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1.
Long-term effects of mineral fertilization on microbial biomass C (MBC), basal respiration (R
B), substrate-induced respiration (R
S), β-glucosidase activity, and the r–K-growth strategy of soil microflora were investigated using a field trial on grassland established in 1969. The experimental
plots were fertilized at three rates of mineral N (0, 80, and 160 kg ha−1 year−1) with 32 kg P ha−1 year−1 and 100 kg K ha−1 year−1. No fertilizer was applied on the control plots (C). The application of a mineral fertilizer led to lower values of the MBC
and R
B, probably as a result of fast mineralization of available substrate after an input of the mineral fertilizer. The application
of mineral N decreased the content of C extracted by 0.5 M K2SO4 (C
ex). A positive correlation was found between pH and the proportion of active microflora (R
S/MBC). The specific growth rate (μ) of soil heterotrophs was higher in the fertilized than in unfertilized soils, suggesting the stimulation of r-strategists, probably as the result of the presence of available P and rhizodepositions. The cessation of fertilization with
320 kg N ha−1 year−1 (NF) in 1989 also stimulated r-strategists compared to C soil, probably as the result of the higher content of available P in the NF soil than in the C
soil. 相似文献
2.
Harvester ants (Messor spp.) function as an essential link between aboveground resources and below-ground biota such as the microbial community.
We examined changes in soil microbial biomass and functional diversity resulting from harvester ant (Messor spp.) activity in the Negev Desert, Israel. Abiotic and biotic soil parameters were recorded during two seasons—wet and dry—also
representing food availability periods for the ants (low and high seed availability, respectively). Soil samples were collected
monthly from the 0- to 10- and 10- to 20-cm soil layers: (1) near the nest entrance, (2) under chaff piles, and (3) at a 2-m
radius from the nest entrance (control). Harvester ant activity increased the percentage of organic matter, total soluble
nitrogen, and microbial activity in nest-modified soils in comparison to the control soils. Higher CO2 evolution was recorded in the low-seed season in ant nest soils than in the control soils. During the high-seed season, higher
carbon dioxide evolution was recorded only at the nest entrance locations. There were no differences in microbial biomass
between the low- and high-seed seasons, but highest microbial biomass was found under chaff in low-seed season and in nest
soils in high-seed season. Microbial functional diversity was higher in nest-modified soils than in the control soils. This
study suggests that the effect of harvester ant nests on soil fertility is due to increased microbial biomass and microbial
activity in ant nest-modified soils. 相似文献
3.
Bio-fertilizer application has been proposed as a strategy for enhancing soil fertility, regulating soil microflora composition, and improving crop yields, and it has been widely applied in the agricultural yields. However, the application of bio-fertilizer in grassland has been poorly studied. We conducted in situ and pot experiments to investigate the practical effects of different fertilization regimes on Leymus chinensis growth, with a focus on the potential microecological mechanisms underlying the responses of soil microbial composition. L. chinensis biomass was significantly (P?<?0.05) increased by treatment with 6000 kg ha?1 of Trichoderma bio-fertilizer compared with other treatments. We found a positive (R2 =?0.6274, P <?0.001) correlation between bacterial alpha diversity and L. chinensis biomass. Hierarchical cluster analysis and nonmetric multidimensional scaling (NMDS) revealed that soil bacterial and fungal community compositions were all separated according to the fertilization regime used. The relative abundance of the most beneficial genera in bio-fertilizer (BOF) (6000 kg ha?1Trichoderma bio-fertilizer) was significantly higher than in organic fertilizer (OF) (6000 kg ha?1 organic fertilizer) or in CK (non-amend fertilizer), there the potential pathogenic genera were reduced. There were significant negative (P?<?0.05) correlations between L. chinensis biomass and the relative abundance of several potential pathogenic genera. However, the relative abundance of most beneficial genera were significantly (P?<?0.05) positively correlated with L. chinensis biomass. Soil properties had different effects on these beneficial and on these pathogenic genera, further influencing L. chinensis biomass. 相似文献
4.
Organically managed farm areas in Denmark are expanding and typically contain clover-grass leys that are known to stimulate accumulation of organic matter in arable soils. We compared the C allocation to roots and soil from clover and grass, and determined for how long assimilated C remained mobile in these plant-soil systems. Pots with perennial ryegrass, white clover or a mixture of both were pulse-labelled with 14CO2, and harvested for analyses after 4, 11, 20, and 30 days. 14C losses by shoot respiration stopped within 4 days and after this incubation time the input of assimilated 14C to below-ground compartments was greater in grass (52%) than in clover (36%). During the next 4 weeks, 14C allocation below ground increased in grass (up to 75% at day 30), but remained constant in clover (37% at day 30). In the grass/clover mixture, the below-ground fraction increased to 50% at day 30. In clover, 14C was incorporated sooner into stable plant and soil pools and less was released in rhizodeposition than in grass. This was confirmed by the 14C in the soil microbial biomass that decreased fastest in the clover treatment. Root-derived C compounds of clover probably decomposed faster than those from grass. The larger size and specific activity of the soil microbial biomass in the mixed treatment suggested a stimulating effect of the two plant species on substrate utilisation by the microbial community. This study showed that a 2- to 3-week distribution period is needed before sampling for quantitative estimates of C allocation. 相似文献
5.
The aim of this work was to assess and compare the influence of Eisenia foetida Savigny earthworms on C mineralization rate, labile C fractions (water-soluble C and water-soluble carbohydrates), microbial biomass C, and enzyme activities (dehydrogenase, urease, phosphatase and ß-glucosidase) in three soils of varying texture treated with a composted organic residue and cropped with Avena sativa L. Mineralization decreased with the addition of earthworms to the sandy and clay-loam soils, especially in sandy soil (by about 4 µg CO 2-C g -1 day -1). There were no significant effects on the amount of CO 2 evolved from clay soil due to the addition of E. foetida. The addition of E. foetida to sandy soil significantly decreased microbial biomass C and increased microbial metabolic quotient the qCO 2 (CO 2-C to biomass C ratio). The addition of E. foetida did not affect the microbial biomass or the qCO 2 of the clay-loam and clay soils. 相似文献
6.
Andreas Fließbach Monika Messmer Bruno Nietlispach Valentina Infante Paul Mäder 《Biology and Fertility of Soils》2012,48(3):315-324
Genetically modified (GM) maize containing genes from the soil bacterium Bacillus thuringiensis (Bt) was cultivated on 29% of the total maize production area worldwide in 2009. Most studies to date compare Bt-maize varieties with their near isogenic lines; however, there is little information on the variability of conventional maize
breeding lines and how the effects of Bt varieties are ranked within. In our study on the potential risks of Bt-maize varieties, we analyzed tissue quality and compared the effects of ten conventional and GM maize varieties on soil microbiological
properties in a replicated climate chamber experiment. All maize varieties were cultivated twice in the same soil microcosm.
Shoot yields and soluble C in leaf tissue of Bt varieties were higher than the ones of non-Bt. Soil dehydrogenase activity was reduced by 5% under Bt varieties compared to non-Bt, while most of the other soil microbial properties (soil microbial biomass, basal respiration) showed no significant differences
between Bt and non-Bt varieties. The leaves and roots of one Bt variety were decomposed to a greater extent than the ones of its near isogenic line; the conventional breeding lines also
showed higher values. Changes in crop and soil parameters were found when comparing the first and the second crops, but the
effects of repeated cropping were the same for all tested varieties. For the studied parameters, the variation among non-Bt-maize varieties was similar to the difference between Bt and non-Bt varieties. 相似文献
7.
The seasonal changes in the contents and compositions of n-alkanes and n-methyl ketones have been studied in typical soddy-podzolic soils (Albic Retisols (Ochric)) under lime forests in the Losiny Ostrov National Park, Moscow. In the humus horizons, the reserves (about 370 mg/m2) of odd n-alkanes with the chain length of C25–C35—the biomarkers of terrestrial vegetation—are 4–5 times below their amount entering with the leaf falloff in autumn. A noticeable contribution of microbial biomass hydrocarbons to the lipid fraction in the AY and AYel horizons manifests itself in the increased fraction of odd and medium-chain (<C25) homologues (OEP = 4–6, LSR = 5–7) in the spectrum of n-alkanes. The lowest content of methyl ketones and odd n-alkanes was observed immediately after the winter period (OEP = 22, A/K = 21–170). In the EL and BT horizons, the n-alkane fraction of organic matter and the relative content of high molecularweight n-alkanes more resistant to microbial destruction (C33, C35) increases by 3–4 times in comparison with that in the abovelying horizons, and the type of distribution of n-alkanes by the carbon chain length changes: the dominance of odd homologues is absent; in the EL horizon, OEP = 1. 相似文献
8.
Cropping in low fertility soils, especially those poor in N, contributes greatly to the low common bean (Phaseolus vulgaris L.) yield, and therefore the benefits of biological nitrogen fixation must be intensively explored to increase yields at a low cost. Six field experiments were performed in oxisols of Paraná State, southern Brazil, with a high population of indigenous common bean rhizobia, estimated at a minimum of 103 cells g–1 soil. Despite the high population, inoculation allowed an increase in rhizobial population and in nodule occupancy, and further increases were obtained with reinoculation in the following seasons. Thus, considering the treatments inoculated with the most effective strains (H 12, H 20, PRF 81 and CIAT 899), nodule occupancy increased from an average of 28% in the first experiment to 56% after four inoculation procedures. The establishment of the selected strains increased nodulation, N2 fixation rates (evaluated by total N and N-ureide) and on average for the six experiments the strains H 12 and H 20 showed increases of 437 and 465 kg ha–1, respectively,in relation to the indigenous rhizobial population. A synergistic effect between low levels of N fertilizer and inoculation with superior strains was also observed, resulting in yield increases in two other experiments. The soil rhizobial population decreased 1 year after the last cropping, but remained high in the plots that had been inoculated. DGGE analysis of soil extracts showed that the massive inoculation apparently did not affect the composition of the bacterial community. 相似文献
9.
A field study was conducted to investigate the nutrient content of green and abscised leaves of Croton macrostachyus Del. and Millettia ferruginea (Hochst.) Baker and their decomposition to return these nutrients to the soil in the short-term. Green and abscised leaves were collected from trees of comparable size in Wondo Genet, Ethiopia, and were incorporated into litterbags to decompose for a period of 12 weeks. Green leaves of C. macrostachyus had significantly higher nutrient concentrations than those of M. ferruginea. In both species, green leaves had significantly higher (P<0.05) C, N and P and significantly lower (P<0.05) lignin and polyphenol concentrations than abscised leaves. Fifty percent of the biomass applied was lost during the first 7 weeks in C. macrostachyus, which was about 3 times faster than that of M. ferruginea. The half-lives of N and P were 5–8 weeks and 4–6 weeks, respectively, in C. macrostachyus; the corresponding values for M. ferruginea were 6–8 and about 22 weeks, respectively. Only 15.7% and 26.8% of green and abscised leaves of C. macrostachyus, respectively, were recovered after the 12 weeks of decomposition. The corresponding values were about 3.5-fold and 2.5-fold higher for M. ferruginea. Generally, leaves with higher initial lignin, polyphenol, lignin:N and C:N ratios had lower decomposition and mineralization rates. In both species, removal of leaf biomass before abscission (e.g. by pruning) could enhance both the quantity and rate of nutrient return to the soil. 相似文献
10.
Valéria Marino Rodrigues Sala Elke Jurandy Bran Nogueira Cardoso Fabiana Fantinatti Garboggini Neusa de Lima Nogueira Adriana Parada Dias da Silveira 《Biology and Fertility of Soils》2008,44(8):1107-1112
This study reports for the first time the presence of diazotrophic bacteria belonging to the genera Achromobacter and Zoogloea associated with wheat plants. These bacterial strains were identified by the analysis of 16S rDNA sequences. The bacterium
IAC-AT-8 was identified as Azospirillum brasiliense, whereas isolates IAC-HT-11 and IAC-HT-12 were identified as Achromobacter insolitus and Zoogloea ramigera, respectively. A greenhouse experiment involving a non-sterilized soil was carried out with the aim to study the endophytic
feature of these strains. After 40 days from inoculation, all the strains were in the inner of roots, but they were not detected
in soil. In order to assess the location inside wheat plants, an experiment was conducted under axenic conditions. Fifteen
days after inoculation, preparations of inoculated plants were observed by the scanning electron microscope, using the cryofracture
technique, and by the transmission electron microscope. It was observed that all isolates were present on the external part
of the roots and in the inner part at the elongation region, in cortex cells, but not in the endodermis or in the vascular
bundle region. No colonizing bacterial cells were observed in wheat leaves. 相似文献
11.
The influence of a soil-feeding termite nest (Cubitermes nikoloensis) on the development of a symbiotic microflora (rhizobia, arbuscular mycorrhizas) was tested in a pot experiment with a tropical legume (Crotalaria ochroleuca). Our results confirmed the role of soil-feeding termite nests as sites of high nutrient concentration, as a significantly higher content of available P and mineral-N was found in the mound wall. Arbuscular mycorrhizal spores increased in the soil near the termite mound. The mound soil itself almost totally depressed mycorrhizal establishment. The positive effect of the soils close to the mound was also evidenced by the number of nodules per root system as well as the nodule biomass per legume plant grown on this medium. Better growth of Crotalaria seedlings was observed in the soils from the mound wall; the shoot biomass increased by a factor of 9 and the root biomass by a factor of 6 as compared to the control soil (10 m away from the mound). Plant growth on soils from the immediate vicinity of the mound showed intermediate results but a higher N content per biomass unit. This probably reflected the association with arbuscular mycorrhiza and rhizobia. This work evidenced the linkage of plant nutrition to nutrient availability in mound material and the indirect mediating effect of the symbiotic microflora. 相似文献
12.
Houyang Kang Meiyu Zhong Quan Xie Haiqin Zhang Xing Fan Lina Sha Lili Xu Yonghong Zhou 《Genetic Resources and Crop Evolution》2012,59(3):445-453
Trigeneric hybrids may help establish evolutionary relationships among different genomes present in the same cellular-genetic
background, and also offers the possibility to transfer different alien characters into cultivated wheat. In this study, a
new trigeneric hybrid involving species from the Triticum, Psathyrostachys and Secale was synthesized by crossing wheat-P. huashanica amphiploid (PHW-SA) with wheat-S. cereale amphiploid (Zhongsi 828). The crossability of F1 hybrid was high with 35.13%, and the fertility was 41.95%. The morphological characteristics of F1 plants resembled the parent Zhongsi 828. The trigeneric hybrids pollen mother cells (PMCs) regularly revealed averagely 19.88
univalents, 9.63 ring bivalents, 3.97 rod bivalents, 0.60 trivalents and 0.03 tetravalents per cell. Multivalents consisted
of trivalents and tetravalents can be observed in 52.7% of cells. A variation of abnormal lagging chromosome, micronuclei
and chromosome bridge were formed at anaphase I and telophase II. The mean chromosomes number of F2 progenies was 2n = 46.13, and the distribution range was 42–53. GISH results revealed that most F2 plants had 6–12 S. cereale chromosomes, and only 0–2 P. huashanica chromosomes were detected. The results indicated that S. cereale chromosomes can be preferentially transmitted in the F2 progenies of trigeneric hybrid than P. huashanica chromosomes. A survey of disease resistances revealed that the stripe rust resistance from the PHW-SA were completely expressed
in the F1 and some F2 plants. The trigeneric hybrid could be a useful bridge for the transference of P. huashanica and S. cereale chromatins to common wheat. 相似文献
13.
A fertile amphidiploid × Brassicoraphanus (RRCC, 2n = 36) between Raphanus sativus cv. HQ-04 (2n = 18, RR) and Brassica alboglabra Bailey (2n = 18, CC) was synthesized and successive selections for seed fertility were made from F4 to F10. F10 plants exhibited good fertility with 14.9 seeds per siliqua and 32.3 g seeds per plant. Cytological observation revealed
that frequent secondary pairing occurred among 3 chromosome pairs in pollen mother cells of plants (F4) with lower fertility, but not of plants with high fertility (F10). GISH analysis indicated that these F10 plants included the expected 18 chromosomes from R. sativus and B. alboglabra, respectively, but they lost approximately 27.6% R. sativus and 35.6% B. alboglabra AFLP (amplified fragment length polymorphism) bands. The crossability of the Raphanobrassica with R. sativus and 5 Brassica species (13 cultivars) were investigated. Seeds or F1 seedlings were easy to be produced from crosses × Brassicoraphanus × R. sativus, and B. napus, B. juncea and B. carinata × Brassicoraphanus. Fewer seeds or seedlings were obtained from crosses × Brassicoraphanus × B. napus, B. juncea and B. carinata. However, few seeds were harvested in the reciprocals of × Brassicoraphanus with B. rapa and B. oleracea. The possible cause of fertility improvements and the potential of the present × Brassicoraphanus for breeding were discussed. 相似文献
14.
Xiaoguang Sheng Guiju Wen Yangdong Guo Hong Yan Hong Zhao Fan Liu 《Genetic Resources and Crop Evolution》2012,59(1):73-81
Black rot is a bacterial disease of Brassica rapa caused by Xanthomonas
campestris pv. campestris (Xcc.). Sources of resistance to this disease within B. rapa are insufficient and control measures are limited, making the development of resistant breeding lines extremely important.
Certain lines of B. nigra exhibit very high resistance to Xcc. For this study, an interspecific cross between Brassica rapa and B. nigra was performed, and a total of 6 F1 hybrids were obtained through ovary culture. Five plants (H1–5) were relatively slow-growing, entirely sterile, and had 18 chromosomes in the majority of pollen mother cells (PMCs). GISH
analysis showed that most of the PMCs had 8 B. nigra chromosomes, which indicated the expected AB genomic constitution. The last plant (H6) was partially fertile and the majority of PMCs contained 10 chromosomes of B. rapa and 16 chromosomes of B. nigra, indicating an ABB genomic constitution. Ovary culture techniques were not necessary for the development of the first- or
second-backcross generation. Sequence-related amplified polymorphism analysis of F1, BC1, and BC2 plants indicated that some fragments from B. nigra were lost, particularly in the genome of BC1/BC2 in successive generation(s). The BC2 plants expressing good resistance to Xcc. were observed. 相似文献
15.
Mohammad-Saeed Safdari Hamid-Reza Kariminia Zahra Ghobadi Nejad Thomas H. Fletcher 《Water, air, and soil pollution》2017,228(1):37
Petroleum products which are used in a wide variety of industries as energy sources and raw materials have become a major concern in pollution of terrestrial and marine environments. The purpose of this study was to assess the potential of indigenous microbial isolates for degradation of diesel fuel. Two most proficient bacterial strains among five isolated strains from polluted soil of an industrial refinery were studied. The isolates then were identified as Pseudomonas aeruginosa and Bacillus subtilis using biochemical tests and 16S rRNA gene sequence analyses. P. aeruginosa showed higher biodegradation efficiency than B. subtilis in shaking flask containing diesel-contaminated water. P. aeruginosa and B. subtilis degraded about 87 and 75% of total hydrocarbons, respectively, in flasks containing 2% diesel and 98% water. The biodegradation efficiency of the isolates decreased as diesel contamination increased from 2 to 5%. The isolates showed significantly higher efficiency on degradation of short-chain hydrocarbons in 20 days, i.e., by using P. aeruginosa, removal efficiency of C10 hydrocarbons was near 90%, while about 69% of C20+ hydrocarbons and 47% of aromatic hydrocarbons were removed. Therefore, the isolates showed high capability in biodegradation of diesel contamination of the refinery. 相似文献
16.
Lantana camara is a recognized weed of worldwide significance due to its extensive distribution and its impacts on primary industries and
nature conservation. However, quantitative data on the impact of the weed on soil ecosystem properties are scanty, especially
in SE Australia, despite the pervasive presence of the weed along its coastal and inland regions. Consequently, mineral soils
for physicochemical analyses were collected beneath and away from L. camara infestations in four sites west of Brisbane, SE Australia. These sites (hoop pine plantation, cattle farm, and two eucalyptus
forests with occasional grazing and a fire regime, respectively) vary in landscape and land-use types. Significant site effect
was more frequently observed than effect due to invasion status. Nonetheless, after controlling for site differences, ~50%
of the 23 soil traits examined differed significantly between infested and non-infested soils. Moisture, pH, Ca, total and
organic C, and total N (but not exchangeable N in form of NO3-) were significantly elevated, while sodium, chloride, copper, iron, sulfur, and manganese, many of which can be toxic to
plant growth if present in excess levels, were present at lower levels in soils supporting L. camara compared to soils lacking the weed. These results indicate that L. camara can improve soil fertility and influence nutrient cycling, making the substratum ideal for its own growth and might explain
the ability of the weed to outcompete other species, especially native ones. 相似文献
17.
Armand W. Koné Ettien F. Edoukou Jérôme E. Tondoh Jean T. Gonnety Pascal K. T. Angui Dominique Masse 《Biology and Fertility of Soils》2012,48(3):337-347
In tropical savannas where soils are generally sandy and nutrient poor, organic farming associated with enhanced soil biological activity may result in increased nutrient availability. Therefore, legumes have been introduced in the humid savanna zone of Côte d’Ivoire, owing to their ability to fix atmospheric N and to continually supply soil with great quantity of organic materials in relatively short time. The main objective of this study was to assess the influence of two legume (Cajanus cajan and Lablab purpureus) cultivations on earthworm communities and P and N availability. Trials were carried out under farmers' field conditions; C. cajan was planted on savanna soils (trial 1) while L. purpureus was established on new Chromolaena odorata-dominated fallow soils (trial 2). Native vegetations were considered as controls. Changes in soil properties (earthworm abundance and diversity, microbial biomass carbon (MBC), and plant available P and N) were assessed using the biosequential sampling. After 1 year, both the legume stands showed a significantly higher density of earthworms, compared with the respective controls. This trend was linked to an increase in the abundance of the detritivores Dichogaster baeri Sciacchitano 1952 and Dichogaster saliens Beddard 1893, and the polyhumic Stuhlmannia zielae Omodeo 1963. Equally, legume had beneficial impacts on the average number of earthworm species, the Shannon–Weaver index of diversity and MBC in savanna (trial 1). Available P and ammonium significantly increased under both legume cultivations and were significantly and concurrently linked to litter quality and earthworm activities as shown by multiple regressions. As a result, legumes could improve nutrient availability in the sandy soils of central Côte d’Ivoire by positively affecting soil biological activity and this could bring farmers to cultivate crops on savanna lands. 相似文献
18.
Background, Aims and Scope Phytoremediation is a promising means for the treatment of heavy metal contamination. Although several species have been identified
as hyperaccumulators, most studies have been conducted with only one metal. Experiments were conducted to investigate the
ability of Helianthus annuus and Thlaspi caerulescens to simultaneously uptake Cd, Cr and Ni.
Materials and Methods The efficiency of plants grown in a sandy-loam soil was investigated. The ability of two EDTA concentrations (0.1 and 0.3
g kg−1) for enhancing the phytoremediation of Cd, Cr and Ni at two different metal concentrations (24.75 mg kg−1 and 90 mg kg−1) was studied.
Results
Thlaspi hyperaccumulated Ni with 0.1 g kg−1 EDTA. When the EDTA dosage was increased to 0.3 g kg−1, Thlaspi was able to hyperaccumulate both Ni and Cr. Since Thlaspi is a low-biomass plant, it was considered insufficient for full-scale applications. Helianthus annuus hyperacummulated Cr (with 0.1 g kg−1 EDTA) and Cd (0.3 g kg−1 EDTA).
Discussion When the contamination was 8.25 mg kg−1 per metal, the total metal uptake was 10–25% (1.35 to 2.12 mg) higher and had the same uptake selectivity (Cr>>Cd>Ni) for
both EDTA levels. It was hypothesized that complexation with EDTA interfered with Ni translocation. For these experiments,
the optimal results were obtained with the H. annuus-0.1 g kg−1 EDTA combination.
Conclusions Although the use of EDTA did increase the amount of metal that could be extracted, care should be taken during in-situ field
applications. Chelators can also increase the amount of metals that are leached past the root zone. Metal leaching and subsequent
migration could lead to ground water contamination as well as lead to new soil contamination.
Recommendations and Perspectives Additional research to identify the optimal EDTA dosage for field applications is warranted. This is necessary to ensure that
the metals do not leach past the root zone.
Identification of a plant that can hyperaccumulate multiple metals is critical for phytoremediation to be a viable remediation
alternative. In addition to being able to hyperaccumulate multiple metals, the optimal plant must be fast growing with sufficient
biomass to sequester the heavy metals. 相似文献
19.
Laboratory tests and greenhouse experiments were carried out to investigate the abilities of Bacillus subtilis Y-IVI to promote plant growth and to colonize the rhizosphere and interior tissues of muskmelon. Laboratory tests showed
that B. subtilis Y-IVI can produce indole acetic acid, siderophores, and ammonia. The inoculation of soil with green fluorescent protein-tagged
Y-IVI (GY-IVI) significantly increased plant shoot and root dry weights as compared with the non-inoculated soils. The inoculation
of soil with B. subtilis GY-IVI maintained approximately 108 colony-forming units (cfu) of GY-IVI per gram of dry rhizosphere soil for 1 month. The GY-IVI recovered from the interior
of crowns and roots in the inoculated soil were 106 and 107 cfu g−1 dry weight, respectively, suggesting that GY-IVI acted as an endophyte. In the present study, we combined the two important
growth promotion ingredients, colonization ability and growth promotion metabolites produced by biological agents, to investigate
B. subtilis Y-IVI’s promotion effects on muskmelon growth. 相似文献
20.
The effects of earthworm (Eisenia fetida) activity on soil pH, dissolved organic carbon (DOC), microbial populations, fraction distribution and bioavailability of heavy metals (Zn, Cu, Cr, Cd, Co, Ni, and Pb) in five Chinese soils were investigated using pot experiments. A three-step extraction procedure recommended by the European Community Bureau of Reference (BCR; now Standards, Measurements and Testing Programme of the European Community) was used to fractionate the metals in soils into water soluble, exchangeable and carbonate bound (B1), Fe-oxides and Mn-oxides bound (B2) and organic matter and sulfide bound (B3). After the soils were treated with earthworms, the soil pH, water-soluble metal fraction and DOC increased. A significant correlation was obtained between the increased DOC and the increased metals in the water-soluble fraction. The heavy metals in fraction B1 increased after earthworm treatments, while those in fraction B3 decreased. No significant differences were observed for heavy metals in fraction B2. The microbial populations in soil were enumerated with the dilution plate method using several media in the presence of earthworms. The microbial populations increased due to earthworm activity. The biomass of wheat shoots and roots, and the heavy metal concentrations in wheat roots and shoots, were also increased due to the earthworm activity. The present results demonstrated that earthworm activity increases the mobility and bioavailability of heavy metals in soils. 相似文献