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1.
Qiang-Sheng Wu Xin-Hua He Ying-Ning Zou Kai-Ping He Ya-Hong Sun Ming-Qin Cao 《Soil biology & biochemistry》2012
Relationships between the spatial distributions of glomalin-related soil protein (GRSP) and soil aggregates, carbohydrates or relevant enzymes are poorly studied. We found that two categories of GRSP, the easily extractable Bradford-reactive soil protein (EE-BRSP) and total BRSP (T-BRSP), respectively ranged between 0.3–0.6 and 0.5–0.8 mg/g DW soil, and these two BRSPs decreased with the increase of soil depth (0–40 cm) in the rhizosphere of a 22-year-old Citrus unshiu orchard. Both EE-BRSP and T-BRSP were significantly positively correlated with mycorrhization, 0.25–0.50 mm soil water-stable aggregates, water-extractable or hydrolyzable carbohydrates, and β-glucosidase, but significantly negatively correlated with protease. Our results demonstrate that the spatial distribution of GRSP is significantly affected by mycorrhization, soil carbohydrate, β-glucosidase and protease. 相似文献
2.
《Soil & Tillage Research》2007,92(1-2):22-29
Sustainable agricultural use of cultivated desert soils has become a concern in Hexi Corridor in Gansu Province of China, because loss of topsoil in dust storms has been recently intensified. We chose four desert sites to investigate the effects of cultivation (cropping) on (i) soil organic C and its size fractions and (ii) soil aggregate stability (as a measure of soil erodibility). These parameters are of vital importance for evaluating the sustainability of agricultural practices.Total organic C as well as organic C fractions in soil (coarse organic C, 0.1–2 mm; young organic C, 0.05–0.1 mm; stable organic C, <0.05 mm) generally increased with the duration of the cultivation period from 0 (virgin soil, non-cultivated) to more than 30 years (p < 0.05). Compared to total organic C in virgin soils (2.3–3.5 g kg−1 soil), significantly greater values were found after 10 to >20 years of cultivation (6.2–7.1 g kg−1 soil). The increase in organic C in desert soils following prolonged cultivation was mainly the consequence of an increase in the coarse organic C. The increase in total organic C in soil was also dependent on clay content [total organic C = 0.96 + 0.249 clay content (%) + 0.05 cultivation year, R2 = 0.48, n = 27, p < 0.001]. This indicates that clay protected soil organic C from mineralization, and also contributed to the increase in soil organic C as time of cultivation increased.There was a significant positive correlation between aggregate stability and total organic C across all field sites. The water stability of aggregates was low (with water-stable aggregate percentage ∼4% of dry-sieved aggregates of size 1–5 mm). There was no consistent pattern of increase in the soil aggregate stability with time of cultivation at different locations, suggesting that desert soils might remain prone to wind erosion even after 50 years of cultivation. Alternative management options, such as retaining harvested crop residues on soil surface and excluding or minimizing tillage, may permit sustainable agricultural use of desert soils. 相似文献
3.
《Applied soil ecology》2006,31(1-2):110-119
A pot culture experiment was carried out to study the effects of arbuscular mycorrhizal (AM) inoculation on the growth of Elsholtzia splendens and Zea mays and the activities of phosphatase and urease in a soil contaminated with Cu, Zn, Pb and Cd. Two AM fungal inocula, MI containing Glomus caledonium and MII containing Gigaspora margarita,Gigaspora decipens, Scutellospora gilmori, Acaulospora spp. and Glomus spp., were applied to the soil. The plants of E. splendens and Z. mays were harvested after 24 and 10 weeks of growth, respectively. Both plant species had a similar trend in mycorrhizal colonization rates, MI > MII > control. Shoot and root biomass of Z. mays was increased by MI, while not affected significantly by MII. Although both MI and MII increased plant dry weight of E. splendens, MII was more effective. Mycorrhizal dependency (MD) with MI and MII was 14.8 and 33.5, respectively for E. splendens, and 11.0 and 0.9, respectively for Z. mays. Both inocula increased the activities of phosphatase and urease in the soils of E. splendens and Z. mays, but MI was more effective than MII for urease, while MII more effective than MI for phosphatase. Although the mechanisms involved in these responses are not clear, AM fungal inoculum may be important and used for the phytoremediation of heavy metal contaminated soils, but both inoculum type and host species must be considered. 相似文献
4.
Arbuscular mycorrhizal fungus (AMF) can enhance plant growth and resistance to toxicity produced by heavy metals (HMs), affect the bioavailability of HMs in soil and the uptake of HMs by plants, and thus has been emerged as the most prominent symbiotic fungus for contribution to phytoremediation. A greenhouse pot experiment was conducted to assess the effect of Glomus versiforme BGC GD01C (Gv) on the growth and Cd accumulation of Cd-hyperaccumulator Solanum nigrum in different Cd-added soils (0, 25, 50, 100 mg Cd kg−1 soil). Mycorrhizal colonization rates were generally high (from 71% to 82%) in Gv-inoculated treatments at all Cd levels. Gv colonization enhanced soil acid phosphatase activity, and hence elevated P acquisition and growth of S. nigrum at all Cd levels. Moreover, the presence of Gv significantly increased DTPA-extractable (phytoavailable) Cd concentrations in 25 and 50 mg Cd kg−1 soils, but did not affect phytoavailable Cd in 100 mg Cd kg−1 soil. Similarly, inoculation with Gv significantly increased Cd concentrations of S. nigrum in 25 and 50 mg Cd kg−1 soils, but decreased Cd concentrations of the plants in 100 mg Cd kg−1 soil. Overall, inoculation with Gv greatly improved the total Cd uptakes in all plant tissues at all Cd levels. The present results indicated that S. nigrum associated with Gv effectively improved the Cd uptake by plant and would be a new strategy in microbe-assisted phytoremediation for Cd-contaminated soils. 相似文献
5.
It is broadly accepted that reduced tillage increases soil organic carbon (Corg) and total nitrogen (N) concentrations in arable soils. However, the underlying processes of sequestration are not completely understood. Thus, our objectives were to investigate the impact of a minimum tillage (MT) system (to 5–8 cm depth) on aggregates, on particulate organic matter (POM), and on storage of Corg and N in two loamy Haplic Luvisols in contrast to conventional tillage (CT) (to 25 cm). Surface soils (0–5 cm) and subsoils (10–20 cm) of two experimental fields near Göttingen, Germany, were investigated. Each site (Garte-Süd and Hohes Feld) received both tillage treatments for 37 and 40 years, respectively. In the bulk soil of both sites Corg, N, microbial carbon (Cmic), and microbial N (Nmic) concentrations were elevated under MT in both depths. Likewise, water-stable macroaggregates (>0.25 mm) were on average 2.6 times more abundant under MT than under CT but differences in the subsoils were generally not significant. For surface soils under MT, all aggregate size classes <1 mm showed approx. 35% and 50% increased Corg concentrations at Garte-Süd and Hohes Feld, respectively. For greater macroaggregates (1–2, 2–10 mm), however, differences were inconsistent. Elevations of N concentrations were regular over all size classes reaching 61% and 52%, respectively. Density fractionation of the surface soils revealed that tillage system affected neither the yields of free POM nor occluded POM nor their Corg and N concentrations. Moreover, more Corg and N (15–238%) was associated within the mineral fractions investigated under MT in contrast to CT. Overall, similar to no-tillage, a long-term MT treatment of soil enhanced the stability of macroaggregates and thus was able to physically protect and to store more organic matter (OM) in the surface soil. The increased storage of Corg and N did not occur as POM, as reported for no-tillage, but as mineral-associated OM. 相似文献
6.
《Soil biology & biochemistry》2001,33(4-5):449-455
The influence of several soil properties on soil conduciveness or suppressiveness to disease caused by the soil fungus Fusarium oxysporum f. sp. cubense was studied in seven field plots of banana plantations, situated in Tenerife and Gran Canaria islands (Canary Islands, Spain). In each plot, soil samples were taken in conducive and suppressive areas to Fusarium wilt. Water-stable aggregates (WSA: 200–2000 μm diameter), soil particle size, and selected soil solution characteristics [pH, electric conductivity (EC) and soluble Na] were determined in the samples. Aggregate water-stability was higher in soils of conducive areas than in suppressive areas. The percentage of WSA in the conducive areas ranged from 460 to 330 g kg−1, while in the suppressive areas the maximum value was 285 g kg−1 and the minimum was 150 g kg−1. The soils had high clay content and the EC and soluble Na tended to be higher in suppressive areas than in conducive areas. Soil solution pH was lower in conducive areas (except sites 1 and 9). Our data provide evidence that in different soil areas of the same plot, the structural stability of aggregates, presumably controlled in part by the clay fraction, soluble Na concentration and EC, is of great importance for the conduciveness or suppressiveness to banana wilt caused by Fusarium oxysporum f. sp. cubense of the soils studied. Finally, we hypothesize that a greater stability of the aggregates forming anaerobiosis could partly explain most of the available Fe found in soil areas where the disease was severe, at least in these types of soils. 相似文献
7.
Metal(loid) accumulation and arbuscular mycorrhizal (AM) status of the dominant plant species, Cynodon dactylon, growing at four multi-metal(loid)s-contaminated sites and an uncontaminated site of China were investigated. Up to 94.7 As mg kg?1, 417 Pb mg kg?1, 498 Zn mg kg?1, 5.8 Cd mg kg?1 and 27.7 Cu mg kg?1 in shoots of C. dactylon were recorded. The plant was colonized consistently by AM fungi (33.0–65.5%) at both uncontaminated site and metal-contaminated sites. Based on morphological characteristics, fourteen species of AM fungi were identified in the rhizosphere of C. dactylon, with one belonging to the genus of Acaulospora and the other thirteen belonging to the genus of Glomus. Glomus etunicatum was the most common species associated with C. dactylon growing at metal-contaminated sites. Spore abundance in the rhizosphere of C. dactylon growing at the metal-contaminated soils (22–82 spores per 25 g soil) was significantly lower than that of the uncontaminated soils (371 spores per 25 g soil). However, AM fungal species diversity in the metal-contaminated soils was significantly higher than that in the uncontaminated soils. This is the first report of AM status in the rhizosphere of C. dactylon, the dominant plant survival in metal-contaminated soils. The investigation also suggests that phytorestoration of metal-contaminated sites might be facilitated using the appropriate plant with the aid of tolerant AM fungi. 相似文献
8.
Extreme droughts and heat waves due to climate change may have permanent consequences on soil quality and functioning in agroecosystems. During November 2010 to August 2011, the Southern High Plains (SHP) region of Texas, U.S., a large cotton producing area, received only 39.6 mm of precipitation (vs. the historical avg. of 373 mm) and experienced the hottest summer since record keeping began in 1911. Several enzyme activities (EAs) important in biogeochemical cycling were evaluated in two soils (a loam and a sandy loam at 0–10 cm) with a management history of monoculture (continuous cotton) or rotation (cotton and sorghum or millet). Samplings occurred under the most extreme drought and heat conditions (July 2011), after precipitation resulted in a reduction in a drought severity index (March 2012), and 12 months after the initial sampling (July 2012; loam only). Eight out of ten EAs, were significantly higher in July 2011 compared to March 2012 for some combinations of soil type and management history. Among these eight EAs, enzymes key to C (β-glucosidase, β-glucosaminidase) and P cycling (phosphodiesterase, acid and alkaline phosphatases) were significantly higher (19–79%) in July 2011 than in March 2012 for both management histories regardless of the soil type (P > 0.05). When comparing all sampling times, the activities of alkaline phosphatase, aspartase and urease (rotation only) showed this trend: July 2011 > March 2012 > July 2012. Activities of phosphodiesterase, acid phosphatase, α-galactosidase, β-glucosidase and β-glucosaminidase were higher in July 2011 than July 2012 in at least one of the two management histories. Total C was reduced significantly from July 2011 to March 2012 in the rotation for both soils. Only the activities of arylsulfatase (avg. 36%) and asparaginase showed an increase from July 2011 to March 2012 for both soil types, which may indicate they have a different origin/location than the other enzymes. EAs continued to be a fingerprint of the soil management history (i.e., higher EAs in the rotation than in monoculture) during the drought/heat wave. This study provided some of the first evidence of the adverse effects of a natural, extreme drought and heat wave on soil quality in agroecosystems as indicated by EAs involved in biogeochemical cycling. 相似文献
9.
P.T. Manoharan V. Shanmugaiah N. Balasubramanian S. Gomathinayagam Mahaveer P. Sharma K. Muthuchelian 《European Journal of Soil Biology》2010,46(2):151-156
The present study investigated the effects of arbuscular mycorrhizal (AM) fungus, Glomus mosseae on the growth and physiology state of Erythrina variegata Linn, grown in sandy loam soil with four water stress levels viz. ?0.06 MPa (well watered/control), ?1.20 MPa (mild), ?2.20 MPa (moderate) and ?3.20 MPa (severe) in a completely randomized design. Plants were harvested after 90 days (60 days after stress induction) of growth. Growth parameters (root &, shoot, dry weight and, leaf area); physiological parameters (chlorophyll content, carotenoids, soluble starch, sugar, protein and proline in shoots); and microbiological parameter (percentage of mycorrhizal infection) were determined. AM fungal plants had significantly higher plant biomass, higher chlorophyll content (chlorophyll a and b), carotenoids and protein content in shoots than non-AM-plants. The AM-inoculation in stressed plants significantly declined the soluble sugar and starch in shoots. Moreover, AM-inoculation also reduced the proline accumulation in shoots and the reduction was significant when plants were severely stressed (?3.2 MPa). Mycorrhizal colonization in roots of E. variegata depressed significantly due to increased water stress. However, the AM colonization did not decline below 11% and enabled the plants to maintain osmotic adjustments and enhanced the plants tolerance against water stress. 相似文献
10.
The near infrared reflectance spectroscopy (NIRS) method was used in the present study to compare earthworm-made soil aggregates to aggregates found in the surrounding bulk soil. After initially assessing the daily cast production of Metaphire posthuma, boxes with soil incubated with M. posthuma and control soils were subjected to wetting in order to reorganize the soil structure. After two months of incubation, soil aggregates produced by earthworms (casts and burrows), soil aggregates that were appeared to be unaffected by earthworms (bulk soil without visible trace of earthworm bioturbation from the earthworm treatment) and soil aggregates that were entirely unaffected by earthworms (control – no earthworm – treatment) were sampled and their chemical signatures analyzed by NIRS. The production of below-ground and surface casts reached 14.9 g soil g worm?1 d?1 and 1.4 g soil g worm?1 d?1, respectively. Soil aggregates from the control soils had a significantly different NIRS signature from those sampled from boxes with earthworms. However, within the earthworm incubation boxes the NIRS signature was similar between cast and burrow aggregates and soil aggregates from the surrounding bulk soil. We conclude that the high cast production by M. posthuma and the regular reorganization of the soil structure by water flow in and through the soil lead to a relatively homogenous soil structure. Given these results, we question the relevance of considering the bulk soil that has no visible activity of earthworm activity as a control to determine the effect of earthworms on soil functioning. 相似文献
11.
Effects of soil depth and aggregate size on weed seed distribution and viability in a silt loam soil
《Applied soil ecology》2001,16(3):209-217
The position of weed seeds within the soil matrix plays an important role in seedling emergence and seed survival. The relationship of weed seeds with soil aggregates and soil depth was evaluated in a Waukegon silt loam soil that had been under a long-term, conventional tillage, annual crop management system. Soil aggregates were separated and classified into eight size classes from ≤5 to >12 mm and weed seeds were extracted from the aggregates. Amaranthus spp., Chenopodium album L. (common lambsquarters), Polygonum pensylvanicum L. (Pennsylvania smartweed), Setaria faberi Herrm. (giant foxtail), and Solanum ptycanthum Dun. (eastern black nightshade) accounted for the majority of seeds recovered. In general, seed viability declined from April to June, but increased in October following seed deposition. Seeds of individual species were most abundant in the aggregate size class most closely matching its seed size. However, seeds were commonly found associated with aggregates larger than 9 mm. Highest seed viability was found in the aggregate fraction closest to the seed size, however, S. faberi viability was also high in the >12 mm aggregate size class. Regardless of aggregate size, seed numbers were generally greatest in the upper 5 cm of soil. The results of this research were species-dependent and variable and demonstrated the complexity of weed seed/soil aggregate associations. However, they did show that seed placement within the soil matrix may play an important role in weed population dynamics. 相似文献
12.
Erika Tobiašová 《Soil & Tillage Research》2011,114(2):183-192
In this study, the soil structure of two soils (Haplic Chernozem and Eutric Fluvisol) of different land uses (forest, meadow, urban and agro-ecosystem – consisted of four crop rotations) in Slovakia was compared. The soil aggregate stability was determined with a dependence on the chemical composition of plant residues. The quantity and quality of the organic matter was assessed through the parameters of the C and N in size fractions of dry-sieved and water-resistant aggregates. The soil structure of the forest ecosystem was evaluated as the best of all of forms of land use. Differences in the soil structure under the grass vegetation of a meadow (natural conditions) and urban ecosystem were also recorded. The agro-ecosystem was characterised by a higher portion (55.95%) of the most valuable (agronomically) water-resistant aggregate size fraction of 0.5–3 mm. Values of the carbon management index showed that the larger water-resistant aggregates were, the greater were the changes in the organic matter (r = ?0.680, P < 0.05). In addition, a smaller content of dry-sieved aggregates of the 3–5 mm size fraction was observed with higher contents of soil organic carbon (SOC) (r = ?0.728, P < 0.05) and labile carbon (CL) (r = ?0.760, P < 0.05); there were also greater changes in the soil organic matter and vice versa, higher contents of SOC (r = 0.744, P < 0.05) and CL (r = 0.806, P < 0.05) greater contents of dry-sieved aggregates of size fraction 0.5–1 mm. The soil structure of agro-ecosystem was superior at a higher content of cellulose (r = ?0.712, P < 0.05) in the plant residues. The higher content of cellulose and hemicellulose in the plant residue of a previous crop was reflected in a smaller CL content in the water-resistant aggregates (r = ?0.984, P < 0.05). A correlation was observed between a high content of lignin in the plant residue and a smaller SOC content in the water-resistant aggregates (r = ?0.967, P < 0.05). Lastly, a higher content of proteins in the plant residues (r = 0.744, P < 0.05) supported a greater content of dry-sieved aggregates of the 0.5–1 mm size fraction. 相似文献
13.
Organic matter influences soil structure and compactibility by binding soil mineral particles, reducing aggregate wettability, and influencing the mechanical strength of soil aggregates, which is the measure of coherence of inter-particle bonds. This work was carried out to examine how differences in water-stable aggregates influence the distribution of soil organic carbon and soil organic nitrogen under two tillage techniques [minimum tillage (only planting holes were opened) and conventional tillage (raised beds, 30 cm high, prepared manually with traditional hoes)] in soils of a Fluvisol in Owerri, southeastern Nigeria. Three pedons were dug and studied for each of the tillage technique along a soil sequence. Soil organic carbon and soil organic nitrogen distribution in whole soil and in water-stable aggregates under minimum tillage and conventional tillage were determined for the soils. Soil organic carbon contents in water-stable aggregates (WSA) of the pedons varied according to method of tillage. The highest mean values of soil organic carbon were obtained from minimum tillage and in water-stable aggregates 4.75–2.00 mm (16.03 Mg C ha−1), 1.00–0.50 mm (14.06 Mg C ha−1) and water-stable aggregates 2.00–1.00 mm (13.99 Mg C ha−1) whereas under conventional tillage, water-stable aggregates 1.00–0.50 mm with soil organic carbon of 24.6 Mg C ha−1 had the highest soil organic carbon content. Soil organic carbon correlated significantly with mean weight diameter (r = 0.48; P = 0.05; n = 15), water-stable aggregates 4.75–2.00 mm (r = 0.73; P = 0.05; n = 15), water-stable aggregates 2.00–1.00 mm (r = 0.55; P = 0.05, n = 15), water-stable aggregates 1.00–0.50 mm (r = 0.44; P = 0.05; n = 15) whereas no relationship was found between soil organic carbon and water-stable aggregates 0.50–0.25 mm (r = 0.15; P = 0.05; n = 15) and water-stable aggregates <0.25 mm (r = 0.17; P = 0.05; n = 15) in soils under minimum tillage. There was a significant correlation (r = 0.45–0.58; P = 0.05; n = 14) between all water-stable aggregates classes studied and soil organic carbon in soils under conventional tillage. Mean values of soil organic nitrogen were higher in soils under minimum tillage with 4.75–2.00 mm and 2.00–1.00 mm aggregate classes having 1.64 Mg N ha−1 and 1.57 Mg N ha−1 soil organic nitrogen when compared to 1.01 Mg N ha−1 and 1.00 Mg N ha−1 in conventionally tilled soils of the same aggregate classes, respectively. Larger water-stable aggregate classes (4.75–2.00; 2.00–1.00) had slightly more soil organic nitrogen (22–26%) than smaller aggregate classes (1.00–0.50; 0.50–0.25; >0.25) with 14–24% soil organic nitrogen in minimum tilled soils. In soils under conventional tillage, 1.00–0.50 mm, 0.50–0.25 mm and <0.25 mm aggregate classes contributed more soil organic nitrogen (19.66–22.40%) to the soil whereas larger water-stable aggregate classes contributed 19.22% soil organic nitrogen. The proportion of soil organic carbon and total nitrogen retained in soils with higher percentage of water-stable aggregates are less likely to be lost through soil and wind erosion. The higher values of SOC in the whole soil and WSA classes less than 2.00 mm are indications of positive influence of SOC on the stability of these peds. 相似文献
14.
Scott N. Johnson Peter J. Gregory James W. McNicol Yasmina Oodally Xiaoxian Zhang Philip J. Murray 《Applied soil ecology》2010,44(1):75-79
Soil-dwelling insect herbivores are significant pests in many managed ecosystems. Because eggs and larvae are difficult to observe, mathematical models have been developed to predict life-cycle events occurring in the soil. To date, these models have incorporated very little empirical information about how soil and drought conditions interact to shape these processes. This study investigated how soil temperature (10, 15, 20 and 25 °C), water content (0.02 (air dried), 0.10 and 0.25 g g?1) and pH (5, 7 and 9) interactively affected egg hatching and early larval lifespan of the clover root weevil (Sitona lepidus Gyllenhal, Coleoptera: Curculionidae). Eggs developed over 3.5 times faster at 25 °C compared with 10 °C (hatching after 40.1 and 11.5 days, respectively). The effect of drought on S. lepidus eggs was investigated by exposing eggs to drought conditions before wetting the soil (2–12 days later) at four temperatures. No eggs hatched in dry soil, suggesting that S. lepidus eggs require water to remain viable. Eggs hatched significantly sooner in slightly acidic soil (pH 5) compared with soils with higher pH values. There was also a significant interaction between soil temperature, pH and soil water content. Egg viability was significantly reduced by exposure to drought. When exposed to 2–6 days of drought, egg viability was 80–100% at all temperatures but fell to 50% after 12 days exposure at 10 °C and did not hatch at all at 20 °C and above. Drought exposure also increased hatching time of viable eggs. The effects of soil conditions on unfed larvae were less influential, except for soil temperature which significantly reduced larval longevity by 57% when reared at 25 °C compared with 10 °C (4.1 and 9.7 days, respectively). The effects of soil conditions on S. lepidus eggs and larvae are discussed in the context of global climate change and how such empirically based information could be useful for refining existing mathematical models of these processes. 相似文献
15.
A real-time PCR assay was developed to quantify in soil the fungus Hirsutella minnesotensis, an important parasite of secondary-stage juvenile (J2) of the soybean cyst nematode. A primer pair 5′-GGGAGGCCCGGTGGA-3′ and 5′-TGATCCGAGGTCAACTTCTGAA-3′ and a TaqMan probe 5′-CGTCCGCCGTAAAACGCCCAAC-3′ were designed based on the sequence of the ITS region of the rRNA gene. The primers were highly species-specific. The PCR reaction system was very sensitive and able to detect as few as 4 conidia g?1 soil. Regression analysis showed similar slopes and efficiency on DNA from pure culture (y = ?3.587x + 41.017, R2 = 0.9971, E = 0.9055) and from Log conidia g?1 soil (y = ?3.855x + 37.669, R2 = 0.9139, E = 0.8172), indicating that the real-time PCR protocol can reliably quantify H. minnesotensis in the soil. The real-time PCR assay was applied to 20 soil samples from soybean fields, and compared with a parasitism assay. The real-time PCR assay detected H. minnesotensis in six of the soils, whereas the parasitism assay detected H. minnesotensis in the same six soils and three additional soils. The real-time PCR assay was weakly correlated (R2 = 0.49) with the percentage of parasitized J2 in the six soils, indicating that different types of soil may interfere the efficiency of the real-time PCR assay, possibly due to the effect of soil types on efficacy of DNA extraction. The parasitism assay appeared to be more sensitive than real-time PCR in detecting presence of H. minnesotensis, but real-time PCR was much faster and less costly and provided a direct assessment of fungal biomass. Using the two assays in combination can obtain more complete information about the fungus in soil than either assay alone. Hirsutella parasitism was widespread and detected in 13 of the 20 field soils, indicating that these fungi may contribute to suppressiveness of soybean cyst nematode in nature and likely have high biological control potential for the nematode. 相似文献
16.
《Pedobiologia》2014,57(4-6):223-233
Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg−1), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal. 相似文献
17.
The crucial role of roots in mediating agricultural sustainability and food security is becoming more widely appreciated. Here we tested the potential impact of barley (Hordeum vulgare L.) breeding (German germplasm) on root architecture and possible ripple-on effects on soil aggregation. In a greenhouse study, we tested two barley breeding lines. We focused on very fine (<0.2 mm) and fine (0.2–1 mm) roots. Soil structure was measured as percentage of water-stable macroaggregates and aggregate size distribution from dry-sieving. Breeding of barley reduced very fine root length of one of the tested lines but had no effect on our measures of soil structure. Our results indicate that breeding practices need not lead to an overall decline in root length. While we did not find that reduced very fine root length propagated to negative effects on soil structure parameters, additional studies should address this important aspect in other crop lineages and soils. 相似文献
18.
The study evaluated the effects of soil intra-aggregate pore distributions on movement and fate of E. coli (a global indicator of fecal pollution) within soil aggregates. The first objective was to characterize pore structure of intact soil aggregates (4–6 mm in size) using X-ray computed microtomography and to quantify the differences in pore structures of the aggregates from the same soil type but under >18 year contrasting land use and management settings. The studied settings were (i) conventionally plowed row crop (CT), (ii) no-till row crop (NT), and (iii) native succession vegetation (NS) treatments from Long Term Ecological Research site, W.K. Kellogg Biological Station, southwest Michigan. The second objective was to examine spatial distribution of E. coli introduced into the aggregates and the relationships between E. coli distributions and intra-aggregate pores. The results indicated that E. coli distribution in the aggregates was driven by specific configurations of the intra-aggregate pores. When the aggregates’ initial water contents were relatively low, presence of large (>100 μm) pores in the aggregate interiors limited water and thus E. coli entry. Such centrally located large pores were more abundant in the aggregates from NT and NS treatments as compared to CT aggregates. Medium-sized pores (30–60 μm) were more abundant in the aggregates from CT soil and such pores were relatively homogeneously distributed through entire bodies of CT aggregates. Thus, upon entering the aggregate, E. coli became more uniformly distributed through the CT aggregates, while in NT and NS aggregates it more commonly remained in the aggregate exterior parts without reaching the interiors. Implications of these distributional patterns for E. coli survival and re-entering water flow in soil under different land use need to be addressed in further studies. 相似文献
19.
Peter Millard Andrew J. Midwood John E. Hunt David Whitehead Thomas W. Boutton 《Soil biology & biochemistry》2008,40(7):1575-1582
We used natural gradients in soil and vegetation δ13C signatures in a savannah ecosystem in Texas to partition soil respiration into the autotrophic (Ra) and heterotrophic (Rh) components. We measured soil respiration along short transects from under clusters of C3 trees into the C4 dominated grassland. The site chosen for the study was experiencing a prolonged drought, so an irrigation treatment was applied at two positions of each transect. Soil surface CO2 efflux was measured along transects and CO2 collected for analysis of the δ13C signature in order to: (i) determine how soil respiration rates varied along transects and were affected by localised change in soil moisture and (ii) partition the soil surface CO2 efflux into Ra and Rh, which required measurement of the δ13C signature of root- and soil-derived CO2 for use in a mass balance model.The soil at the site was unusually dry, with mean volumetric soil water content of 8.2%. Soil respiration rates were fastest in the centre of the tree cluster (1.5 ± 0.18 μmol m?2 s?1; mean ± SE) and slowest at the cluster–grassland transition (0.6 ± 0.12 μmol m?2 s?1). Irrigation produced a 7–11 fold increase in the soil respiration rate. There were no significant differences (p > 0.5) between the δ13C signature of root biomass and respired CO2, but differences (p < 0.01) were observed between the respired CO2 and soil when sampled at the edge of the clusters and in the grassland. Therefore, end member values were measured by root and soil incubations, with times kept constant at 30 min for roots and 2 h for soils. The δ13C signature of the soil surface CO2 efflux and the two end member values were used to calculate that, in the irrigated soils, Rh comprised 51 ± 13.5% of the soil surface CO2 efflux at the mid canopy position and 57 ± 7.4% at the drip line. In non-irrigated soil it was not possible to partition soil respiration, because the δ13C signature of the soil surface CO2 efflux was enriched compared to both the end member values. This was probably due to a combination of the very dry porous soils at our study site (which may have been particularly susceptible to ingress of atmospheric CO2) and the very slow respiration rates of the non-irrigated soils. 相似文献
20.
《Applied soil ecology》2007,35(3):553-565
The underlying influences of soil flooding, pH level and soil-inhabiting Diaprepes abbreviatus (L.) root weevil larval feeding in citrus were examined in two separate greenhouse studies, rootstock × flooding × Diaprepes-larvae (RFD) and liming × rootstock × flooding × Diaprepes-larvae (LRFD). Our objectives were to determine the combined effects of soil flooding and pH level on survival and growth of Diaprepes root weevil larvae to gain insights of insect-environmental relations for the weevil control. We used a Floridana sandy loam (pH 4.8) from a citrus grove infested by Diaprepes root weevil in center Florida. The RFD experiment consisted of two citrus rootstocks (Swingle and Smooth Flat Seville), three flooding durations (0, 20, and 40 days) and two larval infestation rates (0 and 5 larvae) for 40-day feeding. The LRFD experiment consisted of two citrus rootstocks (Swingle and Carrizo), three pH levels (non-limed control, and target pH 6 and 7), two flooding durations (0 and 40 days), and two larval rates (0 and 5 larvae) for 56-day feeding. Dolomite (54% CaCO3 and 46% MgCO3) was used for soil liming in the LRFD. Treatments were arranged with 15 replicates in a completely randomized design. In the RFD, flooded soil pH was 0.3 units higher than non-flooded soil and larval survival was the lowest in the longest flooded treatment (P < 0.05). In the LRFD, soil pH increased 0.5–0.9 units for the target pH 6, and 0.7–1.1 units for the target pH 7. The effects of rootstock, liming and flooding treatments and their interactions were significant on soil pH and larval survival (P < 0.05). Larval survival decreased from 80% to 60% with increasing soil pH from 4.8 to 5.7. Total larval weight per seedling decreased significantly from 0.060 g to 0.012 g when the soil pH increased from 5.1 to 5.7. Flooding reduced larval survival and growth, and increasing acidic soil pH by 1 unit would be an option for controlling soil acidity and for promoting integrated management of Diaprepes root weevil in citrus. 相似文献