Browsing by Author "S.C. Srivastava"

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Agricultural intensification, soil biodiversity and agroecosystem function in the tropics: The role of decomposer biota
(Elsevier, 1997) M.H. Beare; M. Vikram Reddy; G. Tian; S.C. Srivastava
Intensification of agriculture in the tropics has resulted from a shortage of farmland and insufficient food production to satisfy the needs of an expanding population. Many tropical farmers are challenged by the prospect of intensifying their production while sustaining or improving the fertility and productivity of soils with only locally available natural resources. The waste products of plant and animal production represent some of the most abundant natural resources available for use by tropical farmers to achieve these goals. The efficient use and management of these resources depends on understanding the role that decomposer biota play in regulating the structure and function of agricultural ecosystems. Furthermore, the development of agricultural management practices which promote the beneficial attributes of these organisms will be essential to sustaining the productivity and environmental integrity of tropical agriculture. Finally, understanding the role of biodiversity among decomposer biota in maintaining the functional properties of tropical agricultural ecosystems is critical to achieving this goal. The objective of this review is to further that understanding by describing the taxonomic and functional diversity of decomposer biota in the tropics and evaluating known links between their diversity and the function of agricultural ecosystems. We further describe the effects of changing land-use and agricultural intensification on the structure and diversity of decomposer communities in the tropics and suggest some priorities for future research. © 1997 Published by Elsevier Science B.V.
Carbon and phosphorus in the soil biomass of some tropical soils of India
(1988) S.C. Srivastava; J.S. Singh
Microbial biomass C and P were measured for six tropical soils. Biomass C ranged from 149 to 667 μg g-1 soil and biomass P from 17 to 35 μg g-1 soil and the two were linearly related with the soil biomass having a mean P concentration of 3.5%. Soil biomass accounted for 2.5-5.6% of total soil organic C and 9.2-19.2% of the total soil organic P. The amount of biomass P was positively related with NaHCO3-extraclable soil inorganic P. P concentration in biomass on the other hand exhibited an inverse relationship with NaHCO3-extractable soil Pi. © 1988.
Changes with time in soil biomass C, N and P of mine spoils in a dry tropical environment
(1989) S.C. Srivastava; A.K. Jha; J.S. Singh
The data suggest that microbial biomass can be taken as a functional index of soil redevelopment. -from Authors
Effect of cultivation on microbial carbon and nitrogen in dry tropical forest soil
(Springer-Verlag, 1989) S.C. Srivastava; J.S. Singh
Fifteen- and forty-year-old cropfields developed from a dry tropical forest were examined for soil organic C and total N and soil microbial C and N. The 15-year-old field had never been manured while the 40-year-old field had been fertilized with farmyard manure every year. The native forest soil was also examined. The results indicated that the native forest soil lost about 57% and 62% organic C and total N, respectively, in the 0-10 cm layer after 15 years of cultivation. The microbial C and N contents of the forest soil were greater than those of the cultivated soils. Application of farmyard manure increased the biomass-C and -N levels in the cultivated soil but the values were still markedly lower than in the forest soil. There was an appreciable seasonal variation in biomass C and N, the values being highest in summer and lowest in the rainy season. During an annual cycle, biomass-C contents varied from 180 to 727 μg g-1 and N from 20 to 80 μg g-1 dry soil, and both were linearly related. Microbial biomass C represented 1.6%-3.6% of total soil organic C and microbial biomass N represented 1.7% 1-4.4% of soil organic N. © 1989 Springer-Verlag.
Effects of crop growth and soil treatments on microbial C, N, and P in dry tropical arable land
(Springer-Verlag, 1994) S.C. Srivastava; J.P. Lal
We studied the dynamics of microbial C, N, and P in soil cropped with rice (Oryza sativa) and lentils (Lens culinaris) in a dryland farming system. The crop biomass and grain yield were also studied. The microbial biomass and its N and P contents were larger under the lentil than under the rice crop. Microbial nutrients decreased as the crops grew and then increased again. Farmyard manure and NPK fertilizer applications increased the level of microbial nutrients, crop biomass, and grain yield by 35-80%, 55-85%, and 74-86%, respectively. However, these applications had no significant effect on most of the soil physicochemical properties in the short term. The microbial biomass was correlated with the crop biomass and grain yield. The calculated flux of N and P through the microbial biomass ranged from 30-45 and 10-19 kg ha-1 year-1, respectively. Cultivation of a cereal crop followed by a leguminous crop sustains higher levels of microbial nutrients and hence greater fertility in impoverished tropical arable soils. The soil microbial biomass appears to contribute significantly to crop productivity by releasing nutrients, and applications of manure, either alone or with fertilizers, promote this effect more strongly than the application of NPK fertilizers alone. © 1994 Springer-Verlag.
Factors regulating methyl mercury uptake in a cyanobacterium
(1995) Anjana Pant; S.C. Srivastava; S.P. Singh
The simultaneous addition of dithiothreitol (DTT), mercaptoethanol, and glutathione (30 μM each) and CH3Hg+ to Nostoc calcicola cells reduced CH3Hg+ uptake in the order GSH > DTT > mercaptoethanol. However, the preexposure of cyanobacterial cells to similar thiols resulted in different pattern of CH3Hg+ uptake in the sequence: GSH > mercaptoethanol > DTT. Light-grown cyanobacterial cells demonstrated a faster initial uptake of CH3Hg+ (rate 0.619 μmol CH3Hg+ mg-1 protein min-1, 10 min) with a biphasic pattern saturating at 30 min (bioconcentration factor = 2.7 × 103). 3-(3,4-Dichlorophenyl)-1,1′-dimethyl urea (30 μM) reduced the uptake rate by 5% with a corresponding 33% reduction in CH3Hg+ accumulation. Dark exposure (24 hr) of cells reduced the CH3Hg+ uptake rate (22.3%) accompanied by a considerable decline in the bioconcentration factor (1.4 × 103). Of the four permeabilizers used, p-chloromercuribenzoate (1 μM) proved most effective in altering the CH3Hg+ uptake kinetics while dimethyl sulfoxide (5%) and cetyl trimethylammoniun bromide (1%) lowered the bioconcentration factor to 2.2 × 103 and 1.2 × 103, respectively. After toluene exposure, however, the cells revealed no sign of CH3Hg+ uptake. The data have been discussed in light of the role(s) of thiols, photoautotrophy, and membrane integrity in regulating the cellular influx of CH3Hg+. © 1995 Academic Press, Inc.
Hydrogen production by Rhodopseudomonas at the expense of vegetable starch, sugarcane juice and whey
(1994) S.P. Singh; S.C. Srivastava; K.D. Pandey
Four local strains of Rhodopseudomonas sp. (BHU strains 1-4) evolved hydrogen at the expense of potato starch, sugarcane juice and whey (1% in each case) in the presence of light (2 klux), under anaerobic conditions (argon/CO2, 95/5, v/v). Among the three substrates, sugarcane juice supported the maximum level of H2 production, followed by potato starch and whey at the rates of 45, 30 and 25 μl H2 h-1 mg-1 bacterial cell dry weight, respectively. Although elevated temperature (45°C) suppressed H2 evolution by strains 1, 2 and 3, the thermotolerant strain (BHU strain 4) has shown encouraging results. Alginate-immobilized cells under an identical experimental regime, exhibited an almost one-and-a-half times improvement in H2 production in the cases of all the above substrates over their free cell counterpart. Preliminary experiments have shown the presence of amylase in all the bacterial strains and work is in progress to characterize this enzyme so that the system could be used for efficient consumption of starch-based agro- products. © 1994.
Influence of soil properties on microbial C, N, and P in dry tropical ecosystems
(Springer-Verlag, 1992) S.C. Srivastava
Relationships between soil physicochemical characteristics and soil microbial C, N, and P in Indian dry tropical ecosystems are discussed. The major ecosystem studies were on forest, savanna, cropped fields, and mine spoils. The highest microbial C, N, and P levels were recorded from the mixed forest and the lowest levels in 5-year-old mine spoil. Across the sites, microbial C ranged from 226 to 643 μg g-1, microbial N from 19 to 71 μg g-1, and microbial P from 9 to 28 μg g-1 soil. The proportion of soil organic C contained in the microbial biomass ranged from 2.2 to 5.0%. The microbial C: N ratio in these soils ranged from 7.4. to 13.1 and the microbial C: P ratio from 16.6 to 30.6. The concentrations of microbial C, N, and P were correlated with several soil properties and among themselves. The soil properties, in various linear combinations, explained 90-99% of the variability in the microbial nutrients. Grazing of the savanna had some effect on the level of microbial biomass, and as the mine spoil aged, the level of microbial C, N, and P also increased. © 1992 Springer-Verlag.
Isolation of non-sulphur photosynthetic bacterial strains efficient in hydrogen production at elevated temperatures
(1991) S.P. Singh; S.C. Srivastava
Four strains of non-sulphur photosynthetic bacteria were isolated from root zone associations of aquatic plants like Azolla, Salvinia and Eichhornia, as well as the deep-water rice. Based on the gross cell morphology and pigmentation, the isolates resembled Rhodopseudomonas sp. and have been designated as BHU strains 1 to 4, respectively. When subjected to elevated temperature (from 33-45°C), substantial growth/hydrogen production could be observed only in strains 1 and 4. Strains 2 and 3 on the other hand, showed diminished growth and negligible hydrogen photoproduction. The BHU strains 1 and 4 have been selected as the most active (thermostable) hydrogen producing strains of local origin as far as the Indian tropical climate is concerned. © 1991.
Methyl mercury uptake by free and immobilized cyanobacterium
(Kluwer Academic Publishers, 1992) Anjana Pant; S.C. Srivastava; S.P. Singh
Methyl mercury uptake in free cells and different immobilizates of the cyanobacterium Nostoc calcicola has been examined. The general growth of the immobilized cyanobacterial cells could be negatively correlated with methyl mercury uptake. Alginate spheres proved most efficient in terms of uptake rate (0.48 nmol mg protein-1 min-1, 10 min) and total bioaccumulation (10.71 nmol mg protein-1, 1 h) with a bioconcentration factor of 3.3×103. Alginate biofilms showed a faster methyl mercury accumulation rate (0.83 nmol mg protein-1 min-1, 10 min) with a saturation of 10.28 nmol mg protein-1 reached within only 30 min (bioconcentration factor, 3.1×103). Foam preparations with a slow initial uptake approximated biofilms but were characterized by a lower bioconcentration factor (2.8×103). Free cells, in comparison, maintained the initial slow rate of uptake (0.62 nmol mg protein-1 min-1, 10 min), saturating at 30 min (8.81 nmol mg protein-1), and the resultant lowest bioconcentration factor (2.7×103). Cell ageing (30 days) brought a drastic reduction (3-fold) in organomercury uptake by free cells while alginate spheres maintained the same potential. Foam preparations of the same age showed a significant improvement in methyl mercury uptake followed by only a marginal decline in alginate biofilms. Data are discussed in the light of the physiological efficiency and longevity of immobilized cells. © 1992 Rapid Communications of Oxford Ltd.
Microbial biomass acts as a source of plant nutrients in dry tropical forest and savanna
(1989) J.S. Singh; A.S. Raghubanshi; R.S. Singh; S.C. Srivastava
MORE than half of all tropical soils are highly weathered, leached and impoverished, requiring the ecosystem to develop nutrient-conserving mechanisms1,2. Nutrient retention and withdrawal mechanisms are most effective in nutrient-poor systems3,4. Thus, although dry tropical forests and savanna have the potential capacity to grow at high rates5,6, this capacity is strictly limited by climate and nutrients. Our studies on these nutrient-poor ecosystems show that a reciprocal relationship exists between microbial biomass and plant growth rate. This suggests that microbial immobilization may be a main source of nutrients for the plants and may lead to nutrient conservation. © 1989 Nature Publishing Group.
Microbial C, N and P in dry tropical forest soils: Effects of alternate land-uses and nutrient flux
(1991) S.C. Srivastava; J.S. Singh
The effects of alternate land-uses (savanna, cropfield and mine spoil) on microbial C, N and P in dry tropical forest soil of India were studied. The mean microbial C, N and P, respectively, in the four major systems ranged from 250 to 609 μg C g-1, 27 to 65 μg N g-1 and 12 to 26 μg P g-1. The microbial biomass in these systems was characterized by a mean C:N:P ratio of 23:2:1. The microbial C, N and P were positively related to root biomass and total plant biomass (aboveground + root biomass). The derived ecosystems (savanna, cropland and mine spoil) have changed from the original forest ecosystems in terms of soil features and microbial biomass. The conversion of forest into other land-uses resulted in remarkable decline in the amounts of soil nutrients and microbial C, N and P. The microbial nutrients in this dry tropical environment are sensitive to land-use changes. The calculated flux of N and P through the microbial biomass ranged from 27 to 64 kg N ha-1 yr-1 and 13 to 26 kg P ha-1 yr-1. Thus, in this dry tropical environment the microbial biomass appears to contribute substantially to the N and P requirements of higher plants. © 1991.
Microbial C, N and P in dry tropical savanna: effects of burning and grazing
(1991) R.S. Singh; S.C. Srivastava; A.S. Raghubanshi; J.S. Singh; S.P. Singh
In dry tropical Indian savanna of the Vindhyan Plateau, Uttar Pradesh, the maximum amounts of available nutrients and microbial biomass occurred in the dry period and minimum in the wet period. Burning and grazing increased inorganic N by 54% and 15-49%, respectively and also increased bicarbonate-extractable inorganic P by 35% and 27-32%, respectively. Mean annual microbial C varied from 361-466 μg g-1, microbial N from 35-44 μg g-1 and microbial P from 16-23 μg g-1 dry soil. Mean annual microbial C, N and P were positively related to each other. Burning increased microbial C by 18%, microbial N by 26% and microbial P by 35%, and grazing increased microbial C by 15-18%, microbial N by 14-23% and microbial P by 19-29% -from Authors
Microbial c, n and p in dry tropical soils: Seasonal changes and influence of soil moisture
(1992) S.C. Srivastava
[No abstract available]
Nickel uptake and its localization in a cyanobacterium
(1992) A.L. Singh; R.K. Asthana; S.C. Srivastava; S.P. Singh
Nickel bioconcentration in different cell preparations of the cyanobacterium Nostoc muscorum was examined. A two- or three-fold increase in phosphate concentration over that prescribed in growth medium (58 μM), favoured nickel accumulation restricted to a threshold limit. Intact cells showed highest nickel bioconcentration (8.41 μmol mg-1 dry wt) over spheroplasts (6.19 μmol mg-1 dry wt) or polyphosphate bodies (5.88 μmol mg-1 dry wt). Such preparations derived from similar cells indicate that the cyanobacterial cell wall could accommodate around 14-19% of the total nickel taken in by the cell with the overall nickel-bioconcentration sequence as: intact cells > spheroplasts > polyphosphate bodies > cell wall. The data suggest that polyphosphate bodies are the main sink for nickel. © 1992.
Nutrient release in leaf litter
(1990) A.S. Raghubanshi; S.C. Srivastava; R.S. Singh; J.S. Singh
[No abstract available]
Photoproduction of hydrogen by a non-sulphur bacterium isolated from root zones of water fern Azolla pinnata
(1990) S.P. Singh; S.C. Srivastava; K.D. Pandey
A photosynthetic bacterium Rhodopseudomonas sp. BHU strain 1 was isolated from the root zone of water fern Azolla pinnata. The bacterium was found to produce hydrogen with potato starch under phototrophic conditions. The immobilized bacterial cells showed sustained hydrogen production with a more than 4-fold difference over free cell suspensions. The data have been discussed in the light of possible utilization of relatively cheaper raw materials by non-sulphur bacteria to evolve hydrogen. © 1990.