indices, yield, nutrient uptake, and soil enzyme activities of succeeding wheat crops. The four levels of Si (0, 40, 80, and 120 kg Si ha− 1) and P (0, 30, 60, and 90 kg P2O5 ha− 1) were applied to the preceding aerobic rice crop and their effect was evaluated in succeeding wheat crop. The results demonstrated a significant effect of Si and P on wheat growth, yield, nutrient uptake, and soil enzyme activities. The residual effect of 120 kg Si and 90 kg P2O5 ha− 1 significantly improved the grain yield of the succeeding wheat crop by 24–45%. Further, the residual Si and P remarkably improved Si, N, P, and K concentration in wheat grain by 35, 13.2, 45, and 56 %, respectively, over control. Similarly, an increase in the microbial biomass carbon, dehydrogenase, fluorescein diacetate, and alkaline phosphatase activity by 17.2, 33.5, 12.4, and 37.5%, respectively were observed in the residual application of 120 kg Si and 90 kg P2O5 ha− 1 over control. Therefore, the inclusion of Si and P could have great potential to improve soil enzyme activities and productivity of the wheat crop.