1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Evaluation of drought and acid tolerant actinomycetes for rice (Oryza sativa L.)(Department of Agricultural Microbiology, College of Agriculture, Vellanikkara, 2022) Gokul Vigneshwaran, P; Surendra Gopal, KRice (Oryza sativa L). is one of the world's most significant cereal crops. It is widely cultivated food crop in the world, providing staple food to 2.7 billion people. Rice cultivation is facing many challenges due to abiotic stresses like drought, acidity, flood and high temperature. Among the major yield-limiting biotic factors, disease management is one of the most important problems in paddy cultivation. Among the several diseases in rice, sheath blight (Rhizoctonia solani) is a fungal disease that has a high impact on the rice crop from tillering to the heading stage. Rhizospheric microbes, particularly actinomycetes have gained attention due to their ability to promote plant growth, control diseases and reduce harm to the environment. The use of actinomycetes as bio-control agents is sustainable and complementary in improving crop yield and protection that is affordable to farmers. Actinomycetes have been used to mitigate drought and acidic stress. Hence, the present study was carried out on “Evaluation of drought and acid-tolerant actinomycetes for rice (Oryza sativa L).” with the objective of plant growth-promotion and Rhizoctonia solani management under pot culture studies. Ten rhizospheric soil samples were collected from drought and acidic rice-growing areas of the Thrissur and Palakkad districts. All the actinomycetes isolates were subjected to morphological, cultural, and biochemical characterization. The actinomycetes isolates showed gram-positive reaction and varied in spore chain morphology viz., filamentous, spiral and closed spiral. In vitro screening of actinomycetes isolates for plant growth-promoting traits showed that all the actinomycetes isolates were positive for indole acetic acid production. Out of ten isolates, seven isolates were positive for the production of IAA and two isolates viz., MNT7 and CHT-1 were high indole acetic acid producers. IAA production by actinomycetes isolates ranged from 4.41 (μg/ml) to 5.99 (μg/ml). The MNT-7 (Streptomyces spinoverrucosus) isolate showed the highest IAA production (5.99 μg/ml) followed by CHT1 (5.43 μg/ml) and PTK-4 (Streptomyces spp.) (5.23 μg/ml). All the isolates fixed atmospheric nitrogen which ranged from 2.80 μg/ml to 10.50 μg/ml. The MNT-7 (Streptomyces spinoverrucosus (10.50 μg/ml), VLK-2 (9.10 μg/ml) and VER-4 (Streptomyces cellulosae) (7.70 μg/ml) isolates were the most efficient nitrogen-fixing isolates. The amount of phosphate solubilization varied between 3.28 μg/ml to 57.56 μg/ml. nine isolates showed potassium solubilization in the range of 1.86 μg/ml to 5.07 μg/ml. 134 In vitro screening of actinomycetes for antagonistic properties did not show ammonia and siderophore production. Among the ten actinomycetes isolates, MNT-7 (Streptomyces spinoverrucosus) and PTK-4 (Streptomyces spp.) isolates produced hydrogen cyanide. Only MNT-7 (Streptomyces spinoverrucosus) (71.23%) and PTK-4 (Streptomyces spp) (68.82%) isolates inhibited the growth of Rhizoctonia solani indicating their biocontrol potential. In vitro screening of actinomycetes for acidic pH and water stress tolerance showed that MNT-7 (Streptomyces spinoverrucosus) isolate was tolerant to acidic pH upto pH 3.5 and MNT-7 (Streptomyces spinoverrucosus) and PTK-4 (Streptomyces spp.)isolates were water stress tolerant upto 20 % PEG. The three most promising (MNT-7, PTK-4 and VER-4) actinomycetes were identified as Streptomyces spinoverrucosus, Streptomyces spp., Streptomyces cellulosae respectively. On the basis of the plant growth-promoting activities, acidic pH and water stress tolerance, native actinomycetes isolates of Streptomyces spinoverrucosus (MNT-7), Streptomyces spp. (PTK-4) and Streptomyces cellulosae (VER-4) evaluated under pot culture. MNT-7 (Streptomyces spinoverrucosus) significantly increased all the growth parameters and yield also recorded the minimum sheath blight percent disease incidence of 6.79 under pot culture studies. The present study revealed that Streptomyces spinoverrucosus (MNT-7) was the most promising PGPR for plant growth promotion and sheath blight disease management. To, the best of knowledge, Streptomyces spinoverrucosus is the first report of PGPR tolerant to drought and acidic pH. However, further evaluation field is needed to confirm the findings.Item Herbicide mixtures for weed management in direct seeded puddled rice (Oryza sativa L.)(Department of Agronomy,College of Agriculture, Vellayani, 2016) Sheeja K Raj; Elizabeth K SyriacItem Enzyme characterization of the acid sulphate soils of Kuttanad(Department of Soil Science and Agricultural Chemistry, college of Agriculture, Vellayani, 2016) Arya Nath, V; Aparna, BRegarding the enzyme status of the acid sulphate soils, the activity of urease was the highest in Thakazhi (L4-75.78 ppm of urea hydrolyzed g-1 soil h-1) in the surface layer. Acid and alkaline phosphatase activities were found to be the highest in Purakkad (L3-57.58 μg pnp released g-1 soil h-1) and Thakazhi series (L4-46.41 μg pnp released g-1 soil h-1) respectively in the surface layers. The highest activity of dehydrogenase was noticed in Thuravur series (L6-115.74 μg of TPF released g-1 soil 24 h-1) in the surface and Kallara series in the subsurface layers (L2-55.39 μg of TPF released g-1 soil 24 h-1). Karappadam and Kayal recorded the values of 145.73 and 114.80 μg of TPF released g-1 soil 24 h-1 for dehydrogenase activity respectively at surface layers. With regard to the microbial population, Thottappalli (L5) recorded the highest total bacterial count and fungal population in both surface and subsurface layers. Thiobacillus spp. recorded the highest population of 9.08 log cfu g-1 of soil at Kallara series (L2) while P solubilizers recorded the highest count at Ambalapuzha series (L1). Thuravur series recorded the highest actinomycetes population in subsurface soils. Micahelis – Menten constant, Km and the maximum velocity Vmax for different enzymes were determined and it was observed that for dehydrogenase Vmax value was found to be the highest in 6th week and for phosphatase only after 12th week of incubation. Thematic maps were prepared based on themes like microflora and enzyme status using GIS (ARC VIEW). Hence the study conclude that, with respect to biological fertility status of the study area, Purakkad recorded the highest enzyme activity number (23.69) at 0-15 cm, while Kallara series recorded the highest enzyme activity number in the subsurface layer and are observed to be biologically sustainable.Item 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, SItem Soil carbon dynamics in a rice based cropping system(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2019) Chethankumar, P; Meera, A VItem Characterization and evaluation of on-farm liquid organic manures on soil health and crop nutrition(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2017) Sreya U Parvathi; Ushakumari, KItem 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 MIn 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.Item 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 RItem Productivity and soil health of rice based cropping systems under organic management(Department of Agronomy, College of Horticulture, Vellanikkara, 2018) Rajanand Hiremath; Usha, K EItem Quality assessment of organic manures and their effect on okra(Department of Agronomy, College of Horticulture, Vellanikkara, 2018) Santhiya, K; Usha, K E