Browsing by Author "Madawala, H.M.S.P."

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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.
Soil nutrient availability in different vegetation types of Kunckles conservation forest in Sri Lanka.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Rajapaksha, R.P.S.K.; Madawala, H.M.S.P.; Gunathilake, S.K.; Ratnayake, R.R.
Estimates of soil nutrient availability in tropical land use types are critically important to understand the function of soil in the global nutrient cycles and the sustainable management of tropical ecosystems. The aim of this study was to quantify and compare the macro and micro nutrient availability in soils in different vegetation types in the Knuckles Conservation Forest (KCF) of Sri Lanka. Soil samples were collected within two depth layers (0-15 and 15-30 cm) considering the proportion and the accessibility to each vegetation type. The selected vegetation types were montane forest (MF), sub-montane forest (SMF), moist monsoon forest (MMF), open and sparse forest (OSF), grassland (GL) and forest plantation (FP). The macro nutrient (N, P, K, Ca and Mg) and micro nutrient (Fe, Mn, Cu and Zn) availabilities were analyzed for two soil depth layers (0-15 and 15-30 cm). A total of 1224 samples were collected from two depths and pooled to form 408 composite samples. General Linear Model in Analysis of Variance was performed using Minitab 16 to analyze the data. Availability of N and P in KCF soils ranged between 8.18 - 19.76 mg/kg and 0.21 - 0.45 mg/kg, respectively among the vegetation types in the 0-15 cm layer. N and P availability was significantly higher in SMF (21.23 and 0.49 mg/kg respectively) and OSF (22.08 and 0.47 mg/kg) soils compared to other vegetation types. Significantly low N availability was observed in both GL (5.07 mg/kg) and MF (7.32 mg/kg) soils. It was also found that P was significantly deficient in MF soils compared to other vegetation types in KCF. Vegetation types in KCF showed significant differences in the availability of K, Ca, Mg, Fe, Mn, Cu and Zn in soils. Fe availability in soils varied between 187.4 - 682.3 mg/kg while Mn varied from 28.52 - 85.26 mg/kg. Results concluded that spatial availability of nutrients such as N and P in mineral soil may be decreased in MF comparing to the other vegetation types due to the environmental conditions such as acidic soil pH, low temperature and microbial growth existing at high altitudes of KCF. This suggests limitation of plant growth in MF by deficiency of one or several nutrients at higher altitudes. Availability of K and Ca in KCF may be affected by parent material exposed on to the soil surface. This baseline information will address the dearth of data on soil nutrient availability of different ecosystems in the tropics, hence useful in future conservation purposes of the tropical forest ecosystems.