Browsing by Author "Seneviratne, G."

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Effect of Biofilm Biofertilizer and Chemical Fertilizer Application Practices on Growth and Endophytic Bacterial Count of Rice (Oryza sativa L.)
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Lakmini, A.L.A.; Seneviratne, G.; Madushani, K.P.K.
Utilization of beneficial microbes as a biofertilizer has become paramount importance in the agriculture sector for their potential role in sustainable crop production. Nitrogen-fixing bacteria with rhizosphere fungi form fungal-bacterial biofilms which can be developed as biofilm biofertilizers (BFBFs) as an extension of biofertilizer research application which could save chemical fertilizer use (CF) for many crops with a wide range of beneficial biological functions. BFBF application has been reported by many authors to significantly increased rice yield with lower CF inputs, as it facilitates biological nitrogen fixation with non-legumes (rice, tea, wheat, and vegetables), while increasing solubility and availability of phosphorous and other macro, micro nutrients as a result of its beneficial interactions between bacteria and fungi as well as interaction between soil and microorganisms. This study investigates the effect of commercially available biofilm biofertilizer and chemical fertilizer application practices on growth and endophytic bacterial count of rice after the 2013 new chemical fertilizer recommendation by the Department of Agriculture Sri Lanka. This experiment was conducted in two selected fields at Dehiaththakandiya in Mahaweli system C and Rice Research and Development Institute, Bathalegoda. Six different treatments were applied (100% CF, 80% CF, 80% CF + BF, 65% CF, 65% CF + BF and no fertilizer as the control). The experiment was arranged in Randomized Complete Block Design with four replicates to each treatment. Plant growth (root and shoot length, tiller and panicle count, total dry mass) and soil parameters (soil pH, available ammonium, nitrate and phosphate levels) were recorded at both tillering and flowering stages. Endophytic bacteria were isolated from rice leaves and root samples to obtain a colony count. Data were subjected to statistical analysis. Results indicate that BFBFs influenced positively on plant-microbe interactions. BFBF significantly increased both vegetative and reproductive parameters of rice plants with increasing trend of total and diastrophic endophytic bacterial count compared to CF. Therefore, the application of BFBFs to the soil could induce endophytic diversity and their functionality. This indicates that the effects of community based approach of microbial biofilms increases soil and plant well-being for ensuring higher yield with the sustainability of the rice agro-ecosystems to restore their depletion due to chemical agriculture
Effect of Biofilm Biofertilizer on Availability of Soil Diazotrophs, Plant Endophytic Diazotrophs and Increasing of Grain Yield in Rice (Oryza sativa) Cultivation of Sri Lanka
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Rathnathilaka, A.T.D.; Seneviratne, G.; Madawala, H.M.S.P.; Rizvi, E.M.J.M.
Diazotrophs are microorganisms that are able to grow without external sources of fixed nitrogen and play a vital role in the persistence of microbial communities in the soil while increasing the crop productivity. Indiscriminate use of chemical fertilizers (CFs) particularly nitrogen based fertilizers adversely affect on the nitrogen fixers and ultimately cause the declining of soil health, crop productivity and agricultural sustainability in rice cultivation of Sri Lanka. Currently, farmers tend to give their attention to the application of organic fertilizers and biofertilizers. Biofilm biofertilizer (BFBF) is a novel product which can be used effectively to increase soil fertility and crop productivity without suppressing the microbial community in soil. BFBF is consisting of microbial cells and extracellular polymeric substances (EPS), which are secreted by themselves to have structural and biochemical protection. There are no sufficient studies carried out to evaluate BFBF in rice cultivation in farmers’ real field conditions with special reference to the soil and plant endophytic diazotrophs that are vital in biological nitrogen fixation and enhance the crop growth. Therefore, this study focused on the effect of BFBF to enhance the rice yield by increasing the availability of soil diazotrophs and plant endophytic diazotrophs using rice as the test plant. The study was carried out at the farmers’ fields in Ampara district, a major rice growing area in Sri Lanka. Eighteen farmers' fields were selected from different locations in Ampara district. Two consecutive, uniform paddy fields (whole liyaddas-one acre paddy fields) were applied separately with BFBF + 50 % CF practice (90 kg/ac CF NPK + 1000 ml/ac BFBF application) and farmers’ CF alone practice (180 kg/ac CF NPK application). Fertilizer applications were done in multiple applications. Rhizosphere soil and plant samples were collected by uprooting five hills as replicates from each paddy field at flowering in Maha season. Plant dry weight and leaf chlorophyll content were measured. Microbes were isolated and grown in nitrogen free Combine Carbon Media (CCM) prescribed for growing soil diazotrophs and plant endophytic diazotrophs. Rice grain yields were recorded at harvest. Results were analyzed using two sample t-test and ANOVA using R software at α = 0.05 probability level. According to the obtained results, soil diazotrophs (the increase by 69%) and plant endophytic diazorophs (54%) abundances, plant dry weight (49%), leaf chlorophyll content (38%) and grain yield (26%) of BFBF + 50% CF application significantly higher (p<0.05) than the farmers’ CF alone practice. Furthermore, correlation analysis clearly showed a significantly positive correlation between grain yield and soil diazotrophs (r2 = 95.7%, p < 0.05) and plant endophytic diazotrophs (r2 = 91.8%, p < 0.05) respectively. The study concludes that the application of BFBFs together with a reduced dosage of CFs has the potential to increase soil diazotrophs and plant endophytic diazotrophs while increasing the rice yield in comparison to CFs alone, thus showing promising potential of BFBFs in rice cultivation in Sri Lanka
Effect of microbial exudates on breaking dormancy of soil microbial seed bank
(Faculty of Graduate Studies, University of Kelaniya, 2015) Wijepala, P.; Seneviratne, G.; Madawala, H.M.S.P.; Jayasuriya, K.M.G.G.
Soil ecosystem deteriorates due to natural and anthropogenic disturbances, which interrupt the ecosystem functions and its sustainability. As a consequence of this disturbed soil system, plant and microbial seed bank may become dormant contributing to low below-and aboveground diversity. The present experiment was conducted to observe the effect of microbial exudates on rejuvenating a deteriorated soil system by activating the dormant microbial seed bank. Bacterial and fungal-bacterial biofilm exudates were used as treatments with a control (sterilized distilled water). Microbial exudates were applied to 2mm sieved soil in trays and incubated for 7 days at room temperature. Three replicates per treatment were arranged according to completely randomized design. Bacterial colony counts were taken from all treatments after 24 hours and 7 days of incubation. The functional groups present in microbial exudates and emerged bacterial colonies were analysed using Fourier Transform Infrared (FTIR) spectroscopy. Data were analyzed using ANOVA by Minitab (version 16). Significantly higher number of bacterial colonies was observed in soils applied with biofilm exudates than soils applied with bacterial exudates and the control. Cluster analysis demonstrated bacterial cultures emerged from soils applied with biofilm exudates were clustered separately from those emerged from other treatments, implying that it was a different group of bacteria. The results suggested that there is a possibility of using microbial biofilms to break the dormant microbial seed bank to enhance microbial diversity in soil.
Effect of sugars, amino acids, hormones and microbial biofilm exudates on dormancy breaking of culturable soil microbial seed bank.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Wijepala, P. C.; Jayasena, P. G.; Singhalage, I. D.; Seneviratne, G.; Madawala, H. M. S. P.; Jayasuriya, K. M. G. G.
Soil microbial diversity is found to be beneficial for plant growth and productivity. The diversity has decreased to alarming level under stressful soil conditions and microbes form dormant structures like spores to withstand stressful soil conditions. Biofilm Biofertilizer (BFBF) is the most efficient product, newly introduced to the agricultural industry of Sri Lanka, which consists of different compounds like sugars, amino acids and hormones. These compounds assist in breaking the dormancy of microbial seed bank. However, effect of the compounds on the dormancy breaking has been poorly investigated. Therefore in the current study, the effect of glucose, tryphtophan, indole acetic acid (IAA), BFBF exudates on dormancy breaking and growing of culturable soil microbial seed bank was investigated. BFBF exudates and seven types of solutions were prepared by mixing glucose, tryptophan and IAA in different ratios and used them as treatments. Sterile distilled water was used in the control. Sieved (0.5 mm) and air dried garden soil was treated and incubated for 2 months under room temperature. Triplicated treatments were arranged according to completely randomized design. Then the dormancy breaking test was conducted on treated soil following the protocols developed by National Institute of Fundamental Studies. Bacterial colony count and average colony diameters under each treatment were recorded after 1, 2, 4 and 6 weeks. Fourier Transformed Infrared (FTIR) spectra were recorded for exudates and prepared solutions. The highest colony count was observed in BFBF exudate treatment throughout the experiment whereas highest diameter was different among treatments during the incubation period. The lowest colony count was recorded in soil treated by IAA. This implies that the bacterial growth was improved when compounds interacted. The study concludes that colony count and diameter varies among treatments. However, among all treatments, BFBF exudate was the best for microbial seed bank dormancy breaking.
Efficiency of Biofilm Biofertilizer in Increasing Plant Growth Parameters of Rice Cultivation In Sri Lanka
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Meepegamage, S.W.; Seneviratne, G.; Rajapakse, R.G.S.C.
Agricultural land per unit area needed to obtain the highest productivity and quality products, in order to win the challenging need for food products to feed a growing world population. For that, excessive chemical fertilizers (CF) are used for a long period of time for the agricultural lands which affect adversely on soil health and plant production. Application of CFs on cultivated lands suppresses the soil microbial activities and leading to develop poor microbial communities with law biomass. Microbial biofertilizers, a viable substitute for CFs are reported to increase diversity and abundance of soil microbes by introducing beneficial microbes which are depleted in agroecosystems. They consist of live beneficial microbes such as fungi, bacteria and algae which may include single or multiple combinations to enhance microbial activities. Among biofertilizers, more efficient biofilm biofertilizers (BFBF) which consist of developed microbial communities and extra polymeric substances play a crucial role in plant growth and soil processes. BFBFs are observed to produce various plant hormones, hydrogen cyanide and siderophore like exudates and amelioration of plants from stress. Moreover, they are involved in activities like nitrogenase activity, antagonistic activity defense against plant pathogens and solubilization and mineralization of soil nutrients such as phosphorus. BFBFs which ensure the sustainability of agroecosystem help for plant growth and development. Thus, the present study focused on the effect of BFBF on plant growth parameters under CF reduction in the conventional agriculture using rice as the test plant. A rice field experiment was conducted with four treatments viz: 100% CF DOA recommendation (DCF, 136 kg NPK per acre), NIFS CF recommendation for BFBF practice (NCF, 90 kg NPK per acre), NIFS CF recommendation for BFBF practice + BFBF (NCF + BFBF, 1000 ml BFBF per acre), and the control (without CF and BFBF), each having three replicates. Plant samples were collected randomly from all four treatments and leaf chlorophyll content was measured in the field using SPAD-502-Chlorophyll meter. Furthermore, total dry weight per hill, total number of tillers per hill, circumference of plant shoot, thousand seed weight and chaff content were measured. The data were analyzed using Minitab statistical package. There were significant increases in total dry weight of the plant (increase by, with respect to DCF: 89%, NCF: 98%, control: 98%), total number of tillers per hill (with respect to DCF: 93%, NCF: 73%, control: 86%) and circumference of the plant shoot (with respect to DCF: 52%, NCF: 35%, control: 40%) (p < 0.05) in the NCF + BFBF treatment over the other three treatments. NCF + BFBF showed the higher leaf chlorophyll content (with respect to DCF: 6%, NCF: 1%, control: 33%), thousand seed weight (with respect to DCF: 3%, NCF: 1%, control: 9%) and the lower chaff content (decrease by, with respect to DCF: 33%, NCF: 8%, control: 33%) than those of other three treatments. The study concludes that the BFBF application together with a reduced dosage of CFs improves the plant growth and grain yield in conventional rice cultivation