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1.
The effects of three Coniothyrium minitans isolates (Conio, IVT1 and Contans®), applied to soil as conidial suspensions or as maizemeal-perlite (MP) inocula (Conio), on apothecial production and infection of Sclerotinia sclerotiorum sclerotia were assessed in two soil pot bioassays and two novel box bioassays in the glasshouse at different times of the year. C. minitans isolate Conio applied as either MP or ground MP at full rate (106-107 cfu cm−3 soil) consistently decreased the carpogenic germination, recovery and viability of sclerotia and increased C. minitans infection of the sclerotia of S. sclerotiorum by in comparison with either MP or conidial suspension treatments applied at lower rates (103-104 cfu cm−3 soil). Additionally, when applied at the same rate, MP inoculum of C. minitans was consistently more effective at reducing carpogenic germination than a conidial suspension. The effect of MP and ground MP at full rate on carpogenic germination was expressed relatively early as those sclerotia recovered before apothecia appeared on the soil surface already had reduced numbers of apothecial initials. In general, there were few differences between the isolates of C. minitans applied as conidial suspensions. Box bioassays carried out at different times of the year indicated that temperature and soil moisture influenced both apothecial production and mycoparasitism. Inoculum concentration of C. minitans and time of application appear to be important factors in reducting apothecial production by S. sclerotiorum.  相似文献   

2.
Sclerotia are the primary over wintering inoculum of Sclerotinia sclerotiorum (Lib.) de Bary. The effects of tillage on the primary inoculum are not well understood. The purpose of this research was to study sclerotial viability over time and between burial depths in soil, to identify bacteria colonizing and degrading the sclerotia, and determine whether these bacteria may be utilized as biological control agents. Correlation analysis indicated that a significant negative relationship existed between sclerotial viability and elapsed temporal factors (R2=−0.68, P<0.0001), and depth of burial (R2=−0.58, P<0.0001). After twelve months, sclerotia on the soil surface had the highest viability (57.5%), followed by those at the 5 cm depth (12.5%), and only 2.5% of those placed at the 10 cm depth remained viable. A significant negative relationship between sclerotial viability and bacterial populations also existed (R2=−0.60, P<0.0001). Two hundred and sixty-eight bacteria were isolated from sclerotia, 29 of which showed strong in vitro antagonism to the mycelial growth of S. sclerotiorum. Biodiversity of the inhibitory bacterial isolates was minimal on sclerotia from the soil surface and within all depths sampled at three months (i.e. in January). All burial depths within the April and July sampling dates produced bacterial diversities that were distinct from each other.  相似文献   

3.
《Applied soil ecology》2007,35(1):21-24
Field studies were conducted over two seasons to investigate effects of random versus highly aggregated spatial arrangements of sclerotia of S. sclerotiorum, and effects of biocontrol agent density and formulation additives, on colonization of sclerotia by Trichoderma spp. Application of T. harzianum encapsulated in alginate pellets with either bran or polyethylene glycol additives increased the percentages of sclerotia colonized in both years, but there was no difference between additives in either year. Higher pellet densities (200 pellets/m2 versus 40 pellets/m2) resulted in higher proportions of sclerotia colonized by Trichoderma spp. in one season but not in the other. However, when sclerotia were in highly aggregated spatial patterns, significantly higher percentages were colonized in both years, compared to sclerotia in random distributions.  相似文献   

4.
The variance in survival of Sclerotinia sclerotiorum's sclerotia, carpogenic germination (apothecia) as well as Sclerotinia stem rot (SSR) severity (Disease Severity Index (DSI)) on soybean was partitioned among canopy, soil physico-chemistry and microbiology, cultural practices (2 or 3-y-corn rotation/soybean monoculture and mineral fertilization/urban compost), and spatial matrices in two soils. Partial multiple regression was used to partition the individual SSR variables variance while partial canonical redundancy analysis partitioned the DSI-apothecia and apothecia-survival variance. In clay loam, the sclerotial survival and apothecia variance were mainly explained by the spatial structure of soil physico-chemistry while the DSI did not share this spatial structure and was largely explained by the effects of 3-y-corn rotation on canopy and soil, i.e. lower weed biomass, enhanced soybean yield and fewer apothecia were correlated with disease suppressiveness. In sandy loam, the DSI variance was mostly explained by the spatial structure of canopy and physico-chemistry. Disease suppressiveness, by the interaction of 3-y-corn rotation with urban compost, was largely explained by the enhancement of soil properties, i.e. higher aggregate stability, microbial activity and soil solution concentration in exchangeable ions correlated negatively with carpogenic germination. Partitioning the SSR variance among four matrices of spatial and environmental factors allowed for the first time to interpret and quantify the variance of disease development explained by cultural practices in interaction with the main characteristics of this agroecosystem.  相似文献   

5.
Soil amendment with manures from intensive animal industries is nowadays a common practice that may favorably or adversely affect several soil properties, including soil microbial activity. In this work, the effect of consecutive annual additions of pig slurry (PS) at rates of 30, 60, 90, 120 and 150 m3 ha−1 y−1 over a 4-year period on soil chemical properties and microbial activity was investigated and compared to that of an inorganic fertilization and a control (without amendment). Field plot experiment conducted under a continuous barley monoculture and semiarid conditions were used. Eight months after the fourth yearly PS and mineral fertilizer application (i.e. soon after the fourth barley harvest), surface soil samples (Ap horizon, 0-15 cm depth) from control and amended soils were collected and analysed for pH, electrical conductivity (EC), contents of total organic C, total N, available P and K, microbial biomass C, basal respiration and different enzymatic activities. The control soil had a slightly acidic pH (6.0), a small EC (0.07 dS m−1), adequate levels of total N (1.2 g kg−1) and available K (483 mg kg−1) for barley growth, and small contents of total organic C (13.2 g kg−1) and available P (52 mg kg−1). With respect to the control and mineral fertilized soils, the PS-amended soils had greater pH values (around neutrality or slightly alkaline), electrical conductivities (still low) and contents of available P and K, and slightly larger total N contents. A significant decrease of total organic C was observed in soils amended at high slurry rate (12.3 g kg−1). Compared with the control and mineral treatments, which produced almost similar results, the PS-amended soils were characterized by a higher microbial biomass C content (from 311 to 442 g kg−1), microbial biomass C/total organic C ratio (from 2.3 to 3.6%) and dehydrogenase (from 35 to 173 μg INTF g−1), catalase (from 5 to 24 μmol O2 g−1 min−1), BAA-protease (from 0.7 to 1.9 μmol  g−1 h−1) and β-glucosidase (from 117 to 269 μmol PNP g−1 h−1) activities, similar basal respirations (from 48 to 77 μg C-CO2 g−1 d−1) and urease activities (from 1.5 to 2.2 μmol  g−1 h−1), and smaller metabolic quotients (from 6.4 to 7.7 ng C-CO2 μg−1 biomass C h−1) and phosphatese activities (from 374 to 159 μmol PNP g−1 h−1). For example, statistical analysis of experimental data showed that, with the exception of metabolic quotient and total organic C content, these effects generally increased with increasing cumulative amount of PS. In conclusion, cumulative PS application to soil over time under semiarid conditions may produce not only beneficial effects but also adverse effects on soil properties, such us the partial mineralization of soil organic C through extended microbial oxidation. Thus, PS should not be considered as a mature organic amendment and should be treated appropriately before it is applied to soil, so as to enhance its potential as a soil organic fertilizer.  相似文献   

6.
Glomalin concentrations of extra-radical arbuscular mycorrhizal (AM) hyphae were estimated by deploying hyphal in-growth cores containing glomalin-free sand in field soils in a tropical forest and in pot cultures. In field soils, glomalin was 0.044±0.013 μg m−1 hyphae. In pot cultures glomalin concentrations were lower (range 0.0068-0.036 μg m−1), and varied significantly among species. Using this technique, preliminary estimates of extraradical AM hyphal production on Inceptisols were 1.91 Mg ha−1yr−1 and on Oxisol were 1.47 Mg ha−1 yr−1, but they could range between 0.9-5.7 Mg ha−1 yr−1. These rates of hyphal production are approximately 10% (range 5-33%) of estimated above ground primary production of the forest.  相似文献   

7.
Plants of the Brassicaceae contain glucosinolates, the hydrolysis products of which inhibit the growth of many soil-borne fungi that cause plant disease. However, amending soil with green manures of these plants gives inconsistent control of several soil-borne diseases, including those caused by Rhizoctonia solani. To identify factors that contribute to this inconsistency we investigated, in the laboratory and in pot experiments in the glasshouse, the saprophytic behaviour of R. solani AG2-1 (ZG5) in a sandy soil amended with various green manures. Fresh material from either Brassica napus var. Karoo, B. napus B1, B. napus B2, B. nigra, Diplotaxis tenuifolia (a brassicaceous weed) and the non-Brassicaceae species, oat (Avena sativa) or lupin (Lupinus angustifolius) was used at 10 or 100 g of fresh material kg−1 of dry soil in Lancelin sand. At 100 g kg−1 the volatiles of all green manures reduced the hyphal growth of R. solani, except for B. napus B1. D. tenuifolia at 100 g kg−1 inhibited the growth and sclerotial formation of R. solani. Most green manures at 10 g kg−1, and at 40% water holding capacity, stimulated the growth of R. solani for up to 3 months and increased the activity of other microbes. R. solani infected the brassicaceous plants when growing and colonized the residues mixed with soil at 10 g kg−1. This inoculum increased the severity of damping-off in canola, by 27%. Disease was particularly severe when the green manure species, except D. tenuifolia and oat, were grown in situ and residues returned to the pot from which they came, before sowing canola. There is a potential hazard in applying green manures of Brassica species as their residues can, under certain conditions, support the saprophytic activity of R. solani which increases damping-off in canola sown in the amended soils.  相似文献   

8.
Since the introduction of Terrestrial Laser Scanning (TLS) instruments, there now exists a means of rapidly digitizing intricate structural details of vegetation canopies using Light Detection and Ranging (LiDAR) technology. In this investigation, Intelligent Laser Ranging and Imaging System (ILRIS-3D) data was acquired of individual tree crowns at olive (Olea europaea L.) plantations in Córdoba, Spain. In addition to conventional tripod-mounted ILRIS-3D scans, the unit was mounted on a platform (12 m above ground) to provide nadir (top-down) observations of the olive crowns. 24 structurally variable olive trees were selected for in-depth analysis. From the observed 3D laser pulse returns, quantitative retrievals of tree crown structure and foliage assemblage were obtained. Robust methodologies were developed to characterize diagnostic architectural parameters, such as tree height (r2 = 0.97, rmse = 0.21 m), crown width (r2 = 0.97, rmse = 0.13 m), crown height (r2 = 0.86, rmse = 0.14 m), crown volume (r2 = 0.99, rmse = 2.6 m3), and Plant Area Index (PAI) (r2 = 0.76, rmse = 0.26 m2/m2). With the development of such LiDAR-based methodologies to describe vegetation architecture, the forestry, agriculture, and remote sensing communities are now faced with the possibility of replacing current labour-intensive inventory practices with, modern TLS systems. This research demonstrates that TLS systems can potentially be the new observational tool and benchmark for precise characterization of vegetation architecture for improved agricultural monitoring and management.  相似文献   

9.
Soil microbial biomass P is usually determined through fumigation-extraction (FE), in which partially extractable P from lysed biomass is converted to biomass P using a conversion factor (Kp). Estimation of Kp has been usually based on cultured microorganisms, which may not adequately represent the soil microbial community in either nutrient-poor or in altered carbon and nutrient conditions following fertilisation. We report an alternative approach in which changes in microbial P storage are determined as the residual in a mass balance of extractable P before and after incubation. This approach was applied in three low-fertility sandy soils of southwestern Australia, to determine microbial P immobilisation during 5-day incubations in response to the amendment by 2.323 mg C g−1, 100 μg N g−1 and 20 μg P g−1. The net P immobilisation during the amended incubations determined to be 18.1, 14.1 and 16.3 μg P g−1 in the three soils, accounting for 70.6-90.5% of P added through amendment. Such estimates do not rely on fumigation and Kp values, but for comparison with the FE method we estimated ‘nominal’ Kp values to be 0.20-0.31 for the soils under the amended conditions. Our results showed that microbial P immobilisation was a dominant process regulating P concentration in soil water following the CNP amendment. The mass-balance approach provides information not only about changes in the microbial P compartment, but also about other major P-pools and their fluxes in regulating soil-water P concentrations under substrate- and nutrient-amended conditions.  相似文献   

10.
Particulate phosphorus (P) can be transported via soil erosion in overland flow to waters, where it provides a long-term source of P for aquatic biota, and can accelerate freshwater eutrophication. Hence, knowledge of P sources is important for good environmental management. However, data on P, and related Fe, losses from various structures of a post-mining landscape are lacking. A year-long monitoring, and ten short rainfall simulations on plot scale, at ridges and rills and a combination of them, revealed high erosion from bare lignite mining dumps at Schlabendorf-North, Lusatia, Germany. The mean annual soil erosion rate from the year-long monitoring site was 18 × 106 kg km− 2 yr− 1, corresponding to 0.034 g m− 2 min− 1. The erosion rates were lowest at rill plots (1.9–4.4 g m− 2 min− 1), intermediate at ridge plots (14.3–37.1 g m− 2 min− 1), and highest at a combined rill and ridge plot (48.7–63.4 g m− 2 min− 1). These differences in extent were due to small scale differences in morphology and extreme water repellency. The hydrophobicity leads to very low infiltration, thus generating surface runoff even at low rainfall intensities. Loss rates of P and Fe, as deduced from the year-long erosion rate, were 470–650 kg km− 2 yr− 1, and 37.9 × 103–71 × 103 kg km− 2 yr− 1 respectively. However, these P inputs from lignite mining dump erosion, consisting of P-poor (17–90 μg g− 1) tertiary spoil materials, into aborning mining lakes, are negligible since they are accompanied by high Fe inputs, which favour an efficient P co-precipitation in the water column.  相似文献   

11.
Here we present results from a field experiment in a sub-arctic wetland near Abisko, northern Sweden, where the permafrost is currently disintegrating with significant vegetation changes as a result. During one growing season we investigated the fluxes of CO2 and CH4 and how they were affected by ecosystem properties, i.e., composition of species that are currently expanding in the area (Carex rotundata, Eriophorum vaginatum and Eriophorum angustifolium), dissolved CH4 in the pore water, substrate availability for methane producing bacteria, water table depth, active layer, temperature, etc. We found that the measured gas fluxes over the season ranged between: CH4 0.2 and 36.1 mg CH4 m−2 h−1, Net Ecosystem Exchange (NEE) −1000 and 1250 mg CO2 m−2 h−1 (negative values meaning a sink of atmospheric CO2) and dark respiration 110 and 1700 mg CO2 m−2 h−1. We found that NEE, photosynthetic rate and CH4 emission were affected by the species composition. Multiple stepwise regressions indicated that the primary explanatory variables for NEE was photosynthetic rate and for respiration and photosynthesis biomass of green leaves. The primary explanatory variables for CH4 emissions were depth of the water table, concentration of organic acid carbon and biomass of green leaves. The negative correlations between pore water concentration and emission of CH4 and the concentrations of organic acid, amino acid and carbohydrate carbon indicated that these compounds or their fermentation by-products were substrates for CH4 formation. Furthermore, calculation of the radiative forcing of the species expanding in the area as a direct result of permafrost degradation and a change in hydrology indicate that the studied mire may act as an increasing source of radiative forcing in future.  相似文献   

12.
We evaluated the spatial structures of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) fluxes in an Acacia mangium plantation stand in Sumatra, Indonesia, in drier (August) and wetter (March) seasons. A 60 × 100-m plot was established in an A. mangium plantation that included different topographical elements of the upper plateau, lower plateau, upper slope and foot slope. The plot was divided into 10 × 10-m grids and gas fluxes and soil properties were measured at 77 grid points at 10-m intervals within the plot. Spatial structures of the gas fluxes and soil properties were identified using geostatistical analyses. Averaged N2O and CO2 fluxes in the wetter season (1.85 mg N m−2 d−1 and 4.29 g C m−2 d−1, respectively) were significantly higher than those in the drier season (0.55 mg N m−2 d−1 and 2.73 g C m−2 d−1, respectively) and averaged CH4 uptake rates in the drier season (−0.62 mg C m−2 d−1) were higher than those in the wetter season (−0.24 mg C m−2 d−1). These values of N2O fluxes in A. mangium soils were higher than those reported for natural forest soils in Sumatra, while CO2 and CH4 fluxes were in the range of fluxes reported for natural forest soils. Seasonal differences in these gas fluxes appears to be controlled by soil water content and substrate availability due to differing precipitation and mineralization of litter between seasons. N2O fluxes had strong spatial dependence with a range of about 18 m in both the drier and wetter seasons. Topography was associated with the N2O fluxes in the wetter season with higher and lower fluxes on the foot slope and on the upper plateau, respectively, via controlling the anaerobic-aerobic conditions in the soils. In the drier season, however, we could not find obvious topographic influences on the spatial patterns of N2O fluxes and they may have depended on litter amount distribution. CO2 fluxes had no spatial dependence in both seasons, but the topographic influence was significant in the drier season with lowest fluxes on the foot slope, while there was no significant difference between topographic positions in the wetter season. The distributions of litter amount and soil organic matter were possibly associated with CO2 fluxes through their effects on microbial activities and fine root distribution in this A. mangium plantation.  相似文献   

13.
Bacteria, isolated from canola and soybean plants, produced antifungal organic volatile compounds. These compounds inhibited sclerotia and ascospore germination, and mycelial growth of Sclerotinia sclerotiorum, in vitro and in soil tests. Ascospore germination in cavity slides was inhibited 54-90% by the volatile producers. When mycelial plugs or the sclerotia, exposed to these volatiles, were transferred to fresh agar plates, the pathogen could not grow, indicating the fungicidal nature of the volatiles. Head space volatiles, produced by bacteria, were trapped with activated charcoal, by passing nitrogen continuously over shake cultures for 48 h. The compounds were eluted from the charcoal with methylene chloride and identified using Gas Chromatography-Mass Spectrometry (GC-MS). The volatile compounds included aldehydes, alcohols, ketones and sulfides. Of the 23 compounds assayed for antifungal activity in divided Petri plates, with filter-disks soaked with these compounds (100 and 150 μl), only six compounds completely inhibited mycelial growth or sclerotia formation, suggesting their potential role in biological control. The compounds are benzothiazole, cyclohexanol, n-decanal, dimethyl trisulfide, 2-ethyl 1-hexanol, and nonanal. Volatiles may play an important role in the inhibition of sclerotial activity, limiting ascospore production, and reducing disease levels. Studies are under way to understand this phenomenon under field conditions. This is the first report on the identification and use of bacterial antifungal organic volatiles in biocontrol.  相似文献   

14.
Individual animals undergoing ontogenetic shifts in habitat use may establish a mobile link between discrete ecosystems via movement of energy, nutrients and matter, as well as through impacts on ecosystem and habitat structure. The American Alligator (Alligator mississippiensis) is a model species for studying ecological implications of ontogenetic niche shifts, because they grow in size by several orders of magnitude, and they play a critical role as both top predators and ecosystem engineers. We used equal trapping effort, radio telemetry and nest surveys to document ontogenetic habitat shifts of alligators between hydrologically isolated, seasonal wetlands and riverine systems. To estimate the degree of functional connectivity between systems, we quantified alligator biomass and nutrient excretion in both systems. Seasonal wetlands provided nesting and nursery sites for adult females and juveniles, which constituted 0.78 g/m2 biomass and excreted 0.05 g/m2/yr N, P, Ca, Mg, Na and K in that system. In contrast, the riverine system provided non-nesting habitat for adults and sub-adults of both sexes, totaling 0.18 g/m2 biomass and excreting 0.01 g/m2/yr of nutrients. Furthermore, sub-adults and adult females were documented moving across the terrestrial matrix, while adult males spent the duration of the study in the creek. Our results demonstrated that ontogenetic niche shifts in alligators establish connectivity between seasonal wetlands and riverine systems and with the surrounding terrestrial matrix. These findings have implications for the definition of jurisdictional wetlands under the US Supreme Court’s 2001 SWANCC decision and highlight the importance of ecological, as well as hydrological, connectivity.  相似文献   

15.
The main energy sources of soil microorganisms are litter fall, root litter and exudation. The amount on these carbon inputs vary according to basal area of the forest stand. We hypothesized that soil microbes utilizing these soil carbon sources relate to the basal area of trees. We measured the amount of soil microbial biomass, soil respiration and microbial community structure as determined by phospholipid fatty acid (PLFA) profiles in the humus layer (FH) of an even-aged stand of Scots pine (Pinus sylvestris L.) with four different basal area levels ranging from 19.9 m2 ha−1 in the study plot Kasper 1 to 35.7 m2 ha−1 in Kasper 4. Increasing trend in basal respiration, total PLFAs and fungal-to-bacterial ratio was observed from Kasper 1 to Kasper 3 (basal area 29.2 m2 ha−1). The soil microbial community structure in Kasper 3 differed from that of the other study plots.  相似文献   

16.
Earthworms are known to be important regulators of soil structure and soil organic matter (SOM) dynamics, however, quantifying their influence on carbon (C) and nitrogen (N) stabilization in agroecosystems remains a pertinent task. We manipulated population densities of the earthworm Aporrectodea rosea in three maize-tomato cropping systems [conventional (i.e., mineral fertilizer), organic (i.e., composted manure and legume cover crop), and an intermediate low-input system (i.e., alternating years of legume cover crop and mineral fertilizer)] to examine their influence on C and N incorporation into soil aggregates. Two treatments, no-earthworm versus the addition of five A. rosea adults, were established in paired microcosms using electro-shocking. A 13C and 15N labeled cover crop was incorporated into the soil of the organic and low-input systems, while 15N mineral fertilizer was applied in the conventional system. Soil samples were collected during the growing season and wet-sieved to obtain three aggregate size classes: macroaggregates (>250 μm), microaggregates (53-250 μm) and silt and clay fraction (<53 μm). Macroaggregates were further separated into coarse particulate organic matter (cPOM), microaggregates and the silt and clay fraction. Total C, 13C, total N and 15N were measured for all fractions and the bulk soil. Significant earthworm influences were restricted to the low-input and conventional systems on the final sampling date. In the low-input system, earthworms increased the incorporation of new C into microaggregates within macroaggregates by 35% (2.8 g m−2 increase; P=0.03), compared to the no-earthworm treatment. Within this same cropping system, earthworms increased new N in the cPOM and the silt and clay fractions within macroaggregates, by 49% (0.21 g m−2; P<0.01) and 38% (0.19 g m−2; P=0.02), respectively. In the conventional system, earthworms appeared to decrease the incorporation of new N into free microaggregates and macroaggregates by 49% (1.38 g m−2; P=0.04) and 41% (0.51 g m−2; P=0.057), respectively. These results indicate that earthworms can play an important role in C and N dynamics and that agroecosystem management greatly influences the magnitude and direction of their effect.  相似文献   

17.
The annual carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) dynamics were measured with static chambers on two organic agricultural soils with different soil characteristics. Site 1 had a peat layer of 30 cm, with an organic matter (OM) content of 74% in the top 20 cm. Site 2 had a peat layer of 70 cm but an OM content of only 40% in the top 20 cm. On both sites there were plots under barley and grass and also plots where the vegetation was removed. All soils were net sources of CO2 and N2O, but they consumed atmospheric CH4. Soils under barley had higher net CO2 emissions (830 g CO2-C m−2 yr−1) and N2O emissions (848 mg N2O-N m−2 yr−1) than those under grass (395 g CO2-C m−3 yr−1 and 275 mg N2O-N m−2 yr−1). Bare soils had the highest N2O emissions, mean 2350 mg N2O-N m−2 yr−1. The mean CH4 uptake rate from vegetated soils was 100 mg CH4-C m−3 yr−1 and from bare soils 55 mg CH4-C m−2 yr−1. The net CO2 emissions were higher from Site 2, which had a high peat bulk density and a low OM content derived from the addition of mineral soil to the peat during the cultivation history of that site. Despite the differences in soil characteristics, the mean N2O emissions were similar from vegetated peat soils from both sites. However, bare soils from Site 2 with mineral soil addition had N2O emissions of 2-9 times greater than those from Site 1. Site 1 consumed atmospheric CH4 at a higher rate than Site 2 with additional mineral soil. N2O emissions during winter were an important component of the N2O budget even though they varied greatly, ranging from 2 to 99% (mean 26%) of the annual emission.  相似文献   

18.
ABSTRACT

The study aimed to evaluate, in a marginal semi-arid Mediterranean agro-ecosystem (Sicily-Italy), the effects of arbuscular mycorrhizal fungi (AMF) inoculation and raw olive mill wastewater (OMW) (40 and 80 m3 ha?1) on forage (durum wheat-snail medick intercropping) yield, and grain production of broad bean and chickpea. AMF inoculation significantly increased (+13.6%) forage dry biomass and durum wheat nitrogen (+22.8%) and phosphorus (+32.5%) uptake. AMF inoculation, significantly promoted broad bean phosphorus uptake (+11.5%) and root nodule number (+13.9%) in the absence of OMW. OMW spreading reduced weeds in the forage (?31.3%), root nodule number (?29.7%) and dry weight (?22.7%) in broad bean. OMW also significantly increased snail medick dry biomass (+19.3%) as compared to control treatments (0, 40 and 80 m3 H2O ha?1, average production 361 g m?2), and broad bean grain yield with a production of 2.46 ± 0.12 and 1.94 ± 0.09 Mg ha?1 with and without OMW, respectively. During the experiment AMF colonization was not affected by OMW volumes. The results obtained showed that in a marginal Mediterranean agro-ecosystem: 1) OMW, notwithstanding spreading volumes, is a valuable amendment to maximize legume yield while 2) AMF inoculation is a valuable practice to improve biomass production and N and P uptake in wheat.  相似文献   

19.
Nitric oxide (NO) and nitrous oxide (N2O) emissions were measured from experimental dung and urine patches placed on boreal pasture soil during two growing seasons and one autumn period until soil freezing. N2O emissions in situ were studied by a static chamber method. NO was measured with a dynamic chamber method using a NO analyser in situ. Mean emissions from the control plots were 47.6±4.5 μg N2ON m−2 h−1 and 12.6±1.6 μg NON m−2 h−1. N2O and NO emissions from urine plots (132±21.2 μg N2ON m−2 h−1 and 51.9±7.6 μg NON m−2 h−1) were higher than those from dung plots (110.0±20.1 μg N2ON m−2 h−1 and 14.7±2.1 μg NON m−2 h−1). There was a large temporal variation in N2O and NO emissions. Maximum N2O emissions were measured a few weeks after dung or urine application, whereas the maximum NO emissions were detected the following year. NO was responsible on average 14% (autumn) and 34% (summer) of total (NO+N2O)N emissions from the pasture soil. NO emissions increased with increasing soil temperature and with decreasing soil moisture. N2O emissions increased with increasing soil moisture, but did not correlate with soil temperature. Therefore we propose that N2O and NO were produced mainly during different microbial processes, i.e., nitrification and denitrification, respectively. The results show that the overall conditions and mechanism especially for emissions of NO are still poorly understood but that there are differences in the mechanisms regulating N2O and NO production.  相似文献   

20.
Small changes in C cycling in boreal forests can change the sign of their C balance, so it is important to gain an understanding of the factors controlling small exports like water-soluble organic carbon (WSOC) fluxes from the soils in these systems. To examine this, we estimated WSOC fluxes based on measured concentrations along four replicate gradients in upland black spruce (Picea mariana [Mill.] BSP) productivity and soil temperature in interior Alaska and compared them to concurrent rates of soil CO2 efflux. Concentrations of WSOC in organic and mineral horizons ranged from 4.9 to 22.7 g C m−2 and from 1.4 to 8.4 g C m−2, respectively. Annual WSOC fluxes (4.5-12.0 g C m−2 y−1) increased with annual soil CO2 effluxes (365-739 g C m−2 y−1) across all sites (R2=0.55, p=0.02), with higher fluxes occurring in warmer, more productive stands. Although annual WSOC flux was relatively small compared to total soil CO2 efflux across all sites (<3%), its relative contribution was highest in warmer, more productive stands which harbored less soil organic carbon. The proportions of relatively bioavailable organic fractions (hydrophilic organic matter and low molecular weight acids) were highest in WSOC in colder, low-productivity stands whereas the more degraded products of microbial activity (fulvic acids) were highest in warmer, more productive stands. These data suggest that WSOC mineralization may be a mechanism for increased soil C loss if the climate warms and therefore should be accounted for in order to accurately determine the sensitivity of boreal soil organic C balance to climate change.  相似文献   

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