1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Microbial remineralization of the dissolved organic carbon(DOC)derived from the benthic producers of Gulf of Mannar(GoM) reef ecosystem
    (Academy of Climate Change Education and Research, Vellanikkara, 2020-07-01) Alen Mariyam Thomas; Manikandan, B
    Coral reefs are one of the most productive ecosystems with primary production rates compared to the tropical rain forest. Carbon dioxide is fixed as organic matter through photosynthesis and contributes to the temporary or permanent storage of carbon in the ocean. This is achieved by the sedimentation of particulate organic matter (POM) and transport of dissolved organic matter (DOM) to deeper environments through the movement of water masses. Almost, 10-15% of the gross organic production by reef benthic producers is released into the external environment and act as a main source of DOC in the reef environment. DOC represents one of the largest reservoirs of CO2 in the ocean equivalent to the atmospheric CO2 and acts as a source of carbon and energy for many organisms that depend on organic carbon for nutritional sources. DOC released by macroalgae enters into the food web through the microbial loop and plays a vital role in trophic energy transfer, however, not all DOC enters the microbial loop where some amount remains resistant to microbial action representing the recalcitrant DOC. Our results show that the organic matter released by different macroalgae accelerated the growth of bacterioplankton, and differed in their effect on bacterial community composition. All the macroalgae studied in this experiment released a significant amount of DOC into the reef with T. ornata the maximum DOC and H. tuna the least DOC with 72.1 μM C/g/h (dry weight) and 1.9 μM C/g/h (dry weight) respectively. The amount of DOC released by different macroalgae remained recalcitrant to microbial action by the 100th day ranged from 9.2% to 32.2% among different macroalgae. Green macroalgae possessed a weak shift in bacterial community composition whereas the brown macroalgae altered the bacterial community composition. The brown macroalgae contributed to a slight decrease in the dominant bacterial groups thereby enhancing the dormant bacterial groups. However, in this study, the existing bacterial population was able to utilize maximum DOC resulting in a weak shift in the bacterial composition among the green macroalgae giving no chance for the dormant bacterial communities. The type of macroalgae and the composition of DOC they produce are considered critical in determining the effect of DOC on the bacterial community. These comprehensive data provide an important basis for understanding the influence of DOC over coral-associated bacterial communities and the dynamics of carbon cycling in algal dominated reefs.
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    Nutrient management in coconut based cropping system utilizing products from rapid conversion technology of biowastes
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2019) Priya, U K; Sudharmai Devi, C R
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    Organic nano NPK fomulations for enhanching soil health and productivity
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2019) Nibin, P M; Ushakumari, K
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    Fertility investigations on the soils of South Kerala in relation to their physiographic positions
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1986) Wilfred Godwin, G; Alice Abraham
    A study of the soils of South Kerala has been undertaken to investigate the variation in fertility status in relation to their physiographic position. Twelve locations from the districts of Trivandrum and Quilon were selected and from each location soil samples from upper, middle and lower reaches were collected from depths of 0 to 20 cm and 20 to 40 cm. The elevation of the location varied from 20 to 150 meters and the degree of slope from 6 to 27. The lower reaches of all the location were or less level paddy fields. The middle reaches were cultivated to banana, pepper, coconut and tapioca and the upper reaches in addition to the above crop perennials like coconut and rubber.
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    Functional diversity of an evergreen forest ecosystem of Vazhachal forest division, Kerala
    (Department of Forest Management and Utilisation, College of Forestry, Vellanikkara, 2016) Deepakkumar, R; Gopakumar, S
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    Morphological and Physico-chemical properties of the kayal soils of Kuttanad, Kerala State
    (Division of Agricultural Chemistry, College of Agriculture, Vellayani, 1975) Gangadhara Menon, P K; Aiyer, R S
    A study made on the morphological and physico-chemical characteristics of the kayal profiles of the Kuttanad region of Kerala revealed the following salient features. (1) These soils are classified under the order- ENTISOL, Sub order- Aquent and great group- Hydraquent according to the seventh Approximation. (2) Texturally they are classified mostly as silty loan or sandyclay loan, fine sand being the dominating fraction in all the profiles and layers. Only the surface soil of the Chithira kayal profile is clayey in texture with a maximum of 36.5 per cent clay. (3) The physical characteristics of the two profiles from the Rani kayal vary widely. While the profile 1 shows a decrease in clay content with increase in depth, the second profile shows a reverse trend for clay as well as fine sand. Fine sand is maximum in the middle layer of profile 1.
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    Micronutrient management for okra [Abelmoschus esculentus (L.) Moench ] under diffrent irrigation methods
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2019) Arya, P; Anitha, S
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    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, K
    Pokkali 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.
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    Effect of agrochemicals on biological activity in lateritic soil
    (Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2018) Nisha Paul; Durga Devi, K M
    In modern agriculture, agrochemicals are frequently used to boost crop production. The use of pesticides is indispensable in various crops and cropping systems, particularly under tropical climatic condition. However erratic application of these chemicals may affect soil health, which in turn change the population and composition of soil microflora and soil fertility. The land use type also play a significant role in controlling the microbial community. Hence, the present study was undertaken at College of Horticulture, Vellanikkara during 2017-2018 so as to determine the impact of three agrochemicals viz. oxyfluorfen, copper oxychloride and chlorpyriphos on the population of soil microflora and dehydrogenase enzyme activity in lateritic soil collected from two land use types. Representative soil samples were collected from two land use types viz., land under cultivated grass, Agronomy farm, College of Horticulture, Vellanikkara (LUT 1) and cocoa plantation, Cocoa Research Center, KAU, Vellanikkara (LUT 2) during August, 2017. The soil samples were analyzed to assess physical, chemical and biological characteristics before starting experiment and the data revealed that soil collected from LUT 2 was more conducive for microbial growth and dehydrogenase activity. Pot culture experiment with cowpea (variety: Bhagyalakshmi) was conducted during March to June, 2018 with fourteen treatments (3 agrochemicals at 2 different doses under each land use types + 2 controls, one each for two land use types) and three replications. Agrochemicals viz., oxyflourfen (OXY) at 0.15 and 0.30 kg ha-1 (herbicide), copper oxychloride (COC) at 0.75 and 1.50 kg ha-1 (fungicide) and chlorpyriphos (CHL) at 0.30 and 0.60 kg ha-1 (insecticide) were selected for the study. Soil samples were analyzed at four intervals viz., 7, 30, 60 and 90 days after agrochemical spraying (DAS) to evaluate the effect of agrochemicals on chemical and biological characteristics of soil. The chemical characteristics of soil viz., pH, electrical conductivity, organic carbon, available N, P, K, Ca, Mg, S and micro nutrients like Fe, Mn, Cu, and Zn followed a decreasing trend towards the harvest in all the treatments under both the land use types. The effect of agrochemical application on chemical characteristics and nutrient availability of the soil was at lower magnitude compared to their influence on biological activity of the soil. The biological characteristics of soil viz. dehydrogenase activity and microbial population (fungi, bacteria and actinomycetes) were higher in soil samples collected from LUT 2 (cocoa plantation) at all the sampling intervals. Soil samples from both the land use types registered reduction in biological activity due to agrochemical application, which was higher at 7 DAS than the other sampling intervals. The extent of reduction in biological activity after application of agrochemicals was comparatively higher in LUT 1 (land under cultivated grass). Higher doses of the pesticides showed greater decline compared to their lower doses. Biological activity increased from 7 to 60 DAS and the extent of reduction with respect to control also became lower. At 90 DAS, a declining trend in the dehydrogenase activity and microbial population (except fungi) was noticed. The adverse effect of agrochemicals on dehydrogenase activity and bacterial population at 7 DAS followed the order: CHL > COC > OXY and OXY > CHL > COC respectively. However at 90 DAS, oxyflourfen exerted minimum adverse effect on soil bacteria. The study revealed that dehydrogenase activity is highly correlated with the population of soil microflora, especially soil bacteria. The adverse effect of agrochemicals on fungal population can be ranked as: COC > OXY > CHL at both 7 and 90 DAS. The percentage inhibition of actinomycetes population at 7 as well as 90 days after agrochemical application was in the order: OXY > COC > CHL. Cowpea yield was not affected by the agrochemical application and land use types. However higher doses of all the agrochemicals under study reduced the number of root nodules in cowpea.
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    Rhizosphere priming effects of conventional and non conventional organic manures on c and n dynamics
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2018) Geethu Jacob; Sudharmai Devi, C R