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1.
Wei-An Lai P. D. Rekha A. B. Arun Chiu-Chung Young 《Biology and Fertility of Soils》2008,45(2):155-164
Benefits from the application of plant growth-promoting bacteria in agriculture largely depend on the complex interactions
between several factors including the nature of fertilizers selected. This study was designed to determine the fine tuning
between the inoculated bacteria and different fertilizers and their effect on the growth of lettuce plants (Lactuca sativa L.). Plant growth promotion by a novel species of the genus Azospirillum, namely A. rugosum IMMIB AFH-6, was tested by biochemical, bioassay, and greenhouse studies. The treatments used in the greenhouse study were;
unfertilized control (Blank), half recommended dose of chemical fertilizer (1/2CF), full recommended dose of chemical fertilizer
(1CF), pig manure fertilizer (PMF), pig manure fertilizer + half recommended dose of chemical fertilizer (PMF + 1/2CF), and
pig manure fertilizer + full recommended dose of chemical fertilizer (PMF + 1CF). All these treatments when inoculated with
A. rugosum IMMIB AFH-6 inoculation were, respectively, In-Blank, In-1/2CF, In-1CF, In-PMF, In-PMF + 1/2CF, and In-PMF + 1CF. Significant
increase in plant biomass and shoot N, P, Ca, and Fe was shown in the In-Blank treatment. Plant growth in soil amended with
PMF and A. rugosum IMMIB AFH-6 was significantly lower than in soil treated with the chemical fertilizer, but inoculation combined with chemical
fertilizer significantly elevated the plant biomass. The In-PMF + 1/2CF treatment showed the highest yield. A. rugosum IMMIB AFH-6 facilitated the accumulation of trace minerals in higher concentrations when PMF was combined with 1CF. To examine
the benefits of inoculation by A. rugosum IMMIB AFH-6, we have proposed a new type of data analysis which considers both biomass and nutrient content of plants. This
new type of analysis has shown the importance of the mineral content of plant. 相似文献
2.
High yield culture medium is fundamental for production of inoculants for plant growth-promoting bacteria. Based on substitution
of glucose in tryptone–yeast extract–glucose medium by Na-gluconate or glycerol, two new culture media were developed for
mass cultivation of the commonly used plant growth-promoting bacterium Azospirillum sp. After 18 h of incubation, these modifications increased populations of different strains of Azospirillum (to ∼1011 cells ml−1 [single cell count] and ∼5 × 109 CFU ml−1 [plate count method]), significantly reduced generation time, and were also suitable for production of common synthetic inoculants. 相似文献
3.
Shaharah Mohd Idris Paul L. Jones Scott A Salzman Graeme Allinson 《Water, air, and soil pollution》2012,223(2):549-557
Two emergent macrophytes, Arundo donax and Phragmites australis, were established in experimental subsurface flow, gravel-based constructed wetlands (CWs) and challenged by untreated stormwater
collected from the hard-pan and other surfaces of a dairy processing factory in south-west Victoria, Australia. The hydraulic
loading rate was tested at two levels, sequentially, 3.75 and 7.5 cm day−1. Some of the monitored variables were removed more efficiently by the planted beds in comparison to unplanted CWs (biochemical
oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP); p < 0.007) but there was no significant difference between the A. donax and P. australis CWs in removal of BOD, suspended solids (SS) and TN (p > 0.007) at 3.75 cm day−1 or SS and TN at 7.5 cm day−1. At 3.75 cm day−1, BOD, SS, TN and TP removal in the A. donax and P. australis CWs was 71%, 61%, 78% and 75% and 65%, 60%, 73% and 41%, respectively. Nutrient removal at 7.5 cm day−1 in the A. donax and P. australis beds was 87%, 91%, 84% and 71% and 96%, 94%, 87% and 55%, respectively. As expected, the A. donax CWs produced considerably more biomass (10 ± 1.2 kg wet weight) than the P. australis CWs (2.7 ± 1.2 kg wet weight). This equates to approximately 107 and 36 tonnes ha−1 year−1 biomass (dry weight) for A. donax and P. australis, respectively (assuming 250 days of growing season and single-cut harvest). The performance similarity of the A. donax- and P. australis-planted CWs indicates that either may be used in HSSF wetlands treating dairy factory stormwater, although the planting of
A. donax provides additional opportunities for secondary income streams through utilisation of the biomass produced. 相似文献
4.
Allolobophora chlorotica exists as two colour morphs, pink and green. Field observations have indicated that the two morphs have ecological preferences
linked to soil moisture: the green morph dominating in wet soils and the pink morph in dry soils. The aim of this laboratory-based
research was to investigate the potential differences in fitness and adaptation to soil-moisture conditions of the two morphs
measured in terms of growth rate, reproductive output and cocoon viability. An initial experiment maintained hatchlings of
both morphs individually under standard culture conditions. On maturation, these were paired (intra-morph), and cocoon production,
viability and incubation time were determined. The green morph had significantly faster (P < 0.01) growth rates than the pink morph. Cocoon production was also significantly greater in the green compared with the
pink morph (3.2 and 1.5 cocoons worm−1 28 days−1, respectively) with corresponding viabilities of 87 and 58%. In a second experiment, the growth rates of pink and green hatchlings
were assessed under wet and dry soils (29 and 21% soil moisture, respectively). The growth of the pink morph was not influenced
significantly (P > 0.05) by soil moisture. In contrast, lower soil-moisture content significantly (P < 0.05) slowed growth and maturation of the green morph. These results support field observations relating to distribution
of the two A. chlorotica colour morphs. We suggest that soil-moisture content may act to isolate these morphs, providing, in extremes, a barrier to inter-morphic
mating. 相似文献
5.
Plant growth-promoting rhizobacteria (PGPR) play an important role in the biodegradation of natural and xenobiotic organic
compounds in soil. They can also alter heavy metal bioavailability and contribute to phytoremediation in the presence or absence
of synthetic metal chelating agents. In this study, the inhibitory effect of Cd2+ and Ni2+ at different concentrations of Ca2+ and Mg2+, and the influence of the widely used chelator EDTA on growth of the PGPR Pseudomonas brassicacearum in a mineral salt medium with a mixture of four main plant exudates (glucose, fructose, citrate, succinate) was investigated.
Therefore, the bacteriostatic effect of Cd2+, Ni2+ and EDTA on the maximum specific growth rate and the determination of EC50 values was used to quantify inhibitory impact.
At high concentrations of Ca2+ (800 μmol L-1) and Mg2+ (1,250 μmol L-1), only a small inhibitory effect of Cd2+ and Ni2+ on growth of P. brassicacearum was observed (EC50 Cd2+, 18,849 ± 80 μmol L−1; EC50 Ni2+, 3,578 ± 1,002 μmol L−1). The inhibition was much greater at low concentrations of Ca2+ (25 μmol L−1) and Mg2+ (100 μmol L−1) (EC50 Cd2+, 85 ± 0.5 μmol L−1 and EC Ni2+, 62 ± 1.8 μmol L−1). For the chosen model system, a competitive effect of the ions Cd2+ and Ca2+ on the one hand and Ni2+ and Mg2+ on the other hand can be deduced. However, the toxicity of both, Cd2+ and Ni2+, could be significantly reduced by addition of EDTA, but if this chelating agent was added in stoichiometric excess to the
cations, it also exhibited an inhibitory effect on growth of P. brassicacearum. 相似文献
6.
Cotton Verticillium wilt is a destructive soil-borne disease affecting cotton production. In this study, application of bio-organic fertilizer
(BIO) at the beginning of nursery growth and/or at the beginning of transplanting was evaluated for its ability to control
Verticillium dahliae Kleb. The most efficient control of cotton Verticillium wilt was achieved when the nursery application of BIO was combined with a second application in transplanted soil, resulting
in a wilt disease incidence of only 4.4%, compared with 90.0% in the control. Denaturing gradient gel electrophoresis patterns
showed that the consecutive applications of BIO at nursery and transplanting stage resulted in the presence of a unique group
of fungi not found in any other treatments. Humicola sp., Metarhizium anisopliae, and Chaetomium sp., which were considered to be beneficial fungi, were found in the BIO treatment, whereas some harmful fungi, such as Alternaria alternate, Coniochaeta velutina, and Chaetothyriales sp. were detected in the control. After the consecutive applications of BIO at nursery and transplanting stage, the V. dahliae population in the rhizosphere soil in the budding period, flowering and boll-forming stage, boll-opening stage, and at harvest
time were 8.5 × 102, 3.1 × 102, 4.6 × 102, and 1.7 × 102 colony-forming units per gram of soil (cfu g−1), respectively, which were significantly lower than in the control (6.1 × 103, 3.4 × 103, 5.2 × 103, and 7.0 × 103 cfu g−1, respectively). These results indicate that the suggested application mode of BIO could effectively control cotton Verticillium wilt by significantly changing the fungal community structure and reducing the V. dahliae population in the rhizosphere soil. 相似文献
7.
Juxiu Liu Shanjiang Peng Benjamin Faivre-vuillin Zhihong Xu Deqiang Zhang Guoyi Zhou 《Journal of Soils and Sediments》2008,8(6):452-460
Background, aims, and scope Increasing soil acidification is a growing concern in southern China. The traditional green manures applied in the fields
mostly comprise legumes that tend to accelerate soil acidification. Moreover, acid deposition can act as a source of nitrogen.
Hence, we looked for new plant species that would enhance nutrient concentrations when used as green manure and would reduce
soil acidity or at least not worsen it.
Materials and methods We studied the use of Erigeron annuus (L.) Pers. for ameliorating acid soil in a pot experiment with simulated acid rain (SAR) treatments (pH 5.8 to 3.0) in an
open area in Guangzhou City. The pots were divided into two groups named A and B groups. On day 0, pots of A group were filled
with soil and planted with Erigeron annuus seedlings. Pots of B group were only filled with soil as the control. On day 40, seedlings of E. annuus were harvested and buried in the corresponding pots. On day 54, two seeds of Phaseolus vulgaris L. were sown in each pot in both groups. The growth and bean yield of P. vulgaris seedlings were then used to evaluate the effects of E. annuus on acid soil. Plant and/or soil samples were collected on days 0, 40, 54, and 150; corresponding parameters were measured.
Results Results showed that E. annuus could maintain a good growth even on very acid soil. On day 40, the pH decreased significantly (P < 0.0001) in the B group pots without E. annuus compared with the A group. On day 54, after E. annuus was buried as a manure, the soil pH of all A group treatments except the pH 4.0 treatment showed a significant increase compared
to day 40 (P < 0.01). At the same time, the application of E. annuus as a manure produced a significant increase of soil K and P (P < 0.001), Ca (P < 0.05), and Mg (P < 0.001) concentrations of all A group SAR treatments compared to their B group counterparts (except control pots for Ca).
The soil exchangeable K and available P concentration doubled, and Ca and Mg increased by around 25% in the presence of the
E. annuus manure application.
Discussion The higher soil pH in the A group than B group on the day 40 was due to a great absorption of NO3
− by the roots of E. annuus. The soil pH increase after E. annuus was applied to the soil of A group was attributed to the release of high amount of K, the mineralization of organic N, and
the oxidation of organic acid anions. Nutrient increase in the A group after E. annuus application was mostly the result of the nutrient release during the residue decomposition. The amelioration of the soil
was effective as demonstrated by the enhanced growth and bean yield of P. vulgaris seedlings on the manured soil compared to the seedlings grown on a control that was not manured.
Conclusions
E. annuus could maintain a good growth in the acid lateritic field soil. Cultivating this plant and applying it to the soil with a
rate of 1.6 ton ha−1 doubled the soil K and P concentrations and increased soil exchangeable Ca and Mg concentrations by around 25%. This species
would be a good green manure candidate for growing in the acid soils of southern China. Application of E. annuus also has beneficial effects on crop growth through reduced Al toxicity and cation leaching.
Recommendations and perspectives Since E. annuus would improve soil pH and nutrient concentrations with minimum care, it is recommended for treating acid soils with poor
yield whenever a low-cost solution is required. 相似文献
8.
Gang Xin Gengyun Zhang Jun Won Kang James T. Staley Sharon L. Doty 《Biology and Fertility of Soils》2009,45(6):669-674
An endophytic bacterium, wild poplar strain B (WPB), isolated from stems of wild cottonwood (Populus trichocarpa) was identified to Burkholderia vietnamiensis by analyzing the recA and rDNA genes. Phylogenetic analysis of the nifHDK cluster indicates that the WPB isolate shares high sequence similarity with known B. vietnamiensis strains. The nitrogenase activity of WPB was determined by a 15N2 incorporation assay and an acetylene reduction assay. WPB was also monitored for production of indole-3-acetic acid (IAA),
a phytohormone which can promote plant growth, when incubated with l-tryptophan. In addition, its plant growth promotion capacity was assessed by inoculating the WPB strain onto Kentucky bluegrass
in nitrogen-free medium. Compared to uninoculated control plants, the plants inoculated with WPB gained more dry weight (42%,
p = 0.01) and more nitrogen content (37%, p = 0.04) in 50 days. 相似文献
9.
The response of faba bean to the application of four rates of gypsum (0, 2.5, 5.0, 10.0 t ha−1) to a non-saline, alkaline sodic soil was measured in terms of grain yield, dry matter (DM) production, N accumulation and
the proportional dependence of the legume on symbiotic N2 fixation (P
atm). A yield-independent, time-integrated 15N-dilution model was used to estimate symbiotic dependence. A significant decrease in the exchangeable sodium percentage and
significant increases in exchangeable Ca++ and the Ca++:Mg++ ratio in the 0–10-cm soil layer were measured 30 months after application of 10 t ha−1 gypsum. Despite low and erratic rainfall during crop growth, faba bean DM and N uptake responded positively to gypsum application.
The symbiotic dependence of the legume at physiological maturity was little affected by sodicity (P
atm = 0.74 at zero gypsum and 0.81–0.82 at 2.5–10 t ha−1 gypsum). The increase in fixed N due to gypsum application was mainly due to increases in legume DM and total N uptake. At
10 t ha−1 of gypsum, faba bean fixed more than 200 kg N ha−1 in above-ground biomass. 相似文献
10.
We have estimated the production of water-soluble B vitamins by plant growth-promoting rhizobacterium Pseudomonas fluorescens strain 267 in a minimal medium with different C sources and at different pH values. In the minimal medium, strain 267 produced
large amounts of niacin (0.92 μg ml–1) and pantothenic acid (0.75 μg ml–1), but also other vitamins such as biotin, thiamine, cobalamine and pyridoxine. The production of B vitamins was dependent
on the C source and pH of the growth medium. By random Tn5 mutagenesis, thiamine and niacin auxotrophs were isolated from P. fluorescens strain 267 and mutants were used to evaluate the vitamin production on colonization of clover roots under controlled conditions.
Red clover root colonization decreased by about 1 order of magnitude in the case of the niacin auxotroph. The vitamin auxotrophs
of P. fluorescens in a mixed inoculation of clover with R. leguminosarum bv. trifolii strain 24.1 showed no plant growth-promotion activity.
Received: 23 May 2000 相似文献
11.
Alok Kalra Mahesh Chandra Ashutosh Awasthi Anil K. Singh Suman Preet S. Khanuja 《Biology and Fertility of Soils》2010,46(5):521-524
The present study demonstrates the usefulness of natural microbial growth-promoting compounds for improving the stability
and life of vermicompost-based (both granular and its aqueous extract) bioformulations. Granular vermicompost maintained the
number of cells of Rhizobium meliloti Rmd 201 up to 5.9 × 108 after 180 days at 28°C compared with 2.1 × 108 in charcoal (powdered), while aqueous extract of the vermicompost supported the 5.6 × 107 rhizobia numbers even after 270 days. The addition of 25 μL/mL cow urine and 0.01 mM calliterpinone, a natural plant growth
promoter, increased the rhizobia number significantly in granular vermicompost and its aqueous extract, respectively. 相似文献
12.
Many phosphate solubilizing microorganisms (PSM) require external pyrroloquinoline quinone (PQQ) for strong phosphorus (P)
solubilization in vitro. The objective of this study was to isolate efficient and PQQ-independent PSM. A total of 21 PSM were
isolated from the rhizosphere soil of wheat and maize grown in the pots. Acinetobacter strains were the only PQQ-independent and most effective solubilizers of tricalcium phosphate containing agar. The mean P
dissolved in liquid cultures of Acinetobacter strains in a 5-day incubation ranged from 167 to 888 μg/ml P. The pH dropped to below 4.7 from 7.8 in six isolates, which
produced gluconic acid in concentrations ranging between 27.5 and 37.5 mM. There was a linear regression between soluble P
and gluconic acid concentrations in the bacterial cultures (P < 0.05; R
2 = 0.59). Inoculation with Acinetobacter sp. WR922 significantly (P < 0.05) increased wheat (Triticum aestivum L.) P content by 27% at 15 days after emergence (DAE) and dry matter by 15% at 30 DAE compared to the control. The plant
P content in inoculated plants at 30 DAE was linearly correlated with soluble P of the bacterial cultures (P < 0.05; R
2 = 0.69). Gluconic acid production directly affected phosphate solubilization in vitro, which in turn influenced plant P content
of inoculated plants in PQQ-independent P-solubilizing Acinetobacter strains. 相似文献
13.
Phosphorus application decreased the sporulation frequency and number of sporocarps per plant in all the three Azolla species and 21 A. pinnata strains evaluated in this study. The number of megasporocarps tended to be more depressed than the number of microsporocarps.
Nevertheless, the sporulation of A. caroliniana was less sensitive to P than that of A. pinnata and A. microphylla. Its sporulation frequency in the mineral medium did not decrease at 2.5 μg P ml–1 and remained unaffected between 5 and 20 μg P ml–1. The sporulation frequency and sporocarp number in this species in the soil culture also were not significantly affected
by an increase in the dose of P from 10.7 to 21.4 or 21.4 to 32.1 mg pot–1. Large variations in the degree of inhibition of sporulation due to the application of P (21.4 mg pot–1) also occurred among the A. pinnata strains tested.
Received: 20 October 1999 相似文献
14.
Robert John Wilcock Karin Müller Gareth B. van Assema Margaret A. Bellingham Ron Ovenden 《Water, air, and soil pollution》2012,223(2):499-509
Water quantity and quality were monitored for 3 years in a 360-m-long wetland with riparian fences and plants in a pastoral
dairy farming catchment. Concentrations of total nitrogen (TN), total phosphorus (TP) and Escherichia coli were 210–75,200 g N m−3, 12–58,200 g P m−3 and 2–20,000 most probable number (MPN)/100 ml, respectively. Average retentions (±standard error) for the wetland over 3 years
were 5 ± 1%, 93 ± 13% and 65 ± 9% for TN, TP and E. coli, respectively. Retentions for nitrate–N, ammonium–N, filterable reactive P and particulate C were respectively −29 ± 5%,
32 ± 10%, −53 ± 24% and 96 ± 19%. Aerobic conditions within the wetland supported nitrification but not denitrification and
it is likely that there was a high conversion rate from dissolved inputs of N and P in groundwater, to particulate N and P
and refractory dissolved forms in the wetland. The wetland was notable for its capacity to promote the formation of particulate
forms and retain them or to provide conditions suitable for retention (e.g. binding of phosphate to cations). Nitrogen retention
was generally low because about 60% was in dissolved forms (DON and NOX–N) that were not readily trapped or removed. Specific yields for N, P and E. coli were c. 10–11 kg N ha−1 year−1, 0.2 kg P ha−1 year−1 and ≤109 MPN ha−1 year−1, respectively, and generally much less than ranges for typical dairy pasture catchments in New Zealand. Further mitigation
of catchment runoff losses might be achieved if the upland wetland was coupled with a downslope wetland in which anoxic conditions
would promote denitrification. 相似文献
15.
Balaji Anandha Rao Cameron P. Wake Todd Anderson William Andrew Jackson 《Water, air, and soil pollution》2012,223(1):181-188
Temporal depositional rates are important in order to understand the production and occurrence of perchlorate (ClO4−) as limited information exists regarding the impact of anthropogenic production or atmospheric pollution on ClO4− deposition. Perchlorate concentrations in discrete ice core samples from the Eclipse Icefield (Yukon Territory, Canada) and
Upper Fremont Glacier (Wyoming, USA) were analyzed using ion chromatography tandem mass spectrometry to evaluate temporal
changes in the deposition of ClO4
− in North America. The ice core samples cover a time period from 1726 to 1993 and 1970 to 2002 for the Upper Fremont Glacier
(UFG) and Eclipse ice cores, respectively. The average ClO4
− concentration in the Eclipse ice core for the time period from 1970 to 1973 was 0.6 ± 0.3 ng L−1, with higher values of 2.3 ± 1.7 and 2.2 ± 2.0 ng L−1 for the periods 1982–1986 and 1999–2002, respectively. All pre-1980 ice core samples from the UFG had ClO4
− concentrations <0.2 ng L−1, and the post-1980 samples ranged from <0.2 ng L−1 to a maximum of 2.6 ng L−1 for the year 1992. A significant positive correlation (R = 0.75, N = 15, p < 0.001) of ClO4− with SO42− was found for the annual UFG ice core layers and of ClO4
− with SO42− and NO3− in sub-annual Eclipse ice samples (R > 0.3, N = 121, p < 0.002). The estimated yearly ClO4− depositional flux for the Eclipse ice core ranged from 0.6 (1970) to 4.7 μg m−2 year−1 (1982) and the UFG from <0.1 (pre-1980) to 1.4 μg m−2 year−1 (1992). There was no consistent seasonal variation in the ClO4− depositional flux for the Eclipse ice core, in contrast to a previous study on the Arctic region. The presence of ClO4− in these ice cores might correspond to an intermittent source such as volcanic eruptions and/or any anthropogenic forcing
that may directly or indirectly aid in atmospheric ClO4− formation. 相似文献
16.
In soils with low P availability, several legumes have been shown to mobilise less labile P pools and a greater capacity to
take up P than cereals. But there is little information about the size of various soil P pools in the rhizosphere of legumes
in soil fertilised with P although P fertiliser is often added to legumes to improve N2 fixation. The aim of this study was to compare the growth, P uptake and the changes in rhizosphere soil P pools in five grain
legumes in a soil with added P. Nodulated chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), white lupin (Lupinus albus L.), yellow lupin (Lupinus luteus L.) and narrow-leafed lupin (Lupinus angustifolius L.) were grown in a loamy sand soil low in available P to which 80 mg P kg−1 was added and harvested at flowering and maturity. At maturity, growth and P uptake decreased in the following order: faba
bean > chickpea > narrow-leafed lupin > yellow lupin > white lupin. Compared to the unplanted soil, the depletion of labile
P pools (resin P and NaHCO3-P inorganic) was greatest in the rhizosphere of faba bean (54% and 39%). Of the less labile P pools, NaOH-P inorganic was
depleted in the rhizosphere of faba bean while NaOH-P organic and residual P were most strongly depleted in the rhizosphere
of white lupin. The results suggest that even in the presence of labile P, less labile P pools may be depleted in the rhizosphere
of some legumes. 相似文献
17.
Ecological pre-release risk assessment of two genetically engineered, bioluminescent Rhizobium meliloti strains in soil column model systems 总被引:2,自引:0,他引:2
In order to identify potential ecological risks associated with the environmental release of two Rhizobium meliloti strains, genetically engineered with the firefly-derived luciferase gene (luc), a pre-release greenhouse investigation was conducted. The upper 4 cm of soil columns (30 cm diameter; 65 cm depth), which
were filled according to the horizons of an agricultural field (loamy sand), were inoculated with seeds of Medicago sativa (alfalfa) and R. meliloti cells at approximately 5×106 cells·g–1 soil. Four treatments were tested: inoculation with a non-engineered wild type strain (2011), strain L33 (luc
+), strain L1(luc
+, recA–) and non-inoculated controls. The fate of the engineered strains was followed by two methods: (1) selective cultivation and
subsequent detection of bioluminescent colonies and (2) PCR detection of the luc gene in DNA, directly extracted from soil. Strain R. meliloti L33 declined to 9.0×104 cfu·g–1 soil within 24 weeks and to 2.8×103 cfu·g–1 soil within 85 weeks in the upper 25 cm of the soil columns. Decline rates for R. meliloti L1 were not significantly different. Vertical distribution analysis of the recombinant cells after 37 weeks revealed that
in three of four columns tested, the majority of cells (>98%) remained above 10 cm soil depth and no recombinant cells occurred
below 20 cm depth. However, in one column all horizons below 20 cm were colonized with 2.2×104 to 6.8×104 cfu g–1 soil. Ecological monitoring parameters included organic substance, total nitrogen, ammonium and nitrate, microbial biomass,
culturable bacteria on four different growth media and the immediate utilization of 95 carbon sources (BiologGN) by soil-extracted
microbial consortia. None of the parameters was specifically affected by the genetically engineered cells.
Received: 6 December 1996 相似文献
18.
Marcelo A. German Saul Burdman Y. Okon Jaime Kigel 《Biology and Fertility of Soils》2000,32(3):259-264
The effects of inoculation with Azospirillum brasilense Cd on root morphology and growth of common bean (Phaseolus vulgaris L.) were studied under different growth systems and water regimes. The root systems were evaluated by image analysis. In
a PVC-tube growth system, inoculation with A. brasilense at 107 colony forming units (CFU) ml–1 increased root length, root projection area, specific root length (m g–1) and specific root area (cm2 g–1), as compared with non-inoculated controls, resulting in root systems with longer and thinner roots. Water stress induced
similar root responses to those observed after inoculation with A. brasilense. No increase in plant biomass was observed in inoculated plants, suggesting that under the tested growth conditions, a relatively
larger amount of resources is required for the maintenance of the thinner roots. In water-stressed potted plants, the effect
of A. brasilense on tap root length was inoculum-concentration dependent. At 107 CFU ml–1 this effect was significant as compared to non-inoculated controls. In a pouch system without water stress, inoculation with
A. brasilense at a concentration of 105–107 CFU ml–1 2 days after germination resulted initially (2 days after inoculation) in an increase in root length (95%) and root fresh
weight (66%), but reduced root diameter (20%), compared to controls. At this early stage of growth the distribution of root
length among the different root diameter classes changed: the thinner-root classes had the largest proportion of longer roots.
Received: 3 January 2000 相似文献
19.
Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol 总被引:2,自引:0,他引:2
Wisal Muhammad Sarah M. Vaughan Ram C. Dalal Neal W. Menzies 《Biology and Fertility of Soils》2011,47(1):15-23
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N2O emission. Residues were added at the rate of 3 t C ha−1 to soil with, and without, 150 kg urea N ha−1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly (P < 0.05) lower NO3−–N, which reached minimum values of 2.8 mg N kg−1 for sugarcane (at day 28), 10.3 mg N kg−1 for maize (day 7), and 5.9 mg N kg−1 for sorghum (day 7), compared to 22.7 mg N kg−1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg−1 in sugarcane, 34 mg kg−1 in maize, 29 mg kg−1 in sorghum, and 16 mg kg−1 in cotton amended soil compared to soil + N fertilizer, although soil NO3−–N increased by 7 mg kg−1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N2O emission was significantly and positively correlated with NO3−–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO2 in the first 3 and 5 days of incubation (r = 0.59, P < 0.05). 相似文献
20.
A survey of N2 fixation in farmers’ fields of Northern (>1,000 mm rainfall), Central (800–1,000 mm rainfall), and Southern (<800 mm rainfall)
Zambia revealed some significant differences in plant growth and symbiotic performance of different food grain legumes. Of
the three grain legumes (i.e., Bambara groundnut (Vigna subterranea L. Verdc.), cowpea (Vigna unguiculata L. Walp.), and groundnut (Arachis hypogaea L.)) grown in Southern Zambia, cowpea showed greater shoot biomass and significantly lower shoot δ15N values than groundnut and Bambara groundnut. The lower shoot δ15N resulted in greater %Ndfa (59%) in shoots and higher amounts of N-fixed, whether per square meters (6,394.0 mg N), per plant
(650.8 mg N), or per hectare (63.9 kg N) relative to groundnut and Bambara groundnut, even though the number of cowpea plants
per square meter was significantly lower than that of groundnut or Bambara groundnut. Although the shoot δ15N values of cowpea, Bambara groundnut and common bean (Phaseolus vulgaris L.) were significantly lower than those of groundnut in Central Zambia and their %Ndfa values, therefore, greater, the higher
number of groundnut plants per square meter resulted in significantly greater shoot N content, as well as N-fixed per square
meter and per hectare relative to the other species. Despite having similar plant density as cowpea in Central Zambia, common
bean could fix only 6.0 kg N ha−1 compared with 35.4 kg N ha−1 by cowpea. In Northern Zambia, Bambara groundnut showed the lowest mean shoot δ15N value (0.54 ± 0.3‰), followed by groundnut (1.59 ± 1.0‰), and then common bean (the three grain legumes grown in that region).
As a result, %Ndfa and N-fixed were significantly greater in groundnut (69.7% and 566.0 mg N per plant) and Bambara groundnut
(62.9% and 440.1 mg N per plant) than in common bean (2.6% and 2.4 mg N per plant). In Northern Zambia, groundnut, Bambara
groundnut and common bean fixed 78.7, 67.6, and 0.9 kg N ha−1, respectively, even though the plant density per square meter of common bean (which fixed the lowest amount of N per hectare)
was twice that of groundnut and Bambara groundnut. A species × site analysis showed that cowpea fixed relatively greater amounts
of N per plant, per square meter, and per hectare in Southern than Central Zambia. Bambara groundnut and common bean also
had significantly lower δ15N values and higher %Ndfa in Central than Northern Zambia. 相似文献