Representation of rainfed valley ricefields using a soil-water balance model

Soil-water conditions for ricefields located in valleys in micro-catchments are simulated using a daily soil-water balance model. The crop is primarily rainfed but there is also limited irrigation water. The simulation covers a complete year and includes features such as rainfall, irrigation releases, runoff from uplands, actual evaporation and evapotranspiration, percolation losses through the bed and bunds of the ricefield, standing water in the field and overflows from the ricefield. A specific location in Sri Lanka is selected to illustrate the approach. The impacts of different conditions are explored including alternative irrigation releases, increased losses through the bed and bunds of the ricefield and a lower overflow from the ricefield. Simulations indicate that ricefields which are towards the valley sides have an increased inflow due to runoff from adjacent uplands; this can lead to improved rice yields. However, reducing heights of the bunds to half the original value results in substantial overflows during periods of high rainfall while the number of days without submergence almost doubles. This uncomplicated model is consistent with the limited field data and information available; it provides a realistic representation of the important processes and indicates why poor crop yields often occur.     

Pattern and Composition of Secondary Succession Beneath Caribbean Pine Plantations of Southwest Sri Lanka

This study examined the vegetation growing beneath Caribbean pine (Pinus caribaea) plantations established within previously abandoned tea lands adjacent to intact rain forest in southwest Sri Lanka. To examine the pattern and composition of secondary succession and factors affecting it, vegetation was sampled in different relative locations (interior and edge conditions) within plantations. Results demonstrated that more vegetation was found near the plantation edges than in the interior, and this pattern was prominent for both wind- and bird- dispersed species. The vegetation represented a mixture of species belonging to a range of successional guilds representing early (17 species, 42.4% in stem count) and late-successional species (52 species, 40.6%), although native long-lived canopy tree species were mostly absent. Bird-dispersed species dominated the flora (80 species, 86.7% in stem count). Abundance of an exotic shrub Clidemia hirta (Melastomataceae) showed a negative correlation with that of other species, indicating its impact on native flora. Underplanting of native canopy species may be effective in assisting secondary succession and control C. hirta in the plantations.     

The extraparasitic life cycle of Toxocara vitulorum in the village environment of Sri Lanka

The extraparasitic life cycle of Toxocara vitulorum of buffalo in the villages of Sri Lanka is related to observations on buffalo behaviour, experimental studies on the development and persistence of the eggs in soil and in wallows and the presence of eggs in village locations. Calf faeces on soil were rapidly incorporated by insect activity and the eggs developed only slightly slower than in the laboratory. Some infective eggs persisted 3–4 cm deep for 17 months, finally dying during a prolonged hot, dry period. Eggs in a wallow developed intermittently over 16 months as it was flushed with rain water, and eventually died when the wallow dried out. When infected faeces were placed in water, decomposition caused some material to rise to the surface and eggs developed. In villages, eggs are ubiquitous where young calves are kept but survive best where there is moisture and shade around animal pens and wallows. Cows and calves acquire infection from infective eggs in wallow water, soil and pasture, while calves may also be infected from contamination on the udder and teats of the cow. The larvae resulting from this infection do not mature until the infection is passed to the calf through the milk of the cow. At least 72% of village calves have patent infections and current treatment procedures do not reduce the prevalence.The possibility that T. vitulorum is a cause of human visceral larva migrans is discussed.     

The Effect of Providing Feed Supplementation and Anthelmintic to Donkeys during Late Pregnancy and Lactation on Live Weight and Survival of Dams and Their Foals in Central Ethiopia

Anthelmintic treatment (A), feed supplementation (F), anthelmintic and feed supplementation (A + F) or traditional management (Control) was given to 166 pregnant female donkeys in three localities (Holetta, Debre Zeit and Adami Tulu) in Ethiopia during an on-farm study. Treatments started during the last trimester of pregnancy and continued until 6 months after parturition when the foals were weaned. The same treatments were administered to foals once they reached 1 month of age. Live weights of adults and foals were measured throughout the study along with work output of adult donkeys and survival to weaning of the foals. Faecal worm egg counts (FEC) and blood packed cell volumes (PCV) were recorded monthly. When applied alone, anthelmintic treatment (A) or feed supplementation (F) had no significant effect on live weight gain or foal survival. However, when combined, anthelmintic and feed supplementation (A + F) significantly (p < 0.05) improved both live weight gain in adults and foals and foal survival. Workout was not affected by any of the treatments. Treatments A and A+F resulted in a highly significant (p<0.001) reduction in FEC in all three localities during the course of study and for at least 6 months after the last dose of anthelmintic in one of the study areas (Holetta). None of the treatments had any significant effect on PCV. Donkey owners in Ethiopia should be encouraged to adopt both anthelmintic treatment and feed supplementation if they expect tangible benefits in animal performance.     

Agroforestry research and practice in Sri Lanka

A review of agroforestry research and practice in Sri Lanka is provided with emphasis on traditional systems, plantation intercropping, silvopastoral systems, fertility improvement and community approaches. Comments are presented on the potentials and difficulties of each technology along with recommendations for further research and training. Some information on components of a number of agroforestry systems has been collected during the last 8 years. A brief account of the results is presented together with comments on current agroforestry practices.     

A survey of interculture practices and research in Sri Lanka

A survey on interculture research in Sri Lanka is outlined with details of species composition, spatial arrangement and justification for growing the crops as mixtures. The systems include interculture in tea, rubber and coconut plantations, spice gardens and alley cropping between leguminous tree crops. Soil conservation, generation of fuel and fodder, incentives for replanting and export diversification are some of the justifications put forward for interculture along with microclimate modification and reduction of pest incidence. The predominant expected yield criterion was some yield of associated intercrop with no reduction in tree crop yield rather than a land equivalence ratio of greater than unity. Major methodological problems were encountered due to lack of published information in mixture yields and the heterogeneity of experimental sites. Techniques for determining the biological basis of any yield advantage and the optimal spatial arrangement of intercrops were also missing.     

Incidence of brucellosis in Sri Lanka: an overview

Infection by Brucella abortus seems to be a major cause of abortions among cattle and buffaloes in Sri Lanka. The incidence of this disease is more prominent among the animals in the Dry zone of the country raised under extensive management systems. The present low incidence of this disease and the small size of the country may facilitate launching of an effective disease control scheme. The milk ring test (MRT) has proven to be usable in testing milk for the infection at farm level. An ELISA technique could be employed to test the seroprevalence of infection among MRT-positive animals. A program to purchase the diseased animals by the state for slaughter, and a countrywide vaccination program with B. abortus strain RB51 would enable the country’s livestock industry to eventually eradicate this disease.     

Irrigation systems as multiple-use commons: Water use in Kirindi Oya, Sri Lanka

Irrigation systems are recognized as common pool resources supplying water for agricultural production, but their role in supplying water for other uses is often overlooked. The importance of non-agricultural uses of irrigation water in livelihood strategies has implications for irrigation management and water rights, especially as increasing scarcity challenges existing water allocation mechanisms. This paper examines the multiple uses of water in the Kirindi Oya irrigation system in Sri Lanka, who the users are, and implications for water rights and management policies. There are important residential, gender, and class differences among the water users. People use irrigation system water not only for field crops, but also for fishing, homestead gardens, and livestock. Even within irrigated farming households, men have more control over paddy crops in the main fields, whereas homestead gardens are women's domain. Because the irrigation system provides water for birds and animals, even wildlife and non-resident environmental groups can be considered stakeholders. Current policies emphasize user involvement in both irrigation and domestic water supply. While government agencies have had primary responsibility, institutions such as Farmers' Organizations are being promoted. These have the potential to serve as user platforms for negotiating water allocation among irrigated farmers. However, the user organizations reflect the sectoral responsibility of the government agencies. Their membership and structure do not take into account the multiple uses or users of water. Developing platforms that accommodate different user groups remains a major challenge for improving the overall productivity, as well as equity, of water use.     

Participatory forest conservation in Southwest lowland rainforests of Sri Lanka

Natural forest in Sri Lanka has been decreased significantly in the last few decades. The remaining natural forests especially in floristic region seven have undergone less conservation efforts in the past. Considering the capacity of the government and dependence on forest resources by local villagers, the only way for conservation of these forests in the Southwest lowland is forest management through local participation. Management plans for community-based resource management have been completed. However promotion of such management requires integrated measures, which are beyond jurisdiction of Forest Department. A holistic approach with political commitment concerning buffer zone villages and economic incentives with income generation opportunities supported by external inputs are expected to be implemented as a matter of urgency.     

Valuing Water in a Multiple-Use System – Irrigated Agriculture and Reservoir Fisheries

Irrigation projects often provide water formany uses beyond crop irrigation. Sincewater uses within an irrigation system areoften interdependent, failure to addressall uses may result in inefficient,inequitable, unsustainable, or unsafe waterallocations. Accounting for the multipleuses of irrigation water leads to moreinformed decision making, resulting in moreproductive, equitable, and sustainableoutcomes. This paper demonstrates theimportance of accounting for alternativeuses of irrigation water by examining theeconomic contribution of agriculture, arecognized consumptive water use, andreservoir fisheries, an unrecognizednonconsumptive water use. The economicvalues of water for these uses areestimated for the irrigation project areaas a whole and on a per-cubic-meter basis. These values are used to examine theeconomic implications of alternativeintegrative water management practices. Theanalysis focuses on the Kirindi Oyairrigation system, located in southeasternSri Lanka, and has broader implications forother multiple-use systems.