DSpace Collection:

Root fouling organisms of Rhizophora mucronata in Rekawa Lagoon, Sri Lanka

2018-01-01T00:00:00Z

Title: Root fouling organisms of Rhizophora mucronata in Rekawa Lagoon, Sri Lanka Authors: Wanasuriya, W.M.A.P.; Kumara, M.P.; Wijesundara, W.M.I.C. Abstract: Mangrove underwater roots provide habitats for a variety of root fouling organisms. Since there is a dearth of information locally on the fauna and flora growing on such habitats, a study was carried out to study the biodiversity of mangrove root fouling organisms at the Rekawa lagoon (05° 58’ N and 80° 50’ E). In this study, a mangrove prop root that is hanging freely into the water from each one of the 20 randomly selected Rhizophora mucronata trees was cut to collect the fouling organisms from four different zones, namely, the top most, upper middle, lower middle and near the bottom along the root. The number of solitary countable organisms were recorded per unit surface area (m-2) of each one of the four root zones. The abundance of the non-countable colony-forming organisms were determined using the % volume values following the points (volumetric) method. Abundance data were analyzed non-parametrically using the Kruskal Wallis test. Further, the diversity of organisms in each zone of the root were also calculated. Twenty seven different taxa of fouling organisms including countable taxa such as Isopods, Amphipods, Copepods, Polychaets, Bivalves, Heliozoans, Diatoms, Oscillatoria sp., Nematodes, Cryptophyta, Bacillariophyta, Phytoplankton, Foraminfera, Chlorellacea and colony forming non-countable taxa such as Rhodophyta, porifera, Hydra sp., Ascidiacea, Ulothrix sp., Ciliophora and Chlorophyta were recorded. The median abundance of countable organisms was significantly higher in the upper middle zone (2461 m-2) than that in the bottom zone (1057 m-2). Further, the median diversity of these fouling organisms in the upper middle zone was significantly higher (196 m-2) than that in the bottom layer, which showed the minimum diversity (70.83 m-2). However, the median % volume of non-countable organisms did not differ significantly between different root zones. Variation of the abundance and diversity of countable and non-countable fouling organisms in the Rekawa lagoon could be attributed to the prevailing environmental conditions.

Determinants of Herbicide Use in Rice Production Systems of Sri Lanka

2018-01-01T00:00:00Z

Title: Determinants of Herbicide Use in Rice Production Systems of Sri Lanka Authors: Munaweera, T.P.; Jayasinghe, J.A.U.P. Abstract: This study identifies farm-specific and market factors affecting the adoption of herbicides and the level of herbicide use by rice farmers in Sri Lanka. Determinants of adoption and level of herbicide use were explored using a comprehensive data set collected from 240 randomly selected paddy farmers from selected areas in the Anuradhapura, Ampara, Matara and Kurunegala districts. Study employed the cross sectional Double Hurdle model that describe demand decisions on herbicides arising from two hurdles that have to be overcome for positive demand. Household size, farming experience, type of irrigation, training received related to pest control and extent under cultivation were significant determinants of the decision of farmers to adopt herbicide as an alternative to manual weeding, while, age, sex, extent cultivated, farm gate price, tenurial status, type of irrigation and training related to pest control determine the quantity of herbicide use. Findings highlight the complexity of the issue, hence the institutions seeking to avoid the overuse of herbicide or to encourage adoption of alternative methods of weed control are likely to need to use multiple strategies to address the key variables. The insights generated should be of value to agricultural extension officers, researchers and policy makers. These results are potentially relevant when designing policies to reduce excessive herbicide use or to encourage the adoption of alternative weed control methods such as integrated weed management.

Growth and Yield Response of Mechanical Transplanted Rice at Different Plant Densities

2018-01-01T00:00:00Z

Title: Growth and Yield Response of Mechanical Transplanted Rice at Different Plant Densities Authors: Sivaneson, S.; Vijayakumari, V. Abstract: Optimum plant spacing is among key agronomic parameters that influence on growth and yield in rice (Oryza sativa L.). A field experiment was conducted to evaluate the growth and yield response of mechanical transplanted rice at the Rice Research Station, Paranthan during Maha season, 2016/17. The machine transplanting method considered as practical option to minimize the labor usage with the timeliness cultivation of rice. Recent past, rice transplanter was introduced to paddy farmers of Kilinochchi district by the governmentof Sri Lanka. However, adaptation of this method is still low due to socio-economic background and lack of technical information. Four rows of man-propelled paddy KUBOTA (SPW 48c) transplanter was used in this study with 30cm row spacing (non-adjustable) and 5 within row spacing levels (12, 14, 16, 18 and 21 cm), replicated four times in each. The rice variety Co-10 was used with the plot size of 4m×6m. The plant height, number of tillers at different stages, percentage of canopy coverage and yield components such as panicle per hill, panicle length, grain yield and 1000 grains weight were recorded. Results revealed that the spacing of 30cm×16 cm produced significantly higher number of tillers and panicles than others. The spacing of 30cm×16 cm recorded the highest (p<0.05) percentage of canopy coverage (75 %), 1000 grain weight (24.9 g) and grain yield (7921.9 kg/ha). This study concluded that spacing of 30cm×16cm can be considered as optimum plant density for machine transplanted rice for the variety Co-10 compared to other tested spacing in this region.

Trends in Rainfall, Length of Growing Period and Drought Occurrence in Karnataka, India

2018-01-01T00:00:00Z

Title: Trends in Rainfall, Length of Growing Period and Drought Occurrence in Karnataka, India Authors: Shivaramu, H. S.; Venkatesh, H.; Padmashri, H. S. Abstract: Climate has a vital role on biosphere of the earth. Of the major climatic parameters, rainfall is one of the most important parameters that influence the agriculture of the region and food production. A study was undertaken to analyze the trend of the rainfall pattern of Karnataka by using the daily rainfall data from 1980 to 2013 of 392 stations and its length of growing period (LGP) along with drought extent. Annual rainfall normals and rainy days normals over different stations was tested Mann-Kendall test was used for significance of trends in annual rainfall and annual rainy days. Also the frequencies of moderate and severe meteorological droughts were computed. Weekly values of precipitation and potential evapotranspiration were considered for computing length of the growing period. The mean annual rainfall of Karnataka in the last thirty three years was 1122±133 mm with a coefficient of variation (CV) of 12 %. Eighty two percent of the stations in the state shown no significant trend in annual rainfall while seventy one percent of the stations shown no significant trend in annual rainy days. Around 97% of the stations in the state show a probability of <10% of occurrence of severe droughts. Drought prone areas have been defined for Karnataka based on LGP concept. LGP varied between 168 days in Aland Taluk of Kalburagi district to 259 days in Beltangadi taluk of Dakshina Kannada district. According to LGP, agro-climatic zones of Karnataka have been re-delineated into new sub zones.