Improve Soil Environment Research Articles

Whole genome analysis of Enterobacter cloacae Rs-2 and screening of genes related to plant-growth promotion.

The genus Enterobacter is widely recognized for its biotechnology potential in improving soil environment and crop growth promotion. To further explore these biotechnological potentials, we sequenced and analyzed the whole genome of Enterobacter cloacae Rs-2. The analysis showed that the total length of the Rs-2 genome was 6,965,070,514bp, and GC content was 55.80%; the annotation results of GO and COG databases showed that the genome contains a variety of growth-promoting genes, such as iscU, glnA, glnB (nitrogen fixation); iucABCD (siderophore synthesis) and fepA, fcuA, fhuA, and pfeA, etc. (siderophore transport); ipdC (secreted IAA) and gcd, pqqBCDEF (dissolved phosphorus), etc. No pathogenic factors such as virulence genes were found. The application of Rs-2 as a soil inoculant in pot experiments showed great potential for growth promotion. This study proved the plant growth-promoting ability of Rs-2 at the molecular level through genetic screening and analysis, which provided guidance for the further improvement of the strain and laid a foundation for its application in agricultural production.

Impact of Long-Term Manure and Mineral Fertilization on Accumulation of Non-Structural Carbohydrates in Lucerne Forage

Fertilization management affects both productivity and nutritive value of forage legumes. However, there are few studies about changes in lucerne non-structural carbohydrates under long-term fertilization. The aims of this study were to compare the effects of mineral fertilization and organic manure on lucerne plant parts (leaf, stem) starch and water-soluble carbohydrate (WSC) accumulation in association with canopy structure following 60 years of different fertilization management approaches. Treatments investigated were: two contrasting levels of mineral N, P2O5 and K2O application (0:0:0 and 91:71:175), each with and without farmyard manure. Changes were mainly reflected in WSC content where intensive mineral fertilization consistently reduced the stem and forage WSC in contrast to unfertilized control or manure alone. These changes could be associated with a dilution effect presented by the highest increase of maximal stem length at these treatments. Manure improved leaf and forage WSC despite the associated increase in maximal stem length and leaf weight ratio, probably as a result of improved soil environment together with the potentially increased presence of arbuscular mycorrhizal fungi. Results showed that manure fertilization has potential for improvement of lucerne WSC, despite some negative relationships between lucerne canopy traits and sugar content.

Effects of Nitrogen Fertilizer Ratio on Microbial Diversity of Rice Rhizosphere Soil in Cold Region.

The experiment was conducted in the paddy field of a scientific and technological park of an agricultural reclamation farm in Xinxiang province from 2017 to 2019. The soil quality of the experimental field was the rhizosphere soil of rice in the cold region, and Longjing 31 was used as the experimental material. The effects of nitrogen application ratio on microbial diversity of rice rhizosphere soil in the cold region were studied. The aim is to provide a theoretical basis for rational fertilization, improving soil environment and high yield and efficiency. The results showed that: (a) the microbial diversity index of rice rhizosphere soil in the cold region was the best after the second nitrogen application; (b) under the ratio of N4 nitrogen application, the activity of bacteria, fungi and actinomycetes in rice rhizosphere soil in a cold region and their survival were the best; (c) under intensive cultivation conditions, the microbial diversity was the highest under SF1 treatment. SF0 treatment had the highest fungal diversity and SF3 treatment had the highest actinomycete diversity. (d) There was no significant effect on the microbial diversity of rice rhizosphere soil in the cold region without nitrogen fertilizer application in a single season.

Cotton straw biochar and Bacillus compound biofertilizer decreased Cd migration in alkaline soil: Insights from relationship between soil key metabolites and key bacteria

Cadmium (Cd) contamination greatly impacts soil health and ecological environment. In recent years, cotton straw biochar and Bacillus compound biofertilizer have been paid much attention in the remediation of Cd-contaminated soils. In this study, the effects of cotton straw biochar (3%, w/w) and Bacillus compound biofertilizer (1.5%, w/w) on the Cd fractions, Cd migration, bacterial community succession, and metabolites in the soils with different concentrations of Cd (1, 2, and 4 mg kg−1) were explored. The results showed that the relative abundance of Actinobacteriota, Acidobacteriota, Firmicutes, and Cyanobacteric and soil enzyme activities in Cd-contaminated soils decreased, and the soil metabolic pathways also changed compared with those in the control. After the application of cotton straw biochar and Bacillus compound biofertilizer, the soil available Cd concentration in Cd-contaminated soils decreased, and many exchangeable and carbonate-bound Cd were transformed into residual Cd, which decreased the bioavailability of Cd in the soil and the accumulation of Cd in cotton organs. In addition, the application of cotton straw biochar and Bacillus compound biofertilizer improved the activity of soil enzymes and the abundance of dominant bacteria and stimulated Verrucomicrobiota, Methylomirabilota, and Cyanobacteria to secrete organic acids and amino acid compounds, which decreased the toxicity of Cd. Besides, compared with cotton straw biochar, Bacillus compound biofertilizer was more effective in immobilizing Cd and improving soil environment. This study provides guidance for the remediation of Cd-contaminated alkaline soil, and makes contributions to the soil health and sustainable development.

Effects of manure substituting chemical nitrogen fertilizer on rubber seedling growth and soil environment.

The substitution of manure for chemical nitrogen fertilizers has great impacts on the growth of rubber seedlings and soil environment, with implications for rubber cultivation and transplantation and soil environment improvement. In this study, rubber seedlings of thermal research '7-33-97' strain were cultivated under four treatments: No fertilizer application (CK), only application of chemical fertilizer (N), manure replacing 50% chemical fertilizer (M+N), and manure replacing 100% chemical fertilizer (M). Plants parameters (including plant height, basal diameter, biomass, and chlorophyll), soil physicochemical properties (including pH, soil organic carbon and nitrogen, soil enzyme activities), and their relationships were investigated. The results showed that plant height, basal diameter, biomass, and chlorophyll content in the M+N and M treatments were significantly higher, while underground biomass and root-shoot ratio were significantly lower than those of in N treatment. Compared with CK, soil pH was significantly increased in the M treatment, decreased in the N treatment, and was not changed in the M+N treatment. Soil ammonium and nitrate content in the M+N and M treatments were significantly lower, while soil organic carbon content, the activity of β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP) were significantly higher than those of in N treatment. Results of correlation analysis showed that soil pH was negatively correlated with soil ammonium and nitrate content, but positively correlated with BG and NAG activities. The structural equation model analysis showed that soil pH had significant positive effects on seedling quality index, while nitrate content had significant negative effects, and soil enzyme activities had no significant effect. Those results indicated that soil pH and nitrate content were the important driving factors on the growth of rubber seedlings. The manure replacing of 50% and 100% chemical nitrogen fertilizer could promote rubber seedlings growth, improve soil environment, and promote sustainable development of rubber production in Danzhou City, Hainan Province.

Combined Effects of Bacteria and Hydroxyapatite on Rice and Microorganisms in Cadmium Contaminated Soil

Cadmium (Cd) has caused serious soil environmental problems and directly harming plants, microorganisms, and even humans. It is vital and necessary to develop effective methods to solve the problem of soil Cd pollution and improve soil environment. In this study, alkali-producing bacteria combined with hydroxyapatite (HAP) to explore their effects on rice Cd accumulation, rice yield, soil available Cd, and soil microorganisms. Results showed that the soil available Cd content decreased in all groups. The bacteria combined with 0.5% and 2% ratio HAP treatment groups decreased soil available Cd by 7.17% and 0.58%, respectively. However, Cd content of grains in the former treatment group was as high as 0.27 mg/kg, and the latter treatment group was 0.18 mg/kg, they were lower than control group (0.31 mg/kg). As to the rice yield, most treatment groups can increase rice yield comparing to control group, and the bacteria combined with 2% ratio HAP increased by 13.79%. On the soil microorganisms, treatment groups had no obvious impact on diversity of soil microbial communities (p > 0.05), but there were significant differences in phylum classification, and the bacteria combined with 2% ratio HAP had more complex network of soil microorganisms. Besides, the bacteria could to adapt to this soil environment and colonize. So, the bacteria combined with 2% ratio HAP had great potentials for Cd contaminated soil remediation.

Penicillium simplicissimum NL-Z1 Induced an Imposed Effect to Promote the Leguminous Plant Growth.

It is found effective for phytoremediation of the guest soil spraying method by adding microbes to promote the growth of arbor leguminous plant on a high and steep rock slope. However, its underlying mechanisms remain elusive. Here, some experiments were conducted to explore the multifunctions of Penicillium simplicissimum NL-Z1 on rock weathering, nodule growth, and beneficial microbial regulation. The results show that P. simplicissimum NL-Z1 significantly increased the release of phosphorus, potassium, calcium, and magnesium from the rock by 226, 29, 24, and 95%, respectively, compared with that of the control. A significant increase of 153% in Indigofera pseudotinctoria Matsum nodule biomass, accompanied by an increase of 37% in the leguminous plant biomass was observed in the P. simplicissimum NL-Z1 treatment than in the control treatment. Interestingly, even though P. simplicissimum NL-Z1 itself became a minor microbial community in the soil, it induced a significant increase in Mortierella, which, as a beneficial microbe, can promote phosphate-solubilizing and plant growth. The results suggest that P. simplicissimum NL-Z1 could induce an imposed effect to promote leguminous plant growth, which may be conducive to the development of the phytoremediation technique for high and steep rock slope. The study provides a novel thought of using the indirect effect of microbes, i.e., promoting other beneficial microbes, to improve soil environment.

Responses of nitrogen efficiency and antioxidant system of summer maize to waterlogging stress under different tillage.

Waterlogging was one of the main abiotic stresses affecting maize yield and growth in the North China Plain, while ridge tillage effectually improved soil environment, enhanced crop stress resistance to waterlogging, and increased grain yield of waterlogged maize. In order to explore the responses of nitrogen (N) efficiency and antioxidant system of summer maize to waterlogging stress under different tillage, a field experiment was conducted to explore N use efficiency, leaf activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and malondialdehyde (MDA) content of waterlogged maize Denghai 605 (DH605) and Zhengdan 958 (ZD958) under different tillage system (ridge planting and flat planting). Our results showed that ridge tillage was beneficial to ameliorate waterlogging damages on antioxidant system by increasing SOD, POD, and CAT activities, and decreasing MDA content. Moreover, ridge tillage significantly increased N efficiency of waterlogged maize. N translocation amount (NTA), N translocation efficiency (NTE), N contribution proportion (NCP), N harvest index (NHI), and N use efficiency (NUE) of waterlogging treatment under ridge planting system (W-V3+R) for DH605 was increased by 108%, 69%, 60%, 8% and 16%, while ZD958 increased by 248%, 132%, 146%, 13% and 16%, respectively, compared to those of waterlogging treatment under flat planting system (W-V3). Ultimately, ridge tillage led to a significant yield improvement by 39% and 50% for DH605 and ZD958, respectively, compared to that of W-V3. In conclusion, ridge tillage was conducive to retard leaf aging, and enhance nitrogen efficiency, thereby resulting in a yield improvement of waterlogged summer maize.

Biochar-N fertilizer interaction increases N utilization efficiency by modifying soil C/N component under N fertilizer deep placement modes

The situation of imbalance application of nitrogenous fertilizers in maize production is a serious issue in China, and excessive nitrogen (N) application is hazardous to sustainable agricultural production and environment. In this experiment, two biochar levels (C0: 0, C1: 2 %), three different N rates (N1: 50, N2: 100, and N3: 200 mg kg−1), and two fertilization methods (T: traditional N fertilizer application mode and D: deep N fertilizer placement mode) were set up to study the response of different treatments on maize yield, N uptake, and N use efficiency. Herein, we found that fresh and dry biomasses were increased by 292 % and 283 % under C1N3 treatment with the deep application of N fertilizer compared to the control treatment (without nitrogen fertilizers and biochar). According to structural equation modeling (SEM), soil physical and chemical properties, N component and C component in different soil layers were associated with biochar and N fertilizer treatment, especially at 20–40 depth. The combination of N fertilizer and biochar application promoted the effects of biochar on the improving NUE of plants. The biochar alleviated the loss of soil nitrogen (from 52.00 to 25.94 %) under traditional N fertilizer application. Overall, excessive input of N fertilizer not only promotes the growth of crops but also causes a waste of resources and environmental pollution. We suggest that combined application of biochar and N fertilizer could significantly reduce N loss, and improve root growth and N uptake, resulting in improving NUE by improving soil environment (pH, SOM, EC) and adjusting soil C/N component.

Effects of different forms of microbial agents on the growth and quality of Brassica rapa L. ssp. chinensis Makino (non-heading Chinese cabbage).

Reasonable application of microbial agents can significantly improve soil environment and increase the yield and quality of vegetables. In this study, we examined the effects of different forms of microbial agents on the growth and quality of Brassica rapa L. ssp. chinensis Makino (non-heading Chinese cabbage) under the conditions of no microbial agent application, liquid and solid microbe agents application. The results showed that compared with no microbial agent, application of liquid and solid microbial agent significantly improved soil urease activity, plant nitrogen content, leaf area, SPAD value, and net photosynthetic rate, and increased vegetable production by 26.9% and 34.4% respectively. Meanwhile, the total phenol content and ascorbic acid content of non-heading Chinese cabbage were increased and nitrate content was significantly decreased by applying microbial agents. Thus, rational application of microbial agents promoted the yield and quality of non-heading Chinese cabbage. From the perspective of vegetable growth, liquid microbial agents work fast, solid microbial agents had good long-term efficacy. The cooperating application with organic and inorganic fertilizers would facilitate the excellent quality and high yield of vegetables.

Thiol-functionalized nano-silica for in-situ remediation of Pb, Cd, Cu contaminated soils and improving soil environment

Heavy metal contamination has been threatening the health of human beings. To decrease the bio-toxicity of heavy metals, a thiol-functionalized nano-silica (SiO2-SH) was adopted to remediate the soil contaminated by lead (Pb), cadmium (Cd) and copper (Cu). The remediation effect of SiO2-SH on contaminated soils was investigated by the uptake of the heavy metals into lettuce and pakchoi in pot experiment. The bio-toxicity of the SiO2-SH was evaluated, and its immobilization mechanisms were proposed by the fraction distribution of Cd, Pb and Cu. It was found that the SiO2-SH can significantly reduce the uptake of Cd, Pb, Cu into pakchoi by 92.02%, 68.03%, 76.34% and into lettuce by 89.81%, 43.41%, 5.76%, respectively. The chemical species analyses of Cd, Pb, Cu indicate SiO2-SH can transform the heavy metal in acid soluble states into reducible fraction and oxidizable fraction, thereby inhibiting the extraction of heavy metals into soil solution. The concentrations of microbial biomass carbon, organic matter, and cation exchange capacity of the soil increased while the soil bulk density decreased after remediation. Those changes demonstrate that SiO2-SH not only has no bio-toxic impact on the soil environment but also improves the soil environment, which proves the prepared SiO2-SH is environmental-friendly. The SiO2-SH could be a promising amendment for heavy metal contaminated soils.

Effects of vermicompost fertilization on soil, tomato yield and quality in greenhouse.

The excessive use of chemical fertilizer on vegetables in protected facilities resulted in soil degradation, serious soil-borne diseases, and lower vegetable yield and quality. We examined the effects of vermicompost on soil nutrient, enzyme activities, microbial quantity, tomato growth, yield and quality in greenhouse. The results showed that both broadcast and furrow application of vermicompost improved soil environment, and significantly increased contents of soil organic matter and soil nutrients (nitrogen, phosphorus and potassium). Vermicompost application significantly increased sucrase and catalase activities, abundance of bacteria and actinomycetes, and decreased the abundance of fungi in the soil. Furrow application but not the broadcast application promoted the growth of tomato plants. The vermicompost promoted root activities and leaf photosynthesis, increased chlorophyll, nitrogen and potassium contents in leaves. Broadcast and furrow application of vermicompost significantly increased tomato yield by 22.7% and 32.6%, respectively. Furrow application increased the contents of soluble protein, soluble sugar, vitamin C and titratable acid by 66.1%, 11.0%, 122.6% and 29.9%, respectively, and decreased nitrate content in tomato fruits by 65.7%. However, broadcast application did not affect fruit quality.

Comparing tillage methods for growing lowland soybean and corn during wetter-than-normal cropping seasons

Rice monocropping underutilizes the productive potential of lowland soils. A major challenge in cropping low-drainage soils, particularly in wetter-than-normal years, is improving drainage conditions of paddy soils to allow rotation with upland crops. The hypothesis tested was that chiseling and ridging improve soil physical environment in lowland soils for upland crops growth, development and yield, and that short-maturity soybean experiences greater stress from hypoxic conditions in lowlands soils subjected to high moisture in years of high rainfall. The aim of this study was to evaluate the influence of chiseling and ridging, compared with conventional tillage, in providing an improved soil environment for soybean and corn in Hapludalf (Planosols) soils in higher-than-normal rainfall cropping seasons. Experiments were carried out in two high-rainfall cropping seasons (2014/2015 and 2015/2016), in Hapludalf (Planosols) soils in southern Brazil, comprising four tillage methods (conventional, chisel, ridge, and chisel plus ridge) for soybean and corn crops. Soil physical properties were evaluated at sowing, 45 and 140 days after sowing, and plant variables were quantified. Chiseling alone or supplemented by ridge construction increased water infiltration rates by 3.0–10.5 compared with conventional and ridge tillage. Chiseling increased soybean and corn yields, while ridge construction did not differ from conventional tillage, and short-duration soybean group was the least productive. In years of high rainfall, chiseling improves soil physical and hydraulic properties, but excessive rainfall lessens the benefits of tillage and ridging. In conclusion, although chiseling significantly increases soybean and corn yields in lowlands, either an isolated practice or associated with ridge construction, the two wetter-than-normal years clearly show crop yield is highly dependent on the crop development stage when hypoxia occurs in root zone.

Effects of field scale in situ biochar incorporation on soil environment in a tropical highly weathered soil.

Biochar has been proven as a soil amendment to improve soil environment. However, mechanistic understanding of biochar on soil physical properties and microbial community remains unclear. In this study, a wood biochar (WB), was incorporated into a highly weathered tropical soil, and after 1 year the in situ changes in soil properties and microbial community were evaluated. A field trial was conducted for application of compost, wood biochar, and polyacrylamide. Microstructure and morphological features of the soils were characterized through 3D X-ray microscopy and polarized microscopy. Soil microbial communities were identified through next-generation sequencing (NGS). After incubation, the number of pores and connection throats between the pores of biochar treated soil increased by 3.8 and 7.2 times, respectively, compared to the control. According to NGS results, most sequences belonged to Anaerolinea thermolimosa, Caldithrix palaeochoryensis, Chthoniobacter flavus, and Cohnella soli. Canonical correlation analysis (CCA) further demonstrated that the microbial community structure was determined by inorganic N (IN), available P (AP), pH, soil organic C (SOC), porosity, bulk density (BD), and aggregate stability. The treatments with co-application of biochar and compost facilitated the dominance of Cal. palaeochoryensis, Cht. flavus, and Coh. soli, all of which promoted organic matter decomposition and ammonia oxidation in the soil. The apparent increases in IN, AP, porosity, and SOC caused by the addition of biochar and compost may be the proponents of changes in soil microbial communities. The co-application of compost and biochar may be a suitable strategy for real world biochar incorporation in highly weathered soil.

Biological function of Klebsiella variicola and its effect on the rhizosphere soil of maize seedlings.

BackgroundDeterioration of the ecological environment in recent years has led to increasing soil salinization, which severely affects the cultivation of agricultural crops. While research has focused on improving soil environment through the application of pollution-free microbial fertilizers, there are relatively few plant growth-promoting bacteria suitable for saline-alkali environments. Although Klebsiella variicola can adapt to saline-alkali environments to successfully colonize rhizosphere microenvironments, only a few studies have investigated its role in promoting crop growth. Its effect on the crop rhizosphere soil microenvironment is especially unclear.MethodsIn this study, the biological function of K. variicola and its colonization in maize seedling rhizosphere soil were studied in detail through selective media and ultraviolet spectrophotometry. The effects of K. variicola on the rhizosphere soil microenvironment and the growth of maize seedlings in saline-alkali and neutral soils were systematically analysed using the colorimetric method, the potassium dichromate volumetric method, and the diffusion absorption method.ResultsOur results showed that K. variicola played a role in indole acetic acid, acetoin, ammonia, phosphorus, and potassium production, as well as in nitrogen fixation. A high level of colonization was observed in the rhizosphere soil of maize seedlings. Following the application of K. variicola in neutral and saline-alkali soils, the nutrient composition of rhizosphere soil of maize seedlings increased in varying degrees, more notably in saline-alkali soil. The content of organic matter, alkali-hydrolysable nitrogen, available phosphorus, available potassium, alkaline phosphatase, sucrase, urease, and catalase increased by 64.22%, 117.39%, 175.64%, 28.63%, 146.08%, 76.77%, 86.60%, and 45.29%, respectively, insaline-alkalisoil.ConclusionK.variicola, therefore, performed a variety of biological functions to promote the growth of maize seedlings and effectively improve the level of soil nutrients and enzymes in the rhizosphere of maize seedlings, undersaline-alkali stress conditions. It played an important role in enhancing the rhizosphere microenvironment of maize seedlings under saline-alkali stress.

Effects of dazomet fumigation on growth, biological characteristics of Malus hupehensis seedlings and soil environment

In this study, we examined the effects of dazomet fumigation with different concentrations (0, 0.1, 0.2, 0.4 g·kg-1) on the microbial characteristics of continuous cropping soil and growth of Malus hupehensis seedling in greenhouse and open-field pot. The results showed that all the treatment of dazomet fumigation could promote the growth of M. hupehensis seedlings in continuous cropping soil, with 0.2 g·kg-1 treatment showing the strongest effect. Compared to the control, plant height, stem diameter, dry weight of M. hupehensis seedlings in 0.2 g·kg-1 dazomet fumigation were increased by 192.9% and 91.8%, 72.8% and 60.1%, 196.8% and 195.0%, 138.5% and 130.7%, respectively in greenhouse and open-field. The root related indices (root length, root area, root volume, root respiration rate) were significantly promoted. The activities of SOD, POD, CAT in roots were increased by 114.6% and 118.5%, 123.5% and 107.6%, 164.6% and 175.6% respectively compared with the control, whereas the content of malondialdehyde was significantly lowered. Soil bacterial content, fungal content, copy number of Fusarium oxysporum gene and soil enzyme activity were significantly decreased with the increasing dazomet concentrations. In conclusion, 0.2 g·kg-1 dazomet fumigation could increase the biomass of M. hupehensis seedlings in continuous cropping, improve soil environment, and effectively alleviate the continuous cropping obstacle. Therefore, 0.2 g ·kg-1 dazomet fumigation could be given priority during the reconstruction of old apple orchards.

Soil environment and spectra properties coregulate tomato growth, fruit quality, and yield in different colored biodegradable paper mulching during the summer season

Plastic film (PF) is the primary material applied for soil mulching, but it may also cause heat and drought stresses to crops in the summer season. In a previous study, we revealed that biodegradable paper (BP) was a potential mulching material for summer crop production, because it could not only decrease soil temperature, but also increase soil moisture during the summer season. However, it is still unclear whether different colored BPs have various efficiencies in improving soil environment, when used as soil mulching materials. Therefore, in this study, gray PF and different colors (red, dark, blue and yellow) of BPs were used as soil mulching materials to explore their influences on soil temperature and moisture, spectral and photosynthetic characteristics, plant growth, and fruit quality and yield of tomato in the summer season. The non-mulching (NM) served as control. In general, PF exhibited the highest illuminance and photosynthetic irradiance, and thereby led to the highest soil temperature. However, soil temperature decreased on average of 5.73% and 20.28% in BPs as compared to NM and PF, respectively. Soil moisture increased on average of 8.15%, 5.41%, and 10.98% in dark, red, and blue BPs, respectively, as compared to NM. The ratio of blue-violet to red-orange irradiance were 1:2, 2:3, 1:4, 1:3, and 1:1 in NM, PF, yellow BP, red BP, and blue BP, respectively. The red and blue BPs generally enhanced root growth, and thereby increased total fruit yield by 36.56% and 41.64% on average, respectively, as compared to PF. In addition, an overall improvement in fruit quality (vitamin C, soluble sugar, and sugar-acid ratio) was observed in red and blue BPs as compared to PF and other colored BPs. Our results demonstrated that red and blue BPs can be applied to improve soil environment and spectral characteristics, and thereby enhance fruit yield and quality, during the summer crop production.

Improvement of manganese phytoremediation by Broussonetia papyrifera with two plant growth promoting (PGP) Bacillus species

Combining phytoremediation plants and microorganisms is a promising method of remediating heavy metal contaminated soil. In this study, two manganese-tolerant strains were isolated from Mn slag and identified as Bacillus cereus HM5 and Bacillus thuringiensis HM7. These two Bacillus spp. have the ability to dissolve phosphorus, produce IAA and iron carrier. A pot experiment of Broussonetia papyrifera was conducted to explore potential of B. cereus HM5 and B. thuringiensis HM7 to improve effect of remedying Mn pollution by B. papyrifera. The strains were inoculated under different Mn treated (5 mmol/L, 50 mmol/L, Mn slag) respectively and the growth, root structure, root activity, physiological and biochemical characteristics of the leaves and accumulation of Mn for B. papyrifera were determinated. The effects of the soil environment to remediation were observed, the results showed that the biomass, total root length, surface area, crossings, tips, forks and root activity of B. papyrifera with inoculated strain were higher than those of the control group. The inoculation of these two Bacillus spp. increased the absorption of Mn by B. papyrifera and the concentration of Mn in the aerial parts of plants, indicating that the two strains could promote the growth of B. papyrifera and the accumulation of Mn. In addition, microbes reduced malonaldehyde content and the activities of antioxidant enzymes in leaves, suggesting that the two Bacillus spp. reduced Mn-induced oxidative stress. The principal component analysis showed that the added Bacillus strain prefer to promote plant root function maintenance and improve soil environment, rather than direct adsorption of heavy metals. These observations indicated that B. cereus HM5 and B. thuringiensis HM7 were valuable microorganisms, which could improve the remediating efficiency of B. papyrifera under Mn-contaminated soil.

Long-term interactions of reduced tillage and different amounts of residue retaining improved soil environment in a semi-arid tropical climate

Long-term interactions of reduced tillage and different amounts of residue retaining improved soil environment in a semi-arid tropical climate

Effects of residual apple fermentation products on continuous cropping soil environment and the growth of Malus hupehensis Rehd. Seedlings

Effects of fermented apple products on the growth of continuous cropping Malus hupehensis Rehd. seedlings and soil environment were examined in a pot experiment to provide theoretical basis for apple replant disease. There were four treatments, the replanted soil (control, CK), sterilized replant soil (T1), replanted soil applied with apple fermentation products (T2), and replanted soil applied with sterilized apple fermentation products (T3). The results showed that T1, T2 and T3 significantly promoted seedlings growth, with better performance of T1 and T2. T1 increased root respiration rate, plant height, ground diameter, fresh weight, and dry weight by 107.3%, 50.6%, 42.4%, 171.7%, 225.3%, while T3 increased them by 104.4%, 50.6%, 42.3%, 171.8%, 225.5%, respectively over CK. T2 and T3 increased the activities of nutrient conversion-related enzymes in continuous cropping soil. T2 increased the activities of catalase, urease, neutral phosphatase and sucrase by 44.5%, 169.5%, 23.4%, 169.3%, while T3 increased them by 23.7%, 72.6%, 1.5%, 121.5%, respectively. Catalase and sucrase activities under T1 treatment did not differ from that in CK, whereas their urease and neutral phosphatase activities were reduced by 40.8% and 41.6%, respectively. The contents of ammonium, nitrate, available phosphorus and available potassium in T2 soil were increased by 18.6%, 50.6%, 14.0% and 36.7% respectively. T3 only increased the content of available nitrogen, with ammonium and nitrate being increased by 7.0% and 23.6% respectively. The content of available nutrients of T1 decreased compared with CK. T1 and T2 significantly reduced the abundance of actinomycetes and fungi in soil and increased that of bacteria. The abundance of bacteria, actinomycetes and fungi in T3 treatment were all significantly decreased. Results of real-time fluorescence quantitative PCR analysis showed that the gene copies of Fusarium proliferaturn, F. moniliforme, F. solani and F. oxysporum in T1, T2 and T3 were ecreased to different degrees. Apple fermented product could inhibit soil pathogen in replanted orchard soil, improve soil environment, and promote seedling growth, which could be used to alleviate the apple replant disease.