Soils and Rice-Fields

DOI: 10.1007/0-306-46855-7_8 In book: The Ecology of Cyanobacteria, pp.233-255


Cyanobacteria are an important component of many soils. including the surface crusts that sometimes cover extensive areas in semiarid regions and mine spoil wastes. They are also abundant in many areas which are wet or submerged for part of the year. especially rice-fields. Most soils forms have sheaths or mucilage and this polysaccharide has important effects onthe soil. mostly beneficial. such as improved soil structure. but sometimes adverse where a dense surface layer impedes drainage. Nitrogen-fixing species often constitute half or more of the species present in soils not enriched with nitrogenous fertilizer and these can contribute combined nitrogen in several ways to adjacent vascular plants.
Attempts to enhance crop yield by adding cyanobacteria to soils have mostly focussed on paddy rice. Although many studies have reported positive effects of such ‘algalization’. the number of locations where it has been adopted as routine practice appear to be few. in contrast to the relatively widespread use of Azolla with rice culture. Algalization is most successful where local species are used to prepare the inoculum. but there is considerable scope for other improvements. It is important to obtain a much more detailed understanding of cyanobacterial population dynamics over the whole annual cycle in agricultural systems where rice is grown for only part of the year.

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    • "The agricultural importance of cyanobacteria is mainly related with their ability to fix atmospheric nitrogen and supply it to the plants [5] [6] [7] [8] [9]. Cyanobacteria are also known to produce variety of extracellular substances such as plant growth regulators [10] [11] [12] [13] [14] [15], amino acids [16] [17], vitamins [18], polysaccharides [19], and antimicrobial products [20] [21] [22] which have direct or indirect impact on plant growth and subsequent yield. The work described here addresses the role of cyanobacteria in promoting plant growth by the isolation of auxin producing indigenous strains of cyanobacteria from different crop fields and evaluation of their ability for producing accumulation of auxin and potential to release auxin in isolated cultures and under symbiotic conditions. "
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    ABSTRACT: Four non-heterocystous cyanobacterial strains isolated from rhizosphere and soil surface mat of rice, wheat, and maize were identified by 16S rRNA gene sequencing and evaluated for auxin production as well as growth promotion of wheat. Isolated strains produced a diverse amount of auxin in BG11 media supplemented with different concentrations of L-tryptophan. The amount of auxin detected with colorimetric methods was higher as compared to GC-MS analysis. Auxin production by cyanobacterial strains in BG 11 medium supplemented with 250 µg ml(-1) L-tryptophan ranged from 0.20 to 1.63 µg ml(-1) IAA as revealed by gas chromatography and mass spectrometric (GC-MS) analysis. In a hydroponic growth system, the vegetative growth of wheat was stimulated appreciably by inoculation with cyanobacterial strains. The endogenous auxin content of wheat was significantly correlated with the exogenous auxin production of the cyanobacterial strains. It was observed that cyanobacterial strains produced more endogenous and exogenous auxin in the presence of a plant, showing that plants might be releasing some signals responsible for higher auxin production by cyanobacterial cultures. It was concluded that the auxin producing potential of cyanobacterial strains can be exploited for the promotion of wheat growth.
    Full-text · Article · Dec 2013 · Journal of Basic Microbiology
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    • "or the enrichment of soil via inoculation of selected cyanobacterial strains led to the promotion of these biofertilizers among the farming community of South East Asia (Kaushik, 1998; Roger and Kulasooriya 1980; Venkataraman, 1972). In paddy fields, their relative occurrence varies within large limits, ranging from 0 to 85%; and limited systematic analyses on their distribution has been undertaken in relation to major environmental factors (Kaushik, 1998; Roger et al., 1993; Singh and Bisoyi, 1989; Venkataraman, 1972; Whitton, 2000). Analyses of the abundance and genera-wise diversity of cyanobacteria isolated from the rice-based cropping systems of North and Eastern India revealed the dominance of heterocystous forms, with Nostoc and Anabaena comprising 40–90% of isolates (Nayak and Prasanna, 2007; Prasanna and Nayak, 2007; Prasanna et al., 2009a). "
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    ABSTRACT: Cyanobacteria represent promising organic inputs in rice–wheat cropping system, as they contribute towards accretion of N and C, besides secreting growth-promoting substances which influence plant productivity and soil fertility. The present study focused towards using a combinatorial approach for evaluating field-level colonization of cyanobacteria in soil and their effect on soil microbiological and plant parameters, employing agronomic and molecular tools. A consortium of cyanobacterial strains (BF1, Anabaena sp., BF2, Nostoc sp., BF3, Nostoc sp. and BF4, Anabaena sp.) was employed in different three-and four-member combinations along with 75% N + Full dose of P and K fertilizers. A significant enhancement in microbial activity and plant growth/yields and savings of 25% N in the wheat–rice cropping sequence were recorded, especially in treatments involving 75% N + Full dose of PK+BF1+BF2+BF4 and T5, i.e. 75% N + Full dose of PK+BF1+BF2+BF3. Such treatments were significantly higher or statistically at par with fertilizer controls – 75% N + Full dose of PK fertilizers. The use of DNA-based markers further helped to establish the colonization of the inoculated cyanobacteria, especially BF2 and BF3 strains. Our study clearly illustrated the establishment of inoculated cyanobacterial strains and their role in enhancing the crop productivity and soil health of the rice–wheat cropping system.
    Full-text · Article · Jul 2013 · Experimental Agriculture
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    ABSTRACT: Abiotic factors as temperature affect cyanobacterial growth in rice crop fields. The aim of our study was to evaluate cyanobacteria during rice crop development in two crop areas with different water temperature. We worked in a rice crop flooded with subterraneous water. We sampled two sites that differed in the distance from the entrance of water to the field. Total cyanobacterial counts were similar in both sites three days after flooding (tillering) but differed in booting and physiological maturity. Cyanobacteria genera found during rice crop were: Chroococcus, Aphanocapsa and Gloeocapsa (unicellular) Oscillatoria, Lyngbya and Arthrospira (non-heterocystous filamentous) Anabaena, Nostoc, Cylindrospermum and Gloeotrichia (heterocystous filamentous). The heterocystous filamentous cyanobacteria were less than 45% and about 25% in most of the cases. Unicellular cyanobacteria were in a greater proportion in the site with a higher temperature, and non-heterocystous filamentous cyanobacteria were lower and less than 2% during crop cycle. Simpsons diversity indexes were greater in the site with the higher water temperature in each sampling moment. Dominant genera were the unicellular Chroococcus and Gloeocapsa in five of the six sampling moments. In both sampling sites, Chroococcus was always reported during the crop, Gloeocapsa and Nostoc were detected in booting and physiological maturity and Cylindrospermum and Gloeotrichia were only reported in physiological maturity.
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