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1.
Some physical and chemical properties of the two common termite mounds in southeastern Nigeria, Macrotermes (MM) and Cubitermes (CM) mounds, were compared and their relationships with the surrounding top and subsoils investigated. Percentage sand, silt, pH, calcium, magnesium, potassium, sodium, iron, and organic carbon were higher and clay and penetrometer resistance lower in the CM than the MM. Sand, silt, organic carbon, and calcium decreased and clay increased from the forest to the derived savanna in the CM, but no clear trend was shown with the other properties in both the CM and the MM. Most of the nutrients were higher in the CM than in the adjacent top or subsoil but the reverse was the case with the MM. More nutrients are associated with the inorganic fractions of the soil than with the organic carbon in the mounds and the soils surrounding them. The Ca:Mg ratio in the mounds and the top and subsoils adjacent to them was low for most crops but the K:Mg ratio was mostly adequate. Because of these differences in properties and sizes of the mounds, different management strategies are recommended for them and the soils around them.  相似文献   

2.
Summary Experiments were conducted to determine the extent to which populations of Bradyrhizobium sp. strain Tal 209SR were suppressed by the antagonistic activity of a Streptomyces sp. isolated from a highly weathered tropical soil. The activity of the actinomycete was evaluated in culture medium in the presence or absence of clay minerals and in the soil from which the actinomycete was isolated after sterilization by gamma-irradiation. The presence of the actinomycete in culture medium was associated with a significant reduction in the density of Bradyrhizobium sp. (Tal 209SR). Nevertheless, the density of the Bradyrhizobium sp. surviving in the medium in the presence of the actinomycete was much higher than that normally observed when comparable densities of rhizobia are introduced into non-sterile soils. The presence of the antagonistic actinomycete in culture medium was associated with a drastic decrease in the optical density of the medium. This decrease was accompanied by a significant decrease in the insoluble exopolysaccharide content of the medium in addition to the significant decrease in bradyrhizobial cells. The actinomycete did not appear to significantly influence the growth and survival of the test Bradyrhizobium sp. in sterile soil. The inability of the actinomycete to significantly antagonize the test bacterium in sterile soil was not adequately explained by the presence of clay minerals.Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3129  相似文献   

3.
Abstract

Magnesium (Mg) deficiency is one of the major nutritional problems in tropic and subtropic areas, where the most soils are acidic. In this study, the effects of Mg application and Bradyrhizobium inoculation on growth, nodulation, symbiotic nitrogen (N) fixation as well as N nutrition status in soybean (Glycine max L.) were investigated in hydroponics under greenhouse conditions. With the increase of Mg up to 0.75?mM at low N and up to 0.5?mM at high N solutions, the dry weights of shoots, roots, and pod grain yield in soybean were increased, while further increase in Mg supply inhibited soybean growth. The availability of Mg was found to entail an improved uptake of N by plants and nodulation process in the root by Bradyrhizobium. Inoculation with rhizobial inoculants not only formed many nodules, but also increased soybean shoot, root biomass and yield, as well as plant N nutrient status.  相似文献   

4.
Abstract

The high contents of soluble and exchangeable aluminum (Al) in soils are believed to be main factors of forest damage in large areas. Krkono?e National Park, in the Czech Republic, is one of the most damaged areas in Central Europe, although the industrial emissions have declined in the past years. The purpose of this work was to evaluate the present concentration of soluble and exchangeable Al in some soils of that area, with different degrees of forest decline. The total Al concentration in water extracts was found to range within the limits 0.022–0.102 mM. According to the commonly used criteria, these values do not exceed the limit of toxicity for most plant species. Aluminum compounds in water extracts are represented predominantly by Al organic complexes and Al polymers. The percentage of the most toxic for plants, Al monomeric hydroxocomplex, ranges within the limits 0–52% of the total Al concentration and is higher in water extracts from the upper parts of the solum as compared with those from the subsoils, in compliance with the increase in pH values down the profile. The molar ratios of calcium (Ca)/Al and (Ca+Mg+K)/Al in water extracts exceed 1, but no clear relation with the forest status is found. The content of exchangeable Al is instead very high, especially in mineral horizons, and the lowest ratios between Ca or the sum of base cations and Al in the exchange complex occurs under the most degraded forest stands.  相似文献   

5.
Summary Strains of Bradyrhizobium influenced root colonization by a species of vesicular-arbuscular mycorrhizae (VAM), and species of VAM influenced root nodulation by strains of Bradyrhizobium in pot experiments. In a field experiment, the effects of VAM on competition amongst inoculated bradyrhizobia were less evident, but inoculation with Bradyrhizobium strains increased root colonization by VAM. Certain VAM/Bradyrhizobium inoculum strain combinations produced higher nodule numbers. Plants grown without Bradyrhizobium and VAM, but supplied with ammonium nitrate (300 g ml–1) and potassium phosphate (16 g ml–1), produced higher dry-matter yields than those inoculated with both symbionts in the pot experiment. Inoculation with either symbiont in the field did not result in higher pod and haulm yields at harvest.ICRISAT Journal Article No. 886  相似文献   

6.
Summary Two Australian Acacia species, A. mangium and A. auriculiformis were inoculated in vitro with eight strains of Bradyrhizobium spp. and two strains of Rhizobium spp. On the two plant species, only Bradyrhizobium spp. strains formed effective N2-fixing nodules. A. mangium, which nodulates effectively with a restricted range of Bradyrhizobium spp. strains, is a specific host compared to A. auriculiformis. A. auriculiformis is assumed to be a promiscuous host because it nodulates effectively with a wide range of Bradyrhizobium spp. strains. Nodule efficiency as expressed by the ratio of N2 fixed to nodule dry weight appeared to be higher in A. auriculiformis (0.44–0.81) than in A. mangium (0.23–0.55).  相似文献   

7.
Ionic relations in the tops of nine tropical pasture grasses were studied by using K‐Na and K‐Mg nutrient replacement series in sand culture. Rhodes grass, green panic, and pangola grass accumulated Na when K supply was low and Na was available. Sorghum, kikuyu, paspalum, speargrass and setaria accumulated very little Na but considerable quantities of Mg when the K supply was low and Mg was available. There were smaller increases in the amounts of Mg accumulated by rhodes grass, green panic, buffel grass and pangola grass than in the other five species when grown in solutions of low K/Mg ratio.

Concentrations of K, Na, Ca, Mg, P, Cl, NO , and SO. in the plant tops are presented. Although experimental treatments resulted in considerable variations in the concentrations of individual elements, cation‐anion balances (C‐A) remained relatively constant when nutrient deficiency did not depress yield in rhodes grass, green panic, pangola grass, sorghum, kikuyu, paspalum and speargrass. C‐A values in setaria and buffel grass increased as the concentration of K in the nutrient solutions increased.

These results are used as a basis for suggesting management practices that will improve the chemical composition of plant material and avoid a number of nutritional disorders that can occur in animals grazing these grasses.  相似文献   

8.
An incubation experiment was conducted to study the changes that occur in potassium availability and other soil properties with ingestion of soil by earthworms. Two soils were used. Raumai soil with high non-exchangeable K and Milson soil with low non-exchangeable K were incubated with two species of earthworm, Aporrectodea caliginosa and Lumbricus rubellus, for 8 weeks. The casts and soil samples were analysed for exchangeable K, Ca, Mg, Na, and H, pH, organic C, and texture. The results indicated that in Raumai soil, the exchangeable K levels of the casts of both earthworm species were significantly higher than for the control soil, the effect being more marked for L. rubellus than for A. caliginosa. In Milson soil, the exchangeable K levels were significantly lower in the casts of both types of earthworm than in the control soil. The nitric acid-extractable K of the soil and casts was not markedly different for either soil type, but available non-exchangeable K values were significantly higher for the casts of L. rubellus from Milson soil than for the noningested Milson soil. In Raumai soil, the exchangeable Ca was higher in the casts of L. rubellus, exchangeable Mg and H were reduced, and exchangeable Na did not change markedly in the cast compared to the control soil. For Milson soil, the casts contained lower exchangeable Ca and H but higher Na and Mg than the control. The casts of both species of earthworm had significantly higher pH values for both soil types. There was no marked difference in the organic C content of the control soil and cast samples for Milson but a reduction in the casts of A. caliginosa for the Raumai soil. Finer fractions increased in the casts of both earthworm species in both soil types.  相似文献   

9.
Abstract

Forage intake with potassium/(calcium + magnesium) [K/(Mg + Ca)] values in excess of 2.2 are associated with grass tetany and Mg deficiencies in ruminants. This study was conducted to determine the degree to which forage K and Mg concentrations and K/(Ca + Mg) ratios could be predicted from soil bicarbonate (HCO3) extractable phosphate‐phosphorus (PO4‐P), and saturation extract Ca, Mg, K, sodium (Na), and nitrate‐nitrogen (NO3‐N) concentrations. Crested wheatgrass (Agropyron spp) strains and cultivars representing four ploidy levels were grown in the greenhouse on eight calcareous soils with different saturation extract Ca, Mg, K and K/Mg ratios. The plants were harvested three times. Soil solution K/(Ca + Mg) and K/Mg ratios were the only measured soil parameters that showed a consistent correlation with plant K/(Ca + Mg) ratios. Bicarbonate extractable soil P was positively related to plant P and K uptake in the first harvest, but was not related in the second and third harvests nor was soil P related to plant Ca or Mg content. There was a tendency for the higher ploidy level entries to have higher plant K/(Ca + Mg) ratios. It was concluded that soil K/(Ca + Mg) ratios can be used to predict relative forage K/(Ca + Mg) ratios for grasses grown under similar conditions.  相似文献   

10.
Summary The legume Medicago sativa L. was grown in three calcareous soils supplied with increasing amounts of soluble phosphate, or a vesicular-arbuscular mycorrhizal (VAM) inoculum. The three test soils had high concentrations of extractable Ca. Analyses of dry-matter production and of the concentrations and content of the nutrients N, P, K, Ca, and Mg in plant tissues showed that, for each soil, a particular level of P application was able to match the VAM effects on N, P, and K levels. The Ca concentration and content in the VAM inoculated plants were, however, significantly lower than those in the P-supplied non-mycorrhizal treatments that matched the VAM effects. The N:P and the K:P ratios were about the same for mycorrhizal and non-mycorrhizal P-supplied control plants in all the three soils, but VAM inoculation lowered the Ca:P ratio in all soils. The mycorrhizae decreased Mg uptake in one of the soils, where non-mycorrhizal plants had high Mg concentrations in tissues. It is concluded that VAM depress the excessive acquisition of Ca by plants in calcareous soils.  相似文献   

11.
A greenhouse experiment was conducted to study the effect of mycorrhizal colonization by Gigaspora margarita, Glomus intraradices, and Acaulospora laevis on nutrient uptake of K, Ca, Mg, Cu, Zn, Fe, and Mn by Astragalus sinicus L. in soils spiked with lanthanum at five rates (0, 1, 5, 10, and 20 mg kg−1). Lanthanum application significantly decreased the concentrations of K, Ca, Mg, Cu, Zn, and Fe in shoots and the concentrations of Cu and Zn in roots. Mycorrhizal treatments markedly improved uptake of nutrients, and these results are important since nutrient deficiency often occurs in contaminated sites.  相似文献   

12.
The influence of the earthworm Aporrectodea caliginosa on the biomass and the proportion of active and dormant soil microorganisms after the addition of cut perennial ryegrass (Lolium perenne) to upper soil from agricultural field was studied in a microcosm experiment. During a 2-month period, soil samples were taken 1, 8, 22, 36, 50, and 64 days after cut grass addition. A substrate-induced respiration (SIR) method was used to analyse the samples for total microbial biomass and the distribution of active and dormant microbial biomass. It was found that the addition of grass increased the microbial biomass (SIR) because of an increase in the active microbial biomass. After the initially high values, the active microbial biomass decreased slowly, and at day 64, it was still higher in the grass-amended soils than in the control treatment without grass addition. After 1 day, the active microbial biomass was higher in the soil with A. caliginosa than without the earthworm. At the subsequent samplings, there were no differences in microbial biomass or the proportion of dormant vs active microorganisms between the grass-amended soils. The average from all sampling occasions of SIR was higher in earthworm-treated soil.  相似文献   

13.
Abstract

The turf grass Pennisetum clandestinum Hochst. (kikuyu grass) is one of the candidate plants for utilization and reclamation of salinized areas. The capability of kikuyu grass to grow under saline conditions was tested during 6 months, under various irrigation treatments (tap water control, 80‐mM, 150‐mM, 200‐mM, 240‐mM NaCl). Plant biomass production was visibly affected only at NaCl concentrations greater than 150‐mM NaCl. Plant growth and plant regeneration capability in the 200‐ and 240‐mM NaCl treatments gradually decreased as the experiment progressed in time. The photosynthetic potential of the plants remained unchanged and was neither affected by the treatment nor with time. Proline content of leaves as well as the content of Na+ and Cl? increased with increasing salinity stress. Apparently, kikuyu grass can withstand moderate concentrations of NaCl for prolonged periods and under repeated mowing. Thus, this grass can be used as a potential ground cover and as fodder grass in saline habitats.  相似文献   

14.
We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies.  相似文献   

15.
In a greenhouse study, the ability of the earthworms Aporrectodea rosea and A. trapezoides to influence the foliar concentration of elements and the growth of wheat plants was assessed 27 days after sowing in a sandy loam soil. The presence of A. rosea and A. trapezoides (at densities equivalent to 314 and 471 m-2, respectively) caused a significant increase in the shoot dry weight of wheat. The presence of A. rosea and A. trapezoides (at densities equivalent to 314 and 157 m-2, respectively) was also associated with a significant increase in the root dry weight of wheat. The presence of A. rosea caused a significant increase in the foliar concentration of Ca, Cu, K, Mn, N, Na, and P, but did not influence the foliar concentration of Al, B, Fe, Mo, Mg, S, and Zn. The presence of A. trapezoides was associated with a significant increase in the foliar concentration of Al, Ca, Fe, K, Mn, N, and Na, but did not influence the foliar concentration of B, Cu, Mo, Mg, P, S, and Zn. These results demonstrate the potential of A. rosea and A. trapezoides to increase the growth of wheat in a sandy loam soil and suggest that the mechanism by which they increased plant growth was, in part, through increasing the availability and uptake of nutrients from this soil.  相似文献   

16.
Aluminum (Al) toxicity represents one of the main yield-limiting factors for crops in acid soils. Silicon (Si) is known to increase tolerance in higher plants. This study was conducted to determine whether treatment with Si could improve nutrient uptake by peanut under Al stress. Peanut (Arachis hypogaea L. cv Zhonghua 4) was raised with or without Si (1.5 mM) in the growth chamber under 0 and toxic Al (0.3 mM) levels. Aluminum stress significantly decreased the root- and total-dry weight by 52.4% and 32.0%, respectively. The content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) was significantly decreased, but that of Al increased markedly in shoots and roots after Al exposure at seedling, flower-needle, and pod-setting stage. Silicon alleviates Al toxicity in peanut plants in relation to Al distribution and allocation of tissue P, K, Ca, and Mg by favoring the partitioning of dry mass to roots.  相似文献   

17.
Abstract

The response of peanut (Arachis hypogaea L.) to inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi (Glomus etunicatum) and Bradyrhizobiurn sp. was studied in pots by the acetylene reduction activity (ARA) and ‘A-value’ methods. The soil used was a Light-coloured Andosol and the treatments consisted of the inoculation of VAM fungi only, inoculation of Bradyrhizobium only, dual inoculation of VAM fungi and Bradyrhizobium and control, under non-sterilized and sterilized soil conditions.

In the non-sterilized soil the ARA and nitrogen fixation determined by the ‘A-value’ method increased significantly only by dual inoculation of VAM fungi and Bradyrhizobium at 100 days after planting (DAP), but no significant difference was observed at 70 DAP. In the case of dual inoculation, 75% of the nitrogen of the plant was derived from fixation whereas the plants inoculated only with Bradyrhizobium derived 68% of their nitrogen from fixation and the control plants, 64%. Amount of P in plant increased significantly only by dual inoculation with VAM fungi and Bradyrhizobium.

In the sterilized soil a highly significant increase in the ARA was observed of the dual inoculation at all the sampling times. Nitrogen fixation determined by the A-value technique and N and P contents in plant also increased significantly by dual inoculation. Results obtained by the A-value method showed that plants with dual inoculation derived 68% of their nitrogen from fixation while the plants inoculated only with Bradyrhizobium, 38%.

From our this study we conclude that nitrogen fixation as well as N and P contents in peanut increased significantly only by dual inoculation with VAM fungi and Bradyrhizobium.  相似文献   

18.
Five species of collembolans were collected at 24 sampling areas in a copper polluted field. The most abundant species was Isotoma notabilis found at half the sampling sites, in total 490 individuals. Two hundred and fifty-two specimens of these, representing seven sampling areas were analysed by means of random amplified polymorphic DNA using three decamer primers. Two primers each revealed eight phenotypes and the third showed six phenotypes. Distribution of the phenotypes was not homogenous within the sampling area. This result could not be explained as an outcome of either the copper content in the soil or the grass biomass, but was more likely an effect of colonisation from the areas surrounding the field.  相似文献   

19.
Summary The objective of this study was to assess the number and effectiveness of peanut rhizobia in soils of the major peanut-growing areas of Thailand. Three cropping areas, (1) continuously cropped with peanuts, (2) continuously cropped with non-legumes, and (3) non-cultivated fields, were chosen in each region. Peanut rhizobia were found in the soil at 38 to 55 sites sampled. Cultivated fields with a peanut cultivation history contained (as estimated by most probable numbers) an average of 1.6×103 cells g-1 of soil. The numbers of peanut rhizobia in most of the fallow fields and some of the noncultivated shrub or forest locations were much the same as at the sites where Arachis hypogaea was cultivated. In contrast, there were no or few (28–46 cells g-1 soil) peanut rhizobia in the majority of fields continuously cultivated with sugarcane, cassava, corn, and pineapple. It appears that in these areas the indigenous peanut rhizobial populations are not adequate in number for a maximal nodulation of peanuts. A total of 343 Bradyrhizobium isolates were tested for effectiveness and were found to vary widely in their ability to fix N2. In some areas the majority of rhizobia were quite effective while in others they were less effective than the inoculum strain THA 205 recommended in Thailand.  相似文献   

20.
Abstract

Since ryegrass (Lolium sp.) is a widely grown cool‐season forage grass, its magnesium concentration is of special interest to ruminant livestock producers. This study was conducted to investigate the effect of calcitic or dolomitic lime addition on dry matter yield and mineral composition of hybrid ryegrass, Lolium (multiflorum x perenne x perenne) grown in eight acidic soils. Each soil received two levels of calcitic or dolomitic lime, L(C1) and L(C2) or L(D1) and L(D2), which raised pH to approximately 5.3, and 6.0. Dry matter yield response was obtained only in soils having an initial % Al saturation ≥59, % Mg saturation ≤10 and % Ca saturation ≤21. Only in one soil, which had an initial exchangeable Mg level of 0.05 cmolc/kg of soil, was response to dolomitic lime higher than that obtained with calcitic lime. Magnesium concentration in dry matter was increased by both levels of dolomitic lime with the increase dependent on the rate used and on the initial level of exchangeable Mg. The average Mg concentration increased from 0.8 to 3.9 g/kg, from 1.6 to 3.6 g/kg, and from 2.6 to 3.9 g/kg, when ryegrass was grown in soils having low, medium, and high initial exchangeable Mg levels, respectively. Mg concentration in the ryegrass tended to be lower in the unlimed soils than when calcitic lime was used, 1.1 vs. 1.4 g/kg, when the soils had low to medium exchangeable Mg levels. The results suggest that if ryegrass is to be grown in acidic soils containing low to medium levels of exchangeable Mg, the use of dolomitic lime is desirable, even if no yield response to applied Mg is expected, to decrease the probability of the Mg deficiency disease, hypomagnesemia, in ruminant animals.  相似文献   

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