1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Assessment of soil temperature and soil parameters on the population and functional efficiency of pseudomonas fluorescens in the rhizosphere of pokkali rice (Oryza sative L.)(Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2018) Reshma Francis; Surendra Gopal, KPokkali is a umque variety of rice that is cultivated organically in coastal wetlands of Kerala. Pokkali fields are situated close to the sea and therefore prone to flooding and salinity. Pokkali rice has enormous potential for tolerating most of the abiotic stresses. It is the only economic crop which can be grown in waterlogged environment while tolerating salinity. The present study on “Assessment of soil temperature and soil parameters on the population and functional efficiency of Pseudomonas fluorescens in the rhizosphere of Pokkali rice (Oryza sativa L.)”, was conducted in Rice Research Station, Vyttila, under Kerala Agricultural University during 2016 to 2018. Two plots (40 m2) were used for the study. One of the plots was maintained as control (without application of Pseudomonas fluorescens) and another plot with rice was treated with P. fluorescens. P. fluorescens (KAU) was applied as seed treatment (10g kg-1) just before sowing and soil application (2.5 kg ha-1) at 1 week after dismantling. The main objectives were to study the effect of soil temperature and soil parameters on the population and functional efficiency of P. fluorescens / fluorescent Pseudomonas in Pokkali rice. The rhizosphere soils of Pokkali rice were collected at monthly interval from June, 2017 to October, 2017. The population of fluorescent Pseudomonas sp. in the rhizosphere soils of Pokkali rice were recorded at monthly interval. The population was absent before the start of the experiment in treated plot. However, the highest population 3.3x102 cfu g-l) was recorded at 90 DAS (August, 2017). However, the lowest population was recorded at 60 DAS (July, 2017). The population was not found at 30 DAS (June, 2017), 120 DAS (September, 2017) and 150 DAS (October, 2017). In the case of control plot, population of fluorescent Pseudomonas was absent before the start of experiment. At 30 DAS (June, 2017) population of fluorescent Pseudomonas was 3.3 x 102 cfu g-1. However, no fluorescent Pseudomonas were found at 60 DAS (July, 2017), 90 DAS (August, 2017), 120 DAS (September, 2017) and 150 DAS (October, 2017). Out of the six isolates (VPJU, VPJL, VPAU1, VPAU2, VPAU3 and VPAU4) of fluorescent Pseudomonas obtained, all the isolates produced IAA and ammonia with varied intensity. Three isolates (VPAU1, VPAU3 and VPAU4) produced HCN and none of the isolates showed siderophore production. The correlation studies between soil temperature, soil pH, EC and C02 evolution with population, revealed that the population of fluorescent Pseudomonas was affected by soil pH and soil EC. However, soil temperature and C02 evolution did not affect the population of fluorescent Pseudomonas. The functional efficiency of the fluorescent Pseudomonas were correlated with soil temperature, soil pH, EC and C02 evolution It was found that soil temperature, soil pH, EC and C02 evolution did not affect the functional efficiency of fluorescent Pseudomonas. All the six isolates obtained m the study were identified and confirmed through 168 rDNA sequencing. The isolates VPAJU, VPAU1 and VPAU2 were identified as Pseudomonas sp. and VPAJL, VPAU3 and VPAU4 isolates were found to be Pseudomonas aeruginosa. The present studies indicated that the inoculated P.fluorescens did not survive in Pokkali fields. The population of fluorescent Pseudomonas showed negative correlation with soil pH and EC. However, soil temperature and C02 evolution did not had any effect on population. The functional efficiency of fluorescent Pseudomonas was not affected by soil temperature, soil pH, EC and C02 evolution. However, further studies on influence of soil edaphic factors and weather variables on host plant and P. fluorescens needs to be studied and develop a suitable PGPR for Pokkali rice.Item Organic nutrient management of papaya (Carica papaya L.)(Department of Pomology and Floriculture, College of Agriculture, Vellayani, 2018) Divya Hari; Bindu, BItem Population dynamics and management of nematodes in banana using non chemical methods(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2017) Nimisha, A M; Nisha, M SItem Metagenomic analysis of bacterial diversity in the rhizosphere of arecanut palms affected by yellowing in Wayanad(Department of Agricultural Microbiology, College of Horticulture, Vellanikkara, 2017) mahesh Mohan; Girija, DItem Phytoremediation of inorganic contaminants in vellayani wetland ecosystem(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2017) Meera, A V; Manorama Thampatti, K CAn investigation entitled ―Phytoremediation of inorganic contaminants in Vellayani wetland ecosystem‖ was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, during 2013-16. The objective of the study was to track the potential sources of contaminants threatening the Vellayani wetland ecosystem and suggest a viable phytoremediation technology. The experiment comprised of four parts. The first part involved a peripatetic survey in the catchment of Vellayani lake along the rivulets that contribute water to Palappoor, Pallichalthodu, Reservoir bund, Arattukadavu RB, Valiyavilagam, Mannamvarambu and Manamukku sites. Three rivulets per site were identified, and geocoded water and sediment samples were drawn from five sampling points under each rivulet during pre and post monsoon seasons of 2014-15. Among the physical properties of water colour, turbidity and suspended solids were above the maximum permissible limit (MPL). Chemical properties viz., pH, EC, NO3-N, NH4-N, P, Fe, Al, Pb, Cd and BOD of water showed significant difference among the sites during both the seasons but COD was significant only for post monsoon. P content and BOD exceeded the MPL and Al the desirable limit. Coliforms were detected at all sites during both seasons and were above the MPL. Texture of the sediment varied from sandy clay to sandy clay loam. EC, OC, NO3-N, NH4-N and P contents of sediment showed a decreasing trend during the post monsoon season. Arattukadavu RB was the most contaminated site followed by Palppoor and Manamukku the least contaminated site preceeded by Mannamvarambu and Valiyavilagam with respect to water and sediment quality. No pesticide residue was detected in water and sediment. The highest plant density was noticed for Cynadon dactylon L. In the second part, potential sources of contaminants were identified as automobile workshops/servicing centres, domestic wastes from hotels/houses and sewage. Out of the 29 species of dominant macrophytes, highest biomass was recorded by Limnocharis flava L. (Buch.). In shoot, the highest concentration for Fe was recorded by M. vaginalis, Panicum repens L. for Aland S. trilobata for Pb and Cd. In root, the highestconcentration for Fe, Al, Pb and Cd was showed by Eichhornea crassipes Mart., Monochoria vaginalis (Burm.f.), Colacasia esculenta L. and Sphagneticola trilobata L. respectively. Sediment from Arattukadavu recorded the highest contents for Fe, Al, Pb and Cd and count for bacteria, fungi and actinomycetes. It was observed from the study that concentration of Fe, Al, Pb and Cd decreased with the distance from the source of contamination. Higher quantities of Fe was extracted by E.crassipes and M.vaginalis; Al by M. vaginalis and L. flava and Pb and Cd by L.flava and E.crassipes from the wetland ecosystem. In the third part, four pot culture experiments were carried out with graded doses of Fe (1000, 2000 and 3000 mg kg-1), Al (750, 1000 and 1250 mg kg-1)and Pb and Cd (50, 75 and 100 mg kg-1) to determine the hyperaccumulation ability of selected macrophytes based on a screening trial. The macrophytes were grown in sediment and water collected from the Vellayani wetland ecosystem for a period of 45 days. From the study it was observed that E. crassipes was the best hyperaccumulator for Fe, M. vaginalis for Al and L. flava for both Pb and Cd and can be identified as the best phytoextractors for the same. Root was the major retention site for all the metals. Among the rhizosphere microbes, fungi maintained a positive relation with levels of of Fe, Al, Pb and Cd and a negative relation by bacteria and actinomycetes. In the fourth part, the macrophytes showing highest hyperaccumulation ability for each metal (based on part III) were raised in pots containing the respective metals (2000 mg Fe kg-1, 1000 mg Al kg-1 and 75 mg Pb /Cd kg-1) for 60 days. The plants were harvested and the biomass was put to different disposal methods viz., composting, vermicomposting, ashing and production of biochar and was used for the pot culture experiments with amaranthus. The treatment effects were significant for biomass production and metal extraction. Among the four disposal methods, vermicomposting had resulted the highest biomass production for all except Pb. Regarding the metal extraction by amaranthus, application of ash (T4) showed the highest removal and the least by the biochar (T5). The metal retention in soil was highest for biochar and least for ash. Loss of metals from the processed materials was also lowest for biochar. Thus the best disposal technique of phytoextractors /hyperaccumulators is conversion to biochar. The viable phytoremediation technology is to raise suitable phytoextractors / hyperaccumulators in the contaminated area and dispose them through biochar production.