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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 4 (1987), S. 15-19 
    ISSN: 1432-0789
    Keywords: Nitrogen fixation ; N-balance studies ; Azolla ; Blue-green algae ; Chemical N fertilization ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A nitrogen balance study conducted in ceramic pots under net house conditions for four seasons showed that flooded rice soil leaves a positive nitrogen balance (N increase) in soil after rice cropping in both fertilized and unfertilized soil. Recovery of nitrogen from rice soil was more than its input in unfertilized soil, but it was reverse in fertilized soil. Incorporation of Azolla or BGA twice as basal and 20 days after transplanting (DAT) alone or in combination showed higher nitrogen balance and N2-fixation (N gain) in soil than in that where it was applied once either as basal or 20 DAT. Planted soil showed more N2-fixation than that of fallow rice, and flooded soil fixed more nitrogen in comparison to non-flooded soil in light but less in dark. Soil exposed to light fixed more nitrogen than that of unexposed soil in both flooded and non-flooded conditions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: Available N and P ; Azolla ; Blue-green algae ; Mineralization ; Organic manures ; Rice soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pot incubation study with fresh Azolla (Azolla pinnata-India and Vietnam isolates,A. mexicana andA. filiculoides), blue-green algaAulosira sp., green manureSesbania cannabina, Azolla compost, farm yard manure and ammonium sulphate was conducted under flooded condition at CRRI, Cuttack keeping an equivalent amount of 25 ppm N through all the amendments where changes in availability of N and P, C∶N ratio and pH were recorded. Application of chemical N-fertilizer recorded a release of about 87% NH4 +−N at 10th day of flooding which gradually decreased and reached the minimum of 6% at 50 days. The C∶N ratio of the organic manures ranged between 9–10 favouring release of NH4 +−N and among theAzolla speciesA. pinnata isolates released NH4 +−N more efficiently thanA. filiculoides andA. mexicana. A. pinnata Indian isolate released maximum of 88% NH4 +−N, whereas Vietnam isolate recorded 77% at 40 days of flooding; green manure on the other hand, reached a maximum of 50% release at 50 days. The blue-green alga recorded a gradual increase and attained the maximum release of 38% at 40 days of flooding. Farmyard manure recorded a highest NH4 +−N release of 69% at 20 days of flooding and gradual decrease thereafter, whereas Azolla compost released 41% at 40 days of flooding. Soil amended with fresh organic matter achieved reduction upto a pH of 7.2 after 50 days of flooding, whereas the pH in Azolla compost and farmyard manure amendment was 〈7. The P availability increased from 20th day onwards and reached the highest values of 26 and 18 ppm in the fresh organic matter and compost amended soil respectively after 40–50 days of flooding. The cumulative release of available P was found superior in fresh Azolla incorporation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5117
    Keywords: Azolla ; symbiont ; Anabaena azollae ; heterocyst ; acetylene reducing activity ; phosphorus ; fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seven species ofAzolla (A. caroliniana, A. microphylla, A. nilotica, A. filiculoides, A. mexicana, A. rubra, A. pinnata the last from both Malaysia and India) grown in pots of flooded soil were subjected to three different treatments with respect to P: none, single application, split application. The experiments were carried out under greenhouse conditions. Heterocyst frequency inAnabaena azollae and acetylene reducing activity (ARA) were studied in successiveAzolla leaves. Both variables increased from the first leaf (shoot apex) to the last one (before branch) in all species in the presence or absence of P. However, heterocyst frequency, ARA andAzolla biomass were all less in the treatment lacking P. Heterocyst frequency inA. azollae, ARA and biomass ofAzolla were higher when P was applied in split doses than in the other treatments.Azolla plants exhibited more ARA than the isolated leaves.
    Type of Medium: Electronic Resource
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