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1.
ABSTRACT

Vermicomposts (VCs) are the solid excreta of earthworms known to contain plant available nutrients, large amounts of microbial life and diversity, and plant growth regulating hormones. VCs may play an integral role in the nitrogen nutrition of Lupinus angustifolius and function to reduce the reliance of legume crops on chemical fertilizers. The aim of the present study was to determine the role of varying concentrations of chicken manure VC on the biomass production and N nutrition of the legume, L. angustifolius. The effect of increasing concentrations of VCs has been investigated, in conjunction with commercial rhizobia inoculum additions on the biomass yield of L. angustifolius. Plants were germinated and allowed to establish for 10 days in various mixtures of VC, rhizobia inoculum, and quartz sand under glasshouse conditions. After cultivation of a further 30 days, the plants were harvested and analyzed for tissue nutrient concentrations. The VC-containing substrates were assessed for wide-spectrum soil analyses and microbial diversity via Biolog EcoPlates. The combined treatments of 5% VC and rhizobia inoculation yielded the greatest biomass response. Furthermore, the addition of VC allowed for bacterial nitrogen fixation within non-rhizobia treatments. Nematode numbers and diversity grew with increases in VC concentrations, likely driven by similar increases in abundance of their microbial prey. However, changes in VC concentration had no effect on bacterial guild structure. In conclusion VC concentrations should be an important consideration for substrate nutrient availability, microbial abundance, and bacterial nitrogen fixation.  相似文献   

2.
This study was conducted in order to investigate the effects of single, dual, and triple inoculations with Rhizobium, N2-fixing Bacillus subtilis (OSU-142), and P-solubilizing Bacillus megaterium (M-3) on nodulation, plant growth, nutrient uptake and seed yield of common bean (Phaseolus vulgaris L. cv. ‘Elkoca-05’) in comparison to control and mineral fertilizer application under field conditions in 2006 and 2007 in the cold highland in Erzurum plateau (29° 55′ N and 41° 16′ E with an altitude of 1850 m), Turkey. Bacterial inoculations significantly increased all the parameters investigated compared with the control treatment, equal to or higher than nitrogen (N), phosphorus (P), and NP treatments. The lowest shoot dry weight and chlorophyll content values were recorded in the control treatment and the bacterial inoculations increased shoot dry weight by 19.7–54.3% and chlorophyll content by 34.1–59.3% over control. Nodule dry weight significantly increased in Rhizobium alone treatment. Additionally, nodulation by native soil Rhizobium population was increased in single inoculations of OSU-142 and M-3. Significant increases of the seed yield under different inoculation treatments ranged between by 6.6% (Rhizobium + OSU-142 + M-3) and 12.2% (OSU-142 alone) over the control whereas N, P and NP applications corresponded to increases of 5.6%, 4.0% and 7.4%, respectively. All bacterial inoculations, especially triple inoculation, significantly increased uptake of macronutrients and micronutrients by common bean. In conclusion, seed inoculation with Rhizobium, OSU-142 and M-3, especially OSU-142 alone, may substitute partially costly NP fertilizers in common bean production even in cold highland areas such as in Erzurum.  相似文献   

3.
Emissions of nitrous oxide (N2O), a potent greenhouse gas, from agricultural soil have been recognized to be affected by nitrogen (N) application and temperature. Most of the previous studies were carried out to determine effects of temperature on N2O emissions at a fixed N application rate or those of N application rates at a specific temperature. Knowledge about the effects of different ammonium (NH4+) application rates and temperatures on N2O emissions from tropical agricultural soil and their interactions is limited. Five grams of air-dried sandy loam soil, collected in Central Vietnam, were adjusted to 0, 400, 800 and 1200 mg NH4-N kg–1 soil (abbreviated as 0 N, 400 N, 800 N and 1200 N, respectively) at 60% water holding capacity were aerobically incubated at 20°C, 25°C, 30°C or 35°C for 28 days. Mineral N contents and N2O emission rates were determined on days 1, 3, 5, 7, 14, 21 and 28. Cumulative N2O emissions for 28 days increased with increasing NH4+ application rates from 0 to 800 mg N kg–1 and then declined to 1200 mg N kg–1. Cumulative N2O emissions increased in the order of 35°C, 20°C, 30°C and 25°C. This lowest emission at 35°C occurred because N2O production was derived only from autotrophic nitrification while other N2O production processes, e.g., nitrifier denitrification and coupled nitrification-denitrification occurred at lower temperatures. More specifically, cumulative N2O emissions peaked at 800 N and 25°C, and the lowest emissions occurred at 1200 N and 35°C. In conclusion, N2O emissions were not exponentially correlated with NH4+ application rates or temperatures. Higher NH4+ application rates at higher temperatures suppressed N2O emissions.  相似文献   

4.
A long-term field experiment was conducted for 8 years on a Vertisol in central India to assess quantitatively the direct and residual N effects of soybean inoculation with Bradyrhizobium and wheat inoculation with Azotobacter in a soybean–wheat rotation. After cultivation of soybean each year, its aerial residues were removed before growing wheat in the same plots using four N levels (120, 90, 60 and 30 kg ha?1) and Azotobacter inoculation. Inoculation of soybean increased grain yield by 10.1% (180 kg ha?1), but the increase in wheat yields with inoculation was only marginal (5.6%; 278 kg ha?1). There was always a positive balance of soil N after soybean harvest; an average of +28 kg N ha?1 yr?1 in control (nodulated by native rhizobia) plots compared with +41 kg N ha?1 yr?1 in Rhizobium-inoculated plots. Residual and direct effects of Rhizobium and Azotobacter inoculants caused a fertilizer N credit of 30 kg ha?1 in wheat. Application of fertilizers or microbial inoculation favoured the proliferation of rhizobia in crop rhizosphere due to better plant growth. Additional N uptake by inoculation was 14.9 kg N ha?1 by soybean and 20.9 kg N ha?1 by wheat crop, and a gain of +38.0 kg N ha?1 yr?1 to the 0–15 cm soil layer was measured after harvest of wheat. So, total N contribution to crops and soil due to the inoculants was 73.8 kg N ha?1 yr?1 after one soybean–wheat rotation. There was a total N benefit of 13.8 kg N ha?1 yr?1 to the soil due to regular long-term use of microbial inoculants in soybean–wheat rotation.  相似文献   

5.
Western Indian Himalaya is very rich in biodiversity. Being a cold climatic region, it possesses various psychrotolerant and psychrophilic microorganisms. Psychrotolerant bacterium Dyadobacter sp. was isolated from this region and studied for its plant growth promoting potential against four legumes and finger millet. This bacterium was able to grow at nitrogen (N) deficient medium at both 10°C and 28°C and gave positive nifH amplification that confirms the psychrotolerant and diazotrophic nature of this bacterium. Pot trial-based study showed that this bacterium was able to promote plant growth by fixing atmospheric nitrogen (N2) and making it available to plants. Agronomical parameters, leaf nitrate reductase activity, and total chlorophyll content were recorded at 30, 45, 60, and 90 days after sowing and found to be increased over their respective controls. The 16S rDNA and nifH genes were quantified by q-PCR to study the dynamics of total bacterial and diazotrophic abundance due to inoculation of Dyadobacter sp. in soil. Soil chemical properties related to soil fertility were also studied at different time intervals after sowing. We found positive correlation among soil pH, soil nifH gene abundance, soil nitrate concentration, and plant leaf nitrate reductase activity. PCR-DGGE was performed to study persistence of Dyadobacter sp. in soil after inoculation, which showed good persistence of plant growth promoting rhizobacteria (PGPR). Hence, it is concluded that Dyadobacter sp. has potential to promote plant growth by fixing atmospheric N2 and making it available to plant. Further, psychrotolerant nature of this bacterium can be exploited to enhance plant growth in cold climate agriculture due to its ability to fix atmospheric N2 at low temperature.  相似文献   

6.
A composting experiment was carried out to study changes in physical [color, odor, temperature, organic matter (OM) loss], chemical [C:N ratio, water-soluble organic carbon (Cw):organic N (Norg) ratio, NH4 +-N and NO3 ?-N, humic acid (HA):fulvic acid (FA) ratio, humification index (HI) and cation-exchange capacity (CEC):total organic carbon (TOC) ratio)] and biological [seed germination index (GI)] parameters to assess compost maturity and stability over a period of 150 days. Five composts were prepared using a mixture of different farm wastes with or without enrichment of N, rock phosphate (RP) and microorganism (MO) inoculation. All the composts appeared to change to a granular and dark grey color without foul odor, and attained a constant temperature with no measurable changes (ambient level) at 120 days of composting. Correlation analysis showed that the optimal values of the selected parameters for our experimental conditions are as follows: organic matter loss > 42%, C:N ratio < 15, HA:FA ratio > 1.9, HI > 30%, CEC:TOC ratio > 1.7 and Cw:Norg ratio < 0.55. Composts enriched with N + RP or N + RP + MO matured at 150 and 120 days, respectively, whereas composts without any enrichment or enrichment with N or RP + MO did not mature even at 150 days of composting.  相似文献   

7.
Drawbacks of intensive farming practices and environmental costs of N fertilizers have renewed interest in bio‐fertilizers. This study was conducted in order to investigate the effectiveness of 7 N2‐fixing bacterial isolates from various sources in sugar beet and barley production under field conditions in the higland plateau of Erzurum, Turkey (29° 55′ N and 41° 16′ E with an altitude of 1950 m) in 1999 and 2000. Seeds were inoculated with five bacterial strains of Bacillus; BA‐140, BA‐142, M‐3, M‐13, and M‐58, a strain of Burkholderia (BA‐7) and Pseudomonas (BA‐8). The bacterial strains had been demonstrated to grow in N‐free basal medium. The experiment also included applications of mineral nitrogen (N), phosphorous (P), and NP‐fertilizer as well as a control treatment without inoculation and fertilizer application. Two years of trials under field conditions showed that seed inoculation with bacterial strains significantly affected yield, yield components, and quality parameters both in sugar beet and barley. On an average of both years, seed inoculation of sugar beet with BA‐140, BA‐142, M‐58, BA‐7, BA‐8, M‐13, and M‐3 increased root yield by 13.0, 12.6, 10.5, 9.2, 8.1, 6.1, and 6.5% as compared to the control and sugar yield by 7.8, 6.3, 5.1, 4.0, 3.2, 2.3, and 5.3%, respectively. N, P, and NP applications, however, increased root yield up to 13.6, 5.3, and 21.4% and sugar yield by 6.1, 4.0, and 14.8%, respectively. Of the bacteria tested, BA‐140 and BA‐142 had yields equal to N application. All bacterial inoculations also gave higher seed and total biomass yields in barley than control plots. BA‐140 and BA‐142 were top yielding strains. In conclusion, bacterial seed inoculations especially with BA‐140 and BA‐142 may satisfy nitrogen requirements of sugar beet and barley under field conditions even in upland areas.  相似文献   

8.
Degradation of chitin, which is an aminopolysaccharide used as a soil amendment, has been often monitored in soil via its degradation products such as carbon dioxide and ammonium. We report here the applicability of thermogravimetry to measure the amount of chitin added to soil. The maximum pyrolysis rate of the upland surface soil of Brown Forest soil supplemented with chitin was strongly correlated with added chitin content (r = 0.999) when the content exceeded 6.0 g kg?1. The maximum pyrolysis rates of chitin-added soil (around 385°C) was distinctive from those of soil supplemented with cellulose, chitosan, N-acetylglucosamine, and N,N’-diacetylchitobiose (around 340°C, 300°C, 200°C, and 240°C, respectively), indicating the specific detection of chitin. Soil incubation study demonstrated that 60 g kg?1 chitin added to the soil declined exponentially (r = 0.993) within days and could not be detected at 90 days after the addition of chitin. Total carbon (C) content also decreased within days whereas total nitrogen (N) remained almost constant over the 90 days. The amount of ammonium-N increased in the initial 30 days after the addition of chitin and reached about 3.6 g kg?1, which corresponded to the amount of N in the added chitin (4.1 g kg?1) while the amount of nitrite-N and nitrate-N were below 2.0 and 15 mg kg?1, respectively. Comparison of the measured ammonium-N and total-C contents with those calculated from the measured chitin-content implied that addition of chitin enhanced degradation of native organic compounds in soil.  相似文献   

9.

Purpose

The application of organic and inorganic fertilizers to soil can result in increased gaseous emissions, such as NH3, N2O, CO2, and CH4, as well as nitrate leaching, contributing to climate warming and ground and surface water pollution, particularly in regions with hot climates, where high temperatures and high soil nitrification rates often occur. The use of nitrification inhibitors (NIs) has been shown to effectively decrease nitrogen (N) losses from the soil-plant system.

Materials and methods

Non-disruptive laboratory incubation experiments were conducted to assess the extent to which temperature (20 and 30 °C) and nutrient source (mineral and organic fertilizers) influence the rate of carbon (C)- and N-related microbial processes in soil in response to the NI 3,4-dimethylpyrazole phosphate (DMPP). Furthermore, short-term changes in the ability of microbes to degrade C substrates were evaluated in disruptive soil microcosms using microbial community-level physiological profiling and the abundance of the bacterial 16S rRNA gene as a measure of total bacterial population size.

Results and discussion

DMPP reduced net nitrification after 2 and 4 weeks of incubation at 30 and 20 °C by an average of 78.3 and 84.5 %, respectively, and with similar dynamics for mineral or organic fertilization. The addition of labile organic matter with cattle effluent led to a rapid increase in C mineralization that was significantly reduced by DMPP at both temperatures, whereas no changes could be detected after the addition of mineral fertilizer. The culturable heterotrophic microorganisms showed metabolic diversification in the oxidation of C sources, with organic fertilizer playing a major role in the substrate utilization patterns during the first week of incubation and the DMPP effects prevailing from day 14 until day 28. Furthermore, the copy number of the bacterial 16S rRNA gene was reduced by the application of DMPP and organic fertilizer after 28 days.

Conclusions

Our results show the marked efficiency of DMPP as an NI at elevated temperatures of incubation and when associated with both mineral and organic fertilization, providing support for its use as a tool to mitigate N losses in Mediterranean ecosystems. However, we also observed impaired C respiration rates and bacterial abundances, as well as shifts in community-level physiological profiles in soil, possibly indicating a short-term effect of DMPP and organic fertilizers on non-target C-related processes and microorganisms.
  相似文献   

10.
The biodegradable portion of city waste is a potential source of plant nutrients, and appropriate techniques of composting can convert it to quality compost with higher nutrient content and lower levels of pathogenic microorganisms. An amount of 68.19 tons of waste is generated in Imphal City, Manipur, India, of which 24.84 tons were biodegradable. Of the total biodegradable municipality waste (MW), 20.7 tons were produced in households and the vegetable markets of the city. The MW were found to contain pathogenic bacteria (PB), namely, Salmonella spp., Shigella spp., Micrococcus spp., and Enterobacter spp. in the range of 6.35–9.28 (log cfu/g dry biomass), and agriculturally beneficial bacteria (BB), namely, phosphate solubilizers, Azospirillum spp., Azotobacter spp., and cellulose degraders in the range of 6.25–8.83 log cfu/g dry biomass. Pre-treatment of the MW by exposure at temperatures of 27°C–50°C in a greenhouse for 5 days could not reduce the level of PB and BB, but by heating at 100°C for 8 h followed by 30°C for 16 h of a day for three consecutive days, the PB (except Micrococcus spp.) could be eliminated. Aerobic composting of the mixture of MW with cow dung (CD) and rice straw (RS) and by inoculation with epigeic earthworm Eisenia fetida, produced high quality manure as evident from more finer particle (56.6%), higher nutrient (2.19% N) content, higher population of BB (7.03–9.19 log cfu/g dry biomass), and reduced level of PB (6.87–8.09 log cfu/g dry biomass).  相似文献   

11.

Purpose

Impacts of a commercially available decay-facilitating microbial inoculum on carbon (C) and nitrogen (N) mineralization were evaluated during decomposition of rice straw in a paddy soil.

Materials and methods

Two incubation experiments were conducted for 105 days with a typical low-yield high-clay soil in central China to monitor effects of straw and the inoculum on CO2 evolution, as well as dissolved organic C (DOC), NH4 +, NO3 ?, and pH under conditions of 15 °C 70 %, 25 °C 40 %, 25 °C 70 %, 25 °C 100 %, and 35 °C 70 % of water-holding capacity (WHC) with adequate N, supplied as urea or manure, respectively.

Results and discussion

Treatments of 25 °C 70 % WHC, 25 °C 100 % WHC, and 35 °C 70 % WHC generally achieved significant higher CO2 evolution while treatment of 25 °C 40 % WHC had least. This was more evident with added manure compared to urea (P?<?0.05). The inoculum generally increased the decomposition of C inputs and the largest increases were in the initial 28 day in treatments 25 °C 70 % WHC, 25 °C 100 % WHC, and 35 °C 70 % WHC; only the 25 °C 40 % WHC actually immobilized C. The CO2 release rates were positively correlated with DOC, but with different slopes within treatments. Despite equivalent N application rates, manure treatments had significantly less N (including NO3 ?, NH4 +, and total dissolved N) than those with urea. Incubation of 25 °C 40 % WHC decreased soil pH the least, probably due to relative low moisture causing delayed nitrification.

Conclusions

The results implied that the inoculum, especially fungi, would adjust to edaphic and N fertilization in regulating organic C mineralization, during which water potential would exhibit a great role in regulating substrate and nutrient availability.
  相似文献   

12.
Heat stress reduces creeping bentgrass performance in temperate to sub-tropical climates. The research objective was to characterize effects of nitrogen (N) and cytokinin (CK) on creeping bentgrass under heat stress. In a 38°C/28°C chamber, grasses were treated with two nitrogen (2.5 and 7.5 kg N ha?1) and three CK rates (0, 10 and 100 μM) biweekly. Grass grown at high N had better turf quality, higher photochemical efficiency (Fv/Fm), normalized difference vegetation index (NDVI), and chlorophyll concentration at d15 and 28 than low N. CK increased NDVI at d15, with Fv/Fm of the CK100 treatment being 18% higher than that of CK0 at d28. Under high N with 100 μM CK, root trans-zeatin riboside (tZR) and isopentenyl adenosine (iPA) were 160% and 97% higher than under low N without CK, respectively. These results demonstrate positive impacts of N and CK on creeping bentgrass under heat, with N playing a dominant role.  相似文献   

13.
The effects of vermicompost (VC) (0% and 1% w/w) on treated calcareous clay soil with 0 and 50 mg phosphorus (P) kg?1 as calcium phosphate [Ca(H2PO4)2.H2O] was investigated. The soil samples were incubated for 7, 30, 60, 120, and 150 d at 25 ± 1°C and Olsen-P was measured after each incubation time. Results showed that Olsen-P increased 36% and 38% after VC addition in treated soil with 0 and 50 mg P kg?1, respectively. Recovery of Olsen-P in treated soils with VC, combined fertilizer VC + P, and fertilizer P was 42%, 42%, and 17%, respectively. The rate coefficient in treated soils with fertilizer, VC, and combined fertilizer VC + P was 0.033, 0.026, and 0.023 mg kg?1 d?1/2, respectively. It seems that the process that leads to the decrease in available P in amended soils, is controlled by P diffusion into sorption sites in micropores of aggregates.  相似文献   

14.
Steaming of narrow soil bands prior to sowing is a new technique that reduces the need for intra-row weeding in herbicide-free row crops. However, the steam treatment may eliminate both weed seeds and non-target soil organisms, thereby affecting the nutrient cycling in the soil. This study tested the effect of band-steaming on N and C dynamics in a sandy loam soil that was steamed in situ to maximal temperatures of 70–90°C using a prototype band-steamer. Soil samples (0–5 cm depth) were collected during 90 days from band-steamed soil, undisturbed control soil, and control soil treated just mechanically with the band-steamer. In the steamed soil, ammonium concentrations increased from 1.1 to 20.3 μg NH 4 + -N g?1 dry weight during 28 days. This coincided with an immediate and persistent inhibition of potential nitrification (33–61% inhibition during 90 days). Assays of the temperature response of potential nitrification confirmed the temperature sensitivity and showed an optimum temperature of 27.1°C and a temperature coefficient (Q 10) of 1.9. The effects of band-steaming on concentrations of nitrate and water-soluble carbon were divergent and stimulatory, respectively, but generally not statistically significant. Mechanical effects of band-steaming were negligible. The observed ammonium surplus could be of agronomic benefit and should be evaluated in integrated studies of the effects of band-steaming on crop growth and plant N uptake.  相似文献   

15.
Abstract

The agronomic efficiency of nitrogen (N) fixing and phosphate solubilizing microorganisms and an arbuscular mycorrhizal (AM) fungus on vigour, photosynthetic pigments, seed yield, grain protein and nutrient uptake of greengram plants, were assessed in soils, deficient in phosphorous (P). The tripartite inoculation of Glomus fasciculatum + Bradyrhizobium sp. (vigna) + Bacillus subtilis, significantly increased dry matter, chlorophyll content and nutrient uptake of greengram plants. Generally, the number of nodules formed per plant was more at flowering stage, which decreased at podfill stage of plant growth. Seed yield increased significantly by 27% due to inoculation with Bradyrhizobium sp. (vigna) + B. subtilis + G. fasciculatum, relative to the control. Grain protein ranged from 17% (P. variabile) to 28% (Bradyrhizobium sp. (vigna) + B. subtilis + G. fasciculatum) in inoculated greengram. A negative effect occurred on some of the measured parameters when P. variabile was used alone or in combination treatments. The N and P contents in measured plant parts (e.g., roots, shoots, straw and grain) differed considerably among treatments. The populations of PSM, percentage of root infection and density of the AM fungal spore improved in some of the treatments.  相似文献   

16.
Integrating information on nitrogen (N) mineralization potentials into a fertilization plan could lead to improved N use efficiency. A controlled incubation mineralization study examined microbial biomass dynamics and N mineralization rates for two soils receiving 56 and 168 kg N ha?1 in a Panoche clay loam (Typic Haplocambid) and a Wasco sandy loam (Typic Torriorthent), incubated with and without cotton (Gossypium hirsutum L.) residues at 10 and 25°C for 203 days. Microbial biomass activity determined from mineralized carbon dioxide (CO2) was higher in the sandy loam than in clay loam independent of incubation temperature, cotton residue addition and N treatment. In the absence of added cotton residue, N mineralization rates were higher in the sandy loam. Residue additions increased N immobilization in both soils, but were greater in clay loam. Microbial biomass and mineralization were significantly affected by soil type, residue addition and temperature but not by N level.  相似文献   

17.
A field experiment with peppermint (Mentha piperita L.) was conducted in a sandy loam (Typic ustifluvent) soil during 2007 and 2008 at Lucknow, India. Ten treatments consisting of control (no synthetic or organic nitrogen fertilization), synthetic nitrogen fertilization (SN) 75, 150 and 225 kg ha?1 alone, vermicompost (VC) 3 t + 37.5 kg SN ha?1, VC 6 t + 75 kg SN ha?1 and VC 9 t + 112.5 kg SN ha?1 and intercropping of one, two and three rows of cowpea for green manuring in combination with 50, 100 and 150 kg SN ha?1, respectively, were evaluated in a randomized block design. Integrated use of VC 9 t with 112.5 kg SN ha?1 produced maximum essential oil (94.3 kg ha?1), increased the herb and essential oil yields by 104 and 89%, respectively, over control and reduced SN use by 50%, without affecting the quality of essential oil. Application of VC and intercropping of cowpea for green manuring significantly improved the organic carbon, available N, P and K content in soil over SN alone. To get sustainable production of peppermint, application of VC 9 t ha?1 along with 112.5 kg N ha?1 through synthetic fertilizer is recommended for light textured sandy loam soils.  相似文献   

18.
Abstract

Contamination of agricultural soil by fecal pathogenic bacteria poses a potential risk of infection to humans. For the biosafety control of field soil, soil solarization in an upland field was examined to determine the efficiency of solarization on the inactivation of Escherichia coli inoculated into soil as a model microorganism for human pathogenic bacteria. Soil solarization, carried out by sprinkling water and covering the soil surface with thin plastic sheets, greatly increased the soil temperature. The daily average temperature of the solarized soil was 4–10°C higher than that of the non-solarized soil and fluctuated between 31 and 38°C. The daily highest temperature reached more than 40°C for 8 days in total in the solarized soil during the second and third weeks of the experiment. Escherichia coli in the solarized soil became undetectable (< 0.08 c.f.u. g?1 dry soil) within 4 weeks as a result, whereas E. coli survived for more than 6 weeks in the non-solarized soil. Soil solarization, however, had little influence on the total direct count and total viable count of bacteria in the soil. These results indicate that soil solarization would be useful for the biosafety control of soil contaminated by human pathogens via immature compost or animal feces.  相似文献   

19.
Abstract

To clarify the microbiological factors that explain high N2O emission in an arable peat soil in Central Kalimantan, Indonesia, a substrate-induced respiration-inhibition experiment was conducted for N2O production. The N2O emission rate decreased by 31% with the addition of streptomycin, whereas it decreased by 81% with the addition of cycloheximide, compared with a non-antibiotic-added control. This result revealed a greater contribution of the fungal community than bacterial community to the production of N2O in the soil. The population density of fungi in the soil, determined using the dilution plate method, was 5.5 log c.f.u. g?1 soil and 4.9 log c.f.u. g?1 soil in the non-selective medium (rose bengal) and the selective medium for Fusarium, respectively. The N2O-producing potential was randomly examined in each of these isolates by inoculation onto Czapek agar medium (pH 4.3) and incubation at 28°C for 14 days. Significant N2O-producing potential was found in six out of 19 strains and in five out of seven strains isolated from the non-selective and selective media, respectively. Twenty-three out of 26 strains produced more than 20% CO2 during the 14-day incubation period, suggesting the presence of facultative fungi in the soil. These strains were identified to be Fusarium oxysporum and Neocosmospora vasinfecta based on the sequence of 18S rDNA, irrespective of the N2O-producing potential and the growth potential in conditions of low O2 concentration.  相似文献   

20.
The objective of this growth chamber study was to evaluate the effect of adding N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiaminde (DCD) to urea fertilizer, on the physiology and growth of cotton (Gossypiumhirsutum L.) under normal and high temperatures. Treatments consisted of two day temperature regimes, 30°C and 38°C, and five nitrogen fertilization applications: unfertilized control, 125 kg ha?1 of urea, 93 kg ha?1 of urea, 93 kg ha?1 urea + NBPT, and 93 kg ha?1 urea + NBPT + DCD. The addition of NBPT to urea fertilizer had positive effects on leaf chlorophyll, leaf area, dry matter, nitrogen (N) uptake, and N use efficiency. The absence of a significant interaction effect indicated that N fertilization was not influenced by temperature. Deficiency of N significantly decreased leaf chlorophyll, increased glutathione reductase, decreased protein and increased leaf nitrate reductase. Physiological changes under high temperature included increased plant N uptake, glutamine synthetase, leaf chlorophyll, protein content, plant height and leaf area were due to high N uptake and utilization.  相似文献   

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